NETLMM WG                                         S. Gundavelli (Editor)
Internet-Draft                                                  K. Leung
Intended status: Standards Track                                   Cisco
Expires: June 27, August 6, 2008                                   V. Devarapalli
                                                         Azaire Networks
                                                            K. Chowdhury
                                                        Starent Networks
                                                                B. Patil
                                                  Nokia Siemens Networks
                                                       December 25, 2007
                                                       February 03, 2008

                           Proxy Mobile IPv6
                   draft-ietf-netlmm-proxymip6-08.txt
                   draft-ietf-netlmm-proxymip6-09.txt

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Copyright Notice

   Copyright (C) The IETF Trust (2007). (2008).

Abstract

   Network-based mobility management enables IP mobility for a host
   without requiring its participation in any mobility related
   signaling.  The Network is responsible for managing IP mobility on
   behalf of the host.  The mobility entities in the network are
   responsible for tracking the movements of the host and initiating the
   required mobility signaling on its behalf.  This specification
   describes a network-based mobility management protocol and is
   referred to as Proxy Mobile IPv6.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Conventions & Terminology  . . . . . . . . . . . . . . . . . .  4
     2.1.  Conventions used in this document  . . . . . . . . . . . .  5
     2.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Proxy Mobile IPv6 Protocol Overview  . . . . . . . . . . . . .  8
   4.  Proxy Mobile IPv6 Protocol Security  . . . . . . . . . . . . . 14
     4.1.  Peer Authorization Database Entries  . . . . . . . . . . . 15
     4.2.  Security Policy Database Entries . . . . . . . . . . . . . 15
   5.  Local Mobility Anchor Operation  . . . . . . . . . . . . . . . 16
     5.1.  Extensions to Binding Cache Entry Data Structure . . . . . 16
     5.2.  Supported Home Network Prefix Models . . . . . . . . . . . 18
     5.3.  Signaling Considerations . . . . . . . . . . . . . . . . . 18
       5.3.1.  Processing Binding Registrations . . . . . . . . . . . 18
       5.3.2.  Initial Binding Registration (New Mobility Session)  . 20
       5.3.3.  Binding Lifetime Extension (No handoff)  . . . . . . . 21
       5.3.4.  Binding Lifetime Extension (After handoff) . . . . . . 22
       5.3.5.  Binding De-Registration  . . . . . . . . . . . . . . . 22
       5.3.6.  Constructing the Proxy Binding Acknowledgement
               Message  . . . . . . . . . . . . . . . . . . . . . . . 23
     5.4.  Multihoming Support  . . . . . . . . . . . . . . . . . . . 24 25
       5.4.1.  Binding Cache entry lookup considerations  . . . . . . 26
     5.5.  Timestamp Option for Message Ordering  . . . . . . . . . . 28 31
     5.6.  Routing Considerations . . . . . . . . . . . . . . . . . . 30 33
       5.6.1.  Bi-Directional Tunnel Management . . . . . . . . . . . 30 33
       5.6.2.  Forwarding Considerations  . . . . . . . . . . . . . . 31 34
     5.7.  Local Mobility Anchor Address Discovery  . . . . . . . . . 32 35
     5.8.  Mobile Prefix Discovery Considerations . . . . . . . . . . 32 36
     5.9.  Route Optimizations Considerations . . . . . . . . . . . . 33 36
   6.  Mobile Access Gateway Operation  . . . . . . . . . . . . . . . 33 36
     6.1.  Extensions to Binding Update List Entry Data Structure . . 34 37
     6.2.  Mobile Node's Policy Profile . . . . . . . . . . . . . . . 35 38
     6.3.  Supported Access Link Types  . . . . . . . . . . . . . . . 35 38
     6.4.  Supported Address Configuration Models Modes  . . . . . . . . . . 36 39
     6.5.  Access Authentication & Mobile Node Identification . . . . 36 39
     6.6.  Acquiring Mobile Node's Identifier . . . . . . . . . . . . 36 39
     6.7.  Home Network Emulation . . . . . . . . . . . . . . . . . . 37 40
     6.8.  Link-Local and Global Address Uniqueness . . . . . . . . . 38 41
     6.9.  Signaling Considerations . . . . . . . . . . . . . . . . . 39 42
       6.9.1.  Binding Registrations  . . . . . . . . . . . . . . . . 39 42
       6.9.2.  Router Solicitation Messages . . . . . . . . . . . . . 45 49
       6.9.3.  Default-Router Lifetime  . . . . . . . . . . . . . . . 50
       6.9.4.  Retransmissions and Rate Limiting  . . . . . . . . . . 45 51
     6.10. Routing Considerations . . . . . . . . . . . . . . . . . . 46 51
       6.10.1. Transport Network  . . . . . . . . . . . . . . . . . . 46 52
       6.10.2. Tunneling & Encapsulation Modes  . . . . . . . . . . . 46 52
       6.10.3. Routing State  . . . . . . . . . . . . . . . . . . . . 47
       6.10.4. Local Routing  . . . . . . . . . . . . . . . . . . . . 48
       6.10.5. 53
       6.10.4. Tunnel Management  . . . . . . . . . . . . . . . . . . 49
       6.10.6. 53
       6.10.5. Forwarding Rules . . . . . . . . . . . . . . . . . . . 49 53
     6.11. Supporting DHCPv6 based Address Configuration on the
           Access Link  . . . . . . . . . . . . . . . . . . . . . . . 50 55
     6.12. Home Network Prefix Renumbering  . . . . . . . . . . . . . 51 56
     6.13. Mobile Node Detachment Detection and Resource Cleanup  . . 51 56
     6.14. Allowing network access to other IPv6 nodes  . . . . . . . 52 57
   7.  Mobile Node Operation  . . . . . . . . . . . . . . . . . . . . 53 57
     7.1.  Moving into a Proxy Mobile IPv6 Domain . . . . . . . . . . 53 57
     7.2.  Roaming in the Proxy Mobile IPv6 Domain  . . . . . . . . . 54
     7.3.  IPv6 Host Protocol Parameters  . . . . . . . . . . . . . . 54 58
   8.  Message Formats  . . . . . . . . . . . . . . . . . . . . . . . 55 59
     8.1.  Proxy Binding Update Message . . . . . . . . . . . . . . . 56 59
     8.2.  Proxy Binding Acknowledgement Message  . . . . . . . . . . 57 61
     8.3.  Home Network Prefix Option . . . . . . . . . . . . . . . . 58 62
     8.4.  Handoff Indicator Option . . . . . . . . . . . . . . . . . 63
     8.5.  Access Technology Type Option  . . . . . . . . . . . . . . 60
     8.5. 64
     8.6.  Mobile Node Interface Identifier Option  . . . . . . . . . 61
     8.6. 66
     8.7.  Link-local Address Option  . . . . . . . . . . . . . . . . 62
     8.7. 67
     8.8.  Timestamp Option . . . . . . . . . . . . . . . . . . . . . 63
     8.8. 67
     8.9.  Status Values  . . . . . . . . . . . . . . . . . . . . . . 64 68
   9.  Protocol Configuration Variables . . . . . . . . . . . . . . . 66 70
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 67 71
   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 68 72
   12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 69 73
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 69 73
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 69 73
     13.2. Informative References . . . . . . . . . . . . . . . . . . 70 74
   Appendix A.  Proxy Mobile IPv6 interactions with AAA
                Infrastructure  . . . . . . . . . . . . . . . . . . . 71 75
   Appendix B.  Supporting Shared-Prefix Model using DHCPv6 . . . . . 71 75
   Appendix C.  Routing State . . . . . . . . . . . . . . . . . . . . 76
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 72 77
   Intellectual Property and Copyright Statements . . . . . . . . . . 74 79

1.  Introduction

   IP mobility for IPv6 hosts is specified in Mobile IPv6 [RFC-3775].
   Mobile IPv6 requires client functionality in the IPv6 stack of a
   mobile node.  Exchange of signaling messages between the mobile node
   and home agent enables the creation and maintenance of a binding
   between the mobile node's home address and its care-of-address.
   Mobility as specified in [RFC-3775] requires the IP host to send IP
   mobility management signaling messages to the Home Agent, home agent, which is
   located in the network.

   Network-based mobility is another approach to solving the IP mobility
   challenge.  It is possible to support mobility for IPv6 nodes without
   host involvement by extending Mobile IPv6 [RFC-3775] signaling
   messages between a network node and reusing the a home agent.  This approach to
   supporting mobility does not require the mobile node to be involved
   in the exchange of signaling messages between itself and the Home Agent. home
   agent.  A proxy mobility agent in the network performs the signaling
   with the home agent and does the mobility management on behalf of the
   mobile node attached to the network.  Because of the use and
   extension of Mobile IPv6 signaling and home agent functionality, this
   protocol is referred to as Proxy Mobile IPv6 (PMIPv6).

   Network deployments which are designed to support mobility would be
   agnostic to the capability in the IPv6 stack of the nodes which it
   serves.  IP mobility for nodes which have mobile IP client
   functionality in the IPv6 stack as well as those hosts nodes which do not,
   would be supported by enabling Proxy Mobile IPv6 protocol
   functionality in the network.  The advantages of developing a network
   based mobility protocol based on Mobile IPv6 are:

   o  Reuse of home agent functionality and the messages/format used in
      mobility signaling.  Mobile IPv6 is a mature protocol with several
      implementations that have undergone interoperability testing.

   o  A common home agent would serve as the mobility agent for all
      types of IPv6 nodes.

   The problem statement and the need for a network based mobility
   protocol solution has been documented in [RFC-4830].  Proxy Mobile
   IPv6 is a solution that addresses these issues and requirements.

2.  Conventions & Terminology

2.1.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC-2119].

2.2.  Terminology

   All the general mobility related terms used in this document are to
   be interpreted as defined in the Mobile IPv6 base specification [RFC-
   3775].

   This document adopts the terms, Local Mobility Anchor (LMA) and
   Mobile Access Gateway (MAG) from the NETLMM Goals document [RFC-
   4831].  This document also provides the following context specific
   explanation to the following terms used in this document.

   Proxy Mobile IPv6 Domain (PMIPv6-Domain)

      Proxy Mobile IPv6 domain refers to the network where the mobility
      management of a mobile node is handled using the Proxy Mobile IPv6
      protocol as defined in this specification.  The Proxy Mobile IPv6
      domain includes local mobility anchors and mobile access gateways
      between which security associations can be setup and authorization
      for sending Proxy Binding Updates on behalf of the mobile nodes
      can be ensured.

   Local Mobility Anchor (LMA)

      Local Mobility Anchor is the home agent for the mobile node in the
      Proxy Mobile IPv6 domain.  It is the topological anchor point for
      the mobile node's home network prefix and is the entity that
      manages the mobile node's binding state.  The local mobility
      anchor has the functional capabilities of a home agent as defined
      in Mobile IPv6 base specification [RFC-3775] with the additional
      capabilities required for supporting Proxy Mobile IPv6 protocol as
      defined in this specification.

   Mobile Access Gateway (MAG)

      Mobile Access Gateway is a function that manages the mobility
      related signaling for a mobile node that is attached to its access
      link.  It is responsible for tracking the mobile node's movements
      on
      to and from the access link and for signaling the mobile node's
      local mobility anchor.

   Mobile Node (MN)

      Throughout this document, the term mobile node is used to refer to
      an IP host or router whose mobility is managed by the network.
      The mobile node may be operating in IPv6 mode, IPv4 mode or in
      IPv4/IPv6 dual mode.  The mobile node is not required to
      participate in any IP mobility related signaling for achieving
      mobility for an IP address that is obtained in that Proxy Mobile
      IPv6 domain.  This
      document further uses explicit text when referring to a mobile
      node that is involved in mobility related signaling as per the
      Mobile IPv6 specification [RFC-3775].

   LMA Address (LMAA)

      The address that is configured on the interface of the local
      mobility anchor and is the transport endpoint of the bi-
      directional tunnel established between the local mobility anchor
      and the mobile access gateway.  This is the address to where the
      mobile access gateway sends the Proxy Binding Update messages.
      When supporting IPv4 traversal, i.e., when the network between the
      local mobility anchor and the mobile access gateway is an IPv4
      network, this address will be an IPv4 address and will be referred
      to as IPv4-LMAA, as specified in [ID-IPV4-PMIP6].

   Proxy Care-of Address (Proxy-CoA)

      Proxy-CoA is the address configured on the interface of the mobile
      access gateway and is the transport endpoint of the tunnel between
      the local mobility anchor and the mobile access gateway.  The
      local mobility anchor views this address as the Care-of Address of
      the mobile node and registers it in the Binding Cache entry for
      that mobile node.  When the transport network between the mobile
      access gateway and the local mobility anchor is an IPv4 network
      and if the care-of address that is registered at the local
      mobility anchor is an IPv4 address, the term, IPv4-Proxy-CoA is
      used, as specified in [ID-IPV4-PMIP6].

   Mobile Node's Home Address (MN-HoA)

      MN-HoA is the home address of a mobile node in a Proxy Mobile IPv6
      domain.  It is an address from its a mobile node's home network prefix obtained by
      a mobile node in a
      Proxy Mobile IPv6 domain.  The mobile node can
      continue will be able to use
      this address as long as it is attached to the access network that
      is in the scope of that Proxy Mobile IPv6 domain.  Unlike in
      Mobile IPv6 where the home agent is aware of the home address of
      the mobile node, in Proxy Mobile IPv6, the mobility entities are
      only aware of the mobile node's home network prefix and are not
      always aware of the exact address(es) that the mobile node
      configured on its interface from that prefix.

   Mobile Node's Home Network Prefix (MN-HNP)
      This is the on-link IPv6 prefix that is always present in the
      Router Advertisements that the mobile node receives when it is
      attached to any of the access links in that Proxy Mobile IPv6
      domain.  This home network prefix is topologically anchored at the
      mobile node's local mobility anchor.  The mobile node configures
      its interface with an address from this prefix.  If the mobile
      node connects to the Proxy Mobile IPv6 domain through multiple
      interfaces, simultaneously, each of the connected interface will
      be assigned a unique home network prefix and under a different
      mobility session.

   Mobile Node's Home Link

      This is the link on which the mobile node obtained its Layer-3
      address configuration for the attached interface after it moved
      into that Proxy Mobile IPv6 domain.  This is the link that
      conceptually follows the mobile node.  The network will ensure the
      mobile node always sees this link with respect to the layer-3
      network configuration, on any access link that it attaches to in
      that Proxy Mobile IPv6 domain.

   Multihomed Mobile Node

      A mobile node that connects to the Proxy Mobile IPv6 domain
      through more than one interface and uses these interfaces
      simultaneously is referred to as a multihomed mobile node.

   Mobile Node Identifier (MN-Identifier)

      The identity of a mobile node in the Proxy Mobile IPv6 domain.
      This is the stable identifier of a mobile node that the mobility
      entities in a Proxy Mobile IPv6 domain can always acquire and use
      it for predictably identifying a mobile node.  This is typically
      an identifier such as NAI or other identifier such as a MAC
      address.

   Mobile Node Interface Identifier (MN-Interface-Identifier)

      The interface identifier that identifies a given interface of a
      mobile node.  For those interfaces that have a layer-2 identifier,
      the interface identifier can be based on that layer-2 identifier.
      The interface identifier in some cases is generated by the mobile
      node and conveyed to the access router or the mobile access
      gateway.  In some cases, there might not be any interface
      identifier associated with the mobile node's interface.

   Policy Profile
      Policy Profile is an abstract term for referring to a set of
      configuration parameters that are configured for a given mobile
      node.  The mobility entities in the Proxy Mobile IPv6 domain
      require access to these parameters for providing the mobility
      management to a given mobile node.  The specific details on how
      the network entities obtain this policy profile is outside the
      scope of this document.

   Proxy Binding Update (PBU)

      A binding registration request message sent by a mobile access
      gateway to a mobile node's local mobility anchor for establishing
      a binding between the mobile node's MN-HNP and the Proxy-CoA.

   Proxy Binding Acknowledgement (PBA)

      A binding registration reply message sent by a local mobility
      anchor in response to a Proxy Binding Update request message that
      it received from a mobile access gateway.

3.  Proxy Mobile IPv6 Protocol Overview

   This specification describes a network-based mobility management
   protocol.  It is called Proxy Mobile IPv6 and is based on Mobile IPv6
   [RFC-3775].

   Proxy Mobile IPv6 protocol is intended for providing network-based IP
   mobility management support to a mobile node, without requiring the
   participation of the mobile node in any IP mobility related
   signaling.  The mobility entities in the network will track the
   mobile node's movements and will initiate the mobility signaling and
   setup the required routing state.

   The core functional entities in the NETLMM infrastructure are the
   Local Mobility Anchor (LMA) and the Mobile Access Gateway (MAG).  The
   local mobility anchor is responsible for maintaining the mobile
   node's reachability state and is the topological anchor point for the
   mobile node's home network prefix.  The mobile access gateway is the
   entity that performs the mobility management on behalf of a mobile
   node and it resides on the access link where the mobile node is
   anchored.  The mobile access gateway is responsible for detecting the
   mobile node's movements on its to and from the access link and for sending
   initiating binding registrations to the mobile node's local mobility
   anchor.  The architecture of a Proxy Mobile IPv6 domain is shown in
   Figure 1.

               +----+                +----+
               |LMA1|                |LMA2|
               +----+                +----+
        LMAA1 -> |                      | <-- LMAA2
                 |                      |
                 \\                    //\\
                  \\                  //  \\
                   \\                //    \\
                +---\\------------- //------\\----+
               (     \\  IPv4/IPv6 //        \\    )
               (      \\  Network //          \\   )
                +------\\--------//------------\\-+
                        \\      //              \\
                         \\    //                \\
                          \\  //                  \\
              Proxy-CoA1--> |                      | <-- Proxy-CoA2
                         +----+                 +----+
                         |MAG1|-----{MN2}       |MAG2|
                         +----+    |            +----+
                           |       |               |
              MN-HoA1 -->  |     MN-HoA2           | <-- MN-HoA3
                         {MN1}                   {MN3}

                    Figure 1: Proxy Mobile IPv6 Domain

   Once a mobile node enters a Proxy Mobile IPv6 domain and attaches to
   an access link, the mobile access gateway on that access link, after
   identifying the mobile node and acquiring its identity, will
   determine if the mobile node is authorized for the network-based
   mobility management service.

   If the network determines that the network-based mobility management
   service needs to be offered to that mobile node, the network will
   ensure that the mobile node using any of the address configuration
   mechanisms permitted by the network will be able to obtain the
   address configuration on the connected interface and move anywhere in
   that Proxy Mobile IPv6 domain.  The obtained address configuration
   includes the address(es) from its home network prefix, the default-
   router address on the link and other related configuration
   parameters.  From the perspective of the mobile node, the entire
   Proxy Mobile IPv6 domain appears as a single link, the network
   ensures that the mobile node believes it is always on the same link
   where it obtained its initial address configuration, even after
   changing its point of attachment in that network.

   The mobile node may be operating in an IPv4-only mode, IPv6-only mode
   or in dual IPv4/IPv6 mode.  Based on what is enabled in the network
   for that mobile node, the mobile node will be able to obtain an IPv4,
   IPv6 or dual IPv4/IPv6 addresses and move anywhere in that Proxy
   Mobile IPv6 domain.  However, the specific details related to the
   IPv4 addressing or IPv4 transport support are specified in the
   companion document [ID-IPV4-PMIP6].

   If the mobile node connects to the Proxy Mobile IPv6 domain, through
   multiple interfaces and over multiple access networks, the network
   will allocate a unique home network prefix for each of the connected
   interfaces and the mobile node will be able to configure an
   address(es) on those interfaces from the respective home network
   prefixes.  If  However, if the mobile node performs a handover an handoff from one
   interface to another in and if the same Proxy Mobile IPv6 domain, then local mobility anchor receives an
   handoff hint from the serving mobile access gateway about the same,
   the local mobility anchor will assign the same prefix to the new interface, if
   it receives the handover hints from the mobile access gateway in the
   signaling messages.
   interface.

    +-----+                +-----+                +-----+
    | MN  |                | MAG |                | LMA |
    +-----+                +-----+                +-----+
       |                      |                      |
   MN Attached                |                      |
       |                      |                      |
       |               MN Attached Event             |
       |        (Acquire MN-Id and Profile)          |
       |                      |                      |
       |                      |----- PBU ----------->|
       |                      |                      |
       |                      |                  Accept PBU
       |                      |  (Allocate MN-HNP, Setup BCE and Tunnel)
       |                      |                      |
       |                      |<--------- PBA -------|
       |                      |                      |
       |                 Accept PBA                  |
       |          (Setup Tunnel and Routing)         |
       |                      |                      |
       |                      |==== Bi-Dir Tunnel ===|
       |                      |                      |
       |--- Rtr Sol --------->|                      |
       |                      |                      |
       |<------- Rtr Adv -----|                      |
       |                      |                      |
    IP Address                |                      |
   Configuration              |                      |
       |                      |                      |

          Figure 2: Mobile Node Attachment - Signaling Call Flow

   Figure 2 shows the signaling call flow when the mobile node enters
   the Proxy Mobile IPv6 domain.

   For updating the local mobility anchor about the current location of
   the mobile node, the mobile access gateway sends a Proxy Binding
   Update message to the mobile node's local mobility anchor.  Upon
   accepting this Proxy Binding Update message, the local mobility
   anchor sends a Proxy Binding Acknowledgement message including the
   mobile node's home network prefix.  It also creates the Binding Cache
   entry and establishes a bi-directional tunnel to the mobile access
   gateway.

