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Versions: (draft-chan-dmm-distributed-mobility-anchoring) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 RFC 8818

DMM                                                         H. Chan, Ed.
Internet-Draft                                                    X. Wei
Intended status: Informational                       Huawei Technologies
Expires: September 8, 2020                                        J. Lee
                                                    Sangmyung University
                                                                 S. Jeon
                                                 Sungkyunkwan University
                                                      CJ. Bernardos, Ed.
                                                                    UC3M
                                                           March 7, 2020


                     Distributed Mobility Anchoring
            draft-ietf-dmm-distributed-mobility-anchoring-15

Abstract

   This document defines distributed mobility anchoring in terms of the
   different configurations and functions to provide IP mobility
   support.  A network may be configured with distributed mobility
   anchoring functions for both network-based or host-based mobility
   support according to the needs of mobility support.  In a distributed
   mobility anchoring environment, multiple anchors are available for
   mid-session switching of an IP prefix anchor.  To start a new flow or
   to handle a flow not requiring IP session continuity as a mobile node
   moves to a new network, the flow can be started or re-started using
   an IP address configured from the new IP prefix anchored to the new
   network.  If the flow needs to survive the change of network, there
   are solutions that can be used to enable IP address mobility.  This
   document describes different anchoring approaches, depending on the
   IP mobility needs, and how this IP address mobility is handled by the
   network.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."




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   This Internet-Draft will expire on September 8, 2020.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
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   publication of this document.  Please review these documents
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Terminology . . . . . . . . . . . . . . . . .   3
   3.  Distributed Mobility Anchoring  . . . . . . . . . . . . . . .   6
     3.1.  Configurations for Different Networks . . . . . . . . . .   6
       3.1.1.  Network-based DMM . . . . . . . . . . . . . . . . . .   7
       3.1.2.  Client-based DMM  . . . . . . . . . . . . . . . . . .   8
   4.  IP Mobility Handling in Distributed Anchoring Environments -
       Mobility Support Only When Needed . . . . . . . . . . . . . .   9
     4.1.  Nomadic case (no need of IP mobility): Changing to new IP
           prefix/address  . . . . . . . . . . . . . . . . . . . . .  10
     4.2.  Mobility case, traffic redirection  . . . . . . . . . . .  12
     4.3.  Mobility case, anchor relocation  . . . . . . . . . . . .  15
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  17
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  18
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20

1.  Introduction

   A key requirement in distributed mobility management [RFC7333] is to
   enable traffic to avoid traversing a single mobility anchor far from
   an optimal route.  This document defines different configurations,
   functional operations and parameters for distributed mobility
   anchoring and explains how to use them to avoid unnecessarily long
   routes when a mobile node moves.




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   Companion distributed mobility management documents are already
   addressing source address selection [RFC8653], and control-plane
   data-plane signaling [I-D.ietf-dmm-fpc-cpdp].  A number of
   distributed mobility solutions have also been proposed, for example,
   in [I-D.seite-dmm-dma], [I-D.ietf-dmm-pmipv6-dlif],
   [I-D.sarikaya-dmm-for-wifi], [I-D.yhkim-dmm-enhanced-anchoring], and
   [I-D.matsushima-stateless-uplane-vepc].

   Distributed mobility anchoring employs multiple anchors in the data
   plane.  In general, control plane functions may be separated from
   data plane functions and be centralized but may also be co-located
   with the data plane functions at the distributed anchors.  Different
   configurations of distributed mobility anchoring are described in
   Section 3.1.

   As a Mobile Node (MN) attaches to an access router and establishes a
   link between them, a /64 IPv6 prefix anchored to the router may be
   assigned to the link for exclusive use by the MN [RFC6459].  The MN
   may then configure a global IPv6 address from this prefix and use it
   as the source IP address in a flow to communicate with its
   Correspondent Node (CN).  When there are multiple mobility anchors
   assigned to the same MN, an address selection for a given flow is
   first required before the flow is initiated.  Using an anchor in a
   MN's network of attachment has the advantage that the packets can
   simply be forwarded according to the forwarding table.  However,
   after the flow has been initiated, the MN may later move to another
   network which assigns a new mobility anchor to the MN.  Since the new
   anchor is located in a different network, the MN's assigned prefix
   does not belong to the network where the MN is currently attached.

