[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

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                                       Cisco Systems, Inc.
Intended status: Standards Track                                  Q. Xie
Expires: December 14, 2007                                Motorola, Inc.
                                                               M. Tuexen
                                      Univ. of Applied Sciences Muenster
                                                             S. Maruyama
                                                               M. Kozuka
                                                        Kyoto University
                                                           June 12, 2007


      Stream Control Transmission Protocol (SCTP) Dynamic Address
                            Reconfiguration
                   draft-ietf-tsvwg-addip-sctp-21.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
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on December 14, 2007.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   A local host may have multiple points of attachment to the Internet,



Stewart, et al.         Expires December 14, 2007               [Page 1]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   giving it a degree of fault tolerance from hardware failures.  Stream
   Control Transmission Protocol (SCTP) SCTP-BIS
   [I-D.ietf-tsvwg-2960bis] was developed to take full advantage of such
   a multi-homed host to provide a fast failover and association
   survivability in the face of such hardware failures.  This document
   describes an extension to SCTP that will allow an SCTP stack to
   dynamically add an IP Addresses to an SCTP association, dynamically
   delete an IP addresses from an SCTP association, and to request to
   set the primary address the peer will use when sending to an
   endpoint.









































Stewart, et al.         Expires December 14, 2007               [Page 2]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Serial Number Arithmetic . . . . . . . . . . . . . . . . . . .  6
   4.  Additional Chunks and Parameters . . . . . . . . . . . . . . .  6
     4.1.  New Chunk Types  . . . . . . . . . . . . . . . . . . . . .  6
       4.1.1.  Address Configuration Change Chunk (ASCONF)  . . . . .  7
       4.1.2.  Address Configuration Acknowledgment Chunk
               (ASCONF-ACK) . . . . . . . . . . . . . . . . . . . . .  8
     4.2.  New Parameter Types  . . . . . . . . . . . . . . . . . . .  9
       4.2.1.  Add IP Address . . . . . . . . . . . . . . . . . . . . 10
       4.2.2.  Delete IP Address  . . . . . . . . . . . . . . . . . . 11
       4.2.3.  Error Cause Indication . . . . . . . . . . . . . . . . 12
       4.2.4.  Set Primary IP Address . . . . . . . . . . . . . . . . 13
       4.2.5.  Success Indication . . . . . . . . . . . . . . . . . . 14
       4.2.6.  Adaptation Layer Indication  . . . . . . . . . . . . . 15
       4.2.7.  Supported Extensions Parameter . . . . . . . . . . . . 15
     4.3.  New Error Causes . . . . . . . . . . . . . . . . . . . . . 16
       4.3.1.  Error Cause: Request to Delete Last Remaining IP
               Address  . . . . . . . . . . . . . . . . . . . . . . . 17
       4.3.2.  Error Cause: Operation Refused Due to Resource
               Shortage . . . . . . . . . . . . . . . . . . . . . . . 17
       4.3.3.  Error Cause: Request to Delete Source IP Address . . . 18
       4.3.4.  Error Cause: Association Aborted due to illegal
               ASCONF-ACK . . . . . . . . . . . . . . . . . . . . . . 19
       4.3.5.  Error Cause: Request refused - no authorization. . . . 19
   5.  Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     5.1.  ASCONF Chunk Procedures  . . . . . . . . . . . . . . . . . 20
       5.1.1.  Congestion Control of ASCONF Chunks  . . . . . . . . . 22
     5.2.  Upon reception of an ASCONF Chunk. . . . . . . . . . . . . 23
     5.3.  General rules for address manipulation . . . . . . . . . . 26
       5.3.1.  A special case for OOTB ABORT Chunks . . . . . . . . . 29
       5.3.2.  A special case for changing an address.  . . . . . . . 30
     5.4.  Setting of the primary address . . . . . . . . . . . . . . 30
     5.5.  Bundling of multiple ASCONFs . . . . . . . . . . . . . . . 31
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 31
   7.  IANA considerations  . . . . . . . . . . . . . . . . . . . . . 32
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 34
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 34
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 34
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 35
   Appendix A.  Abstract Address Handling . . . . . . . . . . . . . . 35
     A.1.  General remarks  . . . . . . . . . . . . . . . . . . . . . 35
     A.2.  Generalized endpoints  . . . . . . . . . . . . . . . . . . 35
     A.3.  Associations . . . . . . . . . . . . . . . . . . . . . . . 36
     A.4.  Relationship with RFC 4960 . . . . . . . . . . . . . . . . 37
     A.5.  Rules for address manipulation . . . . . . . . . . . . . . 37