   The mobile access gateway on receiving the Proxy Binding
   Acknowledgement message sets up a bi-directional tunnel to the local
   mobility anchor and sets up the data path for the mobile node's
   traffic.  At this point the mobile access gateway will have all the
   required information for emulating the mobile node's home link.  It
   sends Router Advertisement messages to the mobile node on the access
   link advertising the mobile node's home network prefix as the hosted
   on-link-prefix.

   The mobile node on receiving these Router Advertisement messages on
   the access link will attempt to configure its interface either using
   stateful or stateless address configuration modes, based on the modes
   that are permitted on that access link.  At the end of a successful
   address configuration procedure, the mobile node will end up with an
   address from its home network prefix.

   Once the address configuration is complete, the mobile node has a
   valid address from its home network prefix at the current point of
   attachment.  The serving mobile access gateway and the local mobility
   anchor also have proper routing states for handling the traffic sent
   to and from the mobile node using an address from its home network
   prefix.

   The local mobility anchor, being the topological anchor point for the
   mobile node's home network prefix, receives any packets that are sent
   by any correspondent node to the mobile node.  The local mobility
   anchor forwards these received packets to the mobile access gateway
   through the bi-directional tunnel.  The mobile access gateway on
   other end of the tunnel, after receiving the packet, removes the
   outer header and forwards the packet on the access link to the mobile
   node.

   The mobile access gateway typically acts as a default router on the
   access link.  Any packet that the mobile node sends to any
   correspondent node will be received by the mobile access gateway and
   will be sent to its local mobility anchor through the bi-directional
   tunnel.  The local mobility anchor on the other end of the tunnel,
   after receiving the packet, removes the outer header and routes the
   packet to the destination.

    +-----+          +-----+          +-----+          +-----+
    | MN  |          |p-MAG|          | LMA |          |n-MAG|
    +-----+          +-----+          +-----+          +-----+
       |                |                |                |
       |                |==Bi-Dir Tunnel=|                |
   MN Detached          |                |                |
       |         MN Detached Event       |                |
       |                |                |                |
       |                |-- DeReg PBU -->|                |
       |                |                |                |
       |                |            Accept PBU           |
       |                |   (Start MinDelayBeforeBCEDelete Timer)
       |                |                |                |
       |                |<-------- PBA --|                |
       |                |                |                |
   MN Attached          |                |                |
       |                |                |       MN Attached Event
       |                |                |   (Acquire MN-Id and Profile)
                               ....
                                    Registration steps as in fig 2.
                               ....
       |                |                |==Bi-Dir Tunnel=|
       |--- Rtr Sol ------------------------------------->|
       |                |                |                |
       |<------------------------------------ Rtr Adv ----|
       |                |                |                |
   MN retains HoA/HNP
       |                |                |                |

            Figure 3: Mobile Node Handoff - Signaling Call Flow

   Figure 3 shows the signaling call flow for the mobile node's handoff
   from previously attached mobile access gateway (p-MAG) to the newly
   attached mobile access gateway (n-MAG).  This call flow reflects only
   a specific message ordering, it is possible the registration message
   from the n-MAG may arrive before the de-registration message from the
   p-MAG arrives.

   After obtaining the initial address configuration in the Proxy Mobile
   IPv6 domain, if the mobile node changes its point of attachment, the
   mobile access gateway on the previous link will detect the mobile
   node's detachment from the link and will signal the local mobility
   anchor and will remove the binding and routing state for that mobile
   node.  However, the local mobility anchor upon accepting the request
   will wait for certain amount of time before it deletes the binding,
   for allowing a smooth handoff.

   The mobile access gateway on the new access link upon detecting the
   mobile node on its access link will signal the local mobility anchor
   for updating the binding state.  Once that signaling is complete, the
   mobile node will continue to receive the Router Advertisements
   containing its home network prefix, making it believe it is still on
   the same link and it will use the same address configuration on the
   new access link.

4.  Proxy Mobile IPv6 Protocol Security

   The signaling messages, Proxy Binding Update and Proxy Binding
   Acknowledgement, exchanged between the mobile access gateway and the
   local mobility anchor MUST be protected using end-to-end security
   association(s) offering integrity and data origin authentication.

   The mobile access gateway and the local mobility anchor MUST
   implement IPsec for protecting the Proxy Mobile IPv6 signaling
   messages [RFC-4301].  That is, IPsec is the default mandatory to implement
   security mechanism for
   securing the signaling messages.  However in certain deployments of
   this protocol, other security mechanisms MAY be applied and the
   signaling messages must be protected using the semantics provided by
   that respective mechanism.  The specification of the other security
   mechanisms are beyond the scope of this document  However, additional documents may specify
   alternative mechanisms.

   IPsec ESP [RFC-4303] in transport mode with mandatory integrity
   protection SHOULD be used for protecting the signaling messages.
   Confidentiality protection of these messages is not required.

   IKEv2 [RFC-4306] SHOULD be used to setup security associations
   between the mobile access gateway and the local mobility anchor to
   protect the Proxy Binding Update and Proxy Binding Acknowledgement
   messages.  The mobile access gateway and the local mobility anchor
   can use any of the authentication mechanisms, as specified in IKEv2,
   for mutual authentication.

   The Mobile IPv6 specification [RFC-3775] requires the home agent to
   prevent a mobile node from creating security associations or creating
   binding cache entries for another mobile node's home address.  In the
   protocol described in this document, the mobile node is not involved
   in creating security associations for protecting the signaling
   messages or sending binding updates.  Therefore, the local mobility
   anchor MUST allow only restrict the creation and manipulation of proxy bindings
   to specifically authorized mobile access gateways to create
   binding cache entries on behalf of the mobile nodes. and prefixes.  The actual
   mechanism by which the
   local mobility anchor verifies if a specific
   mobile access gateway is authorized MUST be locally configurable to send Proxy Binding Updates on
   behalf of authorize such
   specific combinations.  Additional mechanisms such as a mobile node is policy store
   or AAA may be employed, but these are outside the scope of this document.  One
   possible way this could be achieved is by sending a query to the
   policy store, such as AAA.
   specification.

4.1.  Peer Authorization Database Entries

   This section describes PAD entries [RFC-4301] on the mobile access
   gateway and the local mobility anchor.  The PAD entries are only
   example configurations.  Note that the PAD is a logical concept and a
   particular mobile access gateway or a local mobility anchor
   implementation can implement the PAD in any implementation specific
   manner.  The PAD state may also be distributed across various
   databases in a specific implementation.

       mobile access gateway PAD:
         - IF remote_identity = lma_identity_1
              Then authenticate (shared secret/certificate/EAP)
              and authorize CHILD_SA for remote address lma_addres_1

       local mobility anchor PAD:
         - IF remote_identity = mag_identity_1
              Then authenticate (shared secret/certificate/EAP)
              and authorize CHILD_SAs for remote address mag_address_1

                           Figure 4: PAD Entries

   The list of authentication mechanisms in the above examples is not
   exhaustive.  There could be other credentials used for authentication
   stored in the PAD.

4.2.  Security Policy Database Entries

   This section describes the security policy entries [RFC-4301] on the
   mobile access gateway and the local mobility anchor required to
   protect the Proxy Mobile IPv6 signaling messages.  The SPD entries
   are only example configurations.  A particular mobile access gateway
   or a local mobility anchor implementation could configure different
   SPD entries as long as they provide the required security.

   In the examples shown below, the identity of the mobile access
   gateway is assumed to be mag_1, the address of the mobile access
   gateway is assumed to be mag_address_1, and the address of the local
   mobility anchor is assumed to be lma_address_1.

      mobile access gateway SPD-S:
        - IF local_address = mag_address_1 &
             remote_address = lma_address_1 &
             proto = MH & local_mh_type = BU & remote_mh_type = BA
          Then use SA ESP transport mode
          Initiate using IDi = mag_1 to address lma_address_1

      local mobility anchor SPD-S:
        - IF local_address = lma_address_1 &
             remote_address = mag_address_1 &
             proto = MH & local_mh_type = BA & remote_mh_type = BU
          Then use SA ESP transport mode

                           Figure 5: SPD Entries

5.  Local Mobility Anchor Operation

   The local mobility anchor MUST support the home agent function as
   defined in [RFC-3775] and additionally the extensions defined in this
   specification.  A home agent with these modifications and enhanced
   capabilities for supporting Proxy Mobile IPv6 protocol is referred to
   as the local mobility anchor.

   This section describes the operational details of the local mobility
   anchor.

5.1.  Extensions to Binding Cache Entry Data Structure

   Every local mobility anchor MUST maintain a Binding Cache entry for
   each currently registered mobile node.  Binding Cache entry is a
   conceptual data structure, described in Section 9.1 [RFC-3775].

   For supporting this specification, the Binding Cache Entry data
   structure needs to be extended with the following additional fields.

   o  A flag indicating whether or not this Binding Cache entry is
      created due to a proxy registration.  This flag is enabled for
      Binding Cache entries that are proxy registrations and is turned
      off for all other entries that are created due to the
      registrations directly sent by the mobile node. entries.

   o  The identifier of the registered mobile node, MN-Identifier.  This
      identifier is obtained from the Mobile Node Identifier Option
      [RFC-4283] present in the received Proxy Binding Update request.

   o  The interface identifier of the mobile node's connected interface
      on the access link.  This identifier can be acquired from the
      Mobile Node Interface Identifier option, present in the received
      Proxy Binding Update request.  If the option was not present in
      the request, this the value MUST be set to ALL_ZERO.

   o  The Link-local address of the mobile node on the interface
      attached to the access link.  This is obtained from the Link-local
      Address option, present in the Proxy Binding Update request.  If
      the option was not present in the request, the value MUST be set
      to ALL_ZERO.

   o  The IPv6 home network prefix of that is assigned to the registered mobile node. node's
      connected interface.  The home network prefix of the mobile node
      may have been statically configured in the mobile node's policy
      profile, or, it may have been dynamically allocated by the local
      mobility anchor.  The IPv6 home network prefix also includes the
      corresponding prefix length.

   o  The interface identifier (If-Id) of the bi-directional tunnel established
      between the local mobility anchor and the mobile access gateway
      where the mobile node is currently anchored.  This is internal to
      the local mobility anchor.  The tunnel interface identifier is
      acquired during the tunnel creation.

   o  The access technology through type, using which the mobile node is
      currently
      connected. attached.  This is obtained from the Access Technology
      Type option, present in the Proxy Binding Update message. request.

   o  The 64-bit timestamp value of the most recently accepted Proxy
      Binding Update request sent for this mobile node.  This is
      obtained from the
      time-of-day on the local mobility anchor, when the message was
      received.  If the Timestamp option, option is not present in the request. Proxy
      Binding Update request (i.e., when sequence number based scheme is
      in use), the value MUST be set to ALL_ZERO.

   Typically, the MN-Identifier mobile node's home network prefix is the key for
   locating a Binding Cache
   entry.  However, when supporting multihoming there MAY be more than
   one Binding Cache entry with the same MN-Identifier and in such all cases except when there has
   been an handoff of the entry mobile node's session to a new mobile access
   gateway and that mobile access gateway is unaware of the home network
   prefix that was assigned to the handed of session.  In such handoff
   cases, the Binding Cache entry can be located using any of under the following key combinations:

   o  MN-Identifier, MN-HNP

   o  MN-Identifier, Proxy-CoA

   o  MN-Identifier, MN-Interface-Identifier

   o  MN-Identifier, Access Technology Type (When MN-Interface-
      Identifier is not present)
   considerations specified in Section 5.4.1.

5.2.  Supported Home Network Prefix Models

   This specification supports Per-MN-Prefix model and does not support
   Shared-Prefix model.  As per the Per-MN-Prefix model, there will be a
   unique home network prefix assigned to each mobile node and no other
   node shares an address from that prefix.  The assigned prefix is
   unique to a mobile node and also unique to a given interface of the
   mobile node.  If the mobile node attaches to the Proxy Mobile IPv6
   domain through multiple interfaces and simultaneously, each of those
   connected interfaces will be assigned a different prefix.

   The mobile node's home network prefix is always hosted on the access
   link where the mobile node is anchored.  Conceptually, the entire
   home network prefix follows the mobile node as it moves within the
   Proxy Mobile IPv6 domain.  The local mobility anchor is not required
   to perform any proxy ND operations [RFC-4861] for defending the
   mobile node's home address on the home link.  However, from the
   routing perspective, the home network prefix is topologically
   anchored on the local mobility anchor.

5.3.  Signaling Considerations

   This section provides the rules for processing the signaling
   messages.  The processing rules specified in this section and other
   related sections are chained and are in a specific order.  When
   applying these considerations for processing the signaling messages,
   the specified order MUST be maintained.

5.3.1.  Processing Binding Registrations

   Upon receiving a

   1.   The received Proxy Binding Update request message (a Binding Update
   Request
        message with the 'P' flag set) from a mobile access gateway on behalf
   of a mobile node, the local mobility anchor MUST process the request be authenticated as defined
        described in Section 10.3 [RFC-3775]; additionally 4.0.  When IPsec is used for message
        authentication, the following
   considerations must be applied.

   1. SPI in the IPsec header [RFC-4306] of the
        received packet is needed for locating the security association,
        for authenticating the Proxy Binding Update message.

   2.   The local mobility anchor MUST observe the rules described in
        Section 9.2 [RFC-3775] when processing Mobility Headers Header in the
        received Proxy Binding Update request.

   2.  Additionally, the rules
        specified in Section 10.3 [RFC-3775] MUST be applied when
        processing this message.

   3.   The local mobility anchor MUST ignore the check, specified in
        Section 10.3.1 [RFC-3775], related to the presence of Home
        Address destination option in the Proxy Binding Update request.

   4.   The local mobility anchor MUST identify the mobile node from the
        identifier present in the Mobile Node Identifier option [RFC-
        4283] of the Proxy Binding Update request.  If the Mobile Node
        Identifier option is not present in the Proxy Binding Update
        request, the local mobility anchor MUST reject the request and
        send a Proxy Binding Acknowledgement message with Status field
        set to MISSING_MN_IDENTIFIER_OPTION (Missing mobile node
        identifier)
        identifier option) and the identifier in the Mobile Node
        Identifier Option carried in the message MUST be set to a zero
        length identifier.

   3.   If the

   5.   The local mobility anchor cannot authorize the mobile node
        based on MUST apply the Mobile Node Identifier option [RFC-4283] present required policy checks,
        as explained in Section 4.0, to verify the request, it MUST reject the Proxy Binding Update request and
        send sender is a trusted
        mobile access gateway, authorized to send Proxy Binding Acknowledgement message with Status field
        set to 133 (Not home agent for Update
        requests on behalf of this mobile node).

   4. node.

   6.   If the local mobility anchor determines that the mobile requesting node
        is not authorized to send Proxy Binding Update requests for the network-based mobility management
        service,
        identified mobile node, it MUST reject the request and send a
        Proxy Binding Acknowledgement message with Status field set to
        PROXY_REG_NOT_ENABLED (Proxy Registration not enabled).

   5.   The local mobility anchor MUST ignore the check, specified in
        Section 10.3.1 [RFC-3775], related
        MAG_NOT_AUTHORIZED_FOR_PROXY_REG (not authorized to send proxy
        binding registrations).

   7.   If the presence of Home
        Address destination option in the Proxy Binding Update request.

   6.   The local mobility anchor MUST authenticate cannot identify the Proxy Binding
        Update request as described in Section 4.0.  When IPsec is used
        for message authentication, mobile node
        based on the SPI identifier present in the IPsec header [RFC-
        4306] Mobile Node Identifier
        option [RFC-4283] of the received packet is needed for locating the security
        association, for authenticating the Proxy Binding Update
        request.

   7.   The local mobility anchor request, it MUST apply the required policy checks,
        as explained in Section 4.0, to verify
        reject the sender is a trusted
        mobile access gateway, authorized to request and send a Proxy Binding Update
        requests on behalf of Acknowledgement
        message with Status field set to 133 (Not local mobility anchor
        for this mobile node. node).

   8.   If the local mobility anchor determines that the requesting mobile node is
        not authorized to send Proxy Binding Update requests, for the network-based mobility management
        service, it MUST reject the request and send a Proxy Binding
        Acknowledgement message with Status field set to
        MAG_NOT_AUTHORIZED_FOR_PROXY_REG (Not authorized to send proxy
        registrations).
        PROXY_REG_NOT_ENABLED (Proxy Registration not enabled).

   9.   The local mobility anchor MUST apply the considerations
        specified in Section 5.5, for processing the Sequence Number
        field and the Timestamp option (if present), in the Proxy
        Binding Update request.

   10.  If the Home Network Prefix option (containing either ALL_ZERO or
        some prefix value) is not present in the Proxy Binding Update
        request, the local mobility anchor MUST reject the request and
        send a Proxy Binding Acknowledgement message with Status field
        set to MISSING_HOME_NETWORK_PREFIX_OPTION (Missing mobile node's home network
        prefix option).

   10.

   11.  If the Access Technology Type Handoff Indicator option is not present in the Proxy
        Binding Update request, the local mobility anchor MUST reject
        the request and send a Proxy Binding Acknowledgement message
        with Status field set to MISSING_ACCESS_TECH_TYPE_OPTION MISSING_HANDOFF_INDICATOR_OPTION
        (Missing mobile node's access technology type).

   11.  The local mobility anchor MUST apply the considerations
        specified in Section 5.5, for processing handoff indicator option).

   12.  If the Sequence Number
        field and the Timestamp option, Access Technology Type option is not present in the Proxy
        Binding Update
        request.

   12.  The request, the local mobility anchor MUST use the identifier from the
        Mobile Node Identifier Option [RFC-4283] present in reject
        the Proxy
        Binding Update request and MUST apply multihoming considerations send a Proxy Binding Acknowledgement message
        with Status field set to MISSING_ACCESS_TECH_TYPE_OPTION
        (Missing access technology type option).

   13.  Considerations specified in Section 5.4 5.4.1 MUST be applied for
        performing the Binding Cache entry existence test or for identifying the mobility session. test.  If those
        checks specified in Section 5.4.1, result in associating the
        entry does not exist, the local
        received Proxy Binding Update request to a new mobility anchor session
        creation request, considerations from Section 5.3.2 (Initial
        Binding Registration - New Mobility Session), MUST consider
        this request as an initial binding registration request. be applied.
        If those checks result in associating the
        entry exists, the local mobility anchor MUST consider this request as a binding re-registration request.  However, from to an existing
        mobility session, the
        perspective of following checks determine the mobile access gateway next set of
        processing rules that sent needs to be applied.

        *  If the Handoff Indicator field in the Handoff Indicator
           option present in the request,
        this binding re-registration request may is set to a value of 5 (Handoff
           state not changed), considerations from Section 5.3.3
           (Binding Lifetime Extension- No handoff) MUST be an initial applied.

        *  If the received Proxy Binding Update request after has the mobile node's attachment to that mobile
        access gateway. lifetime
           value of zero, considerations from Section 5.3.5 (Binding De-
           Registration) MUST be applied.

        *  For all other cases, considerations from Section 5.3.4
           (Binding Lifetime Extension - After handoff) MUST be applied.

   14.  When sending the Proxy Binding Acknowledgement message with any
        Status field value, the message MUST be constructed as specified
        in Section 5.3.6.

5.3.2.  Initial Binding Registration: Registration (New Mobility Session)

   1.  If the Home Network Prefix option present in the Proxy Binding
       Update request has the value 0::/0, set to ALL_ZERO, the local mobility
       anchor
       SHOULD MUST allocate a prefix and assign it to a new mobility
       session created for the mobile node and send a Proxy
       Binding Acknowledgement message including the Home Network Prefix
       option containing the allocated prefix value. node.  The local mobility anchor
       MUST ensure the allocated prefix is not in use by any other node. node
       or mobility session.

   2.  If the local mobility anchor is unable to allocate a any home
       network prefix for the mobile node, it MUST reject the request
       and send a Proxy Binding Acknowledgement message with Status
       field set to 130 (Insufficient resources).

   3.  If the Home Network Prefix option present in the request has a
       specific prefix hint, the local mobility anchor before accepting
       that request, MUST ensure the prefix is owned by the local
       mobility anchor and further the mobile node is authorized to use
       that prefix.  If the mobile node is not authorized to use that
       prefix, the local mobility anchor MUST reject the request and
       send a Proxy Binding Acknowledgement message with Status field
       set to NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX (Mobile node not
       authorized to use that prefix).

   4.  Upon accepting the request, the local mobility anchor MUST create
       a Binding Cache entry for the mobile node.  It must set the
       fields in the Binding Cache entry to the accepted values for that
       binding.  If there is a Link-local Address option present in the
       request, the address must be copied to the link-local address
       field in the Binding Cache entry.
       registration.

   5.  Upon accepting the Proxy Binding Update request, the  The local mobility anchor MUST establish a bi-directional tunnel
       to the mobile access gateway, as described in [RFC-2473]. gateway (if there does not exist one) that
       sent the request and setup the routing state.  Considerations
       from Section 5.6 must MUST be applied.

   Binding Re-Registration:

   1.  If the requesting prefix in the Home Network Prefix option is a
       non 0::/0 value and is different from what is present in the
       currently active Binding Cache entry applied for that mobile node, creating the routing state.

   6.  The local mobility anchor MUST reject the request and send a the Proxy Binding
       Acknowledgement message with the Status field set to 129
       (Administratively Prohibited).

   2.  If there is a Link-local Address option present in the request
       with a value other than ALL_ZERO (not set), and upon accepting
       the binding re-registration request, the local mobility anchor 0 (Proxy
       Binding Update Accepted).  The message MUST update the link-local address field be constructed as
       specified in the Section 5.3.6.