   When the MN wants to continue using its assigned prefix to complete
   ongoing data sessions after it has moved to a new network, the
   network needs to provide support for the MN's IP address and session
   continuity, since routing packets to the MN through the new network
   deviates from applying default routes.  The IP session continuity
   needs of a flow (application) determines how the IP address used by
   this flow has to be anchored.  If the ongoing IP flow can cope with
   an IP prefix/address change, the flow can be reinitiated with a new
   IP address anchored in the new network.  On the other hand, if the
   ongoing IP flow cannot cope with such change, mobility support is
   needed.  A network supporting a mix of flows both requiring and not
   requiring IP mobility support will need to distinguish these flows.

2.  Conventions and Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP



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   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   All general mobility-related terms and their acronyms used in this
   document are to be interpreted as defined in the Mobile IPv6 (MIPv6)
   base specification [RFC6275], the Proxy Mobile IPv6 (PMIPv6)
   specification [RFC5213], the "Mobility Related Terminologies"
   [RFC3753], and the DMM current practices and gap analysis [RFC7429].
   These include terms such as Mobile Node (MN), Correspondent Node
   (CN), Home Agent (HA), Home Address (HoA), Care-of-Address (CoA),
   Local Mobility Anchor (LMA), and Mobile Access Gateway (MAG).

   In addition, this document uses the following terms and definitions:

   IP session continuity:  The ability to maintain an ongoing transport
      interaction by keeping the same local endpoint IP address
      throughout the lifetime of the IP socket despite the mobile host
      changing its point of attachment within the IP network topology.
      The IP address of the host may change after closing the IP socket
      and before opening a new one, but that does not jeopardize the
      ability of applications using these IP sockets to work flawlessly.
      Session continuity is essential for mobile hosts to maintain
      ongoing flows without any interruption [RFC8653].


   Higher layer session continuity:  The ability to maintain an ongoing
      transport or higher layer (e.g., application) interaction by
      keeping the session indentifiers throughout the lifetime of the
      session despite the mobile host changing its point of attachment
      within the IP network topology.  This can be achieved by using
      mechanisms at the transport or higher layers.


   IP address reachability:  The ability to maintain the same IP address
      for an extended period of time.  The IP address stays the same
      across independent sessions, even in the absence of any session.
      The IP address may be published in a long-term registry (e.g.,
      DNS) and is made available for serving incoming (e.g., TCP)
      connections.  IP address reachability is essential for mobile
      hosts to use specific/published IP addresses [RFC8653].


   IP mobility:  Combination of IP address reachability and session
      continuity.


   Home network of a home address:  the network that has assigned the
      HoA used as the session identifier by the application running in



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      an MN.  The MN may be running multiple application sessions, and
      each of these sessions can have a different home network.


   Anchoring (of an IP prefix/address):  An IP prefix, i.e., Home
      Network Prefix (HNP), or address, i.e., HoA, assigned for use by
      an MN is topologically anchored to an anchor node when the anchor
      node is able to advertise a route into the routing infrastructure
      for the assigned IP prefix.  The traffic using the assigned IP
      address/prefix must traverse the anchor node.  We can refer to the
      function performed by IP anchor node as anchoring, which is a data
      plane function.


   Location Management (LM) function:  control plane function that keeps
      and manages the network location information of an MN.  The
      location information may be a binding of the advertised IP
      address/prefix, e.g., HoA or HNP, to the IP routing address of the
      MN or of a node that can forward packets destined to the MN.

      When the MN is a Mobile Router (MR), the location information will
      also include the Mobile Network Prefix (MNP), which is the
      aggregate IP prefix delegated to the MR to assign IP prefixes for
      use by the Mobile Network Nodes (MNNs) in the mobile network.

      In a client-server protocol model, secure (i.e., authenticated and
      authorized) location query and update messages may be exchanged
      between a Location Management client (LMc) and a Location
      Management server (LMs), where the location information can be
      updated or queried from the LMc.  Optionally, there may be a
      Location Management proxy (LMp) between LMc and LMs.

      With separation of control plane and data plane, the LM function
      is in the control plane.  It may be a logical function at the
      control plane node, control plane anchor, or mobility controller.

      It may be distributed or centralized.


   Forwarding Management (FM) function:  packet interception and
      forwarding to/from the IP address/prefix assigned for use by the
      MN, based on the internetwork location information, either to the
      destination or to some other network element that knows how to
      forward the packets to their destination.

      This function may be used to achieve traffic indirection.  With
      separation of control plane and data plane, the FM function may




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      split into a FM function in the data plane (FM-DP) and a FM
      function in the control plane (FM-CP).

      FM-DP may be distributed with distributed mobility management.  It
      may be a function in a data plane anchor or data plane node.

      FM-CP may be distributed or centralized.  It may be a function in
      a control plane node, control plane anchor or mobility controller.