Stewart, et al.         Expires December 14, 2007               [Page 3]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 38
   Intellectual Property and Copyright Statements . . . . . . . . . . 40

















































Stewart, et al.         Expires December 14, 2007               [Page 4]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


1.  Introduction

   A local host may have multiple points of attachment to the Internet,
   giving it a degree of fault tolerance from hardware failures.  SCTP
   was developed to take full advantage of such a multi-homed host to
   provide a fast failover and association survivability in the face of
   such hardware failures.  However, many modern computers allow for the
   dynamic addition and deletion of network cards (sometimes termed a
   hot-pluggable interface).  Complicate this with the ability of a
   provider, in IPv6, to dynamically renumber a network, and there still
   is a gap between full fault tolerance and the currently defined SCTP
   protocol.  No matter if a card is added or an interface is
   renumbered, in order to take advantage of this new configuration, the
   transport association must be restarted.  For many fault tolerant
   applications this restart is considered an outage and is undesirable.

   This document describes an extension to SCTP to attempt to correct
   this problem for the more demanding fault tolerant application.  This
   extension will allow an SCTP stack to:

   o  Dynamically add an IP Addresses to an association.
   o  Dynamically delete an IP Addresses from an association.
   o  Request to set the primary address the peer will use when sending
      to an endpoint.

   The dynamic addition and subtraction of IP addresses allows an SCTP
   association to continue to function through host and network
   reconfigurations.  These changes, brought on by provider or user
   action, may mean that the peer would be better served by using the
   newly added address, however this information may only be known by
   the endpoint that had the reconfiguration occur.  In such a case this
   extension allows the local endpoint to advise the peer as to what it
   thinks is the better primary address that the peer should be using.

   One last thing this extension adds is a small 32 bit integer, called
   an adaptation indication, that can be exchanged at startup.  This is
   useful for applications where there is one or more specific layers
   below the application, yet still above SCTP.  In such a case the
   exchange of this indication can allow the proper layer to be enabled
   below the application.


2.  Conventions

   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 RFC2119 [RFC2119].




Stewart, et al.         Expires December 14, 2007               [Page 5]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


3.  Serial Number Arithmetic

   It is essential to remember that the actual ASCONF Sequence Number
   space is finite, though very large.  This space ranges from 0 to
   2**32 - 1.  Since the space is finite, all arithmetic dealing with
   ASCONF Sequence Numbers MUST be performed modulo 2**32.  This
   unsigned arithmetic preserves the relationship of sequence numbers as
   they cycle from 2**32 - 1 to 0 again.  There are some subtleties to
   computer modulo arithmetic, so great care should be taken in
   programming the comparison of such values.  When referring to ASCONF
   Sequence Numbers, the symbol "=<" means "less than or equal"(modulo
   2**32).

   Comparisons and arithmetic on ASCONF sequence numbers in this
   document SHOULD use Serial Number Arithmetic as defined in [RFC1982]
   where SERIAL_BITS = 32.

   ASCONF Sequence Numbers wrap around when they reach 2**32 - 1.  That
   is, the next ASCONF Sequence Number an ASCONF chunk MUST use after
   transmitting ASCONF Sequence Number = 2**32 - 1 is 0.

   Any arithmetic done on Stream Sequence Numbers SHOULD use Serial
   Number Arithmetic as defined in [RFC1982] where SERIAL_BITS = 16.
   All other arithmetic and comparisons in this document uses normal
   arithmetic.


4.  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.

4.1.  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.






Stewart, et al.         Expires December 14, 2007               [Page 6]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


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

              Table 1: Address Configuration Chunks

4.1.1.  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 SCTP-BIS [I-D.ietf-tsvwg-2960bis] for all
   variable parameters.  This chunk MUST be sent in an authenticated way
   by using the mechanism defined in SCTP-AUTH
   [I-D.ietf-tsvwg-sctp-auth].  If this chunk is received
   unauthenticated it MUST be silently discarded as described in SCTP-
   AUTH [I-D.ietf-tsvwg-sctp-auth].

