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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 RFC 5061

Network Working Group                                         R. Stewart
Internet-Draft                                                M. Ramalho
Expires: May 26, 2006                                Cisco Systems, Inc.
                                                                  Q. Xie
                                                          Motorola, Inc.
                                                               M. Tuexen
                                      Univ. of Applied Sciences Muenster
                                                               P. Conrad
                                                  University of Delaware
                                                       November 22, 2005


      Stream Control Transmission Protocol (SCTP) Dynamic Address
                            Reconfiguration
                   draft-ietf-tsvwg-addip-sctp-13.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on May 26, 2006.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document describes extensions to the Stream Control Transmission



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   Protocol (SCTP) [RFC2960] that provides a method to reconfigure IP
   address information on an existing association.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Additional Chunks and Parameters . . . . . . . . . . . . . . .  6
     3.1.  New Chunk Types  . . . . . . . . . . . . . . . . . . . . .  6
       3.1.1.  Address Configuration Change Chunk (ASCONF)  . . . . .  6
       3.1.2.  Address Configuration Acknowledgment Chunk
               (ASCONF-ACK) . . . . . . . . . . . . . . . . . . . . .  7
     3.2.  New Parameter Types  . . . . . . . . . . . . . . . . . . .  8
       3.2.1.  Add IP Address . . . . . . . . . . . . . . . . . . . .  9
       3.2.2.  Delete IP Address  . . . . . . . . . . . . . . . . . . 10
       3.2.3.  Error Cause Indication . . . . . . . . . . . . . . . . 11
       3.2.4.  Set Primary IP Address . . . . . . . . . . . . . . . . 12
       3.2.5.  Success Indication . . . . . . . . . . . . . . . . . . 13
       3.2.6.  Adaptation Layer Indication  . . . . . . . . . . . . . 14
       3.2.7.  Supported Extensions Parameter . . . . . . . . . . . . 14
     3.3.  New Error Causes . . . . . . . . . . . . . . . . . . . . . 15
       3.3.1.  Error Cause: Request to Delete Last Remaining IP
               Address  . . . . . . . . . . . . . . . . . . . . . . . 15
       3.3.2.  Error Cause: Operation Refused Due to Resource
               Shortage . . . . . . . . . . . . . . . . . . . . . . . 16
       3.3.3.  Error Cause: Request to Delete Source IP Address . . . 17
       3.3.4.  Error Cause: Association Aborted due to illegal
               ASCONF-ACK . . . . . . . . . . . . . . . . . . . . . . 18
       3.3.5.  Error Cause: Request refused - no authorization. . . . 18
   4.  Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     4.1.  ASCONF Chunk Procedures  . . . . . . . . . . . . . . . . . 20
       4.1.1.  Congestion Control of ASCONF Chunks  . . . . . . . . . 21
     4.2.  Upon reception of an ASCONF Chunk. . . . . . . . . . . . . 22
     4.3.  General rules for address manipulation . . . . . . . . . . 24
       4.3.1.  A special case for OOTB ABORT chunks . . . . . . . . . 28
       4.3.2.  A special case for changing an address.  . . . . . . . 28
     4.4.  Setting of the primary address . . . . . . . . . . . . . . 29
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 30
   6.  IANA considerations  . . . . . . . . . . . . . . . . . . . . . 31
   7.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 32
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 32
   Appendix A.  Abstract Address Handling . . . . . . . . . . . . . . 33
     A.1.  General remarks  . . . . . . . . . . . . . . . . . . . . . 33
     A.2.  Generalized endpoints  . . . . . . . . . . . . . . . . . . 33
     A.3.  Associations . . . . . . . . . . . . . . . . . . . . . . . 34
     A.4.  Relationship with RFC 2960 . . . . . . . . . . . . . . . . 35
     A.5.  Rules for address manipulation . . . . . . . . . . . . . . 35



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   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 36
   Intellectual Property and Copyright Statements . . . . . . . . . . 38

















































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1.  Introduction

   To extend the utility and application scenarios of SCTP, this
   document introduces optional extensions that provide SCTP with the
   ability to:

   1.  reconfigure IP address information on an existing association.

   2.  set the remote primary path.

   3.  exchange adaptation layer information during association setup.

   These extensions enable SCTP to be utilized in the following
   applications:

   1.  For computational or networking platforms that allow addition/
       removal of physical interface cards this feature can provide a
       graceful method to add to the interfaces of an existing
       association.  For IPv6 this feature allows renumbering of
       existing associations.

   2.  This provides a method for an endpoint to request that its peer
       set its primary destination address.  This can be useful when an
       address is about to be deleted, or when an endpoint has some
       predetermined knowledge about which is the preferred address to
       receive SCTP packets upon.

   3.  This feature can be used to extend the usability of SCTP without
       modifying it by allowing endpoints to exchange some information
       during association setup.





















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2.  Conventions

   The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
   SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when
   they appear in this document, are to be interpreted as described in
   RFC2119 [2].













































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3.  Additional Chunks and Parameters

   This section describes the addition of two new chunks and, seven new
   parameters to allow:

   o  Dynamic addition of IP Addresses to an association.

   o  Dynamic deletion of IP Addresses from an association.

   o  A request to set the primary address the peer will use when
      sending to an endpoint.

   Additionally, this section describes three new error causes that
   support these new chunks and parameters.

3.1.  New Chunk Types

   This section defines two new chunk types that will be used to
   transfer the control information reliably.  Table 1 illustrates the
   two new chunk types.

        Chunk Type  Chunk Name
        --------------------------------------------------------------
        0xC1    Address Configuration Change Chunk        (ASCONF)
        0x80    Address Configuration Acknowledgment      (ASCONF-ACK)

              Table 1: Address Configuration Chunks

   It should be noted that the ASCONF Chunk format requires the receiver
   to report to the sender if it does not understand the ASCONF Chunk.
   This is accomplished by setting the upper bits in the chunk type as
   described in RFC2960 [6] section 3.2.  Note that the upper two bits
   in the ASCONF Chunk are set to one.  As defined in RFC2960 [6]
   section 3.2, setting these upper bits in this manner will cause the
   receiver that does not understand this chunk to skip the chunk and
   continue processing, but report in an Operation Error Chunk using the
   'Unrecognized Chunk Type' cause of error.