   Home Control-Plane Anchor (Home-CPA or H-CPA):  The Home-CPA function
      hosts the mobile node (MN)'s mobility session.  There can be more
      than one mobility session for a mobile node and those sessions may
      be anchored on the same or different Home-CPA's.  The home-CPA
      will interface with the home-DPA for managing the forwarding
      state.


   Home Data Plane Anchor (Home-DPA or H-DPA):  The Home-DPA is the
      topological anchor for the MN's IP address/ prefix(es).  The Home-
      DPA is chosen by the Home-CPA on a session- basis.  The Home-DPA
      is in the forwarding path for all the mobile node's IP traffic.


   Access Control Plane Node (Access-CPN or A-CPN):  The Access-CPN is
      responsible for interfacing with the mobile node's Home-CPA and
      with the Access-DPN.  The Access-CPN has a protocol interface to
      the Home-CPA.


   Access Data Plane Node (Access-DPN or A-DPN):  The Access-DPN
      function is hosted on the first-hop router where the mobile node
      is attached.  This function is not hosted on a layer-2 bridging
      device such as a eNode(B) or Access Point.



3.  Distributed Mobility Anchoring

3.1.  Configurations for Different Networks

   We next describe some configurations with multiple distributed
   anchors.  To cover the widest possible spectrum of scenarios, we
   consider architectures in which the control and data planes are
   separated.  We analyze where LM and FM functions -- which are
   specific sub-functions involved in mobility management -- can be
   placed when looking at the different scenarios with distributed
   anchors.



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3.1.1.  Network-based DMM

   Figure 1 shows a general scenario for network-based distributed
   mobility management.

   The main characteristics of a network-based DMM solution are:

   o  There are multiple data plane anchors, each with a FM-DP function.
   o  The control plane may either be distributed (not shown in the
      figure) or centralized (as shown in the figure).
   o  The control plane and the data plane (Control Plane Anchor -- CPA
      -- and Data Plane Anchor -- DPA) may be co-located or not.  If the
      CPA is co-located with the distributed DPAs, then there are
      multiple co-located CPA-DPA instances (not shown in the figure).
   o  An IP prefix/address IP1 (anchored to the DPA with IP address
      IPa1) is assigned for use to a MN.  The MN uses this IP1 address
      to communicate with CNs (not shown in the figure).
   o  The location management (LM) function may be co-located or split
      (as shown in the figure) into a separate server (LMs) and a client
      (LMc).  In this case, the LMs may be centralized whereas the LMc
      may be distributed or centralized.






























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              ____________  Network
          ___/            \___________
         /      +-----+                \___
        (       |LMs  |    Control         \
       /        +-.---+    plane            \
      /  +--------.---+    functions         \
     (   |CPA:    .   |    in the             )
     (   |FM-CP, LMc  |    network            )
     (   +------------+                        \
    /          . .                              \
   (           .     .                           )
   (           .         .                       )
   (           .             .                   \
    \    +------------+ +------------+Distributed )
     (   |DPA(IPa1):  | |DPA(IPa2):  |DPAs        )
     (   |anchors IP1 | |anchors IP2 |          _/
      \  |FM-DP       | |FM-DP       | etc.    /
       \ +------------+ +------------+        /
        \___                Data plane  _____/
            \______         functions  /
                   \__________________/

         +------------+
         |MN(IP1)     | Mobile node attached
         |flow(IP1,..)| to the network
         +------------+

                 Figure 1: Network-based DMM configuration

3.1.2.  Client-based DMM

   Figure 2 shows a general scenario for client-based distributed
   mobility management.  In this configuration, the mobile node performs
   Control Plane Node (CPN) and Data Plane Node (DPN) mobility
   functions, namely the forwarding management and location management
   (client) roles.















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          +-----+
          |LMs  |
          +-.---+
   +--------.---+
   |CPA:    .   |
   |FM-CP, LMp  |
   +------------+
         . .
         .     .
         .         .
         .             .
   +------------+ +------------+ Distributed
   |DPA(IPa1):  | |DPA(IPa2):  | DPAs
   |anchors IP1 | |anchors IP2 |
   |FM-DP       | |FM-DP       |  etc.
   +------------+ +------------+

   +------------+
   |MN(IP1)     |Mobile node
   |flow(IP1,..)|using IP1
   |FM,    LMc  |anchored to
   +------------+DPA(IPa1)

