NETLMM Working Group                                V. Devarapalli (ed.)
Internet-Draft                                                  WiChorus
Intended status: Standards Track                         R. Koodli (ed.)
Expires: March 18, April 3, 2009                                  Starent Networks
                                                                  H. Lim
                                                                 N. Kant
                                                             S. Krishnan
                                                             J. Laganier
                                                        DOCOMO Euro-Labs
                                                      September 14, 30, 2008

               Heartbeat Mechanism for Proxy Mobile IPv6

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   Proxy Mobile IPv6 is a network-based mobility management protocol.
   The mobility entities involved in the Proxy Mobile IPv6 protocol, the
   Mobile Access Gateway (MAG) and the Local Mobility Anchor (LMA),
   setup tunnels dynamically to manage mobility for a mobile node within
   the Proxy Mobile IPv6 domain.  This document describes a heartbeat
   mechanism between the MAG and the LMA to detect failures quickly and
   take appropriate action.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Heartbeat Mechanism  . . . . . . . . . . . . . . . . . . . . .  3
     3.1.  Failure Detection  . . . . . . . . . . . . . . . . . . . .  4
     3.2.  Restart Detection  . . . . . . . . . . . . . . . . . . . .  4
     3.3.  Heartbeat Message  . . . . . . . . . . . . . . . . . . . .  5
     3.4.  Restart Counter Mobility Option  . . . . . . . . . . . . .  6
   4.  Exchanging Heartbeat Messages over an IPv4 Transport
       Network  . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
   5.  Configuration Variables  . . . . . . . . . . . . . . . . . . .  7
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  7
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  7
   7.  8
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .  7
   8.  8
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     9.1.  Normative References . . . . . . . . . . . . . . . . . . .  8
     9.2.  Informative References . . . . . . . . . . . . . . . . . .  8
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  8  9
   Intellectual Property and Copyright Statements . . . . . . . . . . 11

1.  Introduction

   Proxy Mobile IPv6 [2] enables network-based mobility for IPv6 hosts
   that do not implement any mobility protocols.  The protocol is
   described in detail in [2].  In order to facilitate the network-based
   mobility, the PMIPv6 protocol defines a Mobility Anchor Mobile Access Gateway (MAG),
   which acts as a proxy for the Mobile IPv6 [6] signaling, and the
   Local Mobility Anchor (LMA) which acts similar to a Home Agent,
   anchoring a Mobile Node's sessions within a Proxy Mobile IPv6
   (PMIPv6) domain.  The LMA and the MAG establish a bidirectional
   tunnel for forwarding all data traffic belonging to the Mobile Nodes.

   In a distributed environment such as a PMIPv6 domain consisting of
   LMA and MAGs, it is necessary for the nodes to 1) have a consistent
   state about each others reachability, and 2) quickly inform peers in
   the event of recovery from node failures.  So, when the LMA restarts
   after a failure, the MAG should (quickly) learn about the restart so
   that it could take appropriate actions (such as releasing any
   resources).  When there are no failures, a MAG should know about
   LMA's reachability (and vice versa) so that the path can be assumed
   to be functioning.

   This document specifies a heartbeat mechanism between the MAG and the
   LMA to detect the status of reachability between them.  This document
   also specifies a mechanism to indicate node restarts; the mechanism
   could be used to quickly inform peers of such restarts.  The
   heartbeat message is a mobility header message (protocol type 135)
   which is periodically exchanged at a configurable threshold of time
   or sent unsolicited soon after a node restart.  This document does
   not specify the specific actions (such as releasing resources) that a
   node takes as a response to processing the heartbeat messages.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [1].

3.  Heartbeat Mechanism

   The MAG and the LMA exchange heartbeat messages every
   HEARTBEAT_INTERVAL seconds to detect the current status of
   reachability between them.  The MAG initiates the heartbeat exchange
   to test if the LMA is reachable by sending a Heartbeat Request
   message to the LMA.  Each Heartbeat Request contains a sequence
   number that is incremented monotonically.  The sequence number on the
   last Heartbeat Request message is always recorded by the MAG, and is
   used to match the corresponding Heartbeat Response.  Similarly, the
   LMA also initiates a heartbeat exchange with the MAG, by sending a
   Heartbeat Request message, to check if the MAG is reachable.  The
   format of the Heartbeat message is described in Section 3.3.

