NETEXT WG S. Gundavelli
Internet-Draft K. Leung
Intended status: Standards Track Cisco
Expires: December 4, 2009 R. Koodli
Starent Networks
June 02, 2009
Retransmitted Message Identification Option for Proxy Mobile IPv6
draft-gundavelli-netext-pmipv6-retransmit-option-00.txt
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Abstract
The Proxy Mobile IPv6 base protocol does not provide any mechanism
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for the receiver of a mobility signaling message to determine if the
received message is the original message or a retransmitted message
of an earlier sent message. The absence of such a semantic in some
cases results in inefficient processing of the signaling messages and
will lead to additional processing load and network traffic.
This document defines a new mobility option, Retransmitted Message
Identification option for use in Proxy Binding Update and Proxy
Binding Acknowledgement messages. This option enables the mobility
entities to use proper message identifiers and retransmit markings on
the signaling messages.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Signaling and other Considerations . . . . . . . . . . . . . . 3
4. Retransmitted Message Identification (RMI) Option . . . . . . . 5
5. Protocol Configuration Variables . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . . 8
9.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
The Proxy Mobile IPv6 protocol [RFC-5213] does not provide the
ability for the sender of a signaling message to mark retransmitted
messages with a proper tag, so the receiver can differentiate between
the original message to a retransmitted message. This semantic is
important for the receiver to determine when to ignore processing a
retransmitted packet, or for various other reasons.
This document defines a new mobility option, Retransmitted Message
Identification (RMI) option, that can be used by a local mobility
anchor and a mobile access gateway for exchanging message and
retransmit identifiers. Following explains how the option helps in
detecting retransmitted messages.
MAG LMA
| PBU RMI(MesgId: 1, RetransId: 0) |
|---------------------------------------------->| * New message
| PBA RMI(MesgId: 1, RetransId: 0) |
|<----------------------------------------------|
| |
| |
| PBU RMI(MesgId: 2, RetransId: 0) |
|---------------------------------------------->| * Lost message
| No Response from MAG |
| |
| PBU RMI(MesgId: 2, RetransId: 1) |
|---------------------------------------------->| * Retransmitted
| | message
| PBA RMI(MesgId: 2, RetransId: 1) |
|<----------------------------------------------|
Figure 1: RMI Option Usage
2. Conventions
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 RFC 2119 [RFC-2119].
3. Signaling and other Considerations
The following are the signaling considerations with respect to
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supporting the retransmitted message identification capability.
o The mobile access gateway can choose to enable the retransmitted
message identification feature by including the Retransmitted
Message Identification (RMI) option (Section 4.0) in the Proxy
Binding Update that it sends to the local mobility anchor. The
configuration variable, EnableRetransmittedMessageIdentification,
can be used for controlling this aspect.
o For constructing the RMI option, each newly generated message MUST
have a unique message identifier (mid). This identifier is
specified in the mid field of the RMI option. The retransmit
identifier (rid) for the initial message will be set to value of
zero, this is specified in the rid field of the RMI option. The
mobile access gateway can maintain this message identifier as a
monotonically increasing counter maintained on a per packet basis
for each mobile node's session.
o The mobile access gateway may retransmit a Proxy Binding Update
message if it did not get a response to the previously transmitted
request. When retransmitting a message, the message identifier in
the RMI option MUST remain fixed and the retransmit identifier
MUST be increased by one. All other content in the message
including the options MUST be identical, except the sequence
number and the value in the Time Stamp option which can be
different.
o The conceptual Binding Update List entry data structure maintained
by the mobile access gateway, described in Section 6.1 of [RFC-
5213], MUST be extended to store the last sent message identifier
and the retransmit identifier.
o The local mobility anchor MUST include the RMI option in the Proxy
Binding Acknowledgement message, if the same option was present in
the received Proxy Binding Update. Otherwise, it MUST NOT include
the option. When this option is included in the message, the
message identifier and the retransmit identifier MUST be set to
the option values present in the request.
o If the local mobility anchor does not support the RMI option, it
SHOULD ignore the option and continue processing the rest of the
Proxy Binding Update message. The absence of the RMI option in
the Proxy Binding Acknowledgement indicates that the sender does
not support the Retransmitted Message Identification capability
and in such case the mobile access gateway MUST NOT include the
RMI option in the subsequent Proxy Binding Update messages that it
sends to that local mobility anchor.
