Internet Engineering Task Force (IETF) V. Devarapalli, Ed.

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: [email protected]

Rajeev Koodli (editor)
Cisco Systems
USA

EMail: [email protected]

Heeseon Lim
Stoke
5403 Betsy Ross Drive
Santa Clara, CA 95054
USA

EMail: [email protected]

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: [email protected]

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

EMail: [email protected]

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

EMail: [email protected]

Devarapalli, et al. Standards Track [Page 11]