        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             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                      Sequence Number                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                    Address Parameter                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     ASCONF Parameter #1                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       \                                                               \
       /                             ....                              /
       \                                                               \
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     ASCONF Parameter #N                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Sequence Number : 32 bits (unsigned integer)

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

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

   This field contains an address parameter, either IPv6 or IPv4, from
   SCTP-BIS [I-D.ietf-tsvwg-2960bis].  The address is an address of the



Stewart, et al.         Expires December 14, 2007               [Page 7]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   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 MUST NOT be sent and MUST be ignored if
   received in any ASCONF message.

   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 SCTP-BIS [I-D.ietf-tsvwg-2960bis]. section 3.2.  Note
   that the upper two bits in the ASCONF Chunk are set to one.  As
   defined in SCTP-BIS [I-D.ietf-tsvwg-2960bis] section 3.2, when
   setting these upper bits in this manner the receiver that does not
   understand this chunk MUST skip the chunk and continue processing,
   and report in an Operation Error Chunk using the 'Unrecognized Chunk
   Type' cause of error.  This will NOT abort the association but
   indicates to the sender that it MUST not send any further ASCONF
   chunks.

   ASCONF Parameter: TLV format

   Each Address configuration change is represented by a TLV parameter
   as defined in Section 4.2.  One or more requests may be present in an
   ASCONF Chunk.

4.1.2.  Address Configuration Acknowledgment Chunk (ASCONF-ACK)

   This chunk is used by the receiver of an ASCONF Chunk to acknowledge
   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 [I-D.ietf-tsvwg-sctp-auth].  If this chunk is received
   unauthenticated it MUST be silently discarded as described in SCTP-
   AUTH [I-D.ietf-tsvwg-sctp-auth].












Stewart, et al.         Expires December 14, 2007               [Page 8]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


        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             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     Sequence Number                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                 ASCONF Parameter Response#1                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       \                                                               \
       /                             ....                              /
       \                                                               \
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                 ASCONF Parameter Response#N                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Sequence Number : 32 bits (unsigned integer)

   This value represents the Sequence 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 Sequence Number.

4.2.  New Parameter Types

   The seven new parameters added follow the format defined in section
   3.2.1 of SCTP-BIS [I-D.ietf-tsvwg-2960bis].  Tables 2, 3 and 4
   describe the parameters.

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

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







Stewart, et al.         Expires December 14, 2007               [Page 9]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


        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.
   If the receiver chooses NOT to abort, the parameter MUST be ignored.
   A robust implementation SHOULD ignore the parameter and leave the
   association intact.

4.2.1.  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.  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.  Note that the receiver MUST NOT change this 32 bit value.

   Address Parameter: TLV

   This field contains an IPv4 or IPv6 address parameter as described in



Stewart, et al.         Expires December 14, 2007              [Page 10]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   3.3.2.1 of SCTP-BIS [I-D.ietf-tsvwg-2960bis].  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 192.0.2.1 be added to
   the association would look as follows:

           +--------------------------------+
           |  Type=0xC001   | Length = 16   |
           +--------------------------------+
           |       C-ID = 0x01023474        |
           +--------------------------------+
           |  Type=5        | Length = 8    |
           +----------------+---------------+
           |       Value=0xC0000201         |
           +----------------+---------------+

   Valid Chunk Appearance

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

4.2.2.  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.  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.  Note that the receiver MUST NOT change this 32 bit value.

   Address Parameter: TLV




Stewart, et al.         Expires December 14, 2007              [Page 11]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   This field contains an IPv4 or IPv6 address parameter as described in
   3.3.2.1 of SCTP-BIS [I-D.ietf-tsvwg-2960bis].  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, all addresses of the peer
   except the source address of the packet MUST be deleted.

   An example TLV deleting the IPv4 address 192.0.2.1 from an existing
   association would look as follows:

           +--------------------------------+
           |  Type=0xC002   | Length = 16   |
           +--------------------------------+
           |       C-ID = 0x01023476        |
           +--------------------------------+
           |  Type=5        | Length = 8    |
           +----------------+---------------+
           |       Value=0xC0000201         |
           +----------------+---------------+

   Valid Chunk Appearance

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

4.2.3.  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 Success Indication              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   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.  Note that the receiver MUST NOT change
   this 32 bit value.