5.3.3.  Binding Cache
       entry to the address value received in the request.

   3. Lifetime Extension (No handoff)

   1.  Upon accepting a the Proxy Binding Update request for extending the
       lifetime of a currently active
       binding for a lifetime, received from the same mobile node, access gateway
       that last updated the binding (i.e., when there is no handoff),
       the local mobility anchor MUST update the existing Binding Cache entry for this mobile node.  Unless there exists an established
       bi-directional tunnel to the mobile access gateway
       with the same
       transport and encapsulation mode, accepted registration values.  However, if the link-
       local mobility anchor MUST
       create a tunnel to address value in the mobile access gateway, as described in
       [RFC-2473] and also delete Link-local address option is ALL_ZERO
       value, the existing tunnel route to link-local address field in the
       previous mobile access gateway.  It Binding Cache entry
       MUST NOT be updated.

   2.  The local mobility anchor MUST also send a the Proxy Binding
       Acknowledgement message to the mobile access gateway with the Status field set to 0 (Proxy
       Binding Update Accepted).  The message MUST be constructed as
       specified in Section 5.3.6.

5.3.4.  Binding De-Registration: Lifetime Extension (After handoff)

   1.  If  Upon accepting the received Proxy Binding Update request for extending the
       binding lifetime, received from a new mobile access gateway where
       the mobile node's session is handed off, the local mobility
       anchor MUST update the Binding Cache entry with the lifetime
       value of zero and accepted
       registration values.  However, if the prefix link-local address value in
       the Home Network Prefix Link-local address option is
       a non 0::/0 value and is different from what is present ALL_ZERO value, the link-local
       address field in the
       currently active Binding Cache entry MUST NOT be updated.

   2.  The local mobility anchor MUST remove the previously created
       route for that the mobile node, node's home network prefix.  Additionally,
       if there are no other mobile node's sessions sharing the tunnel
       to the previous mobile access gateway, the tunnel MUST be
       deleted.

   3.  The local mobility anchor MUST reject establish a bi-directional tunnel
       to the request and mobile access gateway that sent the request.
       Considerations from Section 5.6 MUST be applied for creating the
       routing state.

   4.  The local mobility anchor MUST send a the Proxy Binding
       Acknowledgement message with the Status field set to 129
       (Administratively Prohibited).

   2. 0 (Proxy
       Binding Update Accepted).  The message MUST be constructed as
       specified in Section 5.3.6.

5.3.5.  Binding De-Registration

   1.  If the received Proxy Binding Update request with the lifetime
       value of zero, has a Source Address in the IPv6 header (or the
       address in the Alternate Care-of Address option, if the option is
       present) different from what is present in the Proxy-CoA address
       field in the Binding Cache entry existing for that mobile node, entry, the local mobility anchor SHOULD MUST
       ignore the request.

   3.

   2.  Upon accepting the Proxy Binding Update request for a mobile
       node, with the lifetime
       value of zero, the local mobility anchor MUST wait for
       MinDelayBeforeBCEDelete amount of time, before it deletes the mobile node's
       Binding Cache entry.  Within this wait
       period, if  However, it MUST send the local mobility anchor Proxy Binding
       Acknowledgement message with the Status field set to 0 (Proxy
       Binding Update Accepted).  The message MUST be constructed as
       specified in Section 5.3.6.

       *  During this wait period, the local mobility anchor SHOULD drop
          the mobile node's data traffic.

       *  During this wait period, if the local mobility anchor receives
          a valid Proxy Binding Update request message for the same mobile node mobility
          session with the lifetime value of greater than zero, and if
          that request is accepted, then the Binding Cache entry MUST
          NOT be deleted, but must be updated with the newly accepted
          registration values.  The local mobility
       anchor MUST send values and additionally the Proxy Binding Acknowledgement message,
       immediately upon accepting wait period should be
          ended.

       *  By the request.  However, within end of this wait period, if the local mobility anchor does
          did not receive any valid binding registration Proxy Binding Update request for that mobile node, then at
       the end of
          this wait period, mobility session, then it MUST delete the mobile node's Binding Cache
          entry and remove the routing state created for that
       mobile node.  In addition, during this MinDelayBeforeBCEDelete
       wait period, the local mobility anchor MUST continue to route the
       mobile node's data traffic.
          session.

5.3.6.  Constructing the Proxy Binding Acknowledgement Message: Message

   o  The local mobility anchor when sending the Proxy Binding
      Acknowledgement message to the mobile access gateway MUST
      construct the message as specified below.

          IPv6 header (src=LMAA, dst=Proxy-CoA)
            Mobility header
                        -BA /*P
               - BA    /* P flag is set*/ must be set */
              Mobility Options
               - Home Network Prefix Option
                          - Link-local Address Option (optional)
                          - Timestamp Option (optional)
                          - Mobile Node Identifier Option (Mandatory)           (mandatory)
               - Home Network Prefix option              (mandatory)
               - Handoff Indicator option                (mandatory)
               - Access Technology Type option (Mandatory)           (mandatory)
               - Timestamp Option                        (optional)
               - Mobile Node Interface Identifier option
                            (Optional) (optional)
               - Link-local Address option               (optional)

            Figure 6: Proxy Binding Acknowledgement message format

   o  The Source Address field in the IPv6 header of the message MUST be
      set to the destination address of the received Proxy Binding
      Update request.

   o  The Destination Address field in the IPv6 header of the message
      MUST be set to the source address of the received Proxy Binding
      Update request.

   o  The Home Network Prefix  When there is no Alternate Care-of Address option MUST be
      present in the Proxy
      Binding Acknowledgement message.  If request, the option was not present in destination address is the request and if same as the Status field value is set to
      MISSING_HOME_NETWORK_PREFIX_OPTION,
      Proxy-CoA address, otherwise, the value MUST address may not be set to
      ALL_ZERO. the same as
      the Proxy-CoA.

   o  The Access Technology Type Mobile Node Identifier option [RFC-4283] MUST be present.  The access
      technology type value
      identifier field in the option MUST be copied from the Access
      Technology Type Mobile Node
      Identifier option in the received Proxy Binding Update request.
      If the option was not present in the request and if request, the
      Status field value is set to MISSING_ACCESS_TECH_TYPE_OPTION, identifier in
      the
      value option MUST be set to 0. a zero length identifier.

   o  The Mobile Node Interface Identifier Home Network Prefix option MAY MUST be present, if the
      same option was present in the corresponding Proxy Binding Update
      request message.

   o present.

      *  If the Status field is set to a value greater than or equal to
         128, i.e., if the binding request was is rejected, then the prefix
         value in the Home Network Prefix option MUST be set to the
         prefix value from in the received Home Network Prefix option. option of the received
         Proxy Binding Update request.  But, if the option was not
         present in the request, the value in the option MUST be set to
         ALL_ZERO.

      *  For all other cases, the prefix value in the option MUST be set
         to the allocated prefix value for that mobile node. mobility session.

   o  The Link-local Address Handoff Indicator option MUST be present present.  The handoff
      indicator field in the Proxy Binding
      Acknowledgement message if and only if option MUST be copied from the same Handoff
      Indicator option was present in the corresponding received Proxy Binding Update request message.

   o request.  If
      the Status field is set to a value greater than or equal to
      128, i.e., if the binding request option was rejected, then not present in the request, the link-
      local address value in the Link-local Address option
      MUST be set to zero.

   o  The Access Technology Type option MUST be present.  The access
      technology type field in the value option MUST be copied from the Access
      Technology Type option in the received Link-local Address option.

   o  If there is an existing Proxy Binding Cache entry for Update
      request.  If the mobile node
      with option was not present in the request, the link-local address value of ALL_ZERO (value not set), or
      if there was no existing Binding Cache entry, then
      in the link-local
      address option MUST be copied from set to zero.

   o  The Timestamp option MUST be present, if the Link-local Address same option was
      present in the received Proxy Binding Update request.  For all other cases, it
      MUST be copied from the mobile node's Binding Cache entry.

   o
      Considerations from Section 5.5 must be applied for constructing
      the Timestamp option.

   o  The identifier in the Mobile Node Interface Identifier option [RFC-4283] MUST be copied from present, if
      the same option was present in the received Proxy Binding Update
      request.  If
      the Status field value is set to MISSING_MN_IDENTIFIER_OPTION, the  The interface identifier in value MUST be copied from the
      Mobile Node Identifier Option Interface Indicator option present in the received
      Proxy Binding Update request.

   o  The Link-local Address option MUST be set present, if the same option
      was present in the received Proxy Binding Update request.

      *  If the received Proxy Binding Update request has the Link-local
         Address option with any value other than ALL_ZERO, the same
         value MUST be copied to the Link-local Address option in the
         reply.

      *  If there is no existing Binding Cache entry (i.e., if this is a
      zero length identifier.
         request for a new mobility session), or if there is an existing
         Binding Cache entry with the link-local address value set to
         ALL_ZERO, then the link-local address in the option MUST be
         copied from the Link-local Address option present in the
         received Proxy Binding Update request.

      *  For all other cases, the link-local address in the option MUST
         be copied from the Link-local Address field of the Binding
         Cache entry.

   o  If IPsec is used for protecting the signaling messages, the
      message MUST be protected, using the security association existing
      between the local mobility anchor and the mobile access gateway.

   o  The  Unlike in Mobile IPv6 [RFC-3775], the Type 2 Routing header MUST
      NOT be present in the IPv6 header of the packet.

5.4.  Multihoming Support

   This specification allows mobile nodes to connect to a Proxy Mobile
   IPv6 domain through multiple interfaces and for simultaneous access.
   Following are the key aspects of this multihoming support.

   o  When a mobile node connects to a Proxy Mobile IPv6 domain through
      multiple interfaces simultaneously, and for simultaneous access, the local
      mobility anchor MUST allocate a unique home network prefix for
      each of the connected interfaces.

   o  The local mobility anchor MUST manage each of the allocated home
      network prefixes as part of a separate mobility session, each
      under a separate Binding Cache entry and with its own lifetime.

   o  The local mobility anchor MUST allow for a handover an handoff between two
      different interfaces of the mobile node.  In such a case, the home
      network prefix that is associated with a specific interface
      identifier of a mobile node will be updated with the new interface
      identifier.  The decision on when to create a new mobility session
      and when to update an existing mobility session MUST be based on
      the Handover hint present in the signaling messages and under the
      considerations specified in this section.

   The local mobility anchor MUST apply the following multihoming

5.4.1.  Binding Cache entry lookup considerations when

   There can be multiple Binding Cache entries for a given mobile node.
   When doing a lookup for a mobile node's Binding Cache entry for
   processing a received Proxy Binding Update request message.

   Processing De-Registration Message:

   1.  If the received Proxy Binding Update message has lifetime value
       of zero, message, the local
   mobility anchor MUST verify if there is an
       existing Binding Cache entry for apply the mobile node, identified by following multihoming considerations
   (in the MN-Identifier and specified order).  These rules are chained with the Proxy-CoA address matching the
       source address
   processing rules specified in the IPv6 header of the received packet.  If
       there exists a Binding Cache entry, the local mobility anchor
       MUST consider the message as a request for de-registering that
       specific mobility session.  If there does not exist a Binding
       Cache entry, the message MUST be ignored. Section 5.3.

5.4.1.1.  Home Network Prefix Option (Non-Zero Prefix) (NON_ZERO Value) present in the request:
          request

 +=====================================================================+
 |                      Registration/De-Registration Message           |
 +=====================================================================+
 |                          HNP (NON_ZERO Value)                       |
 +=====================================================================+
 |                                 ATT                                 |
 +=====================================================================+
 |       IID Option Present         |      IID Option Not present      |
 +=====================================================================+
 |                                 HI                                  |
 +==================================+==================================+
 |                   BCE Lookup Key: (Home Network Prefix)             |
 +=====================================================================+

              Figure 7: BCE lookup using home network prefix

   1.  The local mobility anchor MUST verify if there is an existing
       Binding Cache entry for the mobile node, identified by the MN-
       Identifier and with the home network prefix value matching
       the prefix value in the Home Network Prefix Option option of the
       received Proxy Binding Update request.  [BCE(HNP) == PBU(HNP)]

   2.  If there is a Mobile Node Interface Identifier Option present in
       the request, it MUST be ignored for this search.  If there exists does not exist a Binding Cache entry matching (matching the specified criteria, MN-
       HNP), the local
       mobility anchor request MUST consider the message be considered as a request for
       updating that specific creating a
       new mobility session.  The local mobility
       anchor upon accepting the request MUST update the existing

   3.  If there exists a Binding Cache entry (matching MN-HNP), and assign if
       the home network prefix present mobile node identifier in the Binding Cache entry.  If there entry does not exist a Binding Cache
       entry matching this specified criteria, match the mobile
       node identifier in the below considerations
       MUST be applied. Mobile Node Interface Identifier Option not present in option of the
       received Proxy Binding Update request, the request:

   1.  The local mobility anchor
       MUST verify if there is an existing
       Binding Cache entry for the mobile node, identified by reject the MN-
       Identifier and request with the interface identifier Status field value set to
       ALL_ZERO.

   2.  If there does not exist
       NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX (mobile node is not
       authorized for the requesting home network prefix).  [BCE(MN-
       Identifier) != PBU(MN-Identifier)]
   4.  If there exists a Binding Cache entry, the local mobility
       anchor upon accepting entry (matching MN-Identifier and
       MN-HNP) and if any one or more of these below stated conditions
       match, the request MUST assign a new home network
       prefix and create be considered as a new request for updating
       that Binding Cache entry.

   3.  [BCE(MN-Identifier) == PBU(MN-
       Identifier)]

       *  If there exists is a Mobile Node Interface Identifier option present
          in the request, and if the interface identifier value in that
          option matches the interface identifier value in the Binding
          Cache entry and if the Handoff
       Indicator access technology type field in the Access
          Technology Type option present in the received Proxy Binding Update message is set to value 1
       (Attachment over a new interface), request matches the local mobility anchor upon
       accepting
          access technology type in the request MUST assign a new home network prefix and
       create a new Binding Cache entry.

   4.  If there exists a Binding Cache entry and if .  [BCE(ATT,
          MN-Interface-Identifier) == PBU(ATT, MN-Interface-Identifier)]

       *  If the Handoff Indicator field in the Access Technology Type Handoff Indicator option
          present in the received Proxy Binding Update message request is set to either a value of 2 (Handoff between interfaces) or 3 (Handoff between mobile
       access gateways for
          two different interfaces of the same mobile node's interface), node).

       *  If there is no Mobile Node Interface Identifier option present
          in the local
       mobility anchor upon accepting request, the request MUST update interface identifier value in the
       existing Binding
          Cache entry and assign is set to ALL_ZERO, the home network prefix access technology type
          field in the Access Technology Type option present in the Binding Cache entry.

   5.  If there exists a
          request matches the access technology type in the Binding
          Cache entry and if the Handoff Indicator field in the Access Technology Type Handoff
          Indicator option present in the received Proxy Binding Update message request is set to a value 4 of 3
          (Handoff state unknown), between mobile access gateways for the local mobility anchor SHOULD wait
       till same
          interface).

       *  If the existing Binding Cache entry is de-registered by the
       previously serving mobile access gateway, before it assigns the
       same home network prefix or updates Proxy-CoA address in the existing Binding Cache
       entry.  However, if there is no de-registration message that is
       received within MinDelayBeforeNewBCEAssign amount of time, entry matches
          the
       local mobility anchor upon accepting source address of the request MUST assign a
       new home network prefix and create a new Binding Cache entry.
       The local mobility anchor MAY also choose to assign a new home
       network prefix and without waiting for a de-registration message.
       It can use (or the access technology type value present address in the
       request and as inputs for this decision.

   6.  Either upon creating a new Binding Cache entry or from matching
       an existing Binding Cache entry, after applying
          alternate Care-of Address option, if the above
       considerations, option is present)
          and if the access technology type field in the Binding Cache
       entry MUST be copied from the Access
          Technology type Type option present in the received Proxy Binding Update message.  The
       interface identifier field request matches the
          access technology type in the Binding Cache entry entry.
          [BCE(Proxy-CoA, ATT) == PBU(Proxy-CoA, ATT)].

   5.  For all other cases, the message MUST be set
       to ALL_ZERO. considered as a request
       for creating a new mobility session.

5.4.1.2.  Mobile Node Interface Identifier Option present in the request: request

 +=====================================================================+
 |                      Registration/De-Registration Message           |
 +=====================================================================+
 |                          HNP (ALL_ZERO Value)                       |
 +=====================================================================+
 |                                 ATT                                 |
 +=====================================================================+
 |                      IID Option Present (NON_ZERO Value)            |
 +=====================================================================+
 |                                 HI                                  |
 +==================================+==================================+
 | BCE Lookup Keys: (MN-Identifier +  Access Technology Type +         |
 |                   MN-Interface-Identifier)                          |
 +=====================================================================+

              Figure 8: BCE Lookup using Interface Identifier

   1.  The local mobility anchor MUST verify if there is an existing
       Binding Cache entry for entry, with the mobile node, identified by node identifier matching the MN-
       identifier in the received Mobile Node Identifier option, access
       technology type matching the value in the received Access
       Technology Type option and with the interface identifier value
       matching the identifier value present in the received Mobile Node Interface
       Identifier Option. option.  [BCE(MN-Identifier, ATT, MN-Interface-
       Identifier) == PBU(MN-Identifier, ATT, MN-Interface-Identifier)]

   2.  If there exists a Binding Cache entry, the local mobility anchor
       upon accepting entry (matching MN-Identifier,
       ATT and MN-Interface-Identifier), the request MUST update the existing Binding Cache
       entry and assign the home network prefix present in the be considered
       as a request for updating that Binding Cache entry.

   3.  If there does not exist a Binding Cache entry (matching MN-
       Identifier, ATT and MN-Interface-Identifier) and if the Handoff
       Indicator field in the Access Technology Type option present in
       the received Proxy Binding Update message is set to value 1
       (Attachment over a new interface), the local mobility anchor upon
       accepting the request MUST assign a new home network prefix and
       create a new Binding Cache entry.

   4.  If there does not exist a Binding Cache entry and if the Handoff Indicator field in the Access Technology Type option present in the received Proxy Binding Update message
       request is set to a value of 2 (Handoff between interfaces), two different
       interfaces of the mobile node).  The local mobility anchor MUST
       apply the following additional considerations.  [PBU(HI) == 2]

       *  The local mobility anchor MUST verify if there exists one and
          only one Binding Cache entry for with the mobile node, identified by node identifier
          matching the MN-Identifier identifier in the Mobile Node Identifier option
          present in the request and with for any interface identifier value.
          If there exists only one such an entry, entry (matching the
       local mobility anchor upon accepting MN-
          Identifier), the request MUST update the
       existing Binding Cache entry and assign the home network prefix
       present in the be considered as a request for
          updating that Binding Cache entry.

   5.  [BCE(MN-Identifier) ==
          PBU(MN-Identifier)]

   4.  If there does not exist a Binding Cache entry (matching MN-
       Identifier, ATT and MN-Interface-Identifier) and if the Handoff
       Indicator field in the Access Technology Type Handoff Indicator option present in the received Proxy Binding Update message
       request is set to a value 2 of 4 (Handoff between interfaces), state unknown), the local
       mobility anchor MUST apply the following additional
       considerations.

       *  The local mobility anchor MUST verify if there exists a one and
          only one Binding Cache entry for the mobile node,
       identified by the MN-Identifier and with the home network prefix
       value mobile node identifier
          matching the prefix value identifier in the received Home Network
       Prefix option. Mobile Node Identifier option
          present in the request and for any interface identifier value.
          If there exists a Binding Cache entry, only one such entry (matching the MN-
          Identifier), the local mobility anchor upon accepting the request MUST assign the same
       prefix, else it MUST assign a new home network prefix and create
       a new Binding Cache entry.

   6.  If there exists a Binding Cache entry and if the Handoff
       Indicator field in the Access Technology Type option present in
       the received Proxy Binding Update message is set to value 4
       (Handoff state unknown), the local mobility anchor SHOULD wait
       till SHOULD wait till the
          existing Binding Cache entry is de-registered by the
          previously serving mobile access gateway. gateway, before the request
          can be considered as a request for updating that Binding Cache
          entry.  However, if there is no de-registration message that
          is received within a given MaxDelayBeforeNewBCEAssign amount of time,
          the local mobility anchor upon accepting the request MUST assign
       a new home network prefix and create
          consider the request as a new request for updating that Binding
          Cache entry.  The local mobility anchor MAY also choose to assign
          create a new home
       network prefix mobility session and without waiting for a de-registration de-
          registration message.

   7.  Either upon

   5.  For all other cases, the message MUST be considered as a request
       for creating a new Binding Cache entry or from matching
       an existing Binding Cache entry, after applying the above
       considerations, the interface identifier field mobility session.

5.4.1.3.  Mobile Node Interface Identifier Option not present in the
          request
 +=====================================================================+
 |                      Registration/De-Registration Message           |
 +=====================================================================+
 |                          HNP (ALL_ZERO Value)                       |
 +=====================================================================+
 |                                 ATT                                 |
 +=====================================================================+
 |                      IID Option Not Present                         |
 +=====================================================================+
 |                                 HI                                  |
 +==================================+==================================+
 | BCE Lookup Key: (MN-Identifier)                                     |
 +=====================================================================+

             Figure 9: BCE Lookup using Mobile Node Identifier

   1.  The local mobility anchor MUST verify if there exists one and
       only one Binding Cache entry MUST be set to with the value present mobile node identifier
       matching the identifier in the received Mobile Node Interface Identifier Option and the access technology
       type MUST be copied from the Access Technology type option
       present in the received Proxy Binding Update message.

