One document matched: draft-haley-mip6-mh-signaling-01.txt
Differences from draft-haley-mip6-mh-signaling-00.txt
Mobile IPv6
Internet Draft B. Haley
Document: draft-haley-mip6-mh-signaling-01.txt Hewlett-Packard
Company
Sri Gundavelli
Cisco Systems
Expires: April, 2006 October 2005
Mobility Header Signaling Message
draft-haley-mip6-mh-signaling-01.txt
Status of this Memo
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Abstract
This document describes an extension to the Mobile IPv6 base protocol
[2] by defining a new Mobility Header message type that can be used
for sending notification messages between a mobile node, its
correspondent nodes, and its home agent. The purpose of this
extension is to provide an extensible framework by which Mobile IPv6
entities can exchange notification messages indicating that certain
events have occurred.
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......................................................3
2.1 Binding Revocation.........................................3
2.2 Home Agent switchover......................................3
2.3 Failure of Back Haul Connectivity..........................3
2.4 Explicit Network Mobility (NEMO) Prefix Recovery...........3
2.5 Billing Event..............................................3
3. Operation Overview.............................................4
3.1 Typical Flow of a Signaling Message........................4
3.2 Participating Entities.....................................4
4. Mobility Header Signaling Messages.............................4
4.1 Mobility Header Signaling Request Message..................5
4.2 Mobility Header Signaling Acknowledgement Message..........6
5. Signaling Requests.............................................7
5.1 Sending Signaling Requests.................................7
5.2 Receiving Signaling Messages...............................8
5.2.1 Mobile Node Operation....................................8
5.2.2 Home Agent Operation.....................................8
5.2.3 Correspondent Node Operation.............................9
5.3 Retransmissions............................................9
6. Signaling Acknowledgements.....................................9
6.1 Sending Signaling Acknowledgements.........................9
7. Protocol Constants............................................10
8. IANA Considerations...........................................10
9. Security Considerations.......................................10
9.1 Mobile Node to Home Agent Messages........................10
9.2 Mobile Node to Correspondent Node Messages................10
10. References...................................................11
10.1 Normative References.....................................11
10.2 Informative references...................................11
Acknowledgments..................................................11
Author's Addresses...............................................11
1. Introduction
The Mobile IPv6 base specification [2] does not provide any mechanism
for a home agent, mobile node or correspondent node to exchange
signaling or status messages among themselves during a mobility
session. The ability to send asynchronous notification events is
useful in many types of services for which cooperation between these
entities is required. For example, a home agent may wish to
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terminate the binding of a mobile node, or it may wish to handoff
that binding to some other home agent on the home network.
This specification defines a generic notification header that can be
used by a home agent, mobile node and correspondent node for sending
and receiving notification events during the lifetime of a mobility
session. This specification, however, does not define any specific
notification message types that can be carried within this generic
notification header. The specific event and the corresponding action
that the receiving entity needs to take on receiving that event
should be defined in the document for that specific message type.
2. Scenarios
Here are some example scenarios where a home agent signaling message
would be useful.
2.1 Binding Revocation
There are a number of reasons a home agent might wish to revoke the
binding of a mobile node, for example it might be overloaded or going
off-line for maintenance. The mobile node must be notified before
such an administrative action can take place. Upon receiving this
event, the mobile node can release the system resources and may
attempt to contact a different home agent, or may take a different
action.
2.2 Home Agent switchover
A home agent may wish to handoff a given mobility binding to a
different home agent on the home network, for example as described in
[ID-HA-Switch].
2.3 Failure of Back Haul Connectivity
Upon detecting a failure of its back haul connectivity, a home agent
may wish to notify all of its mobile nodes about this situation so
they can find other home agents with better service.
2.4 Explicit Network Mobility (NEMO) Prefix Recovery
A home agent may decide to withdraw a routing prefix attached to a
mobile router. The home agent can notify a mobile router about this
action so it can remove the routing state for that prefix.
2.5 Billing Event
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A home agent can notify a mobile node about its service usage, or
about its pending account balance as an informational event.
3. Operation Overview
The concept is that Mobile IPv6 entities can send notifications when
a certain event or a state change occurs. The actual reason for
sending a notification is outside the scope of this document.