                 Figure 2: Client-based DMM configuration

4.  IP Mobility Handling in Distributed Anchoring Environments -
    Mobility Support Only When Needed

   IP mobility support may be provided only when needed instead of being
   provided by default.  Three cases can be considered:

   o  Nomadic case: no address continuity is required.  The IP address
      used by the MN changes after a movement and traffic using the old
      address is disrupted.  If session continuity is required, then it
      needs to be provided by a solution running at L4 or above.
   o  Mobility case, traffic redirection: address continuity is
      required.  When the MN moves, the previous anchor still anchors
      the traffic using the old IP address, and forwards it to the new
      MN's location.  The MN obtains a new IP address anchored to the
      new location, and preferably uses it for new communications,
      established while connected at the new location.
   o  Mobility case, anchor relocation: address continuity is required.
      In this case the route followed by the traffic is optimized, by
      using some means for traffic indirection to deviate from default
      routes.

   A straightforward choice of mobility anchoring is the following: the
   MN's chooses as source IP address for packets belonging to an IP



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   flow, an address allocated by the network the MN is attached to when
   the flow was initiated.  As such, traffic belonging to this flow
   traverses the MN's mobility anchor [I-D.seite-dmm-dma]
   [I-D.ietf-dmm-pmipv6-dlif].

   The IP prefix/address at the MN's side of a flow may be anchored to
   the Access Router (AR) to which the MN is attached.  For example,
   when a MN attaches to a network (Net1) or moves to a new network
   (Net2), an IP prefix from the attached network is assigned to the
   MN's interface.  In addition to configuring new link-local addresses,
   the MN configures from this prefix an IP address which is typically a
   dynamic IP address (meaning that this address is only used while the
   MN is attached to this access router, and therefore the IP address
   configured by the MN dynamically changes when attaching to a
   different access network).  It then uses this IP address when a flow
   is initiated.  Packets from this flow addressed to the MN are simply
   forwarded according to the forwarding table.

   There may be multiple IP prefixes/addresses that an MN can select
   when initiating a flow.  They may be from the same access network or
   different access networks.  The network may advertise these prefixes
   with cost options [I-D.mccann-dmm-prefixcost] so that the mobile node
   may choose the one with the least cost.  In addition, the IP
   prefixes/addresses provided by the network may be of different types
   regarding whether mobility support is supported [RFC8653].  A MN will
   need to choose which IP prefix/address to use for each flow according
   to whether it needs IP mobility support or not, using for example the
   mechanisms described in [RFC8653].

4.1.  Nomadic case (no need of IP mobility): Changing to new IP prefix/
      address

   When IP mobility support is not needed for a flow, the LM and FM
   functions are not utilized so that the configurations in Section 3.1
   are simplified as shown in Figure 3.
















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   Net1                                                Net2

   +---------------+                                   +---------------+
   |AR1            |            AR is changed          |AR2            |
   +---------------+              ------->             +---------------+
   |CPA:           |                                   |CPA:           |
   |---------------|                                   |---------------|
   |DPA(IPa1):     |                                   |DPA(IPa2):     |
   |anchors IP1    |                                   |anchors IP2    |
   +---------------+                                   +---------------+

   +...............+                                   +---------------+
   .MN(IP1)        .              MN moves             |MN(IP2)        |
   .flow(IP1,...)  .              =======>             |flow(IP2,...)  |
   +...............+                                   +---------------+

               Figure 3: Changing to a new IP address/prefix

   When there is no need to provide IP mobility to a flow, the flow may
   use a new IP address acquired from a new network as the MN moves to
   the new network.

   Regardless of whether IP mobility is needed, if the flow has not
   terminated before the MN moves to a new network, the flow may
   subsequently restart using the new IP address assigned from the new
   network.

   When IP session continuity is needed, even if an application flow is
   ongoing as the MN moves, it may still be desirable for the
   application flow to change to using the new IP prefix configured in
   the new network.  The application flow may then be closed at IP level
   and then be restarted using a new IP address configured in the new
   network.  Such a change in the IP address used by the application
   flow may be enabled using a higher layer mobility support which is
   not in the scope of this document.

   In Figure 3, a flow initiated while the MN was using the IP prefix
   IP1 -- anchored to a previous access router AR1 in network Net1 --
   has terminated before the MN moves to a new network Net2.  After
   moving to Net2, the MN uses the new IP prefix IP2 -- anchored to a
   new access router AR2 in network Net2 -- to start a new flow.
   Packets may then be forwarded without requiring IP layer mobility
   support.