3.1.1.  Address Configuration Change Chunk (ASCONF)

   This chunk is used to communicate to the remote endpoint one of the
   configuration change requests that MUST be acknowledged.  The
   information carried in the ASCONF Chunk uses the form of a Type-
   Length-Value (TLV), as described in "3.2.1 Optional/Variable-length
   Parameter Format" in RFC2960 [6], for all variable parameters.  This
   chunk MUST be sent in an authenticated way by using the mechanism
   defined in SCTP-AUTH [7].  If this chunk is received unauthenticated
   it MUST be silently discarded as described in SCTP-AUTH [7].



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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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Type = 0xC1   |  Chunk Flags  |      Chunk Length             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       Serial Number                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                    Address Parameter                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     ASCONF Parameter #1                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       \                                                               \
       /                             ....                              /
       \                                                               \
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     ASCONF Parameter #N                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Serial Number : 32 bits (unsigned integer)

   This value represents a Serial Number for the ASCONF Chunk.  The
   valid range of Serial Number is from 0 to 4294967295 (2**32 - 1).
   Serial Numbers wrap back to 0 after reaching 4294967295.

   Address Parameter : 8 or 20 bytes (depending on type)

   This field contains an address parameter, either IPv6 or IPv4, from
   RFC2960 [6].  The address is an address of the sender of the ASCONF
   chunk, the address MUST be considered part of the association by the
   peer endpoint (the receiver of the ASCONF chunk).  This field may be
   used by the receiver of the ASCONF to help in finding the
   association.  If the address 0.0.0.0 or ::0 is provided the receiver
   MAY lookup the association by other information provided in the
   packet.  This parameter MUST be present in every ASCONF message i.e.
   it is a mandatory TLV parameter.

   Note the host name address parameter is NOT allowed and MUST be
   ignored if received in any ASCONF message.

   ASCONF Parameter: TLV format

   Each Address configuration change is represented by a TLV parameter
   as defined in Section 3.2.  One or more requests may be present in an
   ASCONF Chunk.

3.1.2.  Address Configuration Acknowledgment Chunk (ASCONF-ACK)

   This chunk is used by the receiver of an ASCONF Chunk to acknowledge



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   the reception.  It carries zero or more results for any ASCONF
   Parameters that were processed by the receiver.  This chunk MUST be
   sent in an authenticated way by using the mechanism defined in SCTP-
   AUTH [7].  If this chunk is received unauthenticated it MUST be
   silently discarded as described in SCTP-AUTH [7].

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Type = 0x80   |  Chunk Flags  |      Chunk Length             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       Serial Number                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                 ASCONF Parameter Response#1                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       \                                                               \
       /                             ....                              /
       \                                                               \
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                 ASCONF Parameter Response#N                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Serial Number : 32 bits (unsigned integer)

   This value represents the Serial Number for the received ASCONF Chunk
   that is acknowledged by this chunk.  This value is copied from the
   received ASCONF Chunk.

   ASCONF Parameter Response : TLV format

   The ASCONF Parameter Response is used in the ASCONF-ACK to report
   status of ASCONF processing.  By default, if a responding endpoint
   does not include any Error Cause, a success is indicated.  Thus a
   sender of an ASCONF-ACK MAY indicate complete success of all TLVs in
   an ASCONF by returning only the Chunk Type, Chunk Flags, Chunk Length
   (set to 8) and the Serial Number.

3.2.  New Parameter Types

   The seven new parameters added follow the format defined in section
   3.2.1 of RFC2960 [6].  Table 2, 3 and 4 describes the parameters.

        Address Configuration Parameters   Parameter Type
        -------------------------------------------------
        Set Primary Address                  0xC004
        Adaption Layer Indication            0xC006
        Supported Extensions                 0x8008




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        Table 2: Parameters that can be used in INIT/INIT-ACK chunk


        Address Configuration Parameters   Parameter Type
        -------------------------------------------------
        Add IP Address                       0xC001
        Delete IP Address                    0xC002
        Set Primary Address                  0xC004

        Table 3: Parameters used in ASCONF Parameter


        Address Configuration Parameters   Parameter Type
        -------------------------------------------------
        Error Cause Indication               0xC003
        Success Indication                   0xC005

        Table 4: Parameters used in ASCONF Parameter Response


   Any parameter that appears where it is not allowed (for example a
   0xC002 parameter appearing within an INIT or INIT-ACK) MAY be
   responded to with an ABORT by the receiver of the invalid parameter.

3.2.1.  Add IP Address

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |        Type = 0xC001          |    Length = Variable          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |               ASCONF-Request Correlation ID                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       Address Parameter                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   ASCONF-Request Correlation ID: 32 bits

   This is an opaque integer assigned by the sender to identify each
   request parameter.  It is in host byte order and is only meaningful
   to the sender.  The receiver of the ASCONF Chunk will copy this 32
   bit value into the ASCONF Response Correlation ID field of the
   ASCONF-ACK response parameter.  The sender of the ASCONF can use this
   same value in the ASCONF-ACK to find which request the response is
   for.

   Address Parameter: TLV




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   This field contains an IPv4 or IPv6 address parameter as described in
   3.3.2.1 of RFC2960 [6].  The complete TLV is wrapped within this
   parameter.  It informs the receiver that the address specified is to
   be added to the existing association.  This parameter MUST NOT
   contain a broadcast or multicast address.  If the address 0.0.0.0 or
   ::0 is provided, the source address of the packet MUST be added.

   An example TLV requesting that the IPv4 address 10.1.1.1 be added to
   the association would look as follows:

           +--------------------------------+
           |  Type=0xC001   | Length = 16   |
           +--------------------------------+
           |       C-ID = 0x01023474        |
           +--------------------------------+
           |  Type=5        | Length = 8    |
           +----------------+---------------+
           |       Value=0x0a010101         |
           +----------------+---------------+

   Valid Chunk Appearance

   The Add IP Address parameter may only appear in the ASCONF Chunk
   type.

3.2.2.  Delete IP Address

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |        Type =0xC002           |    Length = Variable          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |               ASCONF-Request Correlation ID                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       Address Parameter                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   ASCONF-Request Correlation ID: 32 bits

   This is an opaque integer assigned by the sender to identify each
   request parameter.  It is in host byte order and is only meaningful
   to the sender.  The receiver of the ASCONF Chunk will copy this 32
   bit value into the ASCONF Response Correlation ID field of the
   ASCONF-ACK response parameter.  The sender of the ASCONF can use this
   same value in the ASCONF-ACK to find which request the response is
   for.