   Error Cause(s): TLV(s)



Stewart, et al.         Expires December 14, 2007              [Page 12]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   When reporting an error this response parameter is used to wrap one
   or more standard error causes normally found within an SCTP
   Operational Error or SCTP Abort (as defined in SCTP-BIS
   [I-D.ietf-tsvwg-2960bis]).  The Error Cause(s) follow the format
   defined in section 3.3.10 of SCTP-BIS [I-D.ietf-tsvwg-2960bis].

   Valid Chunk Appearance

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

4.2.4.  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.  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.  Note that the receiver MUST NOT change this 32 bit value.

   Address Parameter: TLV

   This field contains an IPv4 or IPv6 address parameter as described in
   3.3.2.1 of SCTP-BIS [I-D.ietf-tsvwg-2960bis].  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 SCTP-BIS [I-D.ietf-tsvwg-2960bis]).  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 192.0.2.1 be made the
   primary destination address would look as follows:






Stewart, et al.         Expires December 14, 2007              [Page 13]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


           +--------------------------------+
           |  Type=0xC004   | Length = 16   |
           +--------------------------------+
           |       C-ID = 0x01023479        |
           +--------------------------------+
           |  Type=5        | Length = 8    |
           +----------------+---------------+
           |       Value=0xC0000201         |
           +----------------+---------------+

   Valid Chunk Appearance

   The Set Primary IP Address parameter may appear in the ASCONF, 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.

4.2.5.  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 Sequence 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



Stewart, et al.         Expires December 14, 2007              [Page 14]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   chunk type.

4.2.6.  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                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                   Adaptation 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 an adaptation 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.

   Note: this parameter is not used in either the addition or deletion
   of addresses but is for the convenience of the upper layer.  This
   document includes this parameter to minimize the number of SCTP
   documents.

   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
   based upon the upper layer protocol configuration of the SCTP stack.
   This parameter MUST NOT be sent in any other chunks and if it is
   received in another chunk it MUST be ignored.

4.2.7.  Supported Extensions Parameter

   This parameter is used at startup to identify any additional
   extensions that the sender supports.  The sender MUST support both
   the sending and the receiving of any chunk types listed within the
   Supported Extensions Parameter.  An implementation supporting this
   extension MUST list the ASCONF,the ASCONF-ACK, and the AUTH chunks in
   its INIT and INIT-ACK parameters.









Stewart, et al.         Expires December 14, 2007              [Page 15]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


      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      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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

4.3.  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 5: New Error Causes







Stewart, et al.         Expires December 14, 2007              [Page 16]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


4.3.1.  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.

        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=0xC0000201         |
           +----------------+---------------+

4.3.2.  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.






Stewart, et al.         Expires December 14, 2007              [Page 17]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


        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:

           +--------------------------------+
           | Type = 0xC003  | Length = 28   |
           +--------------------------------+
           |       C-ID = 0x01023474        |
           +--------------------------------+
           |  Cause=0x0101  | Length = 20   |
           +----------------+---------------+
           |  Type=0xC001   | Length = 16   |
           +--------------------------------+
           |       C-ID = 0x01023474        |
           +--------------------------------+
           |  Type=0x0005   | Length = 8    |
           +----------------+---------------+
           |       Value=0xC0000201         |
           +----------------+---------------+

4.3.3.  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:




Stewart, et al.         Expires December 14, 2007              [Page 18]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


           +--------------------------------+
           | Type = 0xC003  | Length = 28   |
           +--------------------------------+
           |       C-ID = 0x01023476        |
           +--------------------------------+
           |  Cause=0x0102  | Length = 20   |
           +----------------+---------------+
           |  Type=0xC002   | Length = 16   |
           +----------------+---------------+
           |       C-ID = 0x01023476        |
           +--------------------------------+
           |   Type=0x0005  | Length = 8    |
           +----------------+---------------+
           |       Value=0xC0000201         |
           +----------------+---------------+

   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.

4.3.4.  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 5.3 Rule F0 ).  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.  Sequence numbers smaller than the last
   acked sequence number are silently ignored.

