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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