5.5.  Timestamp Option for Message Ordering

   Mobile IPv6 [RFC-3775] uses request.

   2.  If there exists only one such entry (matching the Sequence Number MN-Identifier)
       and the Handoff Indicator field in binding the Handoff Indicator option
       present in the request is set to a value of 2 (Handoff between
       two different interfaces of the mobile node), the request MUST be
       considered as a request for updating that Binding Cache entry.
       [PBU(HI) == 2]

   3.  If there exists only one such entry (matching the MN-Identifier)
       and the Handoff Indicator field in the Handoff Indicator option
       present in the request is set to a value of 4 (Handoff state
       unknown), the local mobility anchor SHOULD wait till the existing
       Binding Cache entry is de-registered by the previously serving
       mobile access gateway, before the request can be considered as a
       request for updating that Binding Cache entry.  However, if there
       is no de-registration message that is received within
       MaxDelayBeforeNewBCEAssign amount of time, the local mobility
       anchor upon accepting the request MUST consider the request as a
       request for updating that Binding Cache entry.  The local
       mobility anchor MAY also choose to create a new mobility session
       and without waiting for a de-registration message.

   4.  For all other cases, the message MUST be considered as a request
       for creating a new mobility session.

5.5.  Timestamp Option for Message Ordering

   Mobile IPv6 [RFC-3775] uses the Sequence Number field in binding
   registration messages as a way for the home agent to process the
   binding updates in the order they were sent by a mobile node.  The
   home agent and the mobile node are required to manage this counter
   over the lifetime of a binding.  However, in Proxy Mobile IPv6, as
   the mobile node moves from one mobile access gateway to another and
   in the absence of mechanisms such as context transfer between the
   mobile access gateways, the serving mobile access gateway will be
   unable to determine the sequence number that it needs to use in the
   signaling messages.  Hence, the sequence number scheme, as specified
   in [RFC-3775], will be insufficient for Proxy Mobile IPv6.

   If the local mobility anchor cannot determine the sending order of
   the received binding registration messages, it may potentially
   process an older message sent by a mobile access gateway where the
   mobile node was previously anchored, resulting in an incorrect
   Binding Cache entry.

   For solving this problem, this specification adopts two alternative
   solutions.  One is based on timestamps and the other based on
   sequence numbers, as defined in [RFC-3775].

   The basic principle behind the use of timestamps in binding
   registration messages is that the node generating the message inserts
   the current time-of-day, and the node receiving the message checks
   that this timestamp is greater than all previously accepted
   timestamps.  The timestamp based solution may be used, when the
   serving mobile access gateways in a Proxy Mobile IPv6 domain do not
   have the ability to obtain the last sequence number that was sent in
   a binding registration message for updating a given mobile node's
   binding.

   As an alternative to the Timestamp based approach, the specification
   also allows the use of Sequence Number based scheme, as per [RFC-
   3775].  However, for this scheme to work, the serving mobile access
   gateways in a Proxy Mobile IPv6 domain MUST have the ability to
   obtain the last sequence number that was sent in a binding
   registration message for updating a given mobile node's binding.  The
   sequence number MUST be maintained on a per mobile node basis and
   MUST be synchronized between the serving mobile access gateways.
   This may be achieved by using context transfer schemes or by
   maintaining the sequence number in a policy store.  However, the
   specific details on how the mobile node's sequence number is
   synchronized between different mobile access gateways is outside the
   scope of this document.

   Using Timestamps based approach:

   1.  A local mobility anchor implementation MUST support Timestamp
       option.  If the Timestamp option is present in the received Proxy
       Binding Update request message, then the local mobility anchor
       MUST include a valid Timestamp option in the Proxy Binding
       Acknowledgement message that it sends to the mobile access
       gateway.

   2.  All the mobility entities in a Proxy Mobile IPv6 domain that are
       exchanging binding registration messages using the Timestamp
       option must have adequately synchronized time-of-day clocks.
       This is the essential requirement for this solution to work.  If
       this requirement is not met, the solution will not predictably
       work in all cases.

   3.  The mobility entities in a Proxy Mobile IPv6 domain SHOULD
       synchronize their clocks to a common time source.  For
       synchronizing the clocks, the nodes may use Network Time Protocol
       [RFC-4330].  Deployments may also adopt other approaches suitable
       for that specific deployment.  Alternatively, if there is mobile
       node generated timestamp that is increasing at every attachment
       to the access link and if that timestamp is available to the
       mobile access gateway (Ex: The timestamp option in the SEND
       messages that the mobile node sends), the mobile access gateway
       can use this timestamp or sequence number in the Proxy Binding
       Update messages and does not have to depend on any external clock
       source.  However, the specific details on how this is achieved is
       outside the scope of this document.

   4.  When generating the timestamp value for building the Timestamp
       option, the mobility entities MUST ensure that the generated
       timestamp is the elapsed time past the same reference epoch, as
       specified in the format for the Timestamp option [Section 8.7]. 8.8].

   5.  If the Timestamp option is present in the received Proxy Binding
       Update message, the local mobility anchor MUST ignore the
       sequence number field in the message.  However, it MUST copy the
       sequence number from the received Proxy Binding Update message to
       the Proxy Binding Acknowledgement message.

   6.  Upon receipt of a Proxy Binding Update message with the Timestamp
       option, the local mobility anchor MUST check the timestamp field
       for validity.  In order for it to be considered valid, the
       timestamp value contained in the Timestamp option MUST be close
       enough (within TimestampValidityWindow amount of time difference)
       to the local mobility anchor's time-of-day clock and the
       timestamp MUST be greater than all previously accepted timestamps
       in the Proxy Binding Update messages sent for that mobile node.

   7.  If the timestamp value in the received Proxy Binding Update is
       valid (validity as specified in the above considerations), the
       local mobility anchor MUST return the same timestamp value in the
       Timestamp option included in the Proxy Binding Acknowledgement
       message that it sends to the mobile access gateway.

   8.  If the timestamp value in the received Proxy Binding Update is
       lower than the previously accepted timestamp in the Proxy Binding
       Update messages sent for that mobility binding, the local
       mobility anchor MUST reject the Proxy Binding Update request and
       send a Proxy Binding Acknowledgement message with Status field
       set to TIMESTAMP_LOWER_THAN_PREV_ACCEPTED (Timestamp lower than
       previously accepted timestamp).  The message MUST also include
       the Timestamp option with the value set to the current time-of-
       day on the local mobility anchor.

   9.  If the timestamp value in the received Proxy Binding Update is
       not valid (validity as specified in the above considerations),
       the local mobility anchor MUST reject the Proxy Binding Update
       and send a Proxy Binding Acknowledgement message with Status
       field set to TIMESTAMP_MISMATCH (Timestamp mismatch).  The
       message MUST also include the Timestamp option with the value set
       to the current time-of-day on the local mobility anchor.

   Using Sequence Number based approach:

   1.  If the Timestamp option is not present in the received Proxy
       Binding Update request, the local mobility anchor MUST fallback
       to the Sequence Number based scheme.  It MUST process the
       sequence number field as specified in [RFC-3775].  Also, it MUST
       NOT include the Timestamp option in the Proxy Binding
       Acknowledgement messages that it sends to the mobile access
       gateway.

   2.  An implementation MUST support Sequence Number based scheme, as
       per [RFC-3775].

5.6.  Routing Considerations

5.6.1.  Bi-Directional Tunnel Management

   o  A bi-directional tunnel MUST be established between the local
      mobility anchor and the mobile access gateway with IP-in-IP
      encapsulation, as described in [RFC-2473].  The tunnel end points
      are the Proxy-CoA and LMAA.  When using IPv4 transport with a
      specific encapsulation mode, the end points of the tunnel are the
      IPv4-LMAA and IPv4-Proxy-CoA, as specified in [ID-IPV4-PMIP6].

   o  The bi-directional tunnel MUST be used for routing the mobile
      node's data traffic between the mobile access gateway and the
      local mobility anchor.  The tunnel hides the topology and enables
      a mobile node to use an address from its home network prefix from
      any access link attached to the mobile access gateway.

   o  The bi-directional tunnel is established after accepting the Proxy
      Binding Update request message.  The created tunnel may be shared
      with other mobile nodes attached to the same mobile access gateway
      and with the local mobility anchor having a Binding Cache entry
      for those mobile nodes.  Implementations MAY choose to use static
      tunnels instead of dynamically creating and tearing them down on a
      need basis.

   o  Implementations MAY use a software timer for managing the tunnel
      lifetime and a counter for keeping a count of all the mobile nodes
      that are sharing the tunnel.  The timer value MUST be set to the
      accepted binding lifetime and will be updated after each periodic
      re-registration for extending the lifetime.  If the tunnel is
      shared for multiple mobile nodes, the tunnel lifetime MUST be set
      to the highest binding lifetime that is granted to any one of
      those mobile nodes sharing that tunnel.

5.6.2.  Forwarding Considerations

   Intercepting Packets Sent to the Mobile Node's Home Network:

   o  When the local mobility anchor is serving a mobile node, it MUST
      be able to receive packets that are sent to the mobile node's home
      network.  In order for it to receive those packets, it MUST
      advertise a connected route in to the Routing Infrastructure for
      the mobile node's home network prefix or for an aggregated prefix
      with a larger scope.  This essentially enables IPv6 routers in
      that network to detect the local mobility anchor as the last-hop
      router for that prefix.

   Forwarding Packets to the Mobile Node:

   o  On receiving a packet from a correspondent node with the
      destination address matching a mobile node's home network prefix,
      the local mobility anchor MUST forward the packet through the bi-
      directional tunnel setup for that mobile node.  The format of the
      tunneled packet is shown below.  However, when using IPv4
      transport, the format of the packet is as described in [ID-IPV4-
      PMIP6].

        IPv6 header (src= LMAA, dst= Proxy-CoA  /* Tunnel Header */
           IPv6 header (src= CN, dst= MN-HOA )  /* Packet Header */
              Upper layer protocols             /* Packet Content*/

                 Figure 7: 10: Tunneled Packets from LMA to MAG

   Forwarding Packets Sent by the Mobile Node:

   o  All the reverse tunneled packets that the local mobility anchor
      receives from the mobile access gateway, after removing the tunnel
      header MUST be routed to the destination specified in the inner
      packet header.  These routed packets will have the source address
      field set to the mobile node's home address.

5.7.  Local Mobility Anchor Address Discovery

   Dynamic Home Agent Address Discovery, as explained in Section 10.5
   [RFC-3775], allows a mobile node to discover all the home agents on
   its home link by sending an ICMP Home Agent Address Discovery Request
   message to the Mobile IPv6 Home-Agents anycast address, derived from
   its home network prefix.

   The DHAAD message in the current form cannot be used in Proxy Mobile
   IPv6 for discovering the address of the mobile node's local mobility
   anchor.  In Proxy Mobile IPv6, the local mobility anchor will not be
   able to receive any messages sent to the Mobile IPv6 Home-Agents
   anycast address corresponding to the mobile node's home network
   prefix, as the prefix is not hosted on any of its interfaces.
   Further, the mobile access gateway will not predictably be able to
   locate the serving local mobility anchor that has the mobile node's
   binding cache entry.  Hence, this specification does not support
   Dynamic Home Agent Address Discovery protocol.

   In Proxy Mobile IPv6, the address of the local mobility anchor
   configured to serve a mobile node can be discovered by the mobility
   entities in other ways.  This may be a configured entry in the mobile
   node's policy profile, or it may be obtained through mechanisms
   outside the scope of this document.

5.8.  Mobile Prefix Discovery Considerations

   This specification does not support mobile prefix discovery.  The ICMP
   mobile prefix discovery mechanism as specified in [RFC-3775] is not
   applicable to Proxy Mobile Prefix Advertisement message, described IPv6.

5.9.  Route Optimizations Considerations

   The Route Optimization in Mobile IPv6, as defined in Section
   6.8 and Section 11.4.3 of [RFC-3775], allows
   enables a home agent mobile node to send a
   Mobile Prefix Advertisement to the mobile node.

   In Proxy Mobile IPv6, the mobile node's home network prefix is hosted
   on the access link connected to the mobile access gateway, but it is
   topologically anchored on the local mobility anchor.  Since there is
   no physical home-link for the mobile node's home network prefix on
   the local mobility anchor and as the mobile node is always on the
   link where the prefix is hosted, any prefix change messages can just
   be advertised by the mobile access gateway on the access link and
   thus there is no applicability of this message for Proxy Mobile IPv6.
   Hence, this specification does not support Mobile Prefix Discovery.

5.9.  Route Optimizations Considerations

   The Route Optimization in Mobile IPv6, as defined in [RFC-3775],
   enables a mobile node to communicate with communicate with a correspondent node
   directly using its care-of address and further the Return Routability
   procedure enables the correspondent node to have reasonable trust
   that the mobile node is reachable at both its home address and
   care-of address.

   In Proxy Mobile IPv6, the mobile node is not involved in any IP
   mobility related signaling.  The mobile node uses only its home
   address for all its communication and the Care-of address (Proxy-CoA)
   is not visible to the mobile node.  Hence, the Return Routability
   procedure as defined in Mobile IPv6 [RFC-3775] cannot be used in
   Proxy Mobile IPv6.

6.  Mobile Access Gateway Operation

   The Proxy Mobile IPv6 protocol described in this document introduces
   a new functional entity, the Mobile Access Gateway (MAG).  The mobile
   access gateway is the entity that is responsible for detecting the
   mobile node's movements on its to and from the access link and sending the
   binding registration requests to the local mobility anchor.  In
   essence, the mobile access gateway performs mobility management on
   behalf of a mobile node.

   The mobile access gateway is a function that typically runs on an
   access router.  However, implementations MAY choose to split this
   function and run it across multiple systems.  The specifics on how
   that is achieved or the signaling interactions between those
   functional entities are beyond the scope of this document.

   The mobile access gateway has the following key functional roles:

   o  It is responsible for detecting the mobile node's movements on the
      access link and for initiating the mobility signaling with the
      mobile node's local mobility anchor.

   o  Emulation of the mobile node's home link on the access link by
      sending Router Advertisements with the mobile node's home network
      prefix information.

   o  Responsible for setting up the data path for enabling the mobile
      node to configure an address from its home network prefix and use
      it from its access link.

6.1.  Extensions to Binding Update List Entry Data Structure

   Every mobile access gateway MUST maintain a Binding Update List.
   Each entry in the Binding Update List represents a mobile node's
   mobility binding with its local mobility anchor.  The Binding Update
   List is a conceptual data structure, described in Section 11.1 [RFC-
   3775].

   For supporting this specification, the conceptual Binding Update List
   entry data structure needs be extended with the following additional
   fields.

   o  The Identifier of the attached mobile node, MN-Identifier.  This
      identifier is acquired during the mobile node's attachment to the
      access link through mechanisms outside the scope of this document.

   o  The interface identifier of the mobile node's connected interface.
      This address can be acquired from the received Router Solicitation
      messages from the mobile node or during the mobile node's
      attachment to the access network.  This is typically a Layer-2
      identifier conveyed by the mobile node; however, the specific
      details on how that is conveyed is out of scope for this
      specification.  If this identifier is not available, the value
      MUST be set to ALL_ZERO.

   o  The IPv6 home network prefix of the attached mobile node.  The
      home network prefix of the mobile node is acquired from the mobile
      node's local mobility anchor through the received Proxy Binding
      Acknowledgement messages.  The IPv6 home network prefix also
      includes the corresponding prefix length.

   o  The Link-local address of the mobile node on the interface
      attached to the access link.

   o  The IPv6 address of the local mobility anchor serving the attached
      mobile node.  This address is acquired from the mobile node's
      policy profile or from other means.

   o  The Interface interface identifier (If-Id) of the access link where the
      mobile node is currently attached.  This is internal to the mobile
      access gateway and is used to associate the Proxy Mobile IPv6
      tunnel to the right access link where the mobile node is attached.

   o  The interface identifier (If-Id) of the bi-directional tunnel
      between the mobile node's local mobility anchor and the mobile
      access gateway.  This is internal to the mobile access gateway.
      The tunnel interface identifier is acquired during the tunnel
      creation.

6.2.  Mobile Node's Policy Profile

   A mobile node's policy profile contains the essential operational
   parameters that are required by the network entities for managing the
   mobile node's mobility service.  These policy profiles are stored in
   a local or a remote policy store.  The mobile access gateway and the
   local mobility anchor MUST be able to obtain a mobile node's policy
   profile.  The policy profile MAY also be handed over to a serving
   mobile access gateway as part of a context transfer procedure during
   a handoff or the serving mobile access gateway MAY be able to
   dynamically generate this profile.  The exact details on how this
   achieved is outside the scope of this document.  However, this
   specification requires that a mobile access gateway serving a mobile
   node MUST have access to its policy profile.

   The following are the mandatory fields of the policy profile:

   o  The mobile node's identifier (MN-Identifier)

   o  The IPv6 address of the local mobility anchor (LMAA)

   The following are the optional fields of the policy profile:

   o  The mobile node's IPv6 home network prefix (MN-HNP)

   o  The mobile node's IPv6 home network Prefix lifetime

   o  Supported address configuration procedures (Stateful, Stateless or
      both) on for the access links mobile node in the Proxy Mobile IPv6 domain

6.3.  Supported Access Link Types

   This specification supports only point-to-point access link types and
   thus it assumes that the mobile node and the mobile access gateway
   are the only two nodes on the access link.  The link is assumed to
   have multicast capability.  This protocol may also be used on other
   link types, as long as the link is configured in such a way that it
   guarantees a point-to-point delivery between the mobile node and the
   mobile access gateway for all the protocol traffic.

6.4.  Supported Address Configuration Models Modes

   A mobile node in the Proxy Mobile IPv6 domain can configure one or
   more IPv6 addresses on its interface using Stateless or Stateful
   address autoconfiguration procedures.  The Router Advertisement
   messages sent on the access link specify the address configuration
   methods permitted on that access link for that mobile node.  However,
   the advertised flags with respect to the address configuration will
   be consistent for a mobile node, on any of the access links in that
   Proxy Mobile IPv6 domain.  Typically, these configuration settings
   will be based on the domain wide policy or based on a policy specific
   to each mobile node.

   When stateless address autoconfiguration is supported on the access
   link, the mobile node can generate one or more IPv6 addresses by combining
   the network prefix advertised on the access link with an interface
   identifier, using the techniques described in
   standard IPv6 mechanisms such as Stateless Autoconfiguration
   specification [RFC-4862] or as per Privacy extension specification [RFC-4941]. [RFC-
   4941].

   When stateful address autoconfiguration is supported on the link, the
   mobile node can obtain the address configuration from the DHCPv6
   server using by standard DHCPv6 client protocol, mechanisms, as specified in DHCPv6
   specification [RFC-3315].

   Additionally, other address configuration mechanisms specific to the
   access link between the mobile node and the mobile access gateway may
   also be used for pushing the address configuration to the mobile
   node.  This specification does not change the behavior of address
   configuration mechanisms in any way.

6.5.  Access Authentication & Mobile Node Identification

   When a mobile node attaches to an access link connected to the mobile
   access gateway, the deployed access security protocols on that link
   SHOULD ensure that the network-based mobility management service is
   offered only after authenticating and authorizing the mobile node for
   that service.  The exact specifics on how this is achieved or the
   interactions between the mobile access gateway and the access
   security service is outside the scope of this document.  This
   specification goes with the stated assumption of having an
   established trust between the mobile node and the mobile access
   gateway, before the protocol operation begins.

6.6.  Acquiring Mobile Node's Identifier

   All the network entities in a Proxy Mobile IPv6 domain MUST be able
   to identify a mobile node, using its MN-Identifier.  This identifier
   MUST be stable across the Proxy Mobile IPv6 domain and the entities
   must be able to use this identifier in the signaling messages.
   Typically, this identifier is obtained as part of the access
   authentication or through other means as specified below.

   o  The identifier of the mobile node that the mobile access gateway
      obtains typically as part of the access authentication or from the
      notified network attachment event, can be a temporary identifier
      and this further that temporary identifier may also change be different at each re-authentication.
      However, the re-
      authentication.  The mobile access gateway MUST be able to use
      this temporary identifier and obtain the mobile node's MN-Identifier stable
      identifier from the policy store, such as from store.  For instance, in AAA-based
      systems the RADIUS attribute, Chargeable-User-
      Identifier [RFC-4372]. Chargeable-User-Identifier [RFC-
      4372] may be used.

   o  The MN-Identifier that the policy store delivers to the mobile
      access gateway may not be the true identifier of the mobile node.
      However, the mobility access gateway MUST be able to use this
      identifier in the signaling messages exchanged with the local
      mobility anchor.

   o  The mobile access gateway MUST be able to identify the mobile node
      by its MN-Identifier and it MUST be able to associate this
      identity to the sender of any IPv4 or IPv6 packets on point-to-point link sharing with the access link. mobile node.

6.7.  Home Network Emulation

   One of the key functions of a mobile access gateway is to emulate the
   mobile node's home network on the access link.  It must ensure, the
   mobile node believes it is still connected to its home link or on the
   link where it obtained its initial address configuration after it
   moved into that Proxy Mobile IPv6 domain.

   For emulating the mobile node's home link on the access link, the
   mobile access gateway must be able to send Router Advertisements
   advertising the mobile node's home network prefix and other address
   configuration parameters consistent with its home link properties.
   Typically, these configuration settings will be based on the domain
   wide policy or based on a policy specific to each mobile node.