   An example call flow is outlined in Figure 4.  A MN attaches to AR1,
   which sends a router advertisement (RA) including information about
   the prefix assigned to MN, from which MN configures an IP address
   (IP1).  This address is used for new communications, for example with



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   a correspondent node (CN).  If the MN moves to a new network and
   attaches to AR2, the process is repeated (MN obtains a new IP
   address, IP2, from AR2).  Since the IP address (IP1) configured at
   the previously visited network is not valid at the current attachment
   point, and any existing flows have to be reestablished using IP2.

   Note that in these scenarios, if there is no mobility support
   provided by L4 or above, application traffic would stop.

    MN                    AR1           AR2                           CN
     |MN attaches to AR1:  |             |                             |
     |acquires MN-ID and profile         |                             |
     |--RS---------------->|             |                             |
     |                     |             |                             |
     |<----------RA(IP1)---|             |                             |
     |                     |             |                             |
   Assigned prefix IP1     |             |                             |
   IP1 address configuration             |                             |
     |                     |             |                             |
     |<-Flow(IP1,IPcn,...)-+------------------------------------------>|
     |                     |             |                             |
     |MN detaches from AR1 |             |                             |
     |MN attaches to AR2   |             |                             |
     |                     |             |                             |
     |--RS------------------------------>|                             |
     |                     |             |                             |
     |<--------------RA(IP2)-------------|                             |
     |                     |             |                             |
   Assigned prefix IP2     |             |                             |
   IP2 address configuration             |                             |
     |                     |             |                             |
     |<-new Flow(IP2,IPcn,...)-----------+---------------------------->|
     |                     |             |                             |

          Figure 4: Re-starting a flow with new IP prefix/address

4.2.  Mobility case, traffic redirection

   When IP mobility is needed for a flow, the LM and FM functions in
   Section 3.1 are utilized.  There are two possible cases: (i) the
   mobility anchor remains playing that role and forwards traffic to a
   new locator in the new network, and (ii) the mobility anchor (data
   plane function) is changed but binds the MN's transferred IP address/
   prefix.  The latter enables optimized routes but requires some data
   plane node that enforces traffic indirection.  Next, we focus on the
   first case.  The second one is addressed in Section 4.3.





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   Mobility support can be provided by using mobility management
   methods, such as the several approaches surveyed in the academic
   papers ([Paper-Distributed.Mobility],
   [Paper-Distributed.Mobility.PMIP] and
   [Paper-Distributed.Mobility.Review]).  After moving, a certain MN's
   traffic flow may continue using the IP prefix from the prior network
   of attachment.  Yet, some time later, the application generating this
   traffic flow may be closed.  If the application is started again, the
   new flow may not need to use the prior network's IP address to avoid
   having to invoke IP mobility support.  This may be the case where a
   dynamic IP prefix/address, rather than a permanent one, is used.
   Packets belonging to this flow may then use the new IP prefix (the
   one allocated in the network where the flow is being initiated).
   Routing is again kept simpler without employing IP mobility and will
   remain so as long as the MN which is now in the new network does not
   move again to another network.



































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    MN                    AR1           AR2                           CN
     |MN attaches to AR1:  |             |                             |
     |acquires MN-ID and profile         |                             |
     |--RS---------------->|             |                             |
     |                     |             |                             |
     |<----------RA(IP1)---|             |                             |
     |                     |             |                             |
   Assigned prefix IP1     |             |                             |
   IP1 address configuration             |                             |
     |                     |             |                             |
     |<-Flow(IP1,IPcn,...)-+------------------------------------------>|
     |                     |             |                             |
     |MN detaches from AR1 |             |                             |
     |MN attaches to AR2   |             |                             |
     |                     |             |                             |
     |--RS------------------------------>|                             |
      (some IP mobility support solution)
     |<--------------RA(IP2,IP1)---------|                             |
     |                     |             |                             |
     |                     +<-Flow(IP1,IPcn,...)---------------------->|
     |                     +<===========>+                             |
     |<-Flow(IP1,IPcn,...)-------------->+                             |
     |                     |             |                             |
   Assigned prefix IP2     |             |                             |
   IP2 address configuration             |                             |
     |                     |             |                             |
   Flow(IP1,IPcn) terminates             |                             |
     |                     |             |                             |
     |<-new Flow(IP2,IPcn,...)-----------+---------------------------->|
     |                     |             |                             |

   Figure 5: A flow continues to use the IP prefix from its home network
                    after MN has moved to a new network

   An example call flow in this case is outlined in Figure 5.  In this
   example, the AR1 plays the role of FM-DP entity and redirects the
   traffic (e.g., using an IP tunnel) to AR2.  Another solution could be
   to place an FM-DP entity closer to the CN network to perform traffic
   steering to deviate from default routes (which will bring the packet
   to AR1 per default routing).  The LM and FM functions are implemented
   as shown in Figure 6.










