Internet DRAFT - draft-haley-mip6-mh-signaling
draft-haley-mip6-mh-signaling
Mobile IPv6 B. Haley
Internet Draft Hewlett-Packard
Document: draft-haley-mip6-mh-signaling-02.txt Sri Gundavelli
Intended status: Standards Track Cisco Systems
Expires: September, 2007 March 2007
Mobility Header Signaling Message
draft-haley-mip6-mh-signaling-02.txt
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Abstract
This document specifies a new Mobility Header message type that can
be used between a mobile node and home agent to signal an event that
requires attention.
Conventions used in this document
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].
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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. Mobility Header Signaling Messages.............................5
3.1 Mobility Header Signaling Request Message..................5
3.2 Mobility Header Signaling Acknowledgement Message..........6
4. Signaling Requests.............................................7
4.1 Sending Signaling Requests.................................7
4.2 Receiving Signaling Messages...............................8
4.2.1 Mobile Node Operation....................................8
4.2.2 Home Agent Operation.....................................9
4.3 Retransmissions............................................9
5. Signaling Acknowledgements.....................................9
5.1 Sending Signaling Acknowledgements.........................9
6. Protocol Constants............................................10
7. IANA Considerations...........................................10
8. Security Considerations.......................................10
9. References....................................................10
9.1 Normative Reference.......................................10
9.2 Informative references....................................11
Acknowledgments..................................................11
Author's Addresses...............................................11
1. Introduction
RFC 3775 [2] contains no provision to allow a home agent to inform a
mobile node, or vice-versa, that there is an event that requires its
attention. For example, a home agent may wish to handoff some of its
mobile nodes to another home agent because it has come overloaded or
it is going offline.
This protocol describes a generic signaling message type that can be
used to send messages between home agents and mobile nodes.
This protocol does not describe the type of messages that might be
exchanged, that information should be defined in the document for the
specific Mobility option that will be used.
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 on the link 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
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at a new set of addresses. Note that this may not involve anything
as complex as IPv6 network renumbering, it may just involve changing
the addresses of the home agents. There are various reasons why a
mobility service provider might want to do this; an example is if the
service provider revokes the account of a user it has reason to
believe might use the old home agent address to disrupt service for
other users. With a signaling message, the service provider could
inform mobile nodes to look for a new home agent.
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3. Mobility Header Signaling Messages
The messages described below follow the Mobility Header format
specified in Section 6.1 of [2]:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Proto | Header Len | MH Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Checksum | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
. .
. Message Data .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.1 Mobility Header Signaling Request Message
The Signaling Request is used by the home agent to signal the mobile
node, or vice-versa, that there is an event that requires attention.
This packet is sent as described in Section 4.1.
The Signaling Request 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A| Reserved | Sequence # |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Mobility options .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Acknowledge (A)
The Acknowledge (A) bit is set by the sender to request a Signaling
Acknowledgement (Section 3.2) be returned upon receipt of a
Signaling Request.
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Reserved
These fields are unused. They MUST be initialized to zero by the
sender, and MUST be ignored by the receiver.
Sequence #
An 8-bit unsigned integer used by the receiving node to sequence
Signaling Requests and by the sending node to match a returned
Signaling Acknowledgement with this Signaling Request.
Mobility options
Variable-length field of such length that the complete Mobility
Header is an integer multiple of 8 octets long. This field
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.
This specification does not define any options valid for the
Signaling Request message.
If 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.
3.2 Mobility Header Signaling Acknowledgement Message
The Signaling Acknowledgement is used to acknowledge receipt of a
Signaling Request (Section 3.1). This packet is sent as described in
Section 5.1.
The Signaling Acknowledgement 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status | Sequence # |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Mobility options .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Status
8-bit unsigned integer indicating the disposition of the Signaling
Request. Values of the Status field less than 128 indicate that
the Signaling Request was accepted by the receiving node. Values
greater than or equal to 128 indicate that the Signaling Request
was rejected by the receiving node. The following Status values
are currently defined:
0 Signaling Request accepted
128 Reason unspecified
129 Administratively prohibited
130 Insufficient resources
131 Unsupported mobility option
132 Not home agent for this mobile node
Sequence #
The sequence number in the Signaling Acknowledgement is copied from
the sequence number field in the Signaling Request. It is used by
the receiving node in matching this Signaling Acknowledgement with
an outstanding Signaling Request.
Mobility options
Variable-length field of such length that the complete Mobility
Header is an integer multiple of 8 octets long. This field
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.
This specification does not define any options valid for the
Signaling Request message.
If 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. Signaling Requests
4.1 Sending Signaling Requests
When sending a Signaling Request message, the sending node constructs
the packet as it would any other Mobility Header, except:
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o The MH Type field MUST be set to (TBD).
o The Acknowledge (A) bit MAY be set to indicate the receiver must
send a Signaling Acknowledgement.