   Address Parameter: TLV



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   This field contains an IPv4 or IPv6 address parameter as described in
   3.3.2.1 of RFC2960 [6].  The complete TLV is wrapped within this
   parameter.  It informs the receiver that the address specified is to
   be removed from the existing association.  This parameter MUST NOT
   contain a broadcast or multicast address.  If the address 0.0.0.0 or
   ::0 is provided, the source address of the packet MUST be deleted.

   An example TLV deleting the IPv4 address 10.1.1.1 from an existing
   association would look as follows:

           +--------------------------------+
           |  Type=0xC002   | Length = 16   |
           +--------------------------------+
           |       C-ID = 0x01023476        |
           +--------------------------------+
           |  Type=5        | Length = 8    |
           +----------------+---------------+
           |       Value=0x0a010101         |
           +----------------+---------------+

   Valid Chunk Appearance

   The Delete IP Address parameter may only appear in the ASCONF Chunk
   type.

3.2.3.  Error Cause Indication

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Type = 0xC003              |      Length = Variable        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |             ASCONF-Response Correlation ID                    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |             Error Cause(s) or Return Info on Success          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   ASCONF-Response Correlation ID: 32 bits

   This is an opaque integer assigned by the sender to identify each
   request parameter.  The receiver of the ASCONF Chunk will copy this
   32 bit value from the ASCONF-Request Correlation ID into the ASCONF
   Response Correlation ID field so the peer can easily correlate the
   request to this response.

   Error Cause(s): TLV(s)

   When reporting an error this response parameter is used to wrap one



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   or more standard error causes normally found within an SCTP
   Operational Error or SCTP Abort (as defined in RFC2960 [6]).  The
   Error Cause(s) follow the format defined in section 3.3.10 of RFC2960
   [6].

   Valid Chunk Appearance

   The Error Cause Indication parameter may only appear in the ASCONF-
   ACK chunk type.

3.2.4.  Set Primary IP Address

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |        Type =0xC004           |    Length = Variable          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |               ASCONF-Request Correlation ID                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       Address Parameter                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   ASCONF-Request Correlation ID: 32 bits

   This is an opaque integer assigned by the sender to identify each
   request parameter.  It is in host byte order and is only meaningful
   to the sender.  The receiver of the ASCONF Chunk will copy this 32
   bit value into the ASCONF Response Correlation ID field of the
   ASCONF-ACK response parameter.  The sender of the ASCONF can use this
   same value in the ASCONF-ACK to find which request the response is
   for.

   Address Parameter: TLV

   This field contains an IPv4 or IPv6 address parameter as described in
   3.3.2.1 of RFC2960 [6].  The complete TLV is wrapped within this
   parameter.  It requests the receiver to mark the specified address as
   the primary address to send data to (see section 5.1.2 of RFC2960
   [6]).  The receiver MAY mark this as its primary upon receiving this
   request.  If the address 0.0.0.0 or ::0 is provided, the receiver MAY
   mark the source address of the packet as its primary.

   An example TLV requesting that the IPv4 address 10.1.1.1 be made the
   primary destination address would look as follows:







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           +--------------------------------+
           |  Type=0xC004   | Length = 16   |
           +--------------------------------+
           |       C-ID = 0x01023479        |
           +--------------------------------+
           |  Type=5        | Length = 8    |
           +----------------+---------------+
           |       Value=0x0a010101         |
           +----------------+---------------+

   Valid Chunk Appearance

   The Set Primary IP Address parameter may appear in the ASCONF Chunk,
   the INIT, or the INIT-ACK chunk type.  The inclusion of this
   parameter in the INIT or INIT-ACK can be used to indicate an initial
   preference of primary address.

3.2.5.  Success Indication

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |        Type = 0xC005          |      Length = 8               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |               ASCONF-Response Correlation ID                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   By default if a responding endpoint does not report an error for any
   requested TLV, a success is implicitly indicated.  Thus a sender of a
   ASCONF-ACK MAY indicate complete success of all TLVs in an ASCONF by
   returning only the Chunk Type, Chunk Flags, Chunk Length (set to 8)
   and the Serial Number.

   The responding endpoint MAY also choose to explicitly report a
   success for a requested TLV, by returning a success report ASCONF
   Parameter Response.

   ASCONF-Response Correlation ID: 32 bits

   This is an opaque integer assigned by the sender to identify each
   request parameter.  The receiver of the ASCONF Chunk will copy this
   32 bit value from the ASCONF-Request Correlation ID into the ASCONF
   Response Correlation ID field so the peer can easily correlate the
   request to this response.

   Valid Chunk Appearance

   The Success Indication parameter may only appear in the ASCONF-ACK



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   chunk type.

3.2.6.  Adaptation Layer Indication

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |        Type =0xC006           |    Length = 8                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     Adaption Code point                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This parameter is specified for the communication of peer upper layer
   protocols.  It is envisioned to be used for flow control and other
   adaptation layers that require an indication to be carried in the
   INIT and INIT-ACK.  Each adaptation layer that is defined that wishes
   to use this parameter MUST specify a an adaption code point in an
   appropriate RFC defining its use and meaning.  This parameter SHOULD
   NOT be examined by the receiving SCTP implementation and should be
   passed opaquely to the upper layer protocol.

   Valid Chunk Appearance

   The Adaptation Layer Indication parameter may appear in INIT or INIT-
   ACK chunk and SHOULD be passed to the receivers upper layer protocol.
   This parameter MUST NOT appear in a ASCONF chunk.

3.2.7.  Supported Extensions Parameter

   This parameter is used at startup to identify any additional
   extensions that the sender supports.


        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Parameter Type = 0x8008   |      Parameter Length         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | CHUNK TYPE 1  |  CHUNK TYPE 2 |  CHUNK TYPE 3 |  CHUNK TYPE 4 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                             ....                              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | CHUNK TYPE N  |      PAD      |      PAD      |      PAD      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+







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   Parameter Type This field holds the IANA defined parameter type for
      Supported Extensions Parameter.  The suggested value of this field
      for IANA is 0x8008.

   Parameter Type Length This field holds the length of the parameter,
      including the Parameter Type, Parameter Length and any addition
      supported extensions.  Note the length MUST NOT include any
      padding.

   CHUNK TYPE X This field(s) hold the chunk type of any SCTP
      extension(s) that are currently supported by the sending SCTP.
      Multiple chunk types may be defined listing each additional
      feature that the sender supports.  The sender MUST NOT include
      multiple Supported Extensions Parameter within any chunk.