   A Heartbeat Request message can be sent only if the MAG has at least
   one proxy binding cache entry at the LMA for a mobile node attached
   to the MAG.  If there are no proxy binding cache entries at the LMA
   for any of the mobile nodes attached to the MAG, then the heartbeat
   message MUST NOT be sent.  Similarly, the LMA MUST NOT send a
   Heartbeat Request message to a MAG if there is no active binding
   cache entry created by the MAG.  A PMIPv6 node SHOULD always respond
   to a Heartbeat Request message with a Heartbeat Response message,
   irrespective of whether there is an active binding cache entry.

   The HEARTBEAT_INTERVAL SHOULD NOT be configured to a value less than
   30 seconds.  Sending heartbeat messages too often may become an
   overhead on the path between the MAG and the LMA.  The
   HEARTBEAT_INTERVAL can be set to a much larger value on the LMA, if
   required, to reduce of burden of sending periodic heartbeat messages.

   If the LMA or the MAG do not support the heartbeat messages, they
   should respond with an ICMP Parameter Problem, Code 0, message to the
   initiator.  The 'Pointer' field in the ICMP Parameter Problem message
   SHOULD point to the 'MH Type' field, indicating that the particular
   Mobility Header message is not supported.  When the ICMP Parameter
   Problem message is received in response to Heartbeat Request message,
   the initiating MAG or the LMA MUST NOT use heartbeat messages with
   the other end again.

3.1.  Failure Detection

   A PMIPv6 node, (MAR (MAG or LMA) matches every received Heartbeat Response
   to the Heartbeat Request sent using the sequence number.  Before
   sending the next Heartbeat Request, it increments a local variable
   MISSING_HEARTBEAT if it has not received a Heartbeat Response for the
   previous request.  When this local variable MISSING_HEARTBEAT exceeds
   a configurable parameter MISSING_HEARTBEATS_ALLOWED, the PMIPv6 node
   concludes that the peer PMIPv6 node is not reachable.  The PMIPv6
   node may then take appropriate actions which are outside the scope of
   this document.  If a Heartbeat Response message is received, the
   MISSING_HEARTBEATS counter is reset.

3.2.  Restart Detection

   The section describes a mechanism for detecting failure recovery
   without session persistence.  In case the LMA or the MAG crashes and
   re-boots and loses all state with respect to the PMIPv6 sessions, it
   would be beneficial for the peer PMIPv6 node to discover the failure
   and the loss of session state and establish the sessions again.

   Each PMIPv6 node (both the MAG and LMA) MUST maintain a monotonically
   increasing Restart Counter that is incremented every time the node
   re-boots and looses PMIPv6 session state.  The counter MUST NOT be
   incremented if the recovery happens without losing state for the
   PMIPv6 sessions active at the time of failure.  This counter MUST be
   stored in non-volatile memory.  A PMIPv6 node includes a Restart
   Counter mobility option, described in Section 3.4 in an Heartbeat
   Response message to indicate the current value of the Restart
   Counter.  Each PMIPv6 node MUST also store the Restart Counter for
   all the peer PMIPv6 nodes that it has sessions with currently.
   Storing the Restart Counter values for peer PMIPv6 nodes does not
   require non-volatile memory.

   The PMIPv6 node that receives the Heartbeat Response message compares
   the Restart Counter value with the previously received value.  If the
   value is different, the receiving node assumes that the peer PMIPv6
   node had crashed and recovered.  If the Restart Counter value changes
   or if there was no previously stored value, the new value is stored
   by the receiving PMIPv6 node.

   If a PMIPv6 node restarts and looses PMIPv6 session state, it SHOULD
   send an unsolicited Heartbeat Response message with an incremented
   Restart Counter to all the PMIPv6 nodes that had previously
   established PMIPv6 sessions.  This allows the peer PMIPv6 nodes to
   quickly discover the restart.  The sequence number field in the
   unsolicited Heartbeat Response is ignored and no response to
   necessary; the nodes will synchronize during the next Request and
   Response exchange.

3.3.  Heartbeat Message

   The following illustrates the message format for the Heartbeat
   Mobility Header message.  The 'MH Type' field in the Mobility Header
   indicates that it is a Heartbeat 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
                                     |            Reserved       |U|R|
     |                       Sequence Number                         |

      Set to 0 and ignored by the receiver.


      A 1-bit flag that indicates whether the message is a request or a
      response.  When the 'R' flag is set to 0, it indicates that the
      Heartbeat message is a request.  When the 'R' flag is set to 1, it
      indicates that the Heartbeat message is a response.