The Signaling Request message MUST use the home agent to mobile node
IPsec ESP authentication SA for integrity protection.
4.2 Receiving Signaling Messages
Upon receiving a Signaling Request 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 covered by the home agent to mobile node
IPsec ESP authentication SA for integrity protection.
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 and
MUST NOT send a Signaling Acknowledgement. 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.
If the Signaling Request is valid according to the tests above, then
it is processed further as follows:
o If the receiving node does not allow Signaling Request messages,
it MUST reject the request and SHOULD return a Signaling
Acknowledgement to the sender in which the Status field is set
to 129 (administratively prohibited).
o If the receiving node does not support the type of Mobility
Option in the Signaling Request message, it MUST reject the
request and SHOULD return a Signaling Acknowledgement to the
sender in which the Status field is set to 131 (unsupported
mobility option).
Subsequent checks depend on the current mode of operation of the
node.
4.2.1 Mobile Node Operation
If the mobile node rejects the Signaling Request message for any
other reason than specified in Section 4.2, it SHOULD return a
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Signaling Acknowledgement to the home agent in which the Status field
is set to 128 (reason unspecified).
4.2.2 Home Agent Operation
If the receiving node is a home agent, it MUST perform these
additional checks:
o If the home agent has no entry marked as a home registration in
its Binding Cache for this mobile node, then this node MUST
reject the request and SHOULD return a Signaling Acknowledgement
to the mobile node in which the Status field is set to 132 (not
home agent for this mobile node).
o If the home agent cannot process the Signaling Request message
because it is over-utilized, it MUST reject the request and
SHOULD return a Signaling Acknowledgement to the mobile node in
which the Status field is set to 130 (insufficient resources).
If the home agent rejects the Signaling Request message for any other
reason, it SHOULD return a Signaling Acknowledgement to the mobile
node in which the Status field is set to 128 (reason unspecified).
4.3 Retransmissions
If the sender has set the Acknowledge (A) bit in the Signaling
Request, but does not receive a Signaling Response, then it MAY
retransmit the message, until a response is received. The initial
value for the retransmission timer is INITIAL_MH_SIGNAL_TIMEOUT. The
retransmissions by the sender MUST use an exponential back-off
mechanism, in which the timeout period is doubled upon each
retransmission, until either the sender gets a response from the
target node, or the timeout period reaches the value
MAX_MH_SIGNAL_TIMEOUT.
5. Signaling Acknowledgements
5.1 Sending Signaling Acknowledgements
A Signaling Acknowledgement should be sent to indicate receipt of a
Signaling Request as follows:
o If the Signaling Request was discarded because it does not meet
the requirements as specified in [2] described in Section 4.2, a
Signaling Acknowledgement MUST NOT be sent. Otherwise, the
treatment depends on the below rule.
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o If the Acknowledgement (A) bit is set in the Signaling Request,
a Signaling Acknowledgement MUST be sent. Otherwise, the
treatment depends on the below rule.
o If the Signaling Request was discarded for any other reason, a
Signaling Acknowledgement SHOULD be sent.
If the Source Address field of the IPv6 header that carried the
Signaling Request does not contain a unicast address, the Signaling
Acknowledgement MUST NOT be sent, and the Signaling Request packet
MUST be silently discarded. Otherwise, the acknowledgement MUST be
sent to the Source Address.
6. Protocol Constants
INITIAL_MH_SIGNAL_TIMEOUT 5 seconds
MAX_MH_SIGNAL_TIMEOUT 20 seconds
7. IANA Considerations
A new Mobility Header type is required for the following new message
described in Section 3:
(TBD) Signaling Request
(TBD) Signaling Acknowledgement
8. Security Considerations
As with other messages in [2], the Signaling Request and
Acknowledgement messages MUST use the home agent to mobile node ESP
encryption SA for confidentiality protection, and MUST use the home
agent to mobile node ESP authentication SA for integrity protection.
The Signaling Request 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.
9. References
9.1 Normative Reference
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997
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[2] Johnson, D. Perkins, C., and Arkko, J., "Mobility Support in
IPv6", RFC 3775, June, 2004.
9.2 Informative references
Acknowledgments
Thanks to Hui Deng, James Kempf and Vijay Devarapalli for their
initial review of the draft.
Author's Addresses
Brian Haley
Hewlett-Packard Company
110 Spitbrook Road
Nashua, NH 03062, USA
Email: brian.haley@hp.com
Sri Gundavelli
Cisco Systems
170 W.Tasman Drive
San Jose, CA 95134, USA
Email: sgundave@cisco.com
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