   Typically, the mobile access gateway learns the mobile node's home
   network prefix information from the received Proxy Binding
   Acknowledgement message or it may be obtained from the mobile node's
   policy profile.  However, the mobile access gateway SHOULD send the
   Router Advertisements advertising the mobile node's home network
   prefix only after successfully completing the binding registration
   with the mobile node's local mobility anchor.

   When advertising the home network prefix in the Router Advertisement
   messages, the mobile access gateway MAY set the prefix lifetime value
   for the advertised prefix to any chosen value at its own discretion.
   An implementation MAY choose to tie the prefix lifetime to the mobile
   node's binding lifetime.  The prefix lifetime can also be an optional
   configuration parameter in the mobile node's policy profile.

6.8.  Link-Local and Global Address Uniqueness

   A mobile node in the Proxy Mobile IPv6 domain, as it moves from one
   mobile access gateway to the other, will continue to detect its home
   network and thus making it believe it is still on the same link.
   Every time the mobile node attaches to a new link, the event related
   to the interface state change will trigger the mobile node to perform
   DAD operation on the link-local and global addresses.  However, if
   the mobile node is DNAv6 enabled, as specified in [ID-DNAV6], it may
   not detect the link change due to DNAv6 optimizations and may not
   trigger the duplicate address detection (DAD) procedure for
   establishing the link-local address uniqueness on that new link.
   Further, if the mobile node uses an interface identifier that is not
   based on EUI-64 identifier, such as specified in IPv6 Stateless
   Autoconfiguration specification [RFC-4862], there is a very low
   possibility of
   This leaves a room for link-local address collision between the two
   neighbors on that access link.

   For solving this problem, this specification allows the mobile access
   gateway to upload the mobile node's link-local address to the local
   mobility anchor using the Link-local Address option, exchanged in the
   binding registration messages.  The mobile access gateway can learn
   the mobile node's link-local address, by snooping the DAD messages
   sent by the mobile node for establishing the link-local address
   uniqueness on the access link.  Subsequently, at each handoff, the
   mobile access gateway can obtain this address from the local mobility
   anchor to ensure link-local address uniqueness and change its own
   link-local address, if it detects a collision.

   Alternatively, one of the workarounds for this issue is to set the
   DNAv6 configuration parameter, DNASameLinkDADFlag to TRUE and that
   will force the mobile node to redo DAD operation on the global and
   link-local addresses every time the interface detects a handover, an handoff,
   even when DNAv6 does not detect a link change.

   However, this issue will may not impact point-to-point links based on a
   PPP session. PPP.
   Each time the mobile node moves and attaches to a new mobile access
   gateway, either the PPP session [RFC-1661] is
   reestablished can be re-established, or if
   there are context transfer procedures in place, the entire PPP
   session may can be moved as part of context
   transfer procedures between to the old new link and the new mobile access
   gateway.

   When link-local addresses of
   both the mobile node tries peers will continue to establish a PPP session with remain the mobile
   access gateway, same.  In either of these
   approaches, the PPP goes through link-local address uniqueness on the Network layer Protocol phase
   and link is assured.
   The specific details of how the IPv6 Control Protocol, IPV6CP [RFC-5072] gets triggered.
   Both PPP session is re-established without
   impacting any layer-3 sessions or how the PPP peers negotiate a unique identifier using Interface-
   Identifier option in IPV6CP and session can be moved
   between the negotiated identifier mobile access gateways is used for
   generating a unique link-local outside the scope of this
   document.

   The issue of address on that link.  Now, if collision is not relevant to the mobile node moves to node's
   global address.  Since there is a new unique home network prefix assigned
   for each mobile access gateway, node, the PPP session
   gets torn down with uniqueness for the old mobile node's global
   address is assured on the access gateway link.

6.9.  Signaling Considerations

6.9.1.  Binding Registrations

6.9.1.1.  Mobile Node Attachment and Initial Binding Registration

   1.   After detecting a new PPP
   session gets established with the new mobile node on its access gateway, and link, the mobile node obtains a new link-local address.  So, even if
        access gateway MUST identify the mobile node is DNAv6 capable, the mobile node always configures a new link-
   local address whenever it moves to a new link.

   If the PPP session state is moved to the new mobile access gateway as
   part of context transfer procedures that are in place, there will not
   be any change to the interface identifiers of the two nodes on that
   point-to-point change.  The whole link is moved to the new mobile
   access gateway and there will not be any need for establishing link-
   local address uniqueness on that link.

   The issue of address collision is not relevant to the mobile node's
   global address.  Since there is a unique home network prefix assigned
   for each mobile node, the uniqueness for the mobile node's global
   address is assured on the access link.

6.9.  Signaling Considerations

6.9.1.  Binding Registrations

   Mobile Node Attachment and Initial Binding Registration:

   1.   After detecting a new mobile node on its access link, the mobile
        access gateway must identify the mobile node and acquire its MN-
        Identifier.  If it determines that the network-based mobility
        management service needs to be offered to and acquire its MN-
        Identifier.  If it determines that the network-based mobility
        management service needs to be offered to the mobile node, it
        MUST send a Proxy Binding Update message to the local mobility
        anchor.  If there is no existing Binding Update List entry for
        that mobile node, the mobile access gateway MUST create a
        Binding Update List entry upon sending the Proxy Binding Update
        request.

   2.   The Proxy Binding Update message MUST include the Mobile Node
        Identifier option [RFC-4283], carrying the MN-Identifier for
        identifying the mobile node, the node.

   3.   The Home Network Prefix option, either the Timestamp option or a
        valid sequence number and optionally the Link-local Address
        option.  When Timestamp option is added to MUST be present in the message, Proxy
        Binding Update message.  If the mobile access gateway MAY set learns the Sequence Number field to a
        value of a monotonically increasing counter and
        mobile node's home network prefix either from its policy store
        or from other means, the local
        mobility anchor will ignore this field, but will return mobile access gateway MAY choose to
        specify the same
        value in the Proxy Binding Acknowledgement message.  This will
        be useful Home Network Prefix option for matching
        requesting the reply local mobility anchor to the request message.

   3.   The Home Address option allocate that prefix,
        otherwise it MUST NOT be present in the Destination
        Option extension header specify a value of ALL_ZERO.  If the Proxy Binding Update message. specified
        value is ALL_ZERO, then the local mobility anchor will do the
        prefix assignment.

   4.   The Access Technology Type Handoff Indicator option MUST be present in the Proxy
        Binding Update message.  The access technology Type field in the
        option MUST be set to the access technology using which the
        mobile node is currently attached to the mobile access gateway.
        The Handoff Indicator field in the Access Technology Type
        Handoff Indicator option MUST be set to a value indicating the appropriate value.
        handoff hint.  The specific details on how the mobile access
        gateway is able to determine determines if the mobile node's current attachment is
        due to a an handoff of an existing mobility session or if it is as
        a result of an attachment over a different interface is outside
        the scope of this document.

   5.

        *  The Handoff Indicator field in the Access Technology Type option MUST be set to value 1
           (Attachment over a new interface), if the mobile access
           gateway predictably knows that the mobile node's current
           attachment to the network using the current over this interface is due to
        neither not as a handover between two interfaces
           result of the mobile node nor
        a handover an handoff of the an existing mobility session for (over
           the same interface or through a different interface), but as
           a result of the
        mobile node between two mobile access gateways. an attachment over a new interface.  This
           essentially serves as a request to the local mobility anchor
           to
        allocate create a new home network prefix for this mobility session and not update any existing
           Binding Cache entry created for the same mobile node
           connected to the Proxy Mobile IPv6 domain through a different
           interface.

   6.

        *  The Handoff Indicator field in the Access Technology Type option MUST be set to value 2 (Handoff
           between interfaces), two different interfaces of the mobile node), if the
           mobile access gateway definitively knows the mobile node's
           current attachment is due to a an handoff of the an existing
           mobility session session, between two different interfaces of the
           mobile node.

   7.

        *  The Handoff Indicator field in the Access Technology Type option MUST be set to value 3 (Handoff
           between mobile access gateways for the same interface), if
           the mobile access gateway definitively knows the mobile
           node's current attachment is due to a an handoff of the an existing
           mobility session between different two mobile access gateways and for
           the same interface of the mobile node.

   8.

        *  The Handoff Indicator field in the Access Technology Type option MUST be set to value 4 (Handoff State Unknown),
           state unknown), if the mobile access gateway cannot predictably know determine
           if the mobile node's
        session current attachment is due to an handoff
           of an existing mobility session.

   5.   Either the Timestamp option or a handoff.

   9. valid sequence number
        maintained on a per mobile node basis (if Sequence Number based
        scheme is in use) MUST be present.  When Timestamp option is
        added to the message, the mobile access gateway SHOULD also set
        the Sequence Number field to a value of a monotonically
        increasing counter (not to be confused with the per mobile node
        sequence number specified [RFC-3775]).  The local mobility
        anchor will ignore this field when there is a Timestamp option
        present in the request, but will return the same value in the
        Proxy Binding Acknowledgement message.  This will be useful for
        matching the reply to the request message.

   6.   The Mobile Node Interface Identifier option carrying the
        interface identifier of the currently attached interface MUST be
        present in the Proxy Binding Update message, if the mobile
        access gateway knows the interface identifier of the mobile
        node's currently attached interface.  The "P" Flag in the option MUST
        be set to 0, indicating that the carried identifier is the
        currently attached interface identifier.  If the interface
        identifier is not known, this known or if the identifier value is ALL_ZERO,
        this option MUST NOT be present.

   10.  If

   7.   The Access Technology Type option MUST be present in the mobile Proxy
        Binding Update message.  The access gateway learns technology type field in the
        option SHOULD be set to the type of access technology using
        which the mobile node's home
        network prefix either from its policy store or from other means, node is currently attached to the mobile access gateway
        gateway.

   8.   The Link-local Address option MAY choose to specify the same be present in the
        Home Network Prefix option for requesting Proxy
        Binding Update message.  Considerations from Section 6.8 MUST be
        applied when using the link-local address option.

        *  When uploading the link-local address to the local mobility
        anchor to allocate that prefix.  If
           anchor, the specified value is
        0::/0, then in the local mobility option MUST be set to the link-local
           address that is configured on the currently attached
           interface of the mobile node.

        *  When querying the local mobility anchor will consider this for the mobile node's
           link-local address, the option MUST be set to ALL_ZERO value.
           This essentially serves as a request to the local mobility
           anchor to return the link-local address of the mobile node
           from the binding cache entry corresponding to this mobility
           session.

   9.   The Proxy Binding Update message MUST be constructed as
        specified in Section 6.9.1.5.

   10.  If there is no existing Binding Update List entry for prefix allocation. that
        mobile node, the mobile access gateway MUST create a Binding
        Update List entry for the mobile node upon sending the Proxy
        Binding Update request.

6.9.1.2.  Receiving Binding Registration Reply:

   1.   The Reply

   On receiving a Proxy Binding Acknowledgement message from the local
   mobility anchor, the mobile access gateway MUST observe the rules described in
        Section 9.2 [RFC-3775] when processing Mobility Headers in process the message
   as specified below.

   1.   The received Proxy Binding Acknowledgement message (a Binding
        Acknowledgement message with the 'P' flag set).

   2.   The message set) MUST be
        authenticated as described in Section 4.0.  When IPsec is used
        for message authentication, the SPI in the IPsec header [RFC-4306] [RFC-
        4306] of the received packet is needed for locating the security
        association, for authenticating the Proxy Binding
        Acknowledgement reply. message .

   2.   The mobile access gateway MUST observe the rules described in
        Section 9.2 [RFC-3775] when processing Mobility Headers in the
        received Proxy Binding Acknowledgement message.

   3.   The mobile access gateway MUST apply the considerations
        specified in Section 5.5 for processing the Sequence Number
        field and the Timestamp option, option (if present), in the message.

   4.   The mobile access gateway MUST ignore any checks, specified in
        [RFC-3775] related to the presence of Type 2 Routing header in
        the Proxy Binding Acknowledgement message.

   5.   If the Timestamp option is present in the received Proxy Binding
        Acknowledgement message and with the Status field value set to
        any value other than TIMESTAMP_MISMATCH (Invalid Timestamp), the   The mobile access gateway MAY use the timestamp value for matching
        the response to the request message that it sent recently.  For
        all other cases, it MAY use the sequence number in combination
        with the mobile node identifier
        present in the Mobile Node Identifier option for matching the
        response to the request.

   6.   If the received Proxy Binding Acknowledgement message has the request messages that it sent recently .
        However, if there are more than one request message in its
        request queue for the same mobile node, the sequence number
        field can be used for identifying the exact message from those
        messages.  There are other ways to achieve this and
        implementations are free to adopt the best approach that suits
        their implementation.  Additionally, if the received Proxy
        Binding Acknowledgement message does not match any of the Proxy
        Binding Update messages that it sent recently, the message MUST
        be ignored.

   6.   If the received Proxy Binding Acknowledgement message has any
        one or more of the following options, Handoff Indicator option,
        Access Technology Type option, Mobile Node Interface Identifier
        option, Mobile Node Identifier option, carrying option values
        that are different from the option values present in the
        corresponding request (Proxy Binding Update) message, the
        message MUST be ignored as the local mobility anchor is expected
        to echo back all these listed options and with the same option
        values in the reply message.

   7.   If the received Proxy Binding Acknowledgement message has the
        Status field value set to PROXY_REG_NOT_ENABLED (Proxy
        registration not enabled for the mobile node), the mobile access
        gateway SHOULD NOT send binding registration requests again for
        that mobile node.  It must also MUST deny the mobility service to that
        mobile node.

   7.

   8.   If the received Proxy Binding Acknowledgement message has the
        Status field value set to TIMESTAMP_LOWER_THAN_PREV_ACCEPTED
        (Timestamp value lower than previously accepted timestamp), value), the
        mobile access gateway SHOULD try to register again to reassert
        the mobile node's presence to the mobility anchor. on its access link.  The mobile
        access gateway is not specifically required to synchronize its
        clock upon receiving this error code.

   8.

   9.   If the received Proxy Binding Acknowledgement message has the
        Status field value set to TIMESTAMP_MISMATCH (Invalid
        Timestamp), timestamp
        value), the mobile access gateway SHOULD try to register again
        only after it has synchronized its clock to a common time source
        that is used by all the mobility entities in that domain for
        their clock synchronization.  The mobile access gateway SHOULD
        NOT synchronize its clock to the local mobility anchor's system
        clock, based on the timestamp present in the received message.

   9.

   10.  If the received Proxy Binding Acknowledgement message has the
        Status field value set to NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX
        (Not
        (mobile node is not authorized for that the requesting home network
        prefix), the mobile access gateway SHOULD try to NOT request for that the
        same prefix again, but can request the local mobility anchor to
        dynamically assign a prefix, by specifying a ALL_ZERO value in
        the binding
        registration request, only after it learned Home Network Prefix option carried in the validity of that
        prefix.

   10. subsequent Proxy
        Binding Update message.

   11.  If the received Proxy Binding Acknowledgement message has the
        Status field value set to any value greater than or equal to 128
        (i.e., if the binding is rejected), the mobile access gateway
        MUST NOT advertise the mobile node's home network prefix in the
        Router Advertisements sent on that access link and there by
        denying mobility service to the mobile node.

   11.

   12.  If the received Proxy Binding Acknowledgement message has the
        Status field value set to 0 (Proxy Binding Update accepted), the
        mobile access gateway MUST setup update the routing state, as
        explained in section 6.10, and MUST also update the Binding
        Update List entry for reflecting the accepted binding
        registration status.

   12.

   13.  If the received Proxy Binding Acknowledgement message has the
        address in the Link-local Address option set to a value that
        matches its own link-local address on that access interface
        where the mobile node is anchored, the mobile access gateway
        MUST change its link-local address on that interface. interface, to avoid
        link-local address collision on that access link.

6.9.1.3.  Extending Binding Lifetime: Lifetime

   1.  For extending the lifetime of a currently registered mobile node
       (i.e., if there exists after a Binding Update List entry for that successful initial binding registration from the
       same mobile node), access gateway), the mobile access gateway MUST can send a
       Proxy Binding Update message to the local mobility anchor. anchor with a
       new lifetime value.  This re-registration message MUST be
       constructed with the same set of options as the initial binding
       registration message, under the considerations specified in
       Section 6.9.1.1.  However the following exceptions apply.

   2.  The prefix value in the Home Network Prefix option present in the request SHOULD MUST be set to
       the currently registered assigned home network prefix and prefix.

   3.  The Handoff Indicator field in the Handoff Indicator option MUST
       be set to a value of 5 (Handoff state not changed - Re-
       Registration).

   4.  The value in the Link-local Address option MAY (if the option was
       present in the initial registration message) MUST be set to ALL_ZERO or to the
       link-local address of the mobile node. node's attached interface.

6.9.1.4.  Mobile Node Detachment and Binding De-Registration: De-Registration

   1.  At any point, if the mobile access gateway detects that the mobile
       node has moved away from its access link, or if it decides to
       terminate the mobile node's mobility session, it SHOULD send a
       Proxy Binding Update message to the local mobility anchor with
       the lifetime value set to zero.  This de-registration message
       MUST be constructed with the same set of options as the initial
       binding registration message, under the considerations specified
       in Section 6.9.1.1.  However, the following exceptions apply.

   2.  The prefix value in the Home Network Prefix option MUST be set to
       the currently assigned home network prefix.

   3.  The Handoff Indicator field in the Handoff Indicator option MUST
       be set to a value of 4 (Handoff state unknown).

   4.  The value in the Link-local Address option (if the option was
       present in the initial registration message) MUST be set to the
       link-local address of the mobile node's attached interface.

   Either upon receipt of a Proxy Binding Acknowledgement message from
   the local mobility anchor or after a MinPBUReplyTime INITIAL_BINDINGACK_TIMEOUT [RFC-
   3775] timeout waiting for the reply, the mobile access gateway MUST
   do the following:

   1.  It MUST remove the Binding Cache Update List entry for that the mobile node
       from its Binding Update
       List and List.

   2.  It MUST withdraw the mobile node's home network prefix as the
       hosted on-link prefix on that access link.

   Constructing the Proxy Binding Update Message:

   o  The mobile access gateway when prefix, by sending the Proxy a Router Advertisement message
       with the prefix lifetime value set to zero.

   3.  It MUST remove the created routing state for tunneling the mobile
       node's traffic.

   4.  It SHOULD teardown the point-to-point link shared with the mobile
       node.  This action will force the mobile node to remove any IPv6
       address configuration on the interface connected to this point-
       to-point link.

6.9.1.5.  Constructing the Proxy Binding Update Message

   o  The mobile access gateway when sending the Proxy Binding Update
      request to the local mobility anchor MUST construct the message as
      specified below.

          IPv6 header (src=Proxy-CoA, dst=LMAA)
            Mobility header
                        -BU /*P
               - BU /* P & A flags are set*/ MUST be set */
              Mobility Options
               - Mobile Node Identifier option           (mandatory)
               - Home Network Prefix option              (mandatory)
               - Link-local Address option (Optional)
                          - Timestamp Option (optional)
                          - Mobile Node Identifier Handoff Indicator option                (mandatory)
               - Access Technology Type option (Mandatory)           (mandatory)
               - Timestamp option                        (optional)
               - Mobile Node Interface Identifier option
                            (Optional) (optional)
               - Link-local Address option               (optional)

                Figure 8: 11: Proxy Binding Update message format

   o  The Source Address field in the IPv6 header of the message MUST be
      set to the address configured on the interface of the mobile
      access gateway.  When there is no Alternate Care-of Address option
      present in the request, this address will be considered as the
      Proxy-CoA address for this binding registration request.  However,
      when there is Alternate Care-of Address option present in the
      request, this address will be not be the considered as the Proxy-
      CoA address, but the address in the alternate Care-of Address
      option will be considered as the Proxy-CoA address.

   o  The Destination Address field in the IPv6 header of the message
      MUST be set to the local mobility anchor address.

   o  The Mobile Node Identifier option [RFC-4283] MUST be present.

   o  The Home Network Prefix option MUST be present.  The prefix value
      MAY be set 0::/0 or to a specific prefix value.

   o  The Link-local Address Handoff Indicator option MAY MUST be present.  The value MAY be
      set to ALL_ZERO or the mobile node's link-local address.

   o  The Access Technology Type option MUST be present.

   o  The value MUST Timestamp option MAY be set to the type of the access technology using which the mobile
      node is currently attached to the mobile access gateway. present.

   o  The Mobile Node Interface Identifier option MAY be present.

   o  Considerations from Section 5.5 must  The Link-local Address option MAY be applied for constructing
      the Timestamp option.

   o  The Mobile Node Identifier option [RFC-4283] MUST be present, the
      identifier field in the option MUST be set to mobile node's
      identifier, MN-Identifier. present.

   o  If IPsec is used for protecting the signaling messages, the
      message MUST be protected, using the security association existing
      between the local mobility anchor and the mobile access gateway.

   o  Unlike in Mobile IPv6 [RFC-3775], the Home Address option [RFC-
      3775] MUST NOT be present in the IPv6 Destination Options
      extension header of the Proxy Binding Update message.

6.9.2.  Router Solicitation Messages

   The mobile node may send a Router Solicitation message on the access
   link whenever the link-layer detects a media change.  The Source
   Address in the IPv6 header of the Router Solicitation message may
   either be the link-local address of the mobile node or an unspecified
   address (::).  The Router Solicitation message that the mobile node
   sends is as specified in [RFC-4861].

   1.  The mobile access gateway on receiving the Router Solicitation
       message SHOULD send a Router Advertisement containing the mobile
       node's home network prefix as the on-link prefix.  However,
       before sending the Router Advertisement message containing the
       mobile node's home network prefix, it SHOULD complete the binding
       registration process with the mobile node's local mobility
       anchor.