   Parameter Appearence This parameter may appear in the INIT or INIT-
      ACK chunk.  This parameter MUST NOT appear in any other chunk.

3.3.  New Error Causes

   Five new Error Causes are added to the SCTP Operational Errors,
   primarily for use in the ASCONF-ACK chunk.

       Cause Code
       Value          Cause Code
       ---------      ----------------
       0x0100          Request to Delete Last Remaining IP Address.
       0x0101          Operation Refused Due to Resource Shortage.
       0x0102          Request to Delete Source IP Address.
       0x0103          Association Aborted due to illegal ASCONF-ACK
       0x0104          Request refused - no authorization.

             Table 4: New Error Causes

3.3.1.  Error Cause: Request to Delete Last Remaining IP Address

   Cause of error

   Request to Delete Last Remaining IP address: The receiver of this
   error sent a request to delete the last IP address from its
   association with its peer.  This error indicates that the request is
   rejected.









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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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Cause Code=0x0100         |      Cause Length=Variable    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       \                     TLV-Copied-From-ASCONF                    /
       /                                                               \
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   An example of a failed delete in an Error Cause TLV would look as
   follows in the response ASCONF-ACK message:

           +--------------------------------+
           | Type = 0xC003  | Length = 28   |
           +----------------+---------------+
           |       C-ID = 0x01023476        |
           +--------------------------------+
           |  Cause=0x0100  | Length = 20   |
           +----------------+---------------+
           |  Type= 0xC002  | Length = 16   |
           +----------------+---------------+
           |       C-ID = 0x01023476        |
           +--------------------------------+
           |   Type=0x0005  | Length = 8    |
           +----------------+---------------+
           |       Value=0x0A010101         |
           +----------------+---------------+

3.3.2.  Error Cause: Operation Refused Due to Resource Shortage

   Cause of error

   This error cause is used to report a failure by the receiver to
   perform the requested operation due to a lack of resources.  The
   entire TLV that is refused is copied from the ASCONF into the error
   cause.

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Cause Code=0x0101         |      Cause Length=Variable    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       \                  TLV-Copied-From-ASCONF                      /
       /                                                              \
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   An example of a failed addition in an Error Cause TLV would look as
   follows in the response ASCONF-ACK message:



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           +--------------------------------+
           | Type = 0xC003  | Length = 28   |
           +--------------------------------+
           |       C-ID = 0x01023474        |
           +--------------------------------+
           |  Cause=0x0101  | Length = 20   |
           +----------------+---------------+
           |  Type=0xC001   | Length = 16   |
           +--------------------------------+
           |       C-ID = 0x01023474        |
           +--------------------------------+
           |  Type=0x0005   | Length = 8    |
           +----------------+---------------+
           |       Value=0x0A010101         |
           +----------------+---------------+

3.3.3.  Error Cause: Request to Delete Source IP Address

   Cause of error

   Request to Delete Source IP Address: The receiver of this error sent
   a request to delete the source IP address of the ASCONF message.
   This error indicates that the request is rejected.

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Cause Code=0x0102         |      Cause Length=Variable    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       \                    TLV-Copied-From-ASCONF                     /
       /                                                               \
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   An example of a failed delete in an Error Cause TLV would look as
   follows in the response ASCONF-ACK message:
















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           +--------------------------------+
           | Type = 0xC003  | Length = 28   |
           +--------------------------------+
           |       C-ID = 0x01023476        |
           +--------------------------------+
           |  Cause=0x0102  | Length = 20   |
           +----------------+---------------+
           |  Type=0xC002   | Length = 16   |
           +----------------+---------------+
           |       C-ID = 0x01023476        |
           +--------------------------------+
           |   Type=0x0005  | Length = 8    |
           +----------------+---------------+
           |       Value=0x0A010101         |
           +----------------+---------------+

   IMPLEMENTATION NOTE: It is unlikely that an endpoint would source a
   packet from the address being deleted, unless the endpoint does not
   do proper source address selection.

3.3.4.  Error Cause: Association Aborted due to illegal ASCONF-ACK

   This error is to be included in an ABORT that is generated due to the
   reception of an ASCONF-ACK that was not expected but is larger than
   the current sequence number (see Section 4.3 Rule D0 ).  Note that a
   sequence number is larger than the last acked sequence number if it
   is either the next sequence or no more than 2^^31-1 greater than the
   current sequence number.

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Cause Code=0x0103         |      Cause Length=4           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.3.5.  Error Cause: Request refused - no authorization.

   Cause of error

   This error cause may be included to reject a request based on local
   security policies.










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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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Cause Code=0x0104         |      Cause Length=Variable    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       \                     TLV-Copied-From-ASCONF                    /
       /                                                               \
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+











































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4.  Procedures

   This section will lay out the specific procedures for address
   configuration change chunk type and its processing.

4.1.  ASCONF Chunk Procedures

   When an endpoint has an ASCONF signaled change to be sent to the
   remote endpoint it should do the following:

   A1) Create an ASCONF Chunk as defined in Section 3.1.1.  The chunk
      should contain all of the TLV(s) of information necessary to be
      sent to the remote endpoint, and unique correlation identities for
      each request.

   A2) A serial number should be assigned to the Chunk.  The serial
      number should be a monotonically increasing number.  The serial
      number MUST be initialized at the start of the association to the
      same value as the Initial TSN and every time a new ASCONF chunk is
      created it is incremented by one after assigning the serial number
      to the newly created chunk .

   A3) If no ASCONF Chunk is outstanding (un-acknowledged) with the
      remote peer, send the chunk.

   A4) Start a T-4 RTO timer, using the RTO value of the selected
      destination address (normally the primary path; see RFC2960 [6]
      section 6.4 for details).

   A5) When the ASCONF-ACK that acknowledges the serial number last sent
      arrives, stop the T-4 RTO timer, and clear the appropriate
      association and destination error counters as defined in RFC2960
      [6] section 8.1 and 8.2.

   A6) Process all of the TLVs within the ASCONF-ACK to find out
      particular status information returned to the various requests
      that were sent.  Use the Correlation IDs to correlate the request
      and the responses.

   A7) If an error response is received for a TLV parameter, all TLVs
      with no response before the failed TLV are considered successful
      if not reported.  All TLVs after the failed response are
      considered unsuccessful unless a specific success indication is
      present for the parameter.