        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           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

4.3.5.  Error Cause: Request refused - no authorization.

   Cause of error

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









Stewart, et al.         Expires December 14, 2007              [Page 19]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


        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                    /
       /                                                               \
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


5.  Procedures

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

5.1.  ASCONF Chunk Procedures

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

   A1)  Create an ASCONF Chunk as defined in Section 4.1.1.  The chunk
      MUST 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 sequence number MUST be assigned to the Chunk.  The sequence
      number MUST be larger by one.  The sequence 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
      MUST be incremented by one after assigning the sequence number to
      the newly created chunk .

   A3)  If no SCTP packet with one or more ASCONF Chunk(s) is
      outstanding (un-acknowledged) with the remote peer, send the chunk
      and proceed to step A4.  If an ASCONF chunk is outstanding, then
      the ASCONF chunk should be queued for later transmission and no
      further action should be taken until the previous ASCONF is
      acknowledged or a time out occurs.

   A4)  The sender MUST Start a T-4 RTO timer, using the RTO value of
      the selected destination address (normally the primary path; see
      SCTP-BIS [I-D.ietf-tsvwg-2960bis] section 6.4 for details).

   A5)  When the ASCONF-ACK that acknowledges the sequence number last
      sent arrives, the sender MUST stop the T-4 RTO timer, and clear
      the appropriate association and destination error counters as
      defined in SCTP-BIS [I-D.ietf-tsvwg-2960bis] section 8.1 and 8.2.




Stewart, et al.         Expires December 14, 2007              [Page 20]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   A6)  The endpoint MUST process all of the TLVs within the ASCONF-
      ACK(s) 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.

   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 MUST do the following:

   B1)  Increment the error counters and perform path failure detection
      on the appropriate destination address as defined in SCTP-BIS
      [I-D.ietf-tsvwg-2960bis] section 8.1 and 8.2.

   B2)  Increment the association error counters and perform endpoint
      failure detection on the association as defined in SCTP-BIS
      [I-D.ietf-tsvwg-2960bis] 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 SCTP-BIS
      [I-D.ietf-tsvwg-2960bis] section 6.4.1).  An endpoint MUST NOT add
      new parameters to this chunk, it MUST be the same (including its
      sequence number) as the last ASCONF sent.  An endpoint MAY,
      however, bundle an additional ASCONF with new ASCONF parameters
      with the next sequence number.  For details see Section 5.5







Stewart, et al.         Expires December 14, 2007              [Page 21]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   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 SCTP-BIS [I-D.ietf-tsvwg-2960bis] section 6.4.1
   for details).

5.1.1.  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:

   C1)  One and only one SCTP packet holding ASCONF Chunk(s) 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).  However when an ASCONF Chunk is retransmitted due to a
      time-out, the additional held ASCONF Chunks can be bundled into
      the retransmission packet as described in Section 5.5.

   C2)  An ASCONF Chunk may be bundled with any other chunk type
      including other ASCONF Chunks.  If bundled with other ASCONF
      Chunks, the chunks MUST appear in sequential order with respect to
      their Sequence Number.

   C3)  An ASCONF-ACK Chunk may be bundled with any other chunk type
      including other ASCONF-ACK Chunks.  If bundled with other ASCONF-
      ACK Chunks, the chunks MUST appear in sequential order with
      respect to their Sequence Number.

   C4)  Both ASCONF and ASCONF-ACK Chunks MUST NOT be sent in any SCTP
      state except ESTABLISHED, SHUTDOWN-PENDING, SHUTDOWN-RECEIVED and
      SHUTDOWN-SENT.

   C5)  An ASCONF Chunk and an ASCONF-ACK Chunk SHOULD not be larger
      than the PMTU.  If the PMTU is unknown, then the PMTU should be
      set to the minimum PMTU.  The minimum PMTU depends on the IP
      version used for transmission, and is the lesser of 576 octets and
      the first-hop MTU for IPv4 RFC1122 [RFC1122] and 1280 octets for
      IPv6 RFC2460 [RFC2460].



Stewart, et al.         Expires December 14, 2007              [Page 22]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   An ASCONF sender without these restrictions could possibly flood the
   network with a large number of separate address change operations
   thus causing network congestion.

   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.

5.2.  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:

   D1)  Use the source address and port number of the sender to attempt
      to identify the association (i.e., use the same method defined in
      SCTP-BIS [I-D.ietf-tsvwg-2960bis] used for all other SCTP Chunks).
      If found proceed to rule D4.

   D2)  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 D4.