   2.  If the local mobility anchor rejects the binding registration
       request, or, if the mobile access gateway failed to complete the
       binding registration process for whatever reasons, the mobile
       access gateway MUST NOT advertise the mobile node's home network
       prefix in the Router Advertisement messages that it sends on the
       access link.  However, it MAY choose to advertise a local visited
       network prefix to enable the mobile node for regular IPv6 access.

6.9.3.  Retransmissions  Default-Router Lifetime

   This section is a non-normative section and Rate Limiting

   The only provides some
   general guidance to implementations.

   In Proxy Mobile IPv6, the mobile access gateway is responsible for retransmissions and rate
   limiting typically the binding registration requests that it sends IPv6
   default-router for updating
   a mobile node's binding.  Implementations MUST follow the below
   guidelines.

   1.  When the mobile node on the access gateway sends a Proxy Binding Update
       request, link, as it should use is the constant, INITIAL_BINDINGACK_TIMEOUT
       [RFC-3775], for configuring
   entity that sends the retransmission timer.

   2.  If Router Advertisements on the mobile access gateway fails to receive a valid matching
       response within the retransmission interval, it SHOULD retransmit
       the message until a response is received. link.
   However, the mobile
       access gateway MUST ensure as the mobile node is still attached to
       the connected moves from one access link before retransmitting the message.

   3.  As specified in Section 11.8 [RFC-3775], to another,
   the serving mobile access gateway MUST use an exponential back-off process in which on those respective links will send
   the
       timeout period is doubled upon Router Advertisements and using their own link-local address.
   The mobile node on each retransmission, until either of the node receives attached links will receive Router
   Advertisement messages with a response or the timeout period reaches different source address and this makes
   the
       value MAX_BINDACK_TIMEOUT [RFC-3775]. mobile node believe that there is a new default-router on that
   access link.

   The mobile node will certainly detect the previous default-router
   loss by performing the Neighbor Unreachability Detection procedure
   per the standard IPv6 ND mechanisms, but it is important that the
   mobile access gateway
       MAY continue enables the mobile node to send these messages withdraw the
   previous default-router entry at this slower rate
       indefinitely.

   4.  If Timestamp based scheme is the earliest.  This action will help
   in minimizing packet losses during a hand off switch.  Following are
   some considerations that implementations can apply.

   The Router Lifetime field in use, the retransmitted Proxy
       Binding Update Router Advertisement messages MUST use that
   the latest timestamp.  If
       Sequence number scheme mobile access gateway sends on the access link SHOULD be kept to
   low.

   In access networks where SEND [RFC-3971] is in use, not deployed, the retransmitted Proxy Binding
       Update messages MUST use mobile
   access gateway can withdraw the previous default-router entry, by
   sending a Sequence Number value greater than Router Advertisement using the link-local address that used for of
   the previous transmission of mobile access gateway and with the Router Lifetime field
   set to value zero, then this Proxy Binding
       Update message, just will force the flush of the previous
   default-router entry from the mobile node's cache, as specified in [RFC-3775].

6.10.  Routing Considerations

   This section describes how
   Section 6.3.5 [RFC-4861].  However, this approach requires the
   serving mobile access gateway handles to learn the
   traffic to/from link-local address of the
   previous mobile access gateway where the mobile node that is attached to one was handed off.

   There are other solutions possible for this problem, including the
   assignment of its access
   interface.

                 Proxy-CoA                   LMAA
                    |                          |
    +--+          +---+                      +---+          +--+
    |MN|----------|MAG|======================|LMA|----------|CN|
    +--+          +---+                      +---+          +--+
                            IPv6 Tunnel

                    Figure 9: a fixed link-local address for all the mobility
   entities in a Proxy Mobile IPv6 Tunnel

6.10.1.  Transport Network

   The transport network between the local mobility anchor domain and where SEND [RFC-3971] is
   not deployed.  In such scenario, the mobile access gateway can be either an IPv6 or IPv4 network. node is not required to
   update the default-router entry.  However, this specification only deals with the IPv6 transport is an implementation
   choice and has no bearing on the companion document [ID-IPV4-PMIP6] specifies protocol interoperability.
   Implementations are free to adopt the required
   extensions for negotiating IPv4 transport best approach that suits their
   target deployments.

6.9.4.  Retransmissions and the corresponding
   encapsulation mode for supporting this protocol operation.

6.10.2.  Tunneling & Encapsulation Modes Rate Limiting

   The IPv6 address that a mobile node uses from its home network prefix access gateway is topologically anchored at responsible for retransmissions and rate
   limiting the binding registration requests that it sends to the local
   mobility anchor.  For a  The Retransmission and the Rate Limiting rules are
   as specified in [RFC-3775].  However, the following considerations
   MUST be applied.

   1.  When the mobile
   node to use this address from an access network attached to gateway sends a Proxy Binding Update
       request, it should use the constant, INITIAL_BINDINGACK_TIMEOUT
       [RFC-3775], for configuring the retransmission timer, as
       specified in Section 11.8 [RFC-3775].  However, the mobile access gateway, proper tunneling techniques have
       gateway is not required to be use a longer retransmission interval
       of InitialBindackTimeoutFirstReg as specified in place.
   Tunneling hides [RFC-3775] for
       the network topology and allows initial binding registration request.

   2.  If the mobile node's
   IPv6 datagram access gateway fails to be encapsulated as receive a payload of another IPv6 packet
   and to be routed between valid matching
       response for a registration or re-registration message within the local mobility anchor and
       retransmission interval, it SHOULD retransmit the message until a
       response is received.  However, the mobile access gateway.  The Mobile IPv6 base specification [RFC-3775]
   defines the use of IPv6-over-IPv6 tunneling, between the home agent
   and gateway MUST
       ensure the mobile node and this specification extends the use of is still attached to the
   same tunneling mechanism between connected link
       before retransmitting the local mobility anchor and message.

   3.  As specified in Section 11.8 [RFC-3775], the mobile access gateway.

   On most operating systems, tunnels are implemented as
       gateway MUST use an exponential back-off process in which the
       timeout period is doubled upon each retransmission, until either
       the node receives a virtual
   point-to-point interface.  The source and response or the destination address of timeout period reaches the two end points of
       value MAX_BINDACK_TIMEOUT [RFC-3775].  The mobile access gateway
       MAY continue to send these messages at this virtual interface along with slower rate
       indefinitely.

   4.  If Timestamp based scheme is in use, the
   encapsulation mode are specified for this virtual interface.  Any
   packet that retransmitted Proxy
       Binding Update messages MUST use the latest timestamp.  If
       Sequence number scheme is routed over this interface gets encapsulated with in use, the
   outer header and retransmitted Proxy Binding
       Update messages MUST use a Sequence Number value greater than
       that used for the addresses previous transmission of this Proxy Binding
       Update message, just as specified for that point to point
   tunnel interface.  For creating a point to point tunnel to any local
   mobility anchor, in [RFC-3775].

6.10.  Routing Considerations

   This section describes how the mobile access gateway may implement a tunnel
   interface with handles the source address field set
   traffic to/from the mobile node that is attached to one of its access
   interface.

                 Proxy-CoA address
   and the destination address field set to the LMA address.                   LMAA
                    |                          |
    +--+          +---+                      +---+          +--+
    |MN|----------|MAG|======================|LMA|----------|CN|
    +--+          +---+                      +---+          +--+
                            IPv6 Tunnel

                    Figure 12: Proxy Mobile IPv6 Tunnel

6.10.1.  Transport Network

   The following are the supported packet encapsulation modes that can
   be used by the mobile access gateway and transport network between the local mobility anchor
   for routing and the
   mobile node's IPv6 datagrams.

   o  IPv6-In-IPv6 - IPv6 datagram encapsulated in access gateway can be either an IPv6 packet [RFC-
      2473].

   o  IPv6-In-IPv4 - IPv6 datagram encapsulation in an or IPv4 packet.  The
      details on how network.
   However, this mode is negotiated is specified in [ID-IPV4-
      PMIP6].

   o  IPv6-In-IPv4-UDP - specification only deals with the IPv6 datagram encapsulation in an transport and
   the companion document [ID-IPV4-PMIP6] specifies the required
   extensions for negotiating IPv4 UDP
      packet.  This mode is specified in [ID-IPV4-PMIP6].

6.10.3.  Routing State

   The following section explains transport and the routing state corresponding
   encapsulation mode for supporting this protocol operation.

6.10.2.  Tunneling & Encapsulation Modes

   The IPv6 address that a mobile node on uses from its home network prefix
   is topologically anchored at the local mobility anchor.  For a mobile
   node to use this address from an access gateway.  This routing state reflects only one
   specific way of implementation and one MAY choose network attached to implement it in
   other ways.  The policy based route defined below acts as a traffic
   selection rule for routing a mobile node's traffic through a specific
   tunnel created between the mobile
   access gateway and that mobile
   node's local mobility anchor and with the specific encapsulation
   mode, as negotiated.

   The below example identifies the routing state for two visiting
   mobile nodes, MN1 and MN2 with their respective local mobility
   anchors LMA1 and LMA2.

   For all traffic from the mobile node, identified by the mobile node's
   MAC address, ingress interface or source prefix (MN-HNP) to
   _ANY_DESTINATION_ route via interface tunnel0, next-hop LMAA.

   +==================================================================+
   |  Packet Source    | Destination Address  | Destination Interface |
   +==================================================================+
   | MAC_Address_MN1,  | _ANY_DESTINATION_    |     Tunnel0           |
   | (IPv6 Prefix or   |----------------------------------------------|
   |  Input Interface) | Locally Connected    |     Tunnel0           |
   +------------------------------------------------------------------+
   | MAC_Address_MN2,  | _ANY_DESTINATION_    |     Tunnel1           |
   + (IPv6 Prefix or   -----------------------------------------------|
   |  Input Interface  | Locally Connected    |     direct            |
   +------------------------------------------------------------------+

               Figure 10: Example - Policy based Route Table

   +==================================================================+
   | Interface | Source Address | Destination Address | Encapsulation |
   +==================================================================+
   | Tunnel0   |   Proxy-CoA    |        LMAA1         | IPv6-in-IPv6 |
   +------------------------------------------------------------------+
   | Tunnel1   |IPv4-Proxy-CoA  |    IPv4-LMA2         | IPv6-in-IPv4 |
   +------------------------------------------------------------------+

                Figure 11: Example - Tunnel Interface Table

6.10.4.  Local Routing

   If there is data traffic between a visiting mobile node and a
   correspondent node that is locally attached to an access link
   connected to the mobile access gateway, the mobile access gateway MAY
   optimize on the delivery efforts by locally routing the packets and
   by not reverse tunneling them to the mobile node's local mobility
   anchor.  The configuration variable, EnableMAGLocalRouting MAY be
   used for controlling this aspect.  However, in some systems, this may
   have an implication on the mobile node's accounting and policy
   enforcement as the local mobility anchor is not in the path for that
   traffic and it will not be able to apply any traffic policies or do
   any accounting for those flows.

   This decision of path optimization SHOULD be based on the policy
   configured on the mobile access gateway, but enforced by the mobile
   node's local mobility anchor.  The specific details on how this is
   achieved are beyond of the scope of this document.

6.10.5.  Tunnel Management

   All the considerations mentioned in Section 5.6.1 for the tunnel
   management on the local mobility anchor apply for the mobile access
   gateway as well.

6.10.6.  Forwarding Rules

   Forwarding Packets sent to the Mobile Node's Home Network:

   o  On receiving a packet from the bi-directional tunnel established
      with the mobile node's local mobility anchor, the mobile access
      gateway MUST use the destination address of the inner packet for
      forwarding it on the interface where the destination network
      prefix is hosted.  The mobile access gateway MUST remove the outer
      header before forwarding the packet.  If the mobile access gateway
      cannot find the connected interface for that destination address,
      it MUST silently drop the packet.  For reporting an error in such
      a scenario, in the form of ICMP control message, the
      considerations from Generic Packet Tunneling specification [RFC-
      2473] must be applied.

   o  On receiving a packet from a correspondent node that is locally
      connected and which is destined to a mobile node that is on
      another locally connected access link, the mobile access gateway
      MUST check the configuration variable, EnableMAGLocalRouting, to
      ensure the mobile access gateway is allowed to route the packet
      directly to the mobile node.  If the mobile access gateway is not
      allowed to route the packet directly, it MUST route the packet
      through the bi-directional tunnel established between itself and
      the mobile node's local mobility anchor.  Otherwise, it can route
      the packet directly to the mobile node.

   Forwarding Packets Sent by the Mobile Node:

   o  On receiving a packet from a mobile node connected to its access
      link, the mobile access gateway MUST ensure that there is an
      established binding for that mobile node with its local mobility
      anchor before forwarding the packet directly to the destination or
      before tunneling the packet to the mobile node's local mobility
      anchor.

   o  On receiving a packet from a mobile node connected to its access
      link to a destination that is locally connected, the mobile access
      gateway MUST check the configuration variable,
      EnableMAGLocalRouting, to ensure the mobile access gateway is
      allowed to route the packet directly to the destination.  If the
      mobile access gateway is not allowed gateway, proper tunneling techniques have to route the packet directly,
      it MUST route the packet through be in place.
   Tunneling hides the bi-directional tunnel
      established between itself network topology and allows the mobile node's local mobility
      anchor.  Otherwise, it can route the packet directly
   IPv6 datagram to the
      destination.

   o  On receiving be encapsulated as a payload of another IPv6 packet from the mobile node connected to its access
      link,
   and to a destination that is not directly connected, the packet
      MUST be forwarded to routed between the local mobility anchor through and the bi-
      directional tunnel established mobile
   access gateway.  The Mobile IPv6 base specification [RFC-3775]
   defines the use of IPv6-over-IPv6 tunneling, between itself the home agent
   and the mobile
      node's node and this specification extends the use of the
   same tunneling mechanism between the local mobility anchor.  However, anchor and the packets that
   mobile access gateway.

   On most operating systems, tunnels are sent
      with the link-local implemented as a virtual
   point-to-point interface.  The source and the destination address MUST NOT be forwarded.  The
      format of
   the tunneled packet is shown below.  However, when using
      IPv4 transport, the format two end points of this virtual interface along with the tunneled
   encapsulation mode are specified for this virtual interface.  Any
   packet that is as described
      in [ID-IPV4-PMIP6].

        IPv6 header (src= Proxy-CoA, dst= LMAA  /* Tunnel Header */
           IPv6 header (src= MN-HoA, dst= CN )  /* Packet Header */
              Upper layer protocols             /* Packet Content*/

                 Figure 12: Tunneled Packets from MAG to LMA

6.11.  Supporting DHCPv6 based Address Configuration on the Access Link

   This section explains how Stateful Address Configuration using DHCPv6
   can be enabled on routed over this interface gets encapsulated with the access link attached
   outer header and the addresses as specified for that point to point
   tunnel interface.  For creating a point to point tunnel to any local
   mobility anchor, the mobile access gateway
   and how may implement a mobile node attached to that link can obtain an tunnel
   interface with the source address
   from field set to its home network prefix using DHCPv6.

   o  For supporting Stateful Address Configuration using DHCPv6, the
      DHCPv6 relay agent [RFC-3315] service MUST be enabled on each of
      the access links in the Proxy Mobile IPv6 domain.  Further, as
      specified in Section 20 [RFC-3315], Proxy-CoA address
   and the relay agent should be
      configured to use a list of destination addresses, which MAY
      include unicast addresses, the All_DHCP_Servers multicast address,
      or other addresses selected by address field set to the network administrator.

   o LMA address.

   The DHCPv6 server in following are the Proxy Mobile IPv6 domain supported packet encapsulation modes that can
   be
      configured with a list of prefix pools (P1, P2, ..., Pn).  Each
      one of these prefix pools corresponds to a home network prefix
      that a used by the mobile access gateway and the local mobility anchor allocates to a
   for routing mobile node node's IPv6 datagrams.

   o  IPv6-In-IPv6 - IPv6 datagram encapsulated in that
      domain.  However, the DHCPv6 server will not know the relation
      between a given address pool and a mobile node to which the
      corresponding prefix is allocated.  It just views these pools as
      prefixes hosted an IPv6 packet [RFC-
      2473].

   o  IPv6-In-IPv4 - IPv6 datagram encapsulation in an IPv4 packet.  The
      details on different links how this mode is negotiated is specified in that domain. [ID-IPV4-
      PMIP6].

   o  When  IPv6-In-IPv4-UDP - IPv6 datagram encapsulation in an IPv4 UDP
      packet.  This mode is specified in [ID-IPV4-PMIP6].

6.10.3.  Local Routing

   If there is data traffic between a visiting mobile node sends and a DHCPv6 request message,
   correspondent node that is locally attached to an access link
   connected to the DHCP relay
      agent function on mobile access gateway, the mobile access link will set gateway MAY
   optimize on the link-address field
      in delivery efforts by locally routing the DHCP message packets and
   by not reverse tunneling them to an address the mobile node's local mobility
   anchor.  The configuration variable, EnableMAGLocalRouting MAY be
   used for controlling this aspect.  However, in some systems, this may
   have an implication on the mobile node's home
      network prefix, so accounting and policy
   enforcement as to provide a prefix hint to the DHCP Server local mobility anchor is not in the path for that
   traffic and it will not be able to apply any traffic policies or do
   any accounting for those flows.

   This decision of path optimization SHOULD be based on the address pool selection.  The DHCP server policy
   configured on receiving the
      request from mobile access gateway, but enforced by the mobile node, will allocate an address from
   node's local mobility anchor.  The specific details on how this is
   achieved are beyond of the
      prefix pool present scope of this document.

6.10.4.  Tunnel Management

   All the considerations mentioned in Section 5.6.1 for the link-address field of tunnel
   management on the request. local mobility anchor apply for the mobile access
   gateway as well.

6.10.5.  Forwarding Rules

   Forwarding Packets sent to the Mobile Node's Home Network:

   o  Once  On receiving a packet from the bi-directional tunnel established
      with the mobile node's local mobility anchor, the mobile node obtains an access
      gateway MUST use the destination address and moves to a different
      link and sends a DHCP request, of the DHCP relay agent inner packet for
      forwarding it on the new
      link will set interface where the destination network
      prefix hint in is hosted.  The mobile access gateway MUST remove the DHCP messages to outer
      header before forwarding the packet.  If the mobile
      node's home network prefix.  The DHCP server will identify access gateway
      cannot find the
      client from connected interface for that destination address,
      it MUST silently drop the Client-DUID option and present packet.  For reporting an error in such
      a scenario, in the request and
      will allocate form of ICMP control message, the same address as before.
      considerations from Generic Packet Tunneling specification [RFC-
      2473] must be applied.

   o  The DHCP based address configuration  On receiving a packet from a correspondent node that is not recommended for
      deployments where the local mobility anchor locally
      connected and which is destined to a mobile node that is on
      another locally connected access link, the mobile access
      gateways are located in different administrative domains.  For
      this gateway
      MUST check the configuration variable, EnableMAGLocalRouting, to work, all
      ensure the mobile access gateways in gateway is allowed to route the
      Proxy Mobile IPv6 domain should be able packet
      directly to ensure that the DHCP
      requests from a given mobile node anchored on any of node.  If the mobile access
      links in that domain, will always be handled by the same DHCP
      server.

   o  The DHCP server should be configured to offer low address lease
      times.  A lease time that gateway is too large prevents not
      allowed to route the packet directly, it MUST route the DHCP server
      from reclaiming packet
      through the address even after bi-directional tunnel established between itself and
      the mobile node's local mobility anchor
      deletes anchor.  Otherwise, it can route
      the mobile node's binding cache entry.

6.12.  Home Network Prefix Renumbering

   If packet directly to the mobile node's home network prefix gets renumbered or becomes
   invalid during node.

   Forwarding Packets Sent by the middle of Mobile Node:

   o  On receiving a mobility session, packet from a mobile node connected to its access
      link, the mobile access gateway MUST withdraw ensure that there is an
      established binding for that mobile node with its local mobility
      anchor before forwarding the prefix by sending a Router Advertisement on packet directly to the access link with zero prefix lifetime for destination or
      before tunneling the packet to the mobile node's home
   network prefix.  Also, the local mobility anchor and
      anchor.

   o  On receiving a packet from a mobile node connected to its access
      link to a destination that is locally connected, the mobile access
      gateway MUST delete check the routing state for that prefix.
   However, configuration variable,
      EnableMAGLocalRouting, to ensure the specific details on how mobile access gateway is
      allowed to route the local mobility anchor
   notifies packet directly to the destination.  If the
      mobile access gateway about is not allowed to route the packet directly,
      it MUST route the packet through the bi-directional tunnel
      established between itself and the mobile node's home
   network prefix renumbering are outside local mobility
      anchor.  Otherwise, it can route the scope of this document.

6.13.  Mobile Node Detachment Detection and Resource Cleanup

   Before sending packet directly to the
      destination.

   o  On receiving a Proxy Binding Update message packet from the mobile node connected to its access
      link, to a destination that is not directly connected, the packet
      MUST be forwarded to the local mobility anchor for extending through the lifetime bi-
      directional tunnel established between itself and the mobile
      node's local mobility anchor.  However, the packets that are sent
      with the link-local source address MUST NOT be forwarded.  The
      format of a currently existing binding the tunneled packet is shown below.  Additionally, when
      using IPv4 transport, the format of
   a mobile node, the tunneled packet is as
      described in [ID-IPV4-PMIP6].