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   A8) If there is no response(s) to specific TLV parameter(s), and no
      failures are indicated, then all request(s) are considered
      successful.

   A9) If the peer responds to an ASCONF with an ERROR chunk reporting
      that it did not recognize the ASCONF chunk type, the sender of the
      ASCONF MUST NOT send any further ASCONF chunks and MUST stop its
      T-4 timer.

   If the T-4 RTO timer expires the endpoint should do the following:

   B1) Increment the error counters and perform path failure detection
      on the appropriate destination address as defined in RFC2960 [6]
      section 8.1 and 8.2.

   B2) Increment the association error counters and perform endpoint
      failure detection on the association as defined in RFC2960 [6]
      section 8.1 and 8.2.

   B3) Back-off the destination address RTO value to which the ASCONF
      chunk was sent by doubling the RTO timer value.

      Note: The RTO value is used in the setting of all timer types for
      SCTP.  Each destination address has a single RTO estimate.

   B4) Re-transmit the ASCONF Chunk last sent and if possible choose an
      alternate destination address (please refer to RFC2960 [6] section
      6.4.1).  An endpoint MUST NOT add new parameters to this chunk, it
      MUST be the same (including its serial number) as the last ASCONF
      sent.

   B5) Restart the T-4 RTO timer.  Note that if a different destination
      is selected, then the RTO used will be that of the new destination
      address.

   Note: the total number of re-transmissions is limited by B2 above.
   If the maximum is reached, the association will fail and enter into
   the CLOSED state (see RFC2960 [6] section 6.4.1 for details).

4.1.1.  Congestion Control of ASCONF Chunks

   In defining the ASCONF Chunk transfer procedures, it is essential
   that these transfers MUST NOT cause congestion within the network.
   To achieve this, we place these restrictions on the transfer of
   ASCONF Chunks:






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   R1) One and only one ASCONF Chunk MAY be in transit and
      unacknowledged at any one time.  If a sender, after sending an
      ASCONF chunk, decides it needs to transfer another ASCONF Chunk,
      it MUST wait until the ASCONF-ACK Chunk returns from the previous
      ASCONF Chunk before sending a subsequent ASCONF.  Note this
      restriction binds each side, so at any time two ASCONF may be in-
      transit on any given association (one sent from each endpoint).

   R2) An ASCONF may be bundled with any other chunk type (except other
      ASCONF Chunks).

   R3) An ASCONF-ACK may be bundled with any other chunk type except
      other ASCONF-ACKs.

   R4) Both ASCONF and ASCONF-ACK chunks MUST NOT be sent in any SCTP
      state except ESTABLISHED, SHUTDOWN-PENDING, SHUTDOWN-RECEIVED and
      SHUTDOWN-SENT.

   R5) An ASCONF MUST NOT be larger than the path MTU of the
      destination.

   R6) An ASCONF-ACK SHOULD not be larger than the path MTU.  In some
      circumstances an ASCONF-ACK may exceed the path MTU and in such a
      case IP fragmentation should be used to transmit the chunk.

   If the sender of an ASCONF Chunk receives an Operational Error
   indicating that the ASCONF chunk type is not understood, then the
   sender MUST NOT send subsequent ASCONF Chunks to the peer.  The
   endpoint should also inform the upper layer application that the peer
   endpoint does not support any of the extensions detailed in this
   document.

4.2.  Upon reception of an ASCONF Chunk.

   When an endpoint receives an ASCONF Chunk from the remote peer
   special procedures MAY be needed to identify the association the
   ASCONF Chunk is associated with.  To properly find the association
   the following procedures should be followed:

   L1) Use the source address and port number of the sender to attempt
      to identify the association (i.e. use the same method defined in
      RFC2960 [6] used for all other SCTP chunks).  If found proceed to
      rule L4.

   L2) If the association is not found, use the address found in the
      Address Parameter TLV combined with the port number found in the
      SCTP common header.  If found proceed to rule L4.




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   L3) If neither L1 or L2 locates the association, treat the chunk as
      an Out Of The Blue chunk as defined in RFC2960 [6].

   L4) Follow the normal rules to validate the SCTP verification tag
      found in RFC2960 [6].

   After identification and verification of the association, the
   following should be performed to properly process the ASCONF Chunk:

   C1) Compare the value of the serial number to the value the endpoint
      stored in a new association variable 'Peer-Serial-Number'.  This
      value MUST be initialized to the Initial TSN value minus 1.

   C2) If the value found in the serial number is equal to the ('Peer-
      Serial-Number' + 1), the endpoint MUST:



      V1) Process the TLVs contained within the Chunk performing the
         appropriate actions as indicated by each TLV type.  The TLVs
         MUST be processed in order within the Chunk.  For example, if
         the sender puts 3 TLVs in one chunk, the first TLV (the one
         closest to the Chunk Header) in the Chunk MUST be processed
         first.  The next TLV in the chunk (the middle one) MUST be
         processed second and finally the last TLV in the Chunk MUST be
         processed last.

      V2) In processing the chunk, the receiver should build a response
         message with the appropriate error TLVs, as specified in the
         Parameter type bits for any ASCONF Parameter it does not
         understand.  To indicate an unrecognized parameter, cause type
         8 as defined in the ERROR in 3.3.10.8 of RFC2960 [6] should be
         used.  The endpoint may also use the response to carry
         rejections for other reasons such as resource shortages etc,
         using the Error Cause TLV and an appropriate error condition.

         Note: a positive response is implied if no error is indicated
         by the sender.

      V3) All responses MUST copy the ASCONF-Request Correlation ID
         field received in the ASCONF parameter, from the TLV being
         responded to, into the ASCONF-Request Correlation ID field in
         the response parameter.

      V4) After processing the entire Chunk, the receiver of the ASCONF
         MUST send all TLVs for both unrecognized parameters and any
         other status TLVs inside the ASCONF-ACK chunk that acknowledges
         the arrival and processing of the ASCONF Chunk.



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      V5) Update the 'Peer-Serial-Number' to the value found in the
         serial number field.

   C3) If the value found in the serial number is equal to the value
      stored in the 'Peer-Serial-Number', the endpoint should:



      X1) Parse the ASCONF Chunk TLVs but the endpoint MUST NOT take any
         action on the TLVs parsed (since it has already performed these
         actions).