      Set to 1 in Unsolicited Heartbeat Response.  Otherwise set to 0.

   Sequence Number

      A 32-bit sequence number used for matching the request to the

3.4.  Restart Counter Mobility Option

   The following shows the message format for a new mobility option for
   carrying the Restart Counter Value in the Heartbeat message.  The
   Restart Counter Mobility Option is only valid in a Heartbeat Response
   message.  It has an alignment requirement of 4n+2.

      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    |
     |                       Restart Counter                         |


      A 8-bit field that indicates that it is a Restart Counter mobility


      A 8-bit field that indicates the length of the option in octets
      excluding the 'Type' and 'Length' fields.  It is set to '4'.

   Restart Counter

      A 32-bit field that indicates the current Restart Counter value.

4.  Exchanging Heartbeat Messages over an IPv4 Transport Network

   In some deployments, the network between the MAG and the LMA may not
   be capable of transporting IPv6 packets.  In this case, the Heartbeat
   messages are tunneled over IPv4.  If the Proxy Binding Update and
   Proxy Binding Acknowledgment messages are sent using UDP
   encapsulation to traverse NATs, then the Heartbeat messages are also
   sent with UDP encapsulation.  The UDP port used would be the same as
   the port used for the Proxy Binding Update and Proxy Binding
   Acknowledgement messages.  For more details on tunneling Proxy Mobile
   IPv6 signaling messages over IPv4, see [3].

5.  Configuration Variables

   The LMA and the MAG must allow the following variables to be


      This variable is used to set the time interval in seconds between
      two consecutive Heartbeat Request messages.  The default value is
      60 seconds.  It SHOULD not be set to less than 30 seconds.


      This variable indicates the maximum number of consecutive
      Heartbeat Request messages that a PMIPv6 node can miss before
      concluding that the peer PMIPv6 node is not reachable.  The
      default value for this variable is 3.

6.  Security Considerations

   The heartbeat messages are just used for checking reachability
   between the MAG and the LMA.  They do not carry information that is
   useful for eavesdroppers on the path.  Therefore, confidentiality
   protection is not required.  Integrity protection using IPsec [4] for
   the heartbeat messages MUST be supported on the MAG and the LMA.

   If dynamic key negotiation between the MAG and the LMA is required,
   IKEv2 [5] should be used.


7.  IANA Considerations

   The Heartbeat message defined in Section 3.3 must have the type value
   allocated from the same space as the 'MH Type' field in the Mobility
   Header defined in RFC 3775 [6].

   The Restart Counter mobility option defined in Section 3.4 must have
   the type value allocated from the same space as the Mobility Options
   defined in RFC 3775 [6].


8.  Acknowledgments

   A heartbeat mechanism for a network-based mobility management
   protocol was first described in [7].  The authors would like to thank
   the members of a NETLMM design team that produced that document.  The
   mechanism described in this document also derives from the path
   management mechanism described in [8].

   We would like to thank Alessio Casati for first suggesting a fault
   handling mechanism for Proxy Mobile IPv6.


9.  References


9.1.  Normative References

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

   [2]  Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K., and
        B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.

   [3]  Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy Mobile
        IPv6", draft-ietf-netlmm-pmip6-ipv4-support-04 (work in
        progress), July 2008.

   [4]  Kent, S. and K. Seo, "Security Architecture for the Internet
        Protocol", RFC 4301, December 2005.

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


9.2.  Informative References

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

   [7]  Giaretta, G., "The NetLMM Protocol",
        draft-giaretta-netlmm-dt-protocol-02 (work in progress),
        October 2006.

   [8]  3rd Generation Partnership Project, "3GPP Technical
        Specification 29.060 V7.6.0: "Technical Specification Group Core
        Network and Terminals; General Packet Radio Service (GPRS); GPRS
        Tunnelling Protocol (GTP) across the Gn and Gp interface
        (Release 7)"", July 2007.

Authors' Addresses

   Vijay Devarapalli
   3950 North First Street
   San Jose, CA  95134


   Rajeev Koodli
   Starent Networks


   Heeseon Lim
   5403 Betsy Ross Drve
   Santa Clara, CA  95054


   Nishi Kant
   5403 Betsy Ross Drive
   Santa Clara, CA  95054

   Suresh Krishnan
   8400 Decarie Blvd.
   Town of Mount Royal, QC


   Julien Laganier
   DOCOMO Euro-Labs
   Landsbergerstrasse 312
   Munich, D-80687


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