   D2-ext)  If more than one ASCONF Chunks are packed together, use the
      address found in the ASCONF Address Parameter TLV of each of the
      subsequent ASCONF Chunks.  If found, proceed to rule D4.

   D3)  If neither D1, D2 nor D2-ext locates the association, treat the
      chunk as an Out Of The Blue packet as defined in SCTP-BIS
      [I-D.ietf-tsvwg-2960bis].

   D4)  Follow the normal rules to validate the SCTP verification tag
      found in SCTP-BIS [I-D.ietf-tsvwg-2960bis].

   D5)  After the verification tag has been validated, normal chunk
      processing should occur.  Prior to finding the ASCONF chunk the
      receiver MUST encounter an AUTH chunk as described in SCTP-AUTH
      [I-D.ietf-tsvwg-sctp-auth].  If either authentication fails, or
      the AUTH chunk is missing, the receiver MUST silently discard this
      chunk and the rest of the packet.


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



Stewart, et al.         Expires December 14, 2007              [Page 23]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   E1)

      If the value found in the sequence number of the ASCONF Chunk is
      equal to the ('Peer-Sequence-Number' + 1) and the Sequence Number
      of the ASCONF Chunk is the first in the SCTP Packet, the endpoint
      MAY clean any old cached ASCONF-ACK up to the 'Peer-Sequence-
      Number' and then proceed to rule E4.

   E1-ext  If the value found in the sequence number of the ASCONF Chunk
      is equal to the ('Peer-Sequence-Number' + 1) and the ASCONF chunk
      is NOT the first Sequence Number in the SCTP packet proceed to
      rule E4 but do NOT clear any cached ASCONF-ACK or state
      information.
   E2)

      If the value found in the sequence number is less than the ('Peer-
      Sequence-Number' + 1), simply skip to the next ASCONF, and include
      in the outbound response packet any previously cached ASCONF-ACK
      response that was sent and saved that matches the sequence number
      of the ASCONF.  Note: it is possible that no cached ASCONF-ACK
      Chunk exists.  This will occur when an older ASCONF arrives out of
      order.  In such a case the receiver should skip the ASCONF Chunk
      and not include ASCONF-ACK Chunk for that chunk.

   E3)

      Then, process each ASCONF one by one as above while the Sequence
      Number of the ASCONF is less than the ('Peer-Sequence-Number' +
      1).

   E4)  When the sequence number matches the next one expected, process
      the ASCONF as described below and after processing the ASCONF
      Chunk, append an ASCONF-ACK Chunk to the response packet and cache
      a copy of it (in the event it later needs to be retransmitted).


      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.







Stewart, et al.         Expires December 14, 2007              [Page 24]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


      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 SCTP-BIS
         [I-D.ietf-tsvwg-2960bis] 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 queue the response ASCONF-ACK Chunk for transmission after
         the rest of the SCTP packet has been processed.  This allows
         the ASCONF-ACK Chunk to be bundled with other ASCONF-ACK Chunks
         as well as any additional responses e.g. a SACK Chunk.

      V5)  Update the 'Peer-Sequence-Number' to the value found in the
         sequence number field.

   E5)  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.

   E6)  When all ASCONF Chunks are processed for this SCTP packet, send
      back the accumulated single response packet with all of the
      ASCONF-ACK Chunks.  The destination address of the SCTP packet
      containing the ASCONF-ACK Chunks MUST be the source address of the
      SCTP packet that held the ASCONF Chunks.

   E7)  While processing the ASCONF Chunks in the SCTP packet, if the
      response packet will exceed the PMTU of the return path, the
      receiver MUST stop adding additional ASCONF-ACKs into the response
      packet but MUST continue to process all of the ASCONF Chunks,
      saving ASCONF-ACK Chunk responses in its cached copy.  The sender
      of the ASCONF Chunk will later retransmit the ASCONF Chunks that
      were not responded to, at which time the cached copies of the
      responses that would NOT fit in the PMTU can be sent to the peer.





Stewart, et al.         Expires December 14, 2007              [Page 25]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   Note: These rules have been presented with the assumption that the
   implementation is caching old ASCONF-ACKs in case of loss of SCTP
   packets in the ACK path.  It is allowable for an implementation to
   maintain this state in another form it deems appropriate, as long as
   that form results in the same ASCONF-ACK sequences being returned to
   the peer as outlined above.

