RFC 5847

Internet Engineering Task Force (IETF)               V. Devarapalli, Ed.
Request for Comments: 5847                                      WiChorus
Category: Standards Track                                 R. Koodli, Ed.
ISSN: 2070-1721                                            Cisco Systems
                                                                  H. Lim
                                                                 N. Kant
                                                             S. Krishnan
                                                             J. Laganier
                                                           Qualcomm Inc.
                                                               June 2010

               Heartbeat Mechanism for Proxy Mobile IPv6


   Proxy Mobile IPv6 (PMIPv6) 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), set up 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 inform peers in the event of a recovery from node
   failures, and allow a peer to take appropriate action.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at

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RFC 5847               PMIPv6 Heartbeat Mechanism              June 2010

Copyright Notice

   Copyright (c) 2010 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Heartbeat Mechanism  . . . . . . . . . . . . . . . . . . . . .  3
     3.1.  Failure Detection  . . . . . . . . . . . . . . . . . . . .  4
     3.2.  Restart Detection  . . . . . . . . . . . . . . . . . . . .  5
     3.3.  Heartbeat Message  . . . . . . . . . . . . . . . . . . . .  6
     3.4.  Restart Counter Mobility Option  . . . . . . . . . . . . .  7
   4.  Exchanging Heartbeat Messages over an IPv4 Transport
       Network  . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
   5.  Configuration Variables  . . . . . . . . . . . . . . . . . . .  8
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  9
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     9.1.  Normative References . . . . . . . . . . . . . . . . . . .  9
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 10

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RFC 5847               PMIPv6 Heartbeat Mechanism              June 2010

1.  Introduction

   Proxy Mobile IPv6 (PMIPv6) [RFC5213] enables network-based mobility
   for IPv6 hosts that do not implement any mobility protocols.  The
   protocol is described in detail in [RFC5213].  In order to facilitate
   the network-based mobility, the PMIPv6 protocol defines a mobile
   access gateway (MAG), which acts as a proxy for the Mobile IPv6
   [RFC3775] signaling, and the local mobility anchor (LMA), which acts
   similar to a home agent, anchoring a mobile node's sessions within a
   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
   LMAs and MAGs, it is necessary for the nodes to 1) have a consistent
   state about each other's 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 can take appropriate actions (such as releasing any
   resources).  When there are no failures, a MAG should know about the
   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)
   that 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 [RFC2119].

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

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RFC 5847               PMIPv6 Heartbeat Mechanism              June 2010

   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 SHOULD NOT be sent.  Similarly, the LMA SHOULD NOT send a
   Heartbeat Request message to a MAG if there is no active Binding
   Cache entry created by the MAG.  A PMIPv6 node MUST 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.  Deployments should be careful in setting the value for
   the HEARTBEAT_INTERVAL.  Sending Heartbeat messages too often may
   become an overhead on the path between the MAG and the LMA.  It could
   also create congestion in the network and negatively affect network
   performance.  The HEARTBEAT_INTERVAL can be set to a much larger
   value on the MAG and the LMA, if required, to reduce the burden of
   sending periodic Heartbeat messages.

   If the LMA or the MAG do not support the Heartbeat messages, they
   respond with a Binding Error message with status set to 2
   (unrecognized mobility header (MH) type value) as described in
   [RFC3775].  When the Binding Error message with status set to 2 is
   received in response to a Heartbeat Request message, the initiating
   MAG or the LMA MUST NOT use Heartbeat messages with the other end

   If a PMIPv6 node has detected that a peer PMIPv6 node has failed or
   restarted without retaining the PMIPv6 session state, it should mark
   the corresponding binding update list or binding cache entries as
   invalid.  The PMIPv6 node may also take other actions, which are
   outside the scope of this document.

   The detection of failure and restart events may be signaled to
   network operators by using asynchronous notifications.  Future work
   may define such notifications in a Structure of Management
   Information Version 2 (SMIv2) Management Information Base (MIB)

3.1.  Failure Detection

   A PMIPv6 node (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

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RFC 5847               PMIPv6 Heartbeat Mechanism              June 2010

   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.  If a Heartbeat
   Response message is received, the MISSING_HEARTBEATS counter is

3.2.  Restart Detection

   The section describes a mechanism for detecting failure recovery
   without session persistence.  In the case that the LMA or the MAG
   crashes and reboots 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

   Each PMIPv6 node (both the MAG and LMA) MUST maintain a monotonically
   increasing Restart Counter that is incremented every time the node
   reboots and loses 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
   treated as state that is preserved across reboots.  A PMIPv6 node
   includes a Restart Counter mobility option, described in Section 3.4,
   in a 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 with which it currently has
   sessions.  Stored Restart Counter values for peer PMIPv6 nodes do not
   need to be preserved across reboots.

   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 loses 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.  Note that this is possible only when
   the PMIPv6 node is capable of storing information about the peers
   across reboots.  The unsolicited Heartbeat Response message allows
   the peer PMIPv6 nodes to quickly discover the restart.  The sequence
   number field in the unsolicited Heartbeat Response is ignored and no
   response is necessary; the nodes will synchronize during the next
   request and response exchange.