      X2) Build a response message with the appropriate response TLVs as
         specified in the ASCONF Parameter type bits, for any parameter
         it does not understand or could not process.

      X3) After parsing the entire Chunk, it MUST send any response TLV
         errors and status with an ASCONF-ACK chunk acknowledging the
         arrival and processing of the ASCONF Chunk.

      X4) The endpoint MUST NOT update its 'Peer-Serial-Number'.

      Note: the response to the retransmitted ASCONF MUST be the same as
      the original response.  This MAY mean an implementation must keep
      state in order to respond with the same exact answer (including
      resource considerations that may have made the implementation
      refuse a request).

      IMPLEMENTATION NOTE: As an optimization a receiver may wish to
      save the last ASCONF-ACK for some predetermined period of time and
      instead of re-processing the ASCONF (with the same serial number)
      it may just re-transmit the ASCONF-ACK.  It may wish to use the
      arrival of a new serial number to discard the previously saved
      ASCONF-ACK or any other means it may choose to expire the saved
      ASCONF-ACK.

   C4) Otherwise, the ASCONF Chunk is discarded since it must be either
      a stale packet or from an attacker.  A receiver of such a packet
      MAY log the event for security purposes.

   C5) In both cases C2 and C3 the ASCONF-ACK MUST be sent back to the
      source address contained in the IP header of the ASCONF being
      responded to.

4.3.  General rules for address manipulation

   When building TLV parameters for the ASCONF Chunk that will add or
   delete IP addresses the following rules should be applied:



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   D0) If an endpoint receives an ASCONF-ACK that is greater than or
      equal to the next serial number to be used but no ASCONF chunk is
      outstanding the endpoint MUST ABORT the association.  Note that a
      sequence number is greater than if it is no more than 2^^31-1
      larger than the current sequence number (using serial arithmetic).

   D1) When adding an IP address to an association, the IP address is
      NOT considered fully added to the association until the ASCONF-ACK
      arrives.  This means that until such time as the ASCONF containing
      the add is acknowledged the sender MUST NOT use the new IP address
      as a source for ANY SCTP packet except on carrying an ASCONF
      chunk.  The receiver of the add IP address request may use the
      address as a destination immediately.

   D2) After the ASCONF-ACK of an IP address add arrives, the endpoint
      MAY begin using the added IP address as a source address for any
      type of SCTP chunk.

   D3a) If an endpoint receives an Error Cause TLV indicating that the
      IP address Add or IP address Deletion parameters was not
      understood, the endpoint MUST consider the operation failed and
      MUST NOT attempt to send any subsequent Add or Delete requests to
      the peer.

   D3b) If an endpoint receives an Error Cause TLV indicating that the
      IP address Set Primary IP Address parameter was not understood,
      the endpoint MUST consider the operation failed and MUST NOT
      attempt to send any subsequent Set Primary IP Address requests to
      the peer.

   D4) When deleting an IP address from an association, the IP address
      MUST be considered a valid destination address for the reception
      of SCTP packets until the ASCONF-ACK arrives and MUST NOT be used
      as a source address for any subsequent packets.  This means that
      any datagrams that arrive before the ASCONF-ACK destined to the IP
      address being deleted MUST be considered part of the current
      association.  One special consideration is that ABORT chunks
      arriving destined to the IP address being deleted MUST be ignored
      (see Section 4.3.1 for further details).

   D5) An endpoint MUST NOT delete its last remaining IP address from an
      association.  In other words if an endpoint is NOT multi-homed it
      MUST NOT use the delete IP address without an add IP address
      preceding the delete parameter in the ASCONF chunk.  Or if an
      endpoint sends multiple requests to delete IP addresses it MUST
      NOT delete all of the IP addresses that the peer has listed for
      the requester.




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   D6) An endpoint MUST NOT set an IP header source address for an SCTP
      packet holding the ASCONF Chunk to be the same as an address being
      deleted by the ASCONF Chunk.

   D7) If a request is received to delete the last remaining IP address
      of a peer endpoint, the receiver MUST send an Error Cause TLV with
      the error cause set to the new error code 'Request to Delete Last
      Remaining IP Address'.  The requested delete MUST NOT be performed
      or acted upon, other than to send the ASCONF-ACK.

   D8) If a request is received to delete an IP address which is also
      the source address of the IP packet which contained the ASCONF
      chunk, the receiver MUST reject this request.  To reject the
      request the receiver MUST send an Error Cause TLV set to the new
      error code 'Request to Delete Source IP Address' (unless Rule D5
      has also been violated, in which case the error code 'Request to
      Delete Last Remaining IP Address' is sent).

   D9) If an endpoint receives an ADD IP address request and does not
      have the local resources to add this new address to the
      association, it MUST return an Error Cause TLV set to the new
      error code 'Operation Refused Due to Resource Shortage'.

   D10) If an endpoint receives an 'Out of Resource' error in response
      to its request to ADD an IP address to an association, it must
      either ABORT the association or not consider the address part of
      the association.  In other words if the endpoint does not ABORT
      the association, it must consider the add attempt failed and NOT
      use this address since its peer will treat SCTP packets destined
      to the address as Out Of The Blue packets.

   D11) When an endpoint receiving an ASCONF to add an IP address sends
      an 'Out of Resource' in its response, it MUST also fail any
      subsequent add or delete requests bundled in the ASCONF.  The
      receiver MUST NOT reject an ADD and then accept a subsequent
      DELETE of an IP address in the same ASCONF Chunk.  In other words,
      once a receiver begins failing any ADD or DELETE request, it must
      fail all subsequent ADD or DELETE requests contained in that
      single ASCONF.

   D12) When an endpoint receives a request to delete an IP address that
      is the current primary address, it is an implementation decision
      as to how that endpoint chooses the new primary address.

   D13) When an endpoint receives a valid request to DELETE an IP
      address the endpoint MUST consider the address no longer as part
      of the association.  It MUST NOT send SCTP packets for the
      association to that address and it MUST treat subsequent packets



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      received from that address as Out Of The Blue.

      During the time interval between sending out the ASCONF and
      receiving the ASCONF-ACK it MAY be possible to receive DATA chunks
      out of order.  The following examples illustrate these problems:



       Endpoint-A                                     Endpoint-Z
       ----------                                     ----------
       ASCONF[Add-IP:X]------------------------------>
                                               /--ASCONF-ACK
                                              /
                                    /--------/---New DATA:
                                   /        /    Destination
              <-------------------/        /     IP:X
                                          /
              <--------------------------/


   In the above example we see a new IP address (X) being added to the
   Endpoint-A.  However due to packet re-ordering in the network a new
   DATA chunk is sent and arrives at Endpoint-A before the ASCONF-ACK
   confirming the add of the address to the association.

