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Internet Engineering Task Force (IETF)               V. Devarapalli, Ed.Request for Comments: 5847                                      WiChorusCategory: Standards Track                                 R. Koodli, Ed.ISSN: 2070-1721                                            Cisco Systems                                                                  H. Lim                                                                 N. Kant                                                                   Stoke                                                             S. Krishnan                                                             J. Laganier                                                           Qualcomm Inc.                                                               June 2010Heartbeat Mechanism for Proxy Mobile IPv6Abstract   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 inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc5847.Devarapalli, et al.          Standards Track                    [Page 1]

RFC 5847               PMIPv6 Heartbeat Mechanism              June 2010Copyright Notice   Copyright (c) 2010 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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 Contents1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .32.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .33.  Heartbeat Mechanism  . . . . . . . . . . . . . . . . . . . . .33.1.  Failure Detection  . . . . . . . . . . . . . . . . . . . .43.2.  Restart Detection  . . . . . . . . . . . . . . . . . . . .53.3.  Heartbeat Message  . . . . . . . . . . . . . . . . . . . .63.4.  Restart Counter Mobility Option  . . . . . . . . . . . . .7   4.  Exchanging Heartbeat Messages over an IPv4 Transport       Network  . . . . . . . . . . . . . . . . . . . . . . . . . . .85.  Configuration Variables  . . . . . . . . . . . . . . . . . . .86.  Security Considerations  . . . . . . . . . . . . . . . . . . .87.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .98.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .99.  References . . . . . . . . . . . . . . . . . . . . . . . . . .99.1.  Normative References . . . . . . . . . . . . . . . . . . .99.2.  Informative References . . . . . . . . . . . . . . . . . .10Devarapalli, et al.          Standards Track                    [Page 2]

RFC 5847               PMIPv6 Heartbeat Mechanism              June 20101.  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, theDevarapalli, 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 inSection 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 variableDevarapalli, 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 inSection 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 20103.3.  Heartbeat Message   The Heartbeat message is based on the Mobility Header defined inSection 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 inSection 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 inSection 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 isDevarapalli, 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 inSection 3.3 must have the type value   allocated from the same space as the 'MH Type' name space in the   Mobility Header defined inRFC 3775 [RFC3775].   The Restart Counter mobility option defined inSection 3.4 must have   the type value allocated from the same name space as the mobility   options defined inRFC 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.  References9.1.  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.comDevarapalli, 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.comDevarapalli, et al.          Standards Track                   [Page 11]