5.3.  General rules for address manipulation

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

   F0)  If an endpoint receives an ASCONF-ACK that is greater than or
      equal to the next sequence 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).

   F1)  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.  The receiver MUST use the
      path verification procedure for the added address before using
      that address.  The receiver MUST NOT send packets to the new
      address except for the corresponding ASCONF-ACK Chunk or HEARTBEAT
      Chunks for path verification before the new path is verified.  If
      the ASCONF-ACK is sent to the new address it MAY be bundled with
      the HEARTBEAT chunk for path verification.

   F2)  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.

   F3a)  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.

   F3b)  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.



Stewart, et al.         Expires December 14, 2007              [Page 26]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   F4)  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 5.3.1 for further details).

   F5)  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.

   F6)  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.

   F7)  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.

   F8)  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 F5
      has also been violated, in which case the error code 'Request to
      Delete Last Remaining IP Address' is sent).

   F9)  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'.

   F10)  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.



Stewart, et al.         Expires December 14, 2007              [Page 27]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   F11)  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.

   F12)  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.

   F13)  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
      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:

   F14)  All addresses added by the reception of an ASCONF chunk MUST be
      put into the unconfirmed state and MUST have path verification
      performed on them before the address can be used as described in
      SCTP-BIS [I-D.ietf-tsvwg-2960bis] section 5.4.




       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.




Stewart, et al.         Expires December 14, 2007              [Page 28]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   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 SCTP-BIS [I-D.ietf-tsvwg-2960bis] section 8.4).
   It MAY drop the data 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.

5.3.1.  A special case for OOTB ABORT Chunks

   Another case worth mentioning is illustrated below:













Stewart, et al.         Expires December 14, 2007              [Page 29]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


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

       New DATA:------------\
       Source IP:X           \
                              \
       ASCONF-REQ[DEL-IP:X]----\------------------>
                                \        /---------ASCONF-ACK
                                 \      /
                                  \----/-----------> OOTB
       (Ignored <---------------------/-------------ABORT
        by rule F4)                  /
              <---------------------/


   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.

5.3.2.  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
   found in the IP header in looking up the association.  The receiver
   should attempt to use the address found in the Address Parameter
   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).

5.4.  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 MUST 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).



Stewart, et al.         Expires December 14, 2007              [Page 30]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   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
   requester's 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.

5.5.  Bundling of multiple ASCONFs

   In the normal case a single ASCONF is sent in a packet and a single
   reply ASCONF-ACK is received.  However, in the event of the loss of
   an SCTP packet containing either an ASCONF or ASCONF-ACK it is
   allowable for a sender to bundle additional ASCONFs in the
   retransmission.  In bundling multiple ASCONFs the following rules
   MUST be followed:
   1.  Previously transmitted ASCONF Chunks MUST be left unchanged.
   2.  Each SCTP packet containing ASCONF Chunks MUST be bundled
       starting with the smallest ASCONF Sequence Number first in the
       packet (closest to the Chunk header) and preceding in sequential
       order from lowest to highest ASCONF Sequence Number.
   3.  All ASCONFs within the packet MUST be adjacent to each other
       i.e., no other chunk type must separate the ASCONFs.
   4.  Each new ASCONF lookup address MUST be populated as if the
       previous ASCONFs had been processed and accepted.


6.  Security Considerations

   The addition and or deletion of an IP address to an existing
   association does provide an additional mechanism by which existing
   associations can be hijacked.  Therefore this document requires the
   use of the authentication mechanism defined in SCTP-AUTH
   [I-D.ietf-tsvwg-sctp-auth] to limit the ability of an attacker to
   hijack an association.

   Hijacking an association by using the addition and deletion of an IP
   address is only possible for an attacker who is able to intercept the
   initial two packets of the association setup when the SCTP-AUTH
   extension is used without pre-shared keys.  If such a threat is
   considered a possibility, then the SCTP-AUTH
   [I-D.ietf-tsvwg-sctp-auth] extension MUST be used with a
   preconfigured shared end-point pair key to mitigate this threat.  For



Stewart, et al.         Expires December 14, 2007              [Page 31]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   a more detailed analysis see SCTP-AUTH [I-D.ietf-tsvwg-sctp-auth].