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RFC 5847               PMIPv6 Heartbeat Mechanism              June 2010

3.3.  Heartbeat Message

   The Heartbeat message is based on the Mobility Header defined in
   Section 6.1 of [RFC3775].  The MH Type field in the Mobility Header
   indicates that it is a Heartbeat message.  The value MUST be set to
   13.  This document does not make any other changes to the Mobility
   Header message.  Please refer to [RFC3775] for a description of the
   fields in the Mobility Header 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
     | Payload Proto |  Header Len   |   MH Type     |   Reserved    |
     |           Checksum            |                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
     |                                                               |
     .                                                               .
     .                       Message Data                            .
     .                                                               .
     |                                                               |

                 Figure 1: Mobility Header Message Format

   The Heartbeat message follows the Checksum field in the above
   message.  The following illustrates the message format for the
   Heartbeat Mobility Header 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                         |
     |                                                               |
     .                                                               .
     .                        Mobility Options                       .
     .                                                               .
     |                                                               |

                    Figure 2: Heartbeat Message Format


      Set to 0 and ignored by the receiver.

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RFC 5847               PMIPv6 Heartbeat Mechanism              June 2010


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


      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.

   Sequence Number

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

   Mobility Options

      Variable-length field of such length that the complete Mobility
      Header is an integer that is a multiple of 8 octets long.  This
      field contains zero or more TLV-encoded mobility options.  The
      receiver MUST ignore and skip any options that it does not
      understand.  At the time of writing this document, the Restart
      Counter mobility option, described in Section 3.4, is the only
      valid option in this message.

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                         |

                 Figure 3: Restart Counter Mobility Option


      An 8-bit field that indicates that it is a Restart Counter
      mobility option.  It MUST be set to 28.

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RFC 5847               PMIPv6 Heartbeat Mechanism              June 2010


      An 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 be
   IPv4-only and not capable of routing IPv6 packets.  In this case, the
   Mobility Header containing the Heartbeat message is carried as
   specified in Section 4 of [RFC5844], i.e., the Mobility Header is
   part of the UDP payload inside an IPv4 packet (IPv4-UDP-MH).

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 or more
      than 3600 seconds.


      This variable indicates the maximum number of consecutive
      Heartbeat Request messages for which a PMIPv6 node did not receive
      a response 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
   [RFC4301] for the Heartbeat messages MUST be supported on the MAG and
   the LMA.  RFC 5213 [RFC5213] describes how to protect the Proxy
   Binding Update and Acknowledgement signaling messages with IPsec.
   The Heartbeat message defined in this specification is merely another
   subtype of the same Mobility Header protocol that is already being
   protected by IPsec.  Therefore, protecting this additional message is

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RFC 5847               PMIPv6 Heartbeat Mechanism              June 2010

   possible using the mechanisms and security policy models from these
   RFCs.  The security policy database entries should use the new MH
   Type, the Heartbeat message, for the MH Type selector.

   If dynamic key negotiation between the MAG and the LMA is required,
   Internet Key Exchange Protocol version 2 (IKEv2) [RFC4306] should be

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' name space in the
   Mobility Header defined in RFC 3775 [RFC3775].

   The Restart Counter mobility option defined in Section 3.4 must have
   the type value allocated from the same name space as the mobility
   options defined in RFC 3775 [RFC3775].

8.  Acknowledgements

   A heartbeat mechanism for a network-based mobility management
   protocol was first described in [NETLMM].  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 [GTP].

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

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5213]  Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
              and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.

   [RFC5844]  Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
              Mobile IPv6", RFC 5844, May 2010.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, December 2005.

   [RFC4306]  Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
              RFC 4306, December 2005.

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RFC 5847               PMIPv6 Heartbeat Mechanism              June 2010

   [RFC3775]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
              in IPv6", RFC 3775, June 2004.

9.2.  Informative References

   [NETLMM]   Levkowetz, H., Ed., Giaretta, G., Leung, K., Liebsch, M.,
              Roberts, P., Nishida, K., Yokota, H., and M.
              Parthasarathy, "The NetLMM Protocol", Work in Progress,
              October 2006.

   [GTP]      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 (editor)
   3950 North First Street
   San Jose, CA  95134

   EMail: vijay@wichorus.com

   Rajeev Koodli (editor)
   Cisco Systems

   EMail: rkoodli@cisco.com

   Heeseon Lim
   5403 Betsy Ross Drive
   Santa Clara, CA  95054

   EMail: hlim@stoke.com

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RFC 5847               PMIPv6 Heartbeat Mechanism              June 2010

   Nishi Kant
   5403 Betsy Ross Drive
   Santa Clara, CA  95054

   EMail: nishi@stoke.com

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

   EMail: suresh.krishnan@ericsson.com

   Julien Laganier
   Qualcomm Incorporated
   5775 Morehouse Drive
   San Diego, CA  92121

   EMail: julienl@qualcomm.com

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