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Versions: (draft-haley-mip6-ha-switch) 00 01
02 03 04 05 06 RFC 5142
Mobile IPv6 B. Haley
Internet Draft Hewlett-Packard
Document: draft-ietf-mip6-ha-switch-03.txt V. Devarapalli
Intended status: Standards Track Azaire Networks
Expires: September, 2007 H. Deng
Hitachi
J. Kempf
DoCoMo USA Labs
March 2007
Mobility Header Home Agent Switch Message
draft-ietf-mip6-ha-switch-03.txt
Status of this Memo
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Abstract
This document specifies a new Mobility Header message type that can
be used between a home agent and mobile node to signal a mobile node
that it should acquire a new home agent.
Conventions used in this document
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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 [1].
Table of Contents
1. Introduction...................................................2
2. Scenarios......................................................2
2.1 Overloaded.................................................3
2.2 Load Balancing.............................................3
2.3 Maintenance................................................3
2.4 Functional Load Balancing..................................3
2.5 Home Agent Renumbering.....................................3
3. Home Agent Switch Message......................................4
4. Home Agent Operation...........................................6
4.1 Sending Home Agent Switch Messages.........................6
4.2 Retransmissions............................................7
4.3 Mobile Node Errors.........................................7
5. Mobile Node Operation..........................................8
5.1 Receiving Home Agent Switch Messages.......................8
5.2 Selecting a Home Agent.....................................8
6. Operational Considerations.....................................9
7. Procotol Constants.............................................9
8. IANA Considerations............................................9
9. Security Considerations........................................9
10. References...................................................10
10.1 Normative References.....................................10
10.2 Informative references...................................10
Acknowledgments..................................................10
Author's Addresses...............................................11
1. Introduction
RFC 3775 [2] contains no provision to allow a home agent to inform a
mobile node that it needs to stop acting as the home agent for the
mobile node. For example, a home agent may wish to handoff some of
its mobile nodes to another home agent because it has become
overloaded or it is going offline.
This protocol describes a signaling message type that can be used to
send a handoff notification between a home agent and mobile node.
2. Scenarios
Here are some example scenarios where a home agent signaling message
would be useful.
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2.1 Overloaded
There are a number of reasons a home agent might be considered
overloaded. One might be that it is at, or near, its limit on the
number of home bindings it is willing to accept. Another is that it
has reached a pre-determined level of system resource usage - memory,
cpu cycles, etc. In either case, it would be desirable for a home
agent to reduce the number of home bindings before a failure occurs.
2.2 Load Balancing
A home agent might know of other home agents that are not as heavily
loaded as itself, learned through some other mechanism outside the
scope of this document. An operator may wish to try and balance this
load so a failure disrupts a smaller percentage of mobile nodes.
2.3 Maintenance
Most operators do periodic maintenance in order to maintain
reliability. If a home agent is being shutdown for maintenance, it
would be desirable to inform mobile nodes so they do not lose
mobility service.
2.4 Functional Load Balancing
A Mobile IPv6 home agent provides mobile nodes with two basic
services - a rendezvous server where correspondent nodes can find the
current care-of address for the mobile node, and as an overlay router
to tunnel traffic to/from the mobile node at its current care-of
address.
A mobility service provider could have two sets of home agents to
handle the two functions. The rendezvous function could be handled
by a machine specialized for high-speed transaction processing, while
the overlay router function could be handled by a machine with high
data throughput.
A mobile node would start on the rendezvous server home agent and
stay there if it does route optimization. However, if the original
home agent detects that the mobile node is not doing route
optimization, but instead reverse-tunneling traffic, it could
redirect the mobile node to a home agent with better data throughput.
2.5 Home Agent Renumbering
Periodically, a mobility service provider may want to shut-down home
agent services at a set of IPv6 addresses and bring service back up
at a new set of addresses. Note that this may not involve anything
as complex as IPv6 network renumbering, it may just involve changing
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the addresses of the home agents. With a signaling message, the
service provider could inform mobile nodes to look for a new home
agent.
3. Home Agent Switch Message
The Home Agent Switch message is used by the home agent to signal the
mobile node that it needs to stop acting as the home agent for the
mobile node, and that it should acquire a new home agent. Home Agent
Switch messages are sent as described in Section 4.
The message described below follows the Mobility Header format
specified in Section 6.1 of [2]:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Proto | Header Len | MH Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Checksum | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
. .
. Message Data .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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The Home Agent Switch Message uses the MH Type value (TBD). When
this value is indicated in the MH Type field, the format of the
Message Data field in the Mobility Header is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|# of Addresses | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
. .
. Home Agent Addresses .
. .
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
. .
. Mobility options .
. .