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o If the local mobility anchor receives a Proxy Binding Update
message while in the middle of processing a request (such as
waiting for response from AAA) with the same message identifier,
but with a different retransmit identifier, the message MUST be
silently ignored.
o The conceptual Binding Cache entry data structure maintained by
the local mobility anchor, described in Section 5.1 of [RFC-5213],
MUST be extended to store the last received message identifier and
the retransmit identifier.
4. Retransmitted Message Identification (RMI) Option
A new option, Retransmitted Message Identification (RMI) option is
defined for using it in Proxy Binding Update and Proxy Binding
Acknowledgement messages exchanged between a local mobility anchor
and a mobile access gateway. This option is used for carrying
message and retransmission identifiers.
The alignment requirement for this option is 4n.
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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 | Reserved | Retransmit-Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Identifier (mid) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
<IANA>
Length
8-bit unsigned integer indicating the length in octets of
the option, excluding the type and length fields. The value
for this field MUST be set to 6.
Retransmission Identifier (rid)
A 8-bit field for carrying the retransmission identifier. This
value will be set to zero for the first transmission of any
newly generated signaling message and the value will be
monotonically increased in each of the subsequent
retransmissions of the same message uniquely identified by the
message identifier.
Message Identifier (mid)
A 32-bit field for identifying the message. Each newly
generated Proxy Binding Update message will have a unique
identifier, however the Proxy Binding Acknowledgement will
always carry the identifier that was present in the request.
Any retransmitted messages will carry the same identifier that
was present in the initial message.
Figure 2: Retransmitted Message Identification (RMI) Option
5. Protocol Configuration Variables
The mobile access gateway MUST allow the following variables to be
configured by the system management. The configured values for these
protocol variables MUST survive server reboots and service restarts.
EnableRetransmittedMessageIdentification
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This flag indicates whether or not the mobile access gateway
should include the retransmitted message identification option in
the mobility signaling messages that it sends to the local
mobility anchor.
The default value for this flag is set to FALSE, indicating that
the mobile access gateway MUST NOT include this option in any of
the Proxy Binding Update messages.
When the value for this flag is set to TRUE, the mobile access
gateway MUST include this option in all the Proxy Binding Update
messages.
6. IANA Considerations
This specification defines a new Mobility Header option, the
Retransmitted Message Identification option. This option can be
carried in mobility header messages. This option is described in
Section 4.0. The Type value for this option needs to be assigned
from the same numbering space as allocated for the other mobility
options, as defined in [RFC-3775].
7. Security Considerations
The Retransmitted Message Identification option defined in this
specification is for use in mobility signaling messages, Proxy
Binding Update and Proxy Binding Acknowledgement messages. This
option is carried like any other mobility header option as specified
in [RFC-3775] and does not require any special security
considerations. The required security mechanisms specified in the
base Proxy Mobile IPv6 protocol [RFC-5213] for protecting these
signaling messages are sufficient when carrying these mobility
options.
8. Acknowledgements
The authors would like to thank Venkatesh Gota, Ashwin Kabadi and
Vojislav Vucetic on the discussions related to the similar semantics
present in GTP and making the motivation for this work stronger.
9. References
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9.1. Normative References
[RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC-3775] Johnson, D., Perkins, C., Arkko, J., "Mobility Support in
IPv6", RFC 3775, June 2003.
[RFC-5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
9.2. Informative References
[ID-PMIP6-IPv4] R. Wakikawa and S. Gundavelli, "IPv4 Support for
Proxy Mobile IPv6", draft-ietf-netlmm-pmip6-ipv4-support-12, April
2009.
Authors' Addresses
Sri Gundavelli
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: sgundave@cisco.com
Kent Leung
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: kleung@cisco.com
Rajeev Koodli
Starent Networks
30 International Place
Tewksbury, MA
Email: rkoodli@starentnetworks.com
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