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   Net1                                                Net2

   +---------------+                                   +---------------+
   |AR1            |                                   |AR2            |
   +---------------+                                   +---------------+
   |CPA:           |                                   |CPA:           |
   |               |                                   |LM:IP1 at IPa1 |
   |---------------|      IP1 (anchored to Net1)       |---------------|
   |DPA(IPa1):     |      is redirected to Net2        |DPA(IPa2):     |
   |anchors IP1    |              =======>             |anchors IP2    |
   |FM:IP1 via IPa2|                                   |FM:IP1 via IPa1|
   +---------------+                                   +---------------+

   +...............+                                   +---------------+
   .MN(IP1)        .              MN moves             |MN(IP2,IP1)    |
   .flow(IP1,...)  .              =======>             |flow(IP1,...)  |
   .               .                                   |flow(IP2,...)  |
   +...............+                                   +---------------+

                       Figure 6: Anchor redirection

   Multiple instances of DPAs (at access routers), which are providing
   IP prefixes to the MNs, are needed to provide distributed mobility
   anchoring in an appropriate configuration such as those described in
   Figure 1 (Section 3.1.1) for network-based distributed mobility or in
   Figure 2 (Section 3.1.2) for client-based distributed mobility.

4.3.  Mobility case, anchor relocation

   We focus next on the case where the mobility anchor (data plane
   function) is changed but binds the MN's transferred IP address/
   prefix.  This enables optimized routes but requires some data plane
   node that enforces traffic indirection.

   IP mobility is invoked to enable IP session continuity for an ongoing
   flow as the MN moves to a new network.  The anchoring of the IP
   address of the flow is in the home network of the flow (i.e.,
   different from the current network of attachment).  A centralized
   mobility management mechanism may employ indirection from the anchor
   in the home network to the current network of attachment.  Yet it may
   be difficult to avoid using an unnecessarily long route (when the
   route between the MN and the CN via the anchor in the home network is
   significantly longer than the direct route between them).  An
   alternative is to move the IP prefix/address anchoring to the new
   network.






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   The IP prefix/address anchoring may move without changing the IP
   prefix/address of the flow.  The LM function in Figure 1 in
   Section 3.1.1 is implemented as shown in Figure 7.

   Net1                                              Net2

   +---------------+                                 +---------------+
   |AR1            |                                 |AR2            |
   +---------------+                                 +---------------+
   |CPA:           |                                 |CPA:           |
   |LM:IP1 at IPa1 |                                 |LM:IP1 at IPa2 |
   |   changes to  |                                 |               |
   |   IP1 at IPa2 |                                 |               |
   |---------------|                                 |---------------|
   |DPA(IPa1):     | IP1 anchoring effectively moved |DPA(IPa2):     |
   |anchored IP1   |            =======>             |anchors IP2,IP1|
   +---------------+                                 +---------------+

   +...............+                                 +---------------+
   .MN(IP1)        .            MN moves             |MN(IP2,IP1)    |
   .flow(IP1,...)  .            =======>             |flow(IP1,...)  |
   +...............+                                 +---------------+

                        Figure 7: Anchor relocation

   As an MN with an ongoing session moves to a new network, the flow may
   preserve IP session continuity by moving the anchoring of the
   original IP prefix/address of the flow to the new network.

   One way to accomplish such a move is to use a centralized routing
   protocol, but such a solution may present some scalability concerns
   and its applicability is typically limited to small networks.  One
   example of this type of solution is described in
   [I-D.ietf-rtgwg-atn-bgp].  When a MN associates with an anchor the
   anchor injects the mobile's prefix into the global routing system.
   If the MN moves to a new anchor, the old anchor withdraws the /64 and
   the new anchor injects it instead.

5.  Security Considerations

   As stated in [RFC7333], "a DMM solution MUST support any security
   protocols and mechanisms needed to secure the network and to make
   continuous security improvements".  It "MUST NOT introduce new
   security risks".

   There are different potential deployment models of a DMM solution.
   The present document has presented 3 different scenarios for
   distributed anchoring: (i) nomadic case, (ii) mobility case with



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   traffic redirection, and (iii) mobility case with anchor relocation.
   Each of them has different security requirements, and the actual
   security mechanisms would depend on the specifics of each solution/
   scenario.

   As general rules, for the first distributed anchoring scenario
   (nomadic case), no additional security consideration is needed, as
   this does not involve any additional mechanism at L3.  If session
   connectivity is required, the L4 or above solution used to provide it
   MUST also provide the required authentication and security.