   A similar problem exists with the deletion of an IP address as
   follows:


       Endpoint-A                                     Endpoint-Z
       ----------                                     ----------
                                    /------------New DATA:
                                   /             Destination
                                  /              IP:X
       ASCONF [DEL-IP:X]---------/---------------->
              <-----------------/------------------ASCONF-ACK
                               /
                              /
               <-------------/

   In this example we see a DATA chunk destined to the IP:X (which is
   about to be deleted) arriving after the deletion is complete.  For
   the ADD case an endpoint SHOULD consider the newly adding IP address
   valid for the association to receive data from during the interval
   when awaiting the ASCONF-ACK.  The endpoint MUST NOT source data from
   this new address until the ASCONF-ACK arrives but it may receive out
   of order data as illustrated and MUST NOT treat this data as an OOTB
   datagram (please see RFC2960 [6] section 8.4).  It MAY drop the data



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   silently or it MAY consider it part of the association but it MUST
   NOT respond with an ABORT.

   For the DELETE case, an endpoint MAY respond to the late arriving
   DATA packet as an OOTB datagram or it MAY hold the deleting IP
   address for a small period of time as still valid.  If it treats the
   DATA packet as an OOTB the peer will silently discard the ABORT
   (since by the time the ABORT is sent the peer will have removed the
   IP address from this association).  If the endpoint elects to hold
   the IP address valid for a period of time, it MUST NOT hold it valid
   longer than 2 RTO intervals for the destination being removed.

4.3.1.  A special case for OOTB ABORT chunks

   Another case worth mentioning is illustrated below:


       Endpoint-A                                     Endpoint-Z
       ----------                                     ----------

       New DATA:------------\
       Source IP:X           \
                              \
       ASCONF-REQ[DEL-IP:X]----\------------------>
                                \        /---------ASCONF-ACK
                                 \      /
                                  \----/-----------> OOTB
       (Ignored <---------------------/-------------ABORT
        by rule D4)                  /
              <---------------------/


   For this case, during the deletion of an IP address, an Abort MUST be
   ignored if the destination address of the Abort message is that of a
   destination being deleted.

4.3.2.  A special case for changing an address.

   In some instances the sender may only have one IP address in an
   association that is being renumbered.  When this occurs, the sender
   may not be able to send to the peer the appropriate ADD/DELETE pair
   and use the old address as a source in the IP header.  For this
   reason the sender MUST fill in the Address Parameter field with an
   address that is part of the association (in this case the one being
   deleted).  This will allow the receiver to locate the association
   without using the source address found in the IP header.

   The receiver of such a chunk MUST always first use the source address



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   found in the IP header in looking up the association.  The receiver
   should attempt to use the address found in the Address Bytes field
   only if the lookup fails using the source address from the IP header.
   The receiver MUST reply to the source address of the packet in this
   case which is the new address that was added by the ASCONF (since the
   old address is no longer a part of the association after processing).

4.4.  Setting of the primary address

   A sender of this option may elect to send this combined with a
   deletion or addition of an address.  A sender SHOULD only send a set
   primary request to an address that is already considered part of the
   association.  In other words if a sender combines a set primary with
   an add of a new IP address the set primary will be discarded unless
   the add request is to be processed BEFORE the set primary (i.e. it
   precedes the set primary).

   A request to set primary MAY also appear in an INIT or INIT-ACK
   chunk.  This can give advice to the peer endpoint as to which of its
   addresses the sender of the INIT or INIT-ACK would prefer to be used
   as the primary address.

   The request to set an address as the primary path is an option the
   receiver SHOULD perform.  It is considered advice to the receiver of
   the best destination address to use in sending SCTP packets (in the
   requesters view).  If a request arrives that asks the receiver to set
   an address as primary that does not exist, the receiver should NOT
   honor the request, leaving its existing primary address unchanged.























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5.  Security Considerations

   The ADD/DELETE of an IP address to an existing association does
   provide an additional mechanism by which existing associations can be
   hijacked.

   This document requires the use of the authentication mechanism
   defined in SCTP-AUTH [7] to limit the ability of an attacker to
   hijack an association.  Hijacking an association by using ADD/DELETE
   of an IP address is only possible for an attacker who is able to
   intercept the association setup.  However, if a preconfigured shared
   end-point pair key is used this is not possible.  For a more detailed
   analysis see SCTP-AUTH [7].






































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6.  IANA considerations

   This document defines the following new SCTP parameters, chunks and
   errors:

   o  Two new chunk types,

   o  Seven parameter types, and

   o  Five new SCTP error causes.

   One of the two new chunk types must come from the range of chunk
   types where the upper two bits are one, we recommend 0xC1 but any
   other available code point with the upper bits set is also
   acceptable.

   The second chunk type must come from the range where only the upper
   bit is set to one.  We recommend 0x80 but any other available code
   point with the upper bit set is also acceptable.

   All but one of the parameter types must come from the range of types
   where the upper two bits are set, we recommend 0xC001 - 0xC006, as
   specified in this document.  The other parameter type must come from
   the 0x8000 range, we recommend 0x8008.  Note that for any of these
   values a different unique parameter type may be assigned by IANA as
   long as the upper bits correspond to the ones specified in this
   document.

   The five new error causes can be any value, in this document we have
   used 0x0100-0x0104 in an attempt to seperate these from the common
   ranges of error codes.  Any other unassigned values are also
   acceptable.

   This document also defines a Adaption code point.  The adaption code
   point is a 32 bit integer that is assigned by IANA through an IETF
   Consensus action as defined in RFC2434 [4].















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7.  Acknowledgments

   The authors wish to thank Jon Berger, Greg Kendall, Seok Koh, Peter
   Lei, John Loughney, Ivan Arias Rodriguez, Renee Revis, Marshall Rose,
   and Chip Sharp for their invaluable comments.

   The authors would also like to give special mention to Maria-Carmen
   Belinchon and Ian Rytina for there early contributions to this
   document and their thoughtful comments.

8.  References

   [1]  Bradner, S., "The Internet Standards Process -- Revision 3",
        BCP 9, RFC 2026, October 1996.