        IPv6 header (src= Proxy-CoA, dst= LMAA  /* Tunnel Header */
           IPv6 header (src= MN-HoA, dst= CN )  /* Packet Header */
              Upper layer protocols             /* Packet Content*/
                 Figure 13: Tunneled Packets from MAG to LMA

6.11.  Supporting DHCPv6 based Address Configuration on the Access Link

   This section explains how Stateful Address Configuration using DHCPv6
   can be enabled on the access link attached to a mobile access gateway MUST make sure the
   and how a mobile node is still attached to the connected that link by can obtain an address
   from its home network prefix using some reliable
   method.  If DHCPv6.

   o  For supporting Stateful Address Configuration using DHCPv6, the
      DHCPv6 relay agent [RFC-3315] service MUST be enabled on each of
      the mobile access gateway cannot predictably detect links in the
   presence Proxy Mobile IPv6 domain.  Further, as
      specified in Section 20 [RFC-3315], the relay agent should be
      configured to use a list of destination addresses, which MAY
      include unicast addresses, the mobile node on All_DHCP_Servers multicast address,
      or other addresses selected by the connected link, it MUST NOT
   attempt to extend network administrator.

   o  The DHCPv6 server in the registration lifetime Proxy Mobile IPv6 domain can be
      configured with a list of prefix pools (P1, P2, ..., Pn).  Each
      one of the these prefix pools corresponds to a home network prefix
      that a local mobility anchor allocates to a mobile node.
   Further, node in such scenario, the mobile access gateway SHOULD terminate that
      domain.  However, the binding of DHCPv6 server will not know the relation
      between a given address pool and a mobile node by sending a Proxy Binding Update
   message to which the mobile node's local mobility anchor with lifetime
   value set to 0.
      corresponding prefix is allocated.  It MUST also remove any local state such just views these pools as the
   Binding Update List created for
      prefixes hosted on different links in that mobile node.

   The specific detection mechanism of the loss of domain.

   o  When a visiting mobile node on sends a DHCPv6 request message, the connected link is specific to DHCP relay
      agent function on the access link between the
   mobile node and will set the mobile access gateway and is outside link-address field
      in the scope of
   this document.  Typically, there are various link-layer specific
   events specific DHCP message to each access technology that an address in the mobile access
   gateway can depend on node's home
      network prefix, so as to provide a prefix hint to the DHCP Server
      for detecting the node loss.  In general, address pool selection.  The DHCP server on receiving the
      request from the mobile access gateway can depend on one or more of node, will allocate an address from the following
   methods for
      prefix pool present in the detection presence link-address field of the request.

   o  Once the mobile node obtains an address and moves to a different
      link and sends a DHCP request, the DHCP relay agent on the
   connected link:

   o  Link-layer event specific new
      link will set the prefix hint in the DHCP messages to the access technology

   o  PPP Session termination event on point-to-point link types

   o  IPv6 Neighbor Unreachability Detection event mobile
      node's home network prefix.  The DHCP server will identify the
      client from IPv6 stack the Client-DUID option and present in the request and
      will allocate the same address as before.

   o  Notification event from  The DHCP based address configuration is not recommended for
      deployments where the local mobility anchor

6.14.  Allowing network access to other IPv6 nodes

   In some Proxy Mobile IPv6 deployments, network operators may want to
   provision and the mobile access gateway to offer network-based mobility
   management service only
      gateways are located in different administrative domains.  For
      this configuration to some visiting work, all the mobile nodes and enable just
   regular IP access to some other nodes.  This requires gateways in the network to
   have control on when to enable network-based mobility management
   service to a mobile node and when to enable regular
      Proxy Mobile IPv6 access.
   This specification does not disallow such configuration.

   Upon detecting domain should be able to ensure that the DHCP
      requests from a given mobile node anchored on its access link and after policy
   considerations, any of the mobile access gateway MUST determine if network-
   based mobility management service
      links in that domain, will always be handled by the same DHCP
      server.

   o  The DHCP server should be offered configured to offer low address lease
      times.  A lease time that is too large prevents the DHCP server
      from reclaiming the address even after the local mobility anchor
      deletes the mobile
   node. node's binding cache entry.

6.12.  Home Network Prefix Renumbering

   If the mobile node is entitled for network-based mobile node's home network prefix gets renumbered or becomes
   invalid during the middle of a mobility
   management service, then session, the mobile access
   gateway must ensure MUST withdraw the
   mobile node believes it is prefix by sending a Router Advertisement on its home link, as explained in various
   sections of this specification.

   If
   the mobile node is not entitled access link with zero prefix lifetime for the network-based mobility
   management service, as determined from mobile node's home
   network prefix.  Also, the policy considerations, local mobility anchor and the mobile
   access gateway MAY choose to offer regular IPv6 access to MUST delete the
   mobile node and in such scenario routing state for that prefix.
   However, the normal IPv6 considerations
   apply.  If IPv6 access is enabled, specific details on how the mobile node SHOULD be able to
   obtain an IPv6 address using normal IPv6 address configuration
   procedures.  The obtained address must be from a local visitor
   network prefix.  This essentially ensures that mobility anchor
   notifies the mobile access gateway functions as a normal access router to a mobile node attached
   to its access link and with out impacting its host-based mobility
   protocol operation.

7.  Mobile Node Operation

   This non-normative section explains about the mobile node's operation in a
   Proxy home
   network prefix renumbering are outside the scope of this document.

6.13.  Mobile IPv6 domain.

7.1.  Moving into Node Detachment Detection and Resource Cleanup

   Before sending a Proxy Mobile IPv6 Domain

   Once Binding Update message to the local mobility
   anchor for extending the lifetime of a currently existing binding of
   a mobile node, the mobile access gateway MUST make sure the mobile
   node enters a Proxy Mobile IPv6 domain and attaches is still attached to
   an access network, the connected link by using some reliable
   method.  If the mobile access gateway on the access link
   detects cannot predictably detect the attachment
   presence of the mobile node and completes on the connected link, it MUST NOT
   attempt to extend the binding registration with lifetime of the mobile node's local mobility anchor.  If the
   binding update operation is successfully performed, node.
   Further, in such scenario, the mobile access gateway will create SHOULD terminate
   the required state and setup binding of the data path for mobile node by sending a Proxy Binding Update
   message to the mobile node's data traffic.

   If local mobility anchor with lifetime
   value set to 0.  It MUST also remove any local state such as the
   Binding Update List entry created for that mobile node.

   The specific detection mechanism of the loss of a visiting mobile
   node is IPv6 enabled, on attaching the connected link is specific to the access link,
   it will typically send Router Solicitation message [RFC-4861].  The link between the
   mobile node and the mobile access gateway on and is outside the access link will respond scope of
   this document.  Typically, there are various link-layer specific
   events specific to the Router
   Solicitation message with a Router Advertisement.  The Router
   Advertisement will have each access technology that the mobile node's home network prefix,
   default-router address and other address configuration parameters.

   If access
   gateway can depend on for detecting the node loss.  In general, the
   mobile access gateway can depend on one or more of the access link, receives a Router
   Solicitation message from following
   methods for the detection presence of the mobile node, before it completed node on the
   signaling with
   connected link:

   o  Link-layer event specific to the access technology

   o  PPP Session termination event on point-to-point link types
   o  IPv6 Neighbor Unreachability Detection event from IPv6 stack

   o  Notification event from the mobile node's local mobility anchor, anchor

6.14.  Allowing network access to other IPv6 nodes

   In some Proxy Mobile IPv6 deployments, network operators may want to
   provision the mobile access gateway may not know the to offer network-based mobility
   management service only to some visiting mobile node's home network prefix nodes and
   may not be able enable just
   regular IP access to emulate some other nodes.  This requires the network to
   have control on when to enable network-based mobility management
   service to a mobile node's home link node and when to enable regular IPv6 access.
   This specification does not disallow such configuration.

   Upon detecting a mobile node on the its access
   link.  In such scenario, link and after policy
   considerations, the mobile node may notice a slight delay
   before it receives a Router Advertisement message. access gateway MUST determine if network-
   based mobility management service should be offered to that mobile
   node.  If the received Router Advertisement has the Managed Address
   Configuration flag set, mobile node is entitled for network-based mobility
   management service, then the mobile node, as it would normally do,
   will send a DHCPv6 Request [RFC-3315].  The DHCP relay service
   enabled on that access link will gateway must ensure the
   mobile node will obtain
   its IPv6 address as a lease from believes it is on its home network prefix. link, as explained in various
   sections of this specification.

   If the received Router Advertisement does mobile node is not have entitled for the Managed
   Address Configuration flag set and if network-based mobility
   management service, as determined from the policy considerations, the
   mobile access gateway MAY choose to offer regular IPv6 access to the
   mobile node and in such scenario the normal IPv6 considerations
   apply.  If IPv6 access is allowed to
   use an autoconfigured address, enabled, the mobile node will SHOULD be able to
   obtain an IPv6 address using an interface identifier generated as per the
   Autoconf specification [RFC-4862] or as per the Privacy Extensions
   specification [RFC-4941].

   If the mobile node is IPv4 enabled and if the network permits, it
   will be able to obtain the IPv4 normal IPv6 address configuration for the
   connected interface by using DHCP [RFC-2131].
   procedures.  The details related to
   IPv4 support is specified in the companion document [ID-IPV4-PMIP6].

   Once the obtained address configuration is complete, must be from a local visitor
   network prefix.  This essentially ensures that the mobile node can
   continue to use this address configuration as long access
   gateway functions as it is a normal access router to a mobile node attached
   to its access link and with out impacting its host-based mobility
   protocol operation.

7.  Mobile Node Operation

   This non-normative section explains the network that is mobile node's operation in the scope of that a
   Proxy Mobile IPv6 domain.

7.2.  Roaming in the

7.1.  Moving into a Proxy Mobile IPv6 Domain

   After obtaining the address configuration in the Proxy Mobile IPv6
   domain, as the mobile node moves and changes its point of attachment
   from one mobile access gateway to the other, it can still continue to
   use the same address configuration.  As long as the attached access
   network is in the scope of that Proxy Mobile IPv6 domain, the mobile
   node will always detect the same link, where it obtained its initial
   address configuration.  If the mobile node performs DHCP operation,
   it will always obtain the same address as before.

   However, the

   When a mobile node will always detect enters a new default-router on
   each connected link, but still advertising Proxy Mobile IPv6 domain and attaches to
   an access network, the mobile node's home
   network prefix as access gateway on the on-link prefix access link
   detects the attachment of the mobile node and with completes the other configuration
   parameters consistent binding
   registration with its home link properties.

7.3.  IPv6 Host Protocol Parameters

   This specification does not require any changes to the mobile node's
   IP stack.  It assumes local mobility anchor.  If the mobile node to be a normal IPv4/IPv6 node,
   with its protocol
   binding update operation consistent with is successfully performed, the respective
   specifications.

   However, for achieving protocol efficiency mobile access
   gateway will create the required state and setup the data path for faster hand-offs,
   implementations may choose to adjust
   the following IPv6 operating
   parameters on mobile node's data traffic.

   If the mobile node be adjusted is IPv6 enabled, on attaching to the below recommended
   values.

   Lower Default-Router List Cache Time-out:

   As per access link,
   it will typically send Router Solicitation message [RFC-4861].  The
   mobile access gateway on the base IPv6 specification [RFC-4861], each IPv6 host is
   required access link will respond to maintain certain host data structures including a
   Default-Router list.  This is the list of on-link routers that have
   sent Router
   Solicitation message with a Router Advertisement.  The Router
   Advertisement messages will have the mobile node's home network prefix,
   default-router address and are eligible to be default
   routers other address configuration parameters.

   If the mobile access gateway on that link.  The Router Lifetime field in the received access link, receives a Router Advertisement defines
   Solicitation message from the life of this entry.

   In case of Proxy Mobile IPv6, when a mobile node moves from one link
   to another, node, before it completed the source address of
   signaling with the received Router Advertisement
   messages advertising mobile node's local mobility anchor, the mobile
   access gateway may not know the mobile node's home network prefix will be
   from a different link-local address and thus making
   may not be able to emulate the mobile node
   believe that there is a new default-router node's home link on the access
   link.  It is
   important that  In such scenario, the mobile node uses the newly learnt default-router
   and not may notice a slight delay
   before it receives a Router Advertisement message.

   If the previously known default-router.  The mobile node must
   update its default-router list with received Router Advertisement has the new default router entry and
   must age out Managed Address
   Configuration flag set, the previously learnt default router entry from its
   cache, just mobile node, as specified in Section 6.3.5 [RFC-4861].  This action it would normally do,
   will help in minimizing packet losses during a hand off switch.

   On detecting send a reachability problem, DHCPv6 Request [RFC-3315].  The DHCP relay service
   enabled on that access link will ensure the mobile node will certainly
   detect obtain
   its IPv6 address as a lease from its home network prefix.

   If the default-router loss by performing received Router Advertisement does not have the Neighbor
   Unreachability Detection procedure, but it is important that Managed
   Address Configuration flag set and if the mobile node times out the previous default router entry at the
   earliest.  If a given IPv6 host implementation has the provision to
   adjust these flush timers, still conforming to the base IPv6 ND
   specification, it is desirable to keep the flush-timers allowed to suit the
   above consideration.

   In access network where SEND [RFC-3971] is not deployed,
   use an autoconfigured address, the mobile
   access gateway may withdraw the previous default-router entry, by
   sending a Router Advertisement node will be able to obtain
   an IPv6 address using an interface identifier generated as per the
   Autoconf specification [RFC-4862] or as per the link-local address that of Privacy Extensions
   specification [RFC-4941].

   If the previous mobile access gateway node is IPv4 enabled and with if the Router Lifetime field
   set to value 0, then this network permits, it
   will force be able to obtain the flush of IPv4 address configuration as specified in
   the Previous
   Default-Router entry from companion document [ID-IPV4-PMIP6].

   Once the address configuration is complete, the mobile node's cache.  This certainly
   requires context-transfer mechanisms node can
   continue to use this address configuration as long as it is attached
   to the network that is in place for notifying the link-
   local address scope of that Proxy Mobile IPv6 domain.

7.2.  Roaming in the default-router on Proxy Mobile IPv6 Domain

   After obtaining the previous link to address configuration in the Proxy Mobile IPv6
   domain, as the mobile node moves and changes its point of attachment
   from one mobile access gateway on to the new link.

   There are other solutions possible for this problem, including other, it can still continue to
   use the
   assignment of a fixed link-local same address for all configuration.  As long as the mobility
   entities attached access
   network is in a the scope of that Proxy Mobile IPv6 domain and domain, the mobile
   node will always detect the same link, where SEND [RFC-3971] is
   not deployed.  In such scenario, it obtained its initial
   address configuration.  If the mobile node is not required to
   update performs DHCP operation,
   it will always obtain the default-router entry. same address as before.

   However, this is an implementation
   choice and has no bearing the mobile node will always detect a new default-router on
   each connected link, but still advertising the protocol interoperability.
   Implementations are free to adopt mobile node's home
   network prefix as the best approach that suits their
   target deployments. on-link prefix and with the other configuration
   parameters consistent with its home link properties.

8.  Message Formats

   This section defines extensions to the Mobile IPv6 [RFC-3775]
   protocol messages.

8.1.  Proxy Binding Update Message

       0               1               2               3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                                      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                      |            Sequence #         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |A|H|L|K|M|R|P|  Reserved       |            Lifetime           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      .                                                               .
      .                        Mobility options                       .
      .                                                               .

      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   A Binding Update message that is sent by a mobile access gateway to a
   local mobility anchor is referred to as the "Proxy Binding Update"
   message.  A new flag (P) is included in the Binding Update message.
   The rest of the Binding Update message format remains the same as
   defined in [RFC-3775] and with the additional (R) and (M) flags as
   specified in [RFC-3963] and [RFC-4140] respectively.

   Proxy Registration Flag (P)
      A new flag (P) is included in the Binding Update message to
      indicate to the local mobility anchor that the Binding Update
      message is a proxy registration.  The flag MUST be set to the
      value of 1 for proxy registrations and MUST be set to 0 for direct
      registrations sent by a mobile node.

   Mobility Options

      Variable-length field of such length that the complete Mobility
      Header is an integer multiple of 8 octets long.  This field
      contains zero or more TLV-encoded mobility options.  The encoding
      and format of defined options are described in Section 6.2 [RFC-
      3775].  The local mobility anchor MUST ignore and skip any options
      which it does not understand.

      As per this specification, the following mobility options are
      valid in a Proxy Binding Update message:

         Mobile Node Identifier option

         Home Network Prefix option

         Link-local Address

         Handoff Indicator option

         Mobile Node Identifier Option

         Access Technology Type option

         Timestamp option

         Mobile Node Interface Identifier option

         Timestamp

         Link-local Address option

   For descriptions of other fields present in this message, refer to
   section 6.1.7 [RFC-3775].

8.2.  Proxy Binding Acknowledgement Message

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                                      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                      |   Status      |K|R|P|Reserved |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Sequence #            |           Lifetime            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      .                                                               .
      .                        Mobility options                       .
      .                                                               .
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   A Binding Acknowledgement message that is sent by a local mobility
   anchor to a mobile access gateway is referred to as the "Proxy
   Binding Acknowledgement" message.  A new flag (P) is included in the
   Binding Acknowledgement message.  The rest of the Binding
   Acknowledgement message format remains the same as defined in [RFC-
   3775] and with the additional (R) and (M) flags as specified in [RFC-
   3963] and [RFC-4140] respectively.

   Proxy Registration Flag (P)

      A new flag (P) is included in the Binding Acknowledgement message
      to indicate that the local mobility anchor that processed the
      corresponding Proxy Binding Update message supports proxy
      registrations.  The flag is set only if the corresponding Proxy
      Binding Update had the Proxy Registration Flag (P) set to value of
      1.

   Mobility Options

      Variable-length field of such length that the complete Mobility
      Header is an integer multiple of 8 octets long.  This field
      contains zero or more TLV-encoded mobility options.  The encoding
      and format of defined options are described in Section 6.2 [RFC-
      3775].  The mobile access gateway MUST ignore and skip any options
      which it does not understand.

      As per this specification, the following mobility options are
      valid in a Proxy Binding Acknowledgement message:

         Mobile Node Identifier option

         Home Network Prefix option

         Link-local Address option

         Mobile Node Identifier

         Handoff Indicator option

         Access Technology Type option

         Timestamp option

         Mobile Node Interface Identifier option

         Timestamp

         Link-local Address option

   Status

      8-bit unsigned integer indicating the disposition of the Proxy
      Binding Update.  Values of the Status field less than 128 indicate
      that the Proxy Binding Update was accepted by the local mobility
      anchor.  Values greater than or equal to 128 indicate that the
      binding registration was rejected by the local mobility anchor.
      Section 8.8 8.9 defines the Status values that can used in Proxy
      Binding Acknowledgement message.

   For descriptions of other fields present in this message, refer to
   the section 6.1.8 [RFC-3775].

8.3.  Home Network Prefix Prefix Option

   A new option, Home Network Prefix Option is defined for using it in
   the Proxy Binding Update and Proxy Binding Acknowledgement messages
   exchanged between a local mobility anchor and a mobile access
   gateway.  This option is used for exchanging the mobile node's home
   network prefix information.

   The Home Network Prefix Option has an alignment requirement of 8n+4.
   Its format is as follows:

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Type     |   Length      |   Reserved    | Prefix Length |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                                                               +
      |                                                               |
      +                    Home Network Prefix                        +
      |                                                               |
      +                                                               +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Type
           <IANA>

       Length

           8-bit unsigned integer indicating the length of the option
           in octets, excluding the type and length fields. This field
           MUST be set to 18.

       Reserved (R)

           This 8-bit field is unused for now.  The value MUST be
           initialized to 0 by the sender and MUST be ignored by the
           receiver.

       Prefix Length

           8-bit unsigned integer indicating the prefix length of the
           IPv6 prefix contained in the option.

       Home Network Prefix

           A sixteen-byte field containing the mobile node's IPv6 Home
           Network Prefix.

8.4.  Handoff Indicator Option

   A new option, Home Network Prefix Handoff Indicator Option is defined for using it in the
   Proxy Binding Update and Proxy Binding Acknowledgement messages
   exchanged between a local mobility anchor and a mobile access
   gateway.  This option is used for exchanging the mobile node's home
   network prefix information.
   handoff related hints.

   The Home Network Prefix Handoff Indicator Option has an no alignment requirement of 8n+4. requirement.  Its
   format is as follows:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Type     |   Length      |  Reserved (R) | Prefix Length |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                                                               +
      |                                                               |
      +                    Home Network Prefix                        +
      |                                                               |
      +                                                               +
      |       HI      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Type
        <IANA>

    Length

        8-bit unsigned integer indicating the length of the option
        in octets, excluding the type and length fields. This field
        MUST be set to 18. 2.

    Reserved (R)

        This 8-bit field is unused for now.  The value MUST be
        initialized to 0 by the sender and MUST be ignored by the
        receiver.

       Prefix Length

    Handoff Indicator (HI)

        A 8-bit unsigned integer indicating field that specifies the prefix length type of handoff. The values
        (0 - 255) will be allocated and managed by IANA. The following
        values are currently reserved.

        0: Reserved
        1: Attachment over a new interface
        2: Handoff between two different interfaces of the
           IPv6 prefix contained in the option.

       Home Network Prefix

           A sixteen-byte field containing the mobile node's IPv6 Home
           Network Prefix.