   The second and third distributed anchoring scenarios (mobility case)
   involve mobility signalling among the mobile node and the control and
   data plane anchors.  The control-plane messages exchanged between
   these entitites MUST be protected using end-to-end security
   associations with data-integrity and data-origination capabilities.
   IPsec [RFC8221] ESP in transport mode with mandatory integrity
   protection SHOULD be used for protecting the signaling messages.
   IKEv2 [RFC8247] SHOULD be used to set up security associations
   between the data and control plane anchors.  Note that in scenarios
   in which traffic indirection mechanisms are used to relocate an
   anchor, authentication and authorization mechanisms MUST be used.

   Control-plane functionality MUST apply authorization checks to any
   commands or updates that are made by the control-plane protocol.

6.  IANA Considerations

   This document presents no IANA considerations.

7.  Contributors

   Alexandre Petrescu and Fred Templin had contributed to earlier
   versions of this document regarding distributed anchoring for
   hierarchical network and for network mobility, although these
   extensions were removed to keep the document within reasonable
   length.

   This document has benefited from other work on mobility support in
   SDN network, on providing mobility support only when needed, and on
   mobility support in enterprise network.  These works have been
   referenced.  While some of these authors have taken the work to
   jointly write this document, others have contributed at least
   indirectly by writing these drafts.  The latter include Philippe
   Bertin, Dapeng Liu, Satoru Matushima, Pierrick Seite, Jouni Korhonen,
   and Sri Gundavelli.





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   Some terminology has been incorporated for completeness from draft-
   ietf-dmm-deployment-models-04 document.

   Valuable comments have been received from John Kaippallimalil,
   ChunShan Xiong, Dapeng Liu, Fred Templin, Paul Kyzivat, Joseph
   Salowey, Yoshifumi Nishida, Carlos Pignataro, Mirja Kuehlewind, Eric
   Vyncke, Qin Wu, Warren Kumari, Benjamin Kaduk, Roman Danyliw and
   Barry Leiba.  Dirk von Hugo, Byju Pularikkal, Pierrick Seite have
   generously provided careful review with helpful corrections and
   suggestions.  Marco Liebsch and Lyle Bertz also performed very
   detailed and helpful reviews of this document.

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3753]  Manner, J., Ed. and M. Kojo, Ed., "Mobility Related
              Terminology", RFC 3753, DOI 10.17487/RFC3753, June 2004,
              <https://www.rfc-editor.org/info/rfc3753>.

   [RFC5213]  Gundavelli, S., Ed., Leung, K., Devarapalli, V.,
              Chowdhury, K., and B. Patil, "Proxy Mobile IPv6",
              RFC 5213, DOI 10.17487/RFC5213, August 2008,
              <https://www.rfc-editor.org/info/rfc5213>.

   [RFC6275]  Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
              Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
              2011, <https://www.rfc-editor.org/info/rfc6275>.

   [RFC7333]  Chan, H., Ed., Liu, D., Seite, P., Yokota, H., and J.
              Korhonen, "Requirements for Distributed Mobility
              Management", RFC 7333, DOI 10.17487/RFC7333, August 2014,
              <https://www.rfc-editor.org/info/rfc7333>.

   [RFC7429]  Liu, D., Ed., Zuniga, JC., Ed., Seite, P., Chan, H., and
              CJ. Bernardos, "Distributed Mobility Management: Current
              Practices and Gap Analysis", RFC 7429,
              DOI 10.17487/RFC7429, January 2015,
              <https://www.rfc-editor.org/info/rfc7429>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.



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   [RFC8221]  Wouters, P., Migault, D., Mattsson, J., Nir, Y., and T.
              Kivinen, "Cryptographic Algorithm Implementation
              Requirements and Usage Guidance for Encapsulating Security
              Payload (ESP) and Authentication Header (AH)", RFC 8221,
              DOI 10.17487/RFC8221, October 2017,
              <https://www.rfc-editor.org/info/rfc8221>.

   [RFC8247]  Nir, Y., Kivinen, T., Wouters, P., and D. Migault,
              "Algorithm Implementation Requirements and Usage Guidance
              for the Internet Key Exchange Protocol Version 2 (IKEv2)",
              RFC 8247, DOI 10.17487/RFC8247, September 2017,
              <https://www.rfc-editor.org/info/rfc8247>.

8.2.  Informative References

   [I-D.ietf-dmm-fpc-cpdp]
              Matsushima, S., Bertz, L., Liebsch, M., Gundavelli, S.,
              Moses, D., and C. Perkins, "Protocol for Forwarding Policy
              Configuration (FPC) in DMM", draft-ietf-dmm-fpc-cpdp-12
              (work in progress), June 2018.