   When using a wildcard address for adding or deleting an address the
   source address of the packet is used.  This address is not protected
   by SCTP-AUTH [I-D.ietf-tsvwg-sctp-auth] and an attacker can therefore
   intercept such a packet and modify the source address.

   If an SCTP endpoint that supports this extension receives an INIT
   that indicates that the peer supports the ASCONF extension but does
   NOT support the SCTP-AUTH [I-D.ietf-tsvwg-sctp-auth] extension, the
   receiver of such an INIT MUST send an ABORT in response to such an
   INIT.  Note: that an implementation is allowed to silently discard
   such an INIT as an option as well but under NO circumstance is an
   implementation allowed to proceed with the association setup by
   sending an INIT-ACK in response.

   An implementation that receives an INIT-ACK that indicates that the
   peer does not support the SCTP-AUTH [I-D.ietf-tsvwg-sctp-auth]
   extension MUST NOT send the COOKIE-ECHO to establish the association.
   Instead the implementation MUST discard the INIT-ACK and report to
   the upper layer user that an association cannot be established
   destroying the TCB.

   Other types of attacks, e.g. bombing, are discussed in detail in
   SCTP-THREAT [I-D.ietf-tsvwg-sctpthreat].  The bombing attack, in
   particular, is countered by the use of a random nonce and is required
   by SCTP-BIS [I-D.ietf-tsvwg-2960bis].


7.  IANA considerations

   This document defines the following new SCTP parameters, chunks and
   errors (http://www.iana.org/assignments/sctp-parameters):

   o  Two new chunk types,
   o  Six 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.  The
   chunk types with there suggested values are shown below.






Stewart, et al.         Expires December 14, 2007              [Page 32]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


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


   All of the parameter types, with the exception of the supported
   parameters extension, must come from the range of types where the
   upper two bits are set, we recommend 0xC001 - 0xC006, as shown below.
   The supported parameters type extension must come from the range
   where only the upper bit is set, 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 suggested parameter types are listed below:


        Parameter Type     Parameter Name
        -------------------------------------------------
        0x8008             Supported Extensions
        0xC001             Add IP Address
        0xC002             Delete IP Address
        0xC003             Error Cause Indication
        0xC004             Set Primary Address
        0xC005             Success Indication
        0xC006             Adaptation Layer Indication


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


       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.


   This document also defines an Adaptation code point.  The adaptation
   code point is a 32 bit integer that is assigned by IANA through an
   IETF Consensus action as defined in RFC2434 [RFC2434].  For this new
   registry no initial values are being added by this document, however
   draft-ietf-rddp-sctp will add the first entry.



Stewart, et al.         Expires December 14, 2007              [Page 33]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


8.  Acknowledgments

   The authors would like to express a special note of thanks to Michael
   Ramahlo and Phillip Conrad for their extreme efforts in the early
   formation of this draft.

   The authors wish to thank Jon Berger, Mark Butler, Lars Eggert,
   Janardhan Iyengar, Greg Kendall, Seok Koh, Salvatore Loreto, Peter
   Lei, John Loughney, Ivan Arias Rodriguez, Renee Revis, Marshall Rose,
   Ronnie Sellars, Chip Sharp, and Irene Ruengeler 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.

   And a special thanks to James Polk, abstract writer to the few but
   lucky.


9.  References

9.1.  Normative References

   [RFC1122]  Braden, R., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122, October 1989.

   [RFC1982]  Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982,
              August 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 2434,
              October 1998.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [I-D.ietf-tsvwg-2960bis]
              Stewart, R., "Stream Control Transmission Protocol",
              draft-ietf-tsvwg-2960bis-04 (work in progress),
              April 2007.

   [I-D.ietf-tsvwg-sctp-auth]
              Tuexen, M., "Authenticated Chunks for Stream Control
              Transmission Protocol (SCTP)",



Stewart, et al.         Expires December 14, 2007              [Page 34]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


              draft-ietf-tsvwg-sctp-auth-08 (work in progress),
              February 2007.

9.2.  Informative References

   [I-D.ietf-tsvwg-sctpthreat]
              Stewart, R., "Security Attacks Found Against SCTP and
              Current Countermeasures", draft-ietf-tsvwg-sctpthreat-04
              (work in progress), June 2007.


Appendix A.  Abstract Address Handling

A.1.  General remarks