   [2]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [3]  Kent, S. and R. Atkinson, "IP Authentication Header", RFC 2402,
        November 1998.

   [4]  Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
        Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.

   [5]  Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
        June 1999.

   [6]  Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer,
        H., Taylor, T., Rytina, I., Kalla, M., Zhang, L., and V. Paxson,
        "Stream Control Transmission Protocol", RFC 2960, October 2000.

   [7]  Tuexen, M., Stewart, R., Lei, P., and E. Rescorla,
        "Authenticated Chunks for Stream Control Transmission Protocol
        (SCTP)", draft-tuexen-sctp-auth-chunk-03 (work in progress),
        February 2005.
















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Appendix A.  Abstract Address Handling

A.1.  General remarks

   The following text provides a working definition of the endpoint
   notion to discuss address reconfiguration.  It is not intended to
   restrict implementations in any way, its goal is to provide as set of
   definitions only.  Using these definitions should make a discussion
   about address issues easier.

A.2.  Generalized endpoints

   A generalized endpoint is a pair of a set of IP addresses and a port
   number at any given point of time.  The precise definition is as
   follows:

   A generalized endpoint gE at time t is given by

                  gE(t) = ({IP1, ..., IPn}, Port)

   where {IP1, ..., IPn} is a non empty set of IP addresses.

   Please note that the dynamic addition and deletion of IP-addresses
   described in this document allows the set of IP-addresses of a
   generalized endpoint to be changed at some point of time.  The port
   number can never be changed.

   The set of IP addresses of a generalized endpoint gE at a time t is
   defined as

               Addr(gE)(t) = {IP1, ..., IPn}

   if gE(t) = ({IP1, ..., IPn}, Port) holds at time t.

   The port number of a generalized endpoint gE is defined as

               Port(gE) = Port

   if gE(t) = ({IP1, ..., IPn}, Port) holds at time t.

   There is one fundamental rule which restricts all generalized
   endpoints:

   For two different generalized endpoints gE' and gE'' with the same
   port number Port(gE') = Port(gE'') the address sets Addr(gE')(t) and
   Addr(gE'')(t) must be disjoint at every point of time.





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A.3.  Associations

   Associations consists of two generalized endpoints and the two
   address sets known by the peer at any time.  The precise definition
   is as follows:

   An association A between to different generalized endpoints gE' and
   gE'' is given by

                  A = (gE', S', gE'', S'')

   where S'(t) and S''(t) are set of addresses at any time t such that
   S'(t) is a non-empty subset of Addr(gE')(t) and S''(t) is a non-empty
   subset of Addr(gE'')(t).

   If A = (gE', S', gE'', S'') is an association between the generalized
   endpoints gE' and gE'' the following notion is used:

                  Addr(A, gE') = S'   and  Addr(A, gE'') = S''.

   If the dependency on time is important the notion Addr(A, gE')(t) =
   S'(t) will be used.

   If A is an association between gE' and gE'' then Addr(A, gE') is the
   subset of IP addresses of gE' which is known by gE'' and used by gE'.

   Association establishment between gE' and gE'' can be seen as:

   1.  gE' and gE'' do exist before the association.

   2.  If an INIT has to be send from gE' to gE'' address scoping rules
       and other limitations are applied to calculate the subset S' from
       Addr(gE').  The addresses of S' are included in the INIT chunk.

   3.  If an INIT-ACK has to be send from gE'' to gE' address scoping
       rules and other limitations are applied to calculate the subset
       S'' from Addr(gE'').  The addresses of S'' are included in the
       INIT-ACK chunk.

   4.  After the handshake the association A = (gE', S', gE'', S'') has
       been established.

   5.  Right after the association establishment Addr(A, gE') and
       Addr(A, gE'') are the addresses which have been seen on the wire
       during the handshake.






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A.4.  Relationship with RFC 2960

   RFC2960 [6] defines the notion of an endpoint.  This subsection will
   show that these endpoints are also (special) generalized endpoints.

   RFC2960 [6] has no notion of address scoping or other address
   handling limitations and provides no mechanism to change the
   addresses of an endpoint.

   This means that an endpoint is simply a generalized endpoint which
   does not depend on the time.  Neither the Port nor the address list
   changes.

   During association setup no address scoping rules or other
   limitations will be applied.  This means that for an association A
   between two endpoints gE' and gE'' the following is true:

   Addr(A, gE') = Addr(gE') and Addr(A, gE'') = Addr(gE'').

A.5.  Rules for address manipulation

   The rules for address manipulation can now be stated in a simple way:

   1.  An address can be added to a generalized endpoint gE only if this
       address is not an address of a different generalized endpoint
       with the same port number.

   2.  An address can be added to an association A with generalized
       endpoint gE if it has been added to the generalized endpoint gE
       first.  This means that the address must be an element of
       Addr(gE) first and then it can become an element of Addr(A, gE).
       But this is not necessary.  If the association does not allow the
       reconfiguration of the addresses only Addr(gE) can be modified.

   3.  An address can be deleted from an association A with generalized
       endpoint gE as long as Addr(A, gE) stays non-empty.

   4.  An address can be deleted from an generalized endpoint gE only if
       it has been removed from all associations having gE as a
       generalized endpoint.

   These rules simply make sure that the rules for the endpoints and
   associations given above are always fulfilled.








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Authors' Addresses

   Randall R. Stewart
   Cisco Systems, Inc.
   4875 Forest Drive
   Suite 200
   Columbia, SC  29206
   USA

   Phone:
   Email: rrs@cisco.com


   Michael A. Ramalho
   Cisco Systems, Inc.
   1802 Rue de la Porte
   Wall Township, NJ  07719-3784
   USA

   Phone: +1.732.449.5762
   Email: mramalho@cisco.com


   Qiaobing Xie
   Motorola, Inc.
   1501 W. Shure Drive, #2309
   Arlington Heights, IL  60004
   USA

   Phone: +1-847-632-3028
   Email: qxie1@email.mot.com


   Michael Tuexen
   Univ. of Applied Sciences Muenster
   Stegerwaldstr. 39
   48565 Steinfurt
   Germany

   Email: tuexen@fh-muenster.de











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   Phillip T. Conrad
   University of Delaware
   Department of Computer and Information Sciences
   Newark, DE  19716
   US

   Phone: +1 302 831 8622
   Email: conrad@acm.org
   URI:   http://www.cis.udel.edu/~pconrad










































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