Network Working Group S. Krishnan
Internet-Draft S. Touati
Intended status: Informational Z. Qiang
Expires: August 28, 2008 Ericsson
February 25, 2008
Redirecting Proxy Binding Updates in PMIPv6
draft-krishnan-mext-ha-redirect-01
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Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This document specifies a new LMA Redirect mechanism, where an
initially contacted LMA can let the MAG know that it needs to connect
to an alternate LMA to get mobility services, either for overload
prevention and/or load balancing purposes. This document proposes a
new error code for the proxy binding acknowledgement message and a
new mobility option to be carried on the binding acknowledgement
message for this purpose.
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Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Proposed method . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Alternate LMA List Option . . . . . . . . . . . . . . . . . . . 3
5. LMA Operation . . . . . . . . . . . . . . . . . . . . . . . . . 6
6. MAG Operation . . . . . . . . . . . . . . . . . . . . . . . . . 6
7. Operational Considerations . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
9. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
10. Normative References . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . . . 9
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1. Requirements notation
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].
2. Introduction
In PMIPv6 [PMIPv6], LMAs are responsible for the registration of
mobile nodes in the home network, intercepting packets destined for
them, and tunneling these packets to their proxy care-of address
hosted on a MAG. When the LMA has to support a large number of
mobile nodes and actively tunnel traffic to them, it could become
overloaded, leading to dropped packets and connections.
An LMA might not want to accept any new bindings of mobile nodes
other than the ones it is currently supporting, for various reasons.
i.e., it might be overloaded, it wants to achieve better load
balancing with another known LMA in the same network, or it has some
scheduled maintenance coming up soon.
[RFC5142] provides a mechanism that allows a Home Agent to signal the
Mobile Node that it should contact a new Home Agent, but it is not
clear if this mechanism can be used for PMIPv6 in the interaction
between the MAG and the LMA.
3. Proposed method
When an LMA receives a PBU message from a MAG and is not able to
serve the MN specified in the PBU, it sends a PBA message back with
an error code describing the cause for why it cannot accept the
binding. Along with the status code, the LMA optionally includes a
mobility option called the Alternate LMA list, that contains a list
of LMA addresses that the MAG can contact to obtain mobility service
for the MN. The method by which the alternate LMA list is created on
the LMA is out of scope of this document.
A new status code is defined in this document. The PMIPV6-LMA-
REDIRECT status code is used when the LMA wishes to redirect the MAG.
4. Alternate LMA List Option
This document defines a new mobility option called the Alternate LMA
List Option. This option MUST be used only in PBA messages sent from
a LMA towards the MAG. This option SHOULD be present if the status
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code is PMIPV6-LMA-REDIRECT. It MUST NOT be present if the status
code is not PMIPV6-LMA-REDIRECT.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Num LMAs | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: :
: LMA1 Address :
: :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: :
: LMA2 Address :
: :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
: :
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: :
: LMAn Address :
: :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option Type
TBA3
Option Length
Length of the Alternate LMA List mobility option.
Num LMAs
Number of LMA addresses in the following list
Reserved
This field MUST be set to zero and ignored on reception
LMA1 Address
128 bit address of the first LMA
LMAn Address
128 bit address of the nth LMA
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Figure 1: Alternate LMA List Option Format
5. LMA Operation
Upon receiving a Proxy Binding Update message from a MAG, the LMA may
reject the binding and provide a list of alternate LMAs. This may be
done for various reasons like administrative, load balancing, or
policy reasons as described earlier.
The LMA MUST prepare a Proxy Binding Acknowledgment message, as
described in [PMIPv6], with a status code PMIPV6-LMA-REDIRECT. The
LMA needs to be aware of alternate LMAs that can serve the MN, and it
MUST include an Alternate LMA List option containing the addresses of
the alternate LMAs.
6. MAG Operation
Upon receiving the Proxy Binding Acknowledgment from the LMA with the
status code set to PMIPV6-LMA-REDIRECT, the MAG SHOULD parse the
Alternate LMA List Option, and extract the IPv6 addresses of the
LMA(s).
The MAG MUST then send a Proxy Binding Update message to the first
LMA address received in the Alternate LMA List Option, containing the
same information as the initial PBU message.
If the connection to the alternate LMA fails and the Status code is
not PMIPV6-LMA-REDIRECT, the Mobile node MUST select, if available,
the next LMAA address received in the initial PBA message. This
process continues until the exhaustion of the list of LMAs.
If the MAG receives a Proxy Binding acknowledgment message from an
alternate LMA with status code PMIPV6-LMA-REDIRECT, then this newly
received list of LMAs MUST override the previously received one. The
MAG MUST select the first LMA in the newly received list, and send it
a Proxy Binding Update message.
In general, each time a new redirect is received by the MAG it will
override the previously received redirect(s) if any and the MAG
always acts only upon the latest Alternate LMA List.
7. Operational Considerations
In case the Redirect Mobility Option is used for redirect purposes,
the potential LMA that can be returned to a MAG MUST be able to
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handle the Home Prefix of the Home Address of the Mobile Node.
There could be a limit to how many redirects can be accepted by a MAG
before it gives up. This can be configured on the MAG. This doesn't
preclude the LMA from sending the Redirect Mobility Option.
It is possible that two or more LMAs can send redirects that can send
an MAG on a loop. This can be avoided by careful configuration of
the network. A protocol based solution is possible but will
unnecessarily complicate the MAG.
8. IANA Considerations
This document requests the assignment of the following status code
from the Mobile IPv6 parameters Status Codes registry located at
http://www.iana.org/assignments/mobility-parameters .
TBA2 PMIPV6-LMA-REDIRECT
This also requests the assignment of the following option code from
the Mobile IPv6 parameters Mobility Options registry located at
http://www.iana.org/assignments/mobility-parameters .
TBA3 Alternate LMAA List
9. Security Considerations
This document specifies an option in the proxy binding
acknowledgement message that redirects the MAG towards another LMA.
A malicious or compromised LMA can send this message to redirect an
MAG towards a possibly unavailable set of LMA addresses.
10. Normative References
[PMIPv6] Gundavelli, S., "Proxy Mobile IPv6",
draft-ietf-netlmm-proxymip6-11 (work in progress),
March 2007.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5142] Haley, B., Devarapalli, V., Deng, H., and J. Kempf,
"Mobility Header Home Agent Switch Message", RFC 5142,
January 2008.
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Authors' Addresses
Suresh Krishnan
Ericsson
8400 Decarie Blvd.
Town of Mount Royal, QC
Canada
Phone: +1 514 345 7900 x42871
Email: suresh.krishnan@ericsson.com
Samy Touati
Ericsson
8400 Decarie Blvd.
Town of Mount Royal, QC
Canada
Phone: +1 514 345 7900 x42366
Email: samy.touati@ericsson.com
Zu Qiang
Ericsson
8400 Decarie Blvd.
Town of Mount Royal, QC
Canada
Phone: +1 514 345 7900 x47370
Email: zu.qiang@ericsson.com
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