   [I-D.ietf-dmm-pmipv6-dlif]
              Bernardos, C., Oliva, A., Giust, F., Zuniga, J., and A.
              Mourad, "Proxy Mobile IPv6 extensions for Distributed
              Mobility Management", draft-ietf-dmm-pmipv6-dlif-05 (work
              in progress), November 2019.

   [I-D.ietf-rtgwg-atn-bgp]
              Templin, F., Saccone, G., Dawra, G., Lindem, A., and V.
              Moreno, "A Simple BGP-based Mobile Routing System for the
              Aeronautical Telecommunications Network", draft-ietf-
              rtgwg-atn-bgp-05 (work in progress), January 2020.

   [I-D.matsushima-stateless-uplane-vepc]
              Matsushima, S. and R. Wakikawa, "Stateless user-plane
              architecture for virtualized EPC (vEPC)", draft-
              matsushima-stateless-uplane-vepc-06 (work in progress),
              March 2016.

   [I-D.mccann-dmm-prefixcost]
              McCann, P. and J. Kaippallimalil, "Communicating Prefix
              Cost to Mobile Nodes", draft-mccann-dmm-prefixcost-03
              (work in progress), April 2016.

   [I-D.sarikaya-dmm-for-wifi]
              Sarikaya, B. and L. Li, "Distributed Mobility Management
              Protocol for WiFi Users in Fixed Network", draft-sarikaya-
              dmm-for-wifi-05 (work in progress), October 2017.



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   [I-D.seite-dmm-dma]
              Seite, P., Bertin, P., and J. Lee, "Distributed Mobility
              Anchoring", draft-seite-dmm-dma-07 (work in progress),
              February 2014.

   [I-D.yhkim-dmm-enhanced-anchoring]
              Kim, Y. and S. Jeon, "Enhanced Mobility Anchoring in
              Distributed Mobility Management", draft-yhkim-dmm-
              enhanced-anchoring-05 (work in progress), July 2016.

   [Paper-Distributed.Mobility]
              Lee, J., Bonnin, J., Seite, P., and H. Chan, "Distributed
              IP Mobility Management from the Perspective of the IETF:
              Motivations, Requirements, Approaches, Comparison, and
              Challenges",  IEEE Wireless Communications, October 2013.

   [Paper-Distributed.Mobility.PMIP]
              Chan, H., "Proxy Mobile IP with Distributed Mobility
              Anchors",  Proceedings of GlobeCom Workshop on Seamless
              Wireless Mobility, December 2010.

   [Paper-Distributed.Mobility.Review]
              Chan, H., Yokota, H., Xie, J., Seite, P., and D. Liu,
              "Distributed and Dynamic Mobility Management in Mobile
              Internet: Current Approaches and Issues", February 2011.

   [RFC6459]  Korhonen, J., Ed., Soininen, J., Patil, B., Savolainen,
              T., Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation
              Partnership Project (3GPP) Evolved Packet System (EPS)",
              RFC 6459, DOI 10.17487/RFC6459, January 2012,
              <https://www.rfc-editor.org/info/rfc6459>.

   [RFC8653]  Yegin, A., Moses, D., and S. Jeon, "On-Demand Mobility
              Management", RFC 8653, DOI 10.17487/RFC8653, October 2019,
              <https://www.rfc-editor.org/info/rfc8653>.

Authors' Addresses

   H. Anthony Chan (editor)
   Huawei Technologies
   5340 Legacy Dr. Building 3
   Plano, TX 75024
   USA

   Email: h.a.chan@ieee.org






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   Xinpeng Wei
   Huawei Technologies
   Xin-Xi Rd. No. 3, Haidian District
   Beijing, 100095
   P. R. China

   Email: weixinpeng@huawei.com


   Jong-Hyouk Lee
   Sangmyung University
   31, Sangmyeongdae-gil, Dongnam-gu
   Cheonan 31066
   Republic of Korea

   Email: jonghyouk@smu.ac.kr


   Seil Jeon
   Sungkyunkwan University
   2066 Seobu-ro, Jangan-gu
   Suwon, Gyeonggi-do
   Republic of Korea

   Email: seiljeon@skku.edu


   Carlos J. Bernardos (editor)
   Universidad Carlos III de Madrid
   Av. Universidad, 30
   Leganes, Madrid  28911
   Spain

   Phone: +34 91624 6236
   Email: cjbc@it.uc3m.es
   URI:   http://www.it.uc3m.es/cjbc/















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