8.4. node
        3: Handoff between mobile access gateways for the same interface
        4: Handoff state unknown
        5: Handoff state not changed (Re-registration)

8.5.  Access Technology Type Option

   A new option, Access Technology Type Option is defined for using it
   in the Proxy Binding Update and Proxy Binding Acknowledgement
   messages exchanged between a local mobility anchor and a mobile
   access gateway.  This option is used for exchanging the type of the
   access technology using which the mobile node is currently attached
   to the mobile access gateway.

   The Access Technology Type Option has no alignment requirement.  Its
   format is as follows:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      Type     |   Length      |   Acc Tech  Reserved (R) |  HI      ATT      | Reserved|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Type
         <IANA>

     Length

         8-bit unsigned integer indicating the length of the option
         in octets, excluding the type and length fields. This field
         MUST be set to 2.

    Access Technology Type (Acc Tech)

        A 8-bit field that specifies the access technology through
        which the mobile node is connected to the access link on the
        mobile access gateway.

        The values 0-255 will be allocated and managed by IANA. The
        following values are currently reserved for the below specified
        access technology types.

        0x00: Reserved
        0x01: Virtual
        0x02: PPP
        0x02: 802.3 (Ethernet)
        0x03: 802.11a
        0x04: 802.11b
        0x05: 802.11g
        0x06: 802.16e
        0x07: CDMA2000 1xEV-DO Release 0
        0x08: CDMA2000 1xEV-DO Revision A
        0x09: CDMA2000 1xEV-DO Revision B
        0x0a: 3GPP LTE

    Handoff Indicator (HI)

        A 3-bit field that specifies the type of handoff. The values
        (0-3) will be allocated and managed by IANA. The following
        values are currently reserved.

        0: Reserved
        1: Attachment over a new interface
        2: Handoff between interfaces
        3: Handoff between mobile access gateways for the same interface
        4: Handoff state unknown to 2.

     Reserved (R)

         This 5-bit 8-bit field is unused for now.  The value MUST be
         initialized to 0 by the sender and MUST be ignored by the
         receiver.

8.5.

     Access Technology Type (ATT)

         A 8-bit field that specifies the access technology through
         which the mobile node is connected to the access link on the
         mobile access gateway.

         The values (0 - 255) will be allocated and managed by IANA. The
         following values are currently reserved for the below specified
         access technology types.

         0: Reserved
         1: Virtual
         2: PPP
         3: 802.3 (Ethernet)
         4: 802.11a/b/g
         5: 802.16e

8.6.  Mobile Node Interface Identifier Option

   A new option, Mobile Node Interface Identifier Option is defined for
   using it in the Proxy Binding Update and Proxy Binding
   Acknowledgement messages exchanged between a local mobility anchor
   and a mobile access gateway.  This option is used for exchanging the
   mobile node's interface identifier.

   The format of the Interface Identifier option when the interface
   identifier is 8 bytes is shown below.  When the size is different,
   the option MUST be aligned appropriately, as per mobility option
   alignment requirements specified in [RFC-3775].

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Type        |    Length     |          Reserved             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    +                     Interface Identifier                      +
    .                              ...                              .
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Type
         <IANA>

     Length
         8-bit unsigned integer indicating the length of the option
         in octets, excluding the type and length fields. This field
         MUST be set to 10.

     Reserved

         This field is unused for now.  The value MUST be initialized to
         0 by the sender and MUST be ignored by the receiver.

     Interface Identifier

         A variable length field containing the mobile node's interface
         identifier.

8.6.

         The content and format of this field (including byte and bit
         ordering) is as specified in Section 4.6 [RFC-4861] for
         carrying Link-Layer Address.

8.7.  Link-local Address Option

   A new option, Link-local Address Option is defined for using it in
   the Proxy Binding Update and Proxy Binding Acknowledgement messages
   exchanged between a local mobility anchor and a mobile access
   gateway.  This option is used for exchanging the mobile node's link-
   local address.

   The Link-local Address option has an alignment requirement of 8n+6.
   Its format is as follows:

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                                      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                      |   Type        |    Length     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                                                               +
      |                                                               |
      +                  Link-local Address                           +
      |                                                               |
      +                                                               +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Type
           <IANA>

       Length

           8-bit unsigned integer indicating the length of the option
           in octets, excluding the type and length fields. This field
           MUST be set to 16.

       Link-local Address

           A sixteen-byte field containing the mobile node's link-local
           address.

8.7.

8.8.  Timestamp Option

   A new option, Timestamp Option is defined for use in the Proxy
   Binding Update and Proxy Binding Acknowledgement messages.

   The Timestamp option has an alignment requirement of 8n+2.  Its
   format is as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   |      Type     |   Length      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                          Timestamp                            +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Type
        <IANA>

    Length

        8-bit unsigned integer indicating the length in octets of
        the option, excluding the type and length fields.  The value
        for this field MUST be set to 8.

    Timestamp

      A 64-bit unsigned integer field containing a timestamp.  The value
      indicates the number of seconds since January 1, 1970, 00:00 UTC,
      by using a fixed point format.  In this format, the integer number
      of seconds is contained in the first 48 bits of the field, and the
      remaining 16 bits indicate the number of 1/65536 fractions of a
      second.

8.8.

8.9.  Status Values

   This document defines the following new Status values for use in
   Proxy Binding Acknowledgement message.  These values are to be
   allocated from the same number space, as defined in Section 6.1.8
   [RFC-3775].

   Status values less than 128 indicate that the Proxy Binding Update
   request was accepted by the local mobility anchor.  Status values
   greater than 128 indicate that the Proxy Binding Update was rejected
   by the local mobility anchor.

   PROXY_REG_NOT_ENABLED:

      Proxy Registration registration not enabled for the mobile node. node

   MAG_NOT_AUTHORIZED_FOR_PROXY_REG:

      The mobile access gateway is not authorized to send proxy binding.
      updates. binding
      registrations

   NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX

      The mobile node is not authorized for the requesting home network
      prefix.
      prefix

   TIMESTAMP_MISMATCH:

      Invalid timestamp value in the received Proxy Binding Update
      message (the clocks are out of sync). sync)

   TIMESTAMP_LOWER_THAN_PREV_ACCEPTED:

      The timestamp value in the received Proxy Binding Update message is lower than the previously accepted value. value

   MISSING_HOME_NETWORK_PREFIX_OPTION

      Missing mobile node home network prefix option. option

   MISSING_MN_IDENTIFIER_OPTION:

      Missing mobile node identifier in the Proxy Binding Update
      message. option

   MISSING_HANDOFF_INDICATOR_OPTION

      Missing handoff indicator option

   MISSING_ACCESS_TECH_TYPE_OPTION

      Missing mobile node's access technology type in the Proxy Binding
      Update message. option

   Additionally, the following Status values defined in [RFC-3775] can
   also be used in Proxy Binding Acknowledgement message.

      0 Proxy Binding Update accepted

      128 Reason unspecified

      129 Administratively prohibited

      130 Insufficient resources

      133 Not local mobility anchor for this mobile node

9.  Protocol Configuration Variables

   The local mobility anchor MUST allow the following variables to be
   configured by the system management.

   MinDelayBeforeBCEDelete

      This variable specifies the amount of time in milliseconds the
      local mobility anchor MUST wait before it deletes a Binding Cache
      entry of a mobile node, upon receiving a Proxy Binding Update
      message from a mobile access gateway with a lifetime value of 0.
      During this wait time, if the local mobility anchor receives a
      Proxy Binding Update for the same mobility binding, with lifetime
      value greater than 0, then it must update the binding cache entry
      with the accepted binding values.  By the end of this wait-time,
      if the local mobility anchor did not receive any valid Proxy
      Binding Update message for that mobility binding, it MUST delete
      the Binding Cache entry.  This delay essentially ensures a mobile
      node's Binding Cache entry is not deleted too quickly and allows
      some time for the new mobile access gateway to complete the
      signaling for the mobile node.

      The default value for this variable is 10000 milliseconds.

   MinDelayBeforeNewBCEAssign

   MaxDelayBeforeNewBCEAssign

      This variable specifies the amount of time in milliseconds the
      local mobility anchor MUST wait for the de-registration message
      for an existing mobility session before it decides to create a new
      mobility session.

      The default value for this variable is 500 milliseconds.

   TimestampValidityWindow

      This variable specifies the maximum amount of time difference in
      milliseconds between the timestamp in the received Proxy Binding
      Update message and the current time-of-day on the local mobility
      anchor, that is allowed by the local mobility anchor for the
      received message to be considered valid.

      The default value for this variable is 300 milliseconds.  This
      variable MUST be adjusted to suit the deployments.

   The mobile access gateway MUST allow the following variables to be
   configured by the system management.

   EnableMAGLocalrouting

      This flag indicates whether or not the mobile access gateway is
      allowed to enable local routing of the traffic exchanged between a
      visiting mobile node and a correspondent node that is locally
      connected to one of the interfaces of the mobile access gateway.
      The correspondent node can be another visiting mobile node as
      well, or a local fixed node.

      The default value for this flag is set to "FALSE", indicating that
      the mobile access gateway MUST reverse tunnel all the traffic to
      the mobile node's local mobility anchor.

      When the value of this flag is set to "TRUE", the mobile access
      gateway MUST route the traffic locally.

      This aspect of local routing MAY be defined as policy on a per
      mobile basis and when present will take precedence over this flag.

   MinPBUReplyTime

      This variable specifies the amount of time in milliseconds the
      mobile access gateway SHOULD wait for the reply message for the
      Proxy Binding Update request that it sent to the local mobility
      anchor.

      The default value for this variable is 2000 milliseconds.

10.  IANA Considerations

   This document defines five six new Mobility Header Options, options, the Home
   Network Prefix option, Handoff Indicator option, Access Technology
   Type option, Interface Identifier option, Link-local Address option
   and Timestamp option.  These options are described in Sections 8.3, 8.4, 8.5, 8.6 and 8.7
   respectively. Section 8.  The
   Type value for these options needs to be assigned from the same
   numbering space as allocated for the other mobility options, as
   defined in [RFC-3775].

   The Mobility Header Option, Access Technology Type option defined in Section 8.4 8.5 of this
   document introduces a new Access Technology type numbering space,
   where the values from 0 to 5 have been reserved by this document.
   Approval of new Access Technology type numbers are to be made through
   IANA Expert Review.

   This document also defines new Binding Acknowledgement status values
   as described in Section 8.8. 8.9.  The status values MUST be assigned from
   the same number space used for Binding Acknowledgement status values,
   as defined in [RFC-3775].  The allocated values for each of these
   status values MUST be greater than 128.

11.  Security Considerations

   The potential security threats against any network-based mobility
   management protocol are described in [RFC-4832].  This section
   explains how Proxy Mobile IPv6 protocol defends itself against those
   threats.

   Proxy Mobile IPv6 protocol requires the signaling messages, Proxy
   Binding Update and Proxy Binding Acknowledgement, exchanged between
   the mobile access gateway and the local mobility anchor to be
   protected using IPsec, using the established security association
   between them.  This essentially eliminates the threats related to the
   impersonation of the mobile access gateway or the local mobility
   anchor.

   This specification allows a mobile access gateway to send binding
   registration messages on behalf of a mobile node.  If proper
   authorization checks are not in place, a malicious node may be able
   to hijack a mobile node's session or may carry out a denial-of-
   service attack.  To prevent this attack, this specification requires
   the local mobility anchor to allow only authorized mobile access
   gateways that are part of that Proxy Mobile IPv6 domain to send
   binding registration messages on behalf of a mobile node.

   To eliminate the threats on the interface between the mobile access
   gateway and the mobile node, this specification requires an
   established trust between the mobile access gateway and the mobile
   node and to authenticate and authorize the mobile node before it is
   allowed to access the network.  Further, the established
   authentication mechanisms enabled on that access link will ensure
   that there is a secure binding between the mobile node's identity and
   its link-layer address.  The mobile access gateway will definitively
   identify the mobile node from the packets that it receives on that
   access link.

   To address the threat related to a compromised mobile access gateway,
   the local mobility anchor, before accepting a Proxy Binding Update
   message for a given mobile node, may ensure that the mobile node is
   definitively attached to the mobile access gateway that sent the
   proxy binding registration request.  This may be accomplished by
   contacting a trusted entity which is able to track the mobile node's
   current point of attachment.  However, the specific details of the
   actual mechanisms for achieving this is outside the scope of this
   document.

12.  Acknowledgements

   The authors would like to specially thank Julien Laganier, Christian
   Vogt, Pete McCann, Brian Haley, Ahmad Muhanna, JinHyeock Choi for
   their thorough review of this document.

   The authors would also like to thank Alex Petrescu, Alice Qinxia,
   Alper Yegin, Ashutosh Dutta, Behcet Sarikaya, Fred Templin, Genadi
   Velev, George Tsirtsis, Gerardo Giaretta, Henrik Levkowetz, Hesham
   Soliman, James Kempf, Jari Arkko, Jean-Michel Combes, John Zhao,
   Jong-Hyouk Lee, Jonne Soininen, Jouni Korhonen, Kalin Getov, Kilian
   Weniger, Marco Liebsch, Mohamed Khalil, Nishida Katsutoshi, Phil
   Roberts, Ryuji Wakikawa, Sangjin Jeong, Suresh Krishnan, Ved Kafle,
   Vidya Narayanan, Youn-Hee Han and many others for their passionate
   discussions in the working group mailing list on the topic of
   localized mobility management solutions.  These discussions
   stimulated much of the thinking and shaped the draft to the current
   form.  We acknowledge that !

   The authors would also like to thank Ole Troan, Akiko Hattori, Parviz
   Yegani, Mark Grayson, Michael Hammer, Vojislav Vucetic, Jay Iyer and
   Tim Stammers for their input on this document.

13.  References

13.1.  Normative References

   [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
   Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC-2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
   IPv6 Specification", RFC 2473, December 1998.

   [RFC-3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and
   M.Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
   RFC 3315, July 2003.

   [RFC-3775] Johnson, D., Perkins, C., Arkko, J., "Mobility Support in
   IPv6", RFC 3775, June 2004.

   [RFC-3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
   Thubert, "Network Mobility (NEMO) Basic Support Protocol", RFC 3963,
   January 2005.

   [RFC-4283] Patel, A., Leung, K., Khalil, M., Akhtar, H., and K.
   Chowdhury, "Mobile Node Identifier Option for Mobile IPv6", RFC 4283,
   November 2005.

   [RFC-4301] Kent, S. and Atkinson, R., "Security Architecture for the
   Internet Protocol", RFC 4301, December 2005.

   [RFC-4303] Kent, S. "IP Encapsulating Security Protocol (ESP)", RFC
   4303, December 2005.

   [RFC-4861] Narten, T., Nordmark, E. and W. Simpson, Soliman, H.,
   "Neighbor Discovery for IP Version 6 (IPv6)", RFC 4861, September
   2007.

13.2.  Informative References

   [RFC-1661] Simpson, W., Ed., "The Point-To-Point Protocol (PPP)", STD
   51, RFC 1661, July 1994.

   [RFC-2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
   2131, March 1997.

   [RFC-3971] Arkko, J., Ed., Kempf, J., Sommerfeld, B., Zill, B., and
   P. Nikander, "SEcure Neighbor Discovery (SEND)", RFC 3971, March
   2005.

   [RFC-4140] Soliman, H., Castelluccia, C., El Malki, K., and L.
   Bellier, "Hierarchical Mobile IPv6 Mobility Management (HMIPv6)", RFC
   4140, August 2005.

   [RFC-4306] Kaufman, C, et al, "Internet Key Exchange (IKEv2)
   Protocol", RFC 4306, December 2005.

   [RFC-4330] Mills, D., "Simple Network Time Protocol (SNTP) Version 4
   for IPv4, IPv6 and OSI", RFC 2030, October 1996.

   [RFC-4372] Adrangi, F., Lior, A., Korhonen, J., and J. Loughney,
   "Chargeable User Identity", RFC 4372, January 2006.

   [RFC-4830] Kempf, J., Leung, K., Roberts, P., Nishida, K., Giaretta,
   G., Liebsch, M., "Problem Statement for Network-based Localized
   Mobility Management", September 2006.

   [RFC-4831] Kempf, J., Leung, K., Roberts, P., Nishida, K., Giaretta,
   G., Liebsch, M., "Goals for Network-based Localized Mobility
   Management", October 2006.

   [RFC-4832] Vogt, C., Kempf, J., "Security Threats to Network-Based
   Localized Mobility Management", September 2006.

   [RFC-4862] Thompson, S., Narten, T., Jinmei, T., "IPv6 Stateless
   Address Autoconfiguration", RFC 4862, September 2007.

   [RFC-4941] Narten, T., Draves, R., Krishnan, S., "Privacy Extensions
   for Stateless Address Autoconfiguration in IPv6", RFC 4941, September
   2007.

   [RFC-5072] Varada, S., Haskin, D. and Allen, E., "IP version 6 over
   PPP", RFC 5072, September 2007.

   [ID-IPV4-PMIP6] Wakikawa, R. and Gundavelli, S., "IPv4 Support for
   Proxy Mobile IPv6", draft-ietf-netlmm-pmip6-ipv4-support-02.txt,
   November 2007.

   [ID-DNAV6] Kempf, J., et al "Detecting Network Attachment in IPv6
   Networks (DNAv6)", draft-ietf-dna-protocol-06.txt, October 2006.

Appendix A.  Proxy Mobile IPv6 interactions with AAA Infrastructure

   Every mobile node that roams in a proxy Mobile IPv6 domain, would
   typically be identified by an identifier, MN-Identifier, and that
   identifier will have an associated policy profile that identifies the
   mobile node's home network prefix, permitted address configuration
   modes, roaming policy and other parameters that are essential for
   providing network-based mobility service.  This information is
   typically configured in AAA.  It is possible the home network prefix
   is dynamically allocated for the mobile node when it boots up for the
   first time in the network, or it could be a statically configured
   value on per mobile node basis.  However, for all practical purposes,
   the network entities in the proxy Mobile IPv6 domain, while serving a
   mobile node will have access to this profile and these entities can
   query this information using RADIUS/DIAMETER protocols.

Appendix B.  Supporting Shared-Prefix Model using DHCPv6

   This specification supports Per-MN-Prefix model.  However, it is
   possible to support Shared-Prefix model under the following
   guidelines.

   The mobile node is allowed to use stateful address configuration
   using DHCPv6 for obtaining its address configuration.  The mobile
   node is not allowed to use any of the stateless autoconfiguration
   techniques.  The permitted address configuration models for the
   mobile node on the access link can be enforced by the mobile access
   gateway, by setting the relevant flags in the Router Advertisements,
   as per [RFC-4861].

   The Home Network Prefix option that is sent by the mobile access
   gateway in the Proxy Binding Update message, must contain the 128-bit
   host address that the mobile node obtained via DHCPv6.

   Routing state at the mobile access gateway:

   For all IPv6 traffic from the source MN-HoA::/128 to
   _ANY_DESTINATION_, route via tunnel0, next-hop LMAA, where tunnel0 is
   the MAG to LMA tunnel.

   Routing state at the local mobility anchor:

   For all IPv6 traffic to destination MN-HoA::/128, route via tunnel0,
   next-hop Proxy-CoA, where tunnel0 is the LMA to MAG tunnel.

Appendix C.  Routing State

   The following section explains the routing state for a mobile node on
   the mobile access gateway.  This routing state reflects only one
   specific way of implementation and one MAY choose to implement it in
   other ways.  The policy based route defined below acts as a traffic
   selection rule for routing a mobile node's traffic through a specific
   tunnel created between the mobile access gateway and that mobile
   node's local mobility anchor and with the specific encapsulation
   mode, as negotiated.

   The below example identifies the routing state for two visiting
   mobile nodes, MN1 and MN2 with their respective local mobility
   anchors LMA1 and LMA2.

   For all traffic from the mobile node, identified by the mobile node's
   MAC address, ingress interface or source prefix (MN-HNP) to
   _ANY_DESTINATION_ route via interface tunnel0, next-hop LMAA.

   +==================================================================+
   |  Packet Source    | Destination Address  | Destination Interface |
   +==================================================================+
   | MAC_Address_MN1,  | _ANY_DESTINATION_    |     Tunnel0           |
   | (IPv6 Prefix or   |----------------------------------------------|
   |  Input Interface) | Locally Connected    |     Tunnel0           |
   +------------------------------------------------------------------+
   | MAC_Address_MN2,  | _ANY_DESTINATION_    |     Tunnel1           |
   + (IPv6 Prefix or   -----------------------------------------------|
   |  Input Interface  | Locally Connected    |     direct            |
   +------------------------------------------------------------------+

               Figure 22: Example - Policy based Route Table

   +==================================================================+
   | Interface | Source Address | Destination Address | Encapsulation |
   +==================================================================+
   | Tunnel0   |   Proxy-CoA    |        LMAA1         | IPv6-in-IPv6 |
   +------------------------------------------------------------------+
   | Tunnel1   |IPv4-Proxy-CoA  |    IPv4-LMA2         | IPv6-in-IPv4 |
   +------------------------------------------------------------------+

                Figure 23: Example - Tunnel Interface Table

Authors' Addresses

   Sri Gundavelli
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134
   USA

   Email: sgundave@cisco.com

   Kent Leung
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134
   USA

   Email: kleung@cisco.com
   Vijay Devarapalli
   Azaire Networks
   4800 Great America Pkwy
   Santa Clara, CA  95054
   USA

   Email: vijay.devarapalli@azairenet.com

   Kuntal Chowdhury
   Starent Networks
   30 International Place
   Tewksbury, MA

   Email: kchowdhury@starentnetworks.com

   Basavaraj Patil
   Nokia Siemens Networks
   6000 Connection Drive
   Irving, TX  75039
   USA

   Email: basavaraj.patil@nsn.com

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