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rfc:rfc5847

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
                                                                 Stoke
                                                           S. Krishnan
                                                           J. Laganier
                                                         Qualcomm Inc.
                                                             June 2010
             Heartbeat Mechanism for Proxy Mobile IPv6

Abstract

 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
 http://www.rfc-editor.org/info/rfc5847.

Devarapalli, et al. Standards Track [Page 1] 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

Devarapalli, et al. Standards Track [Page 2] 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",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 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

Devarapalli, et al. Standards Track [Page 3] 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
 again.
 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)
 module.

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

Devarapalli, et al. Standards Track [Page 4] 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
 reset.

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
 again.
 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.

Devarapalli, et al. Standards Track [Page 5] 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
 Reserved
    Set to 0 and ignored by the receiver.

Devarapalli, et al. Standards Track [Page 6] RFC 5847 PMIPv6 Heartbeat Mechanism June 2010

 'U'
    Set to 1 in Unsolicited Heartbeat Response.  Otherwise, set to 0.
 'R'
    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
    reply.
 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
 Type
    An 8-bit field that indicates that it is a Restart Counter
    mobility option.  It MUST be set to 28.

Devarapalli, et al. Standards Track [Page 7] RFC 5847 PMIPv6 Heartbeat Mechanism June 2010

 Length
    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
 configurable.
 HEARTBEAT_INTERVAL
    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.
 MISSING_HEARTBEATS_ALLOWED
    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

Devarapalli, et al. Standards Track [Page 8] 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
 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' 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.

Devarapalli, et al. Standards Track [Page 9] 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)
 WiChorus
 3950 North First Street
 San Jose, CA  95134
 USA
 EMail: vijay@wichorus.com
 Rajeev Koodli (editor)
 Cisco Systems
 USA
 EMail: rkoodli@cisco.com
 Heeseon Lim
 Stoke
 5403 Betsy Ross Drive
 Santa Clara, CA  95054
 USA
 EMail: hlim@stoke.com

Devarapalli, et al. Standards Track [Page 10] RFC 5847 PMIPv6 Heartbeat Mechanism June 2010

 Nishi Kant
 Stoke
 5403 Betsy Ross Drive
 Santa Clara, CA  95054
 USA
 EMail: nishi@stoke.com
 Suresh Krishnan
 Ericsson
 8400 Decarie Blvd.
 Town of Mount Royal, QC
 Canada
 EMail: suresh.krishnan@ericsson.com
 Julien Laganier
 Qualcomm Incorporated
 5775 Morehouse Drive
 San Diego, CA  92121
 USA
 EMail: julienl@qualcomm.com

Devarapalli, et al. Standards Track [Page 11]

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