3.1 Typical Flow of a Signaling Message
+----+ Signaling Request +----+
| |------------------------------>| |
| |<------------------------------| |
+----+ Signaling Acknowledgement +----+
MIPv6 Entity MIPv6 Entity
3.2 Participating Entities
Signaling messages may be exchanged between a mobile node and its
home agent, or a mobile node and a Mobile IPv6 capable correspondent
node that has a current binding cache entry for that mobile node.
Signaling messages MUST NOT be exchanged between a mobile node and a
correspondent node that is not Mobile IPv6 capable or has no binding
cache entry for that mobile node.
Signaling messages MUST NOT be exchanged between the home agent of a
mobile node and a correspondent node of the mobile node, as there
will not be any trust relationship between these two entities.
The two participating entities exchanging signaling messages MUST
have a security relationship and should have the ability to detect
message replay and man-in-the-middle attacks.
4. 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 | |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
. .
. Message Data .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.1 Mobility Header Signaling Request Message
The Signaling Request is used by one Mobile IPv6 entity to signal
another entity that there is an event that requires attention. This
packet is sent as described in Section 5.1.
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 4.2) be returned upon receipt of a
Signaling Request.
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.
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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.
4.2 Mobility Header Signaling Acknowledgement Message
The Signaling Acknowledgement is used to acknowledge receipt of a
Signaling Request (Section 4.1). This packet is sent as described in
Section 6.1.
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 .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
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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 [3]. 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.
5. Signaling Requests
5.1 Sending Signaling Requests
When sending a Signaling Request 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 The Acknowledge (A) bit MAY be set to indicate the receiver must
send a Signaling Acknowledgement.
The Signaling Request message MUST meet the security requirements
outlined in Section 9.1 or 9.2, depending on the association it has
with the target entity.
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5.2 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 Signaling Request message MUST meet the security
requirements outlined in Section 9.1 or 9.2, depending on the
association it has with the sending entity.
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.
5.2.1 Mobile Node Operation
If the mobile node rejects the Signaling Request message for any
other reason than specified in Section 5.2, it SHOULD return a
Signaling Acknowledgement to the sender in which the Status field is
set to 128 (reason unspecified).
5.2.2 Home Agent Operation
If the receiving node is a home agent, it MUST perform these
additional checks:
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o If the home agent has no entry marked as a home registration in
its Binding Cache for the sending node, then this node MUST
reject the request and SHOULD return a Signaling Acknowledgement
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 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 in which the
Status field is set to 128 (reason unspecified).
5.2.3 Correspondent Node Operation
If the correspondent node rejects the Signaling Request message for
any other reason than specified in Section 5.2, it SHOULD return a
Signaling Acknowledgement to the sender in which the Status field is
set to 128 (reason unspecified).
5.3 Retransmissions
If the sender has set the Acknowledge (A) bit in the Signaling
Request, but does not receive a Signaling Acknowledgement, 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.
6. Signaling Acknowledgements
6.1 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 5.2, 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.
7. Protocol Constants
INITIAL_MH_SIGNAL_TIMEOUT 5 seconds
MAX_MH_SIGNAL_TIMEOUT 20 seconds
8. IANA Considerations
A new Mobility Header type is required for the following new message
described in Section 4:
(TBD) Signaling Request
(TBD) Signaling Acknowledgement
9. Security Considerations
9.1 Mobile Node to Home Agent Messages
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.
9.2 Mobile Node to Correspondent Node Messages
The entities exchanging Signaling Requests and Acknowledgements MUST
have a trust relation and the messages MUST be protected by an IPSec
SA. These messages are thus not vulnerable to replay or man-in-the-
middle attacks.
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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.
[3] Arkko, J., Devarapalli, V., and F. Dupont, "Using IPsec to
Protect Mobile IPv6 Signaling Between Mobile Nodes and Home
Agents", RFC 3776, June, 2004.
10.2 Informative references
[ID-HA-Switch] Haley, B., Devarapalli, V., Kempf, J., and Deng, H.,
"Mobility Header Home Agent Switch Message", draft-haley-mip6-ha-
switch-00.txt (work in progress), April, 2005.
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 West Tasman Drive
San Jose, CA 95134, USA
Email: sgundave@cisco.com
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