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
# of Addresses
An 8-bit unsigned integer indicating the number of IPv6 home agent
addresses in the message. If set to zero, the mobile node MUST
perform home agent discovery.
Reserved
8-bit field reserved for future use. The value MUST be initialized
to zero by the sender, and MUST be ignored by the receiver.
Home Agent Addresses
A list of alternate home agent addresses for the mobile node. The
number of addresses present in the list is indicated by the "# of
Addresses" field in the Home Agent Switch message.
Mobility options
Variable-length field of such length that the complete Mobility
Header is an integer multiple of 8 octets long. This field
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contains zero of more TLV-encoded mobility options. The encoding
and format of defined options MUST follow the format specified in
Section 6.2 of [2]. The receiver MUST ignore and skip any options
with it does not understand.
The Binding Refresh Advice mobility option defined in Section 6.2.4
of [2] is valid for the Home Agent Switch message.
If no home agent addresses and no options are present in this
message, no padding is necessary and the Header Len field in the
Mobility Header will be set to 0.
4. Home Agent Operation
4.1 Sending Home Agent Switch Messages
When sending a Home Agent Switch message, the sending node constructs
the packet as it would any other Mobility Header, except:
o The MH Type field MUST be set to (TBD).
o If alternative home agent addresses are known, the sending home
agent SHOULD include them in the list of suggested alternate
home agents. The home agent addresses field should be
constructed as described in Section 10.5.1 of [2], which will
randomize addresses of the same preference in the list.
o The "# of addresses" field MUST be filled-in corresponding to
the number of home agent addresses included in the message. If
no addresses are present, the field MUST be set to zero, forcing
the mobile node to perform home agent discovery by some other
means.
o If the home agent is able to continue offering services to the
mobile node for some period of time, it MAY include a Binding
Refresh Advice mobility option indicating the time (in units of
4 seconds) until the binding will be deleted.
The Home Agent Switch message MUST be authenticated in one of the
following ways:
o The home agent to mobile node IPsec ESP authentication SA for
integrity protection.
o A home agent to mobile node authentication option, such as [3].
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A home agent SHOULD send a Home Agent Switch message when a known
period of unavailability is pending so the mobile node has sufficient
time to find another suitable home agent.
The sending node does not need to be the current home agent for the
mobile node, for example as described in [4], but it MUST have a
security association with the mobile node so the message is not
rejected. In this case, the Home Agent Switch message SHOULD only
contain the address of the home agent sending the message in the Home
Agent Addresses field, which implies the mobile node should switch to
using the sender as its new home agent.
4.2 Retransmissions
If the home agent does not receive a response from the mobile node -
either a Binding Update message to delete its home binding if it is
the current home agent, or a Binding Update message to create a home
binding if it is not the current home agent, then it SHOULD
retransmit the message, until a response is received. The initial
value for the retransmission timer is INITIAL-HA-SWITCH-TIMEOUT.
The retransmissions by the home agent MUST use an exponential back-
off mechanism, in which the timeout period is doubled upon each
retransmission, until either the home agent gets a response from the
mobile node to delete its binding, or the timeout period reaches the
value MAX-HA-SWITCH-TIMEOUT.
If the home agent included a Binding Refresh Advice mobility option,
then it SHOULD delay any retransmissions until at least one half of
the time period has expired, or INITIAL-HA-SWITCH-TIMEOUT, whichever
value is less.
4.3 Mobile Node Errors
If a mobile node does not understand how to process a Home Agent
Switch Message, it will send a Binding Error message as described in
Section 5.1.
If a mobile node is unreachable, in other words, it still has a home
binding with the home agent after reaching the timeout period of MAX-
HA-SWITCH-TIMEOUT, the home agent SHOULD NOT make any conclusions
about its status.
In either case, the home agent SHOULD attempt to continue providing
services until the lifetime of the binding expires.
Attempts by the mobile node to extend the binding lifetime with a
Binding Update message SHOULD be rejected, and a Binding
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Acknowledgement SHOULD be returned with status value 129
(Administratively prohibited) as specified in Section 6.1.8 of [2].
5. Mobile Node Operation
5.1 Receiving Home Agent Switch Messages
Upon receiving a Home Agent Switch message, the Mobility Header MUST
be verified as specified in [2], specifically:
o The Checksum, MH type, Payload Proto and Header Len fields
MUST meet the requirements of Section 9.2 of [2].
o The packet MUST be authenticated, either by the home agent to
mobile node IPsec ESP authentication SA for integrity
protection, or a home agent to mobile node authentication
option.
If the packet is dropped due to the above tests, the receiving node
MUST follow the processing rules as Section 9.2 of [2] defines. For
example, it MUST send a Binding Error message with the Status field
set to 2 (unrecognized MH Type value) if it does not support the
message type.
Upon receipt of a Home Agent Switch message, the mobile node MUST
stop using its current home agent for services and MUST delete its
home binding by sending a Binding Update message as described in [2].
This acts as an acknowledgement of the Home Agent Switch message.
Alternately, if the sender of the message is not the current home
agent, sending a Binding Update message to create a home binding will
act as an acknowledgement of the Home Agent Switch message.
If a Binding Refresh Advice mobility option is present, the mobile
node MAY delay the deletion of its home binding and continue to use
its current home agent until the calculated time period has expired.
If the Home Agent Switch message contains a list of alternate home
agent addresses, the mobile node SHOULD select a new home agent as
described in Section 5.2, and establish the necessary IPsec security
associations with the new home agent by whatever means required as
part of the mobile node/home agent bootstrapping protocol for the
home agent's mobility service provider. If no alternate home agent
addresses are included in the list, the mobile node MUST first
perform home agent discovery.
5.2 Selecting a Home Agent
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In most cases, the home agent addresses in the Home Agent Switch
message will be of other home agents on the home link of the mobile
node. In this case, the mobile node SHOULD select a new home agent
from the addresses as they are ordered in the list. If the first
address in the list is unable to provide service, then the subsequent
addresses in the list should be tried in-order.
In the case that the home agent addresses in the Home Agent Switch
message are not all home agents on the home link of the mobile node
(the computed prefix is different), the mobile node SHOULD select one
on the home link first, if available, followed by home agents not on
the home link. Choosing a home agent not on the home link might
require a change of the home address for the mobile node, which could
cause a loss of connectivity for any connections using the current
home address.
6. Operational Considerations
This document does not specify how an operator might use the Home
Agent Switch message in its network. However, it might be the case
that a home agent provides service for many thousands of mobile
nodes. Care should be taken to reduce the signaling overhead
required for handing off many mobile nodes to an alternate home
agent.
7. Procotol Constants
INITIAL-HA-SWITCH-TIMEOUT 5 seconds
MAX-HA-SWITCH-TIMEOUT 20 seconds
8. IANA Considerations
A new Mobility Header type is required for the following new message
described in Section 3:
(TBD) Home Agent Switch message
9. Security Considerations
The Home Agent Switch message MUST be authenticated by one of the
following methods:
o The home agent to mobile node IPsec ESP authentication SA for
integrity protection as described in [2].
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o A home agent to mobile node authentication option, such as
[3].
The Home Agent Switch message MAY use the IPsec ESP SA in place for
Binding Updates and Acknowledgements as specified in Section 5.1 of
[2], in order to reduce the number of configured security
associations. This also gives the message authenticity protection.
Some operators may not want to reveal the list of home agents to on-
path listeners. In such a case, the Home Agent Switch message should
use the home agent to mobile node IPsec ESP encryption SA for
confidentiality protection.
10. References
10.1 Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997
[2] Johnson, D., Perkins, C., and Arkko, J., "Mobility Support in
IPv6", RFC 3775, June, 2004.
10.2 Informative references
[3] Patel, A., Leung, K., Khalil, M., Akhtar, H., and Chowdhury, K.,
"Authentication Protocol for Mobile IPv6", RFC 4285, January,
2006.
[4] Wakikawa, R. (Editor), "Home Agent Reliability Protocol", draft-
ietf-mip6-hareliability-01.txt, October, 2006.
Acknowledgments
We would like to thank the authors of a number of previous drafts
that contributed content to this document:
o draft-wakikawa-mip6-nemo-haha-spec-00.txt
o draft-deng-mip6-ha-loadbalance-02.txt
o draft-kempf-mip6-ha-alert-00.txt
o draft-haley-mip6-mh-signaling-00.txt
Thanks also to Kilian Weniger, Jixing Liu, Alexandru Petrescu, Jouni
Korhonen, and Wolfgang Fritsche for their review and feedback.
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Author's Addresses
Brian Haley
Hewlett-Packard Company
110 Spitbrook Road
Nashua, NH 03062, USA
Email: brian.haley@hp.com
Vijay Devarapalli
Azaire Networks
3121 Jay Street
Santa Clara, CA 95054 USA
Email: vijay.devarapalli@azairenet.com
James Kempf
DoCoMo USA Labs
181 Metro Drive
Suite 300
San Jose, CA 95110 USA
Email: kempf@docomolabs-usa.com
Hui Deng
Research & Development Center
Hitachi (China), Investment Ltd.
Beijing Fortune Bldg. 1701, 5 Dong San Huan Bei-Lu
Chao Yang District, Beijing 100004, China
Email: hdeng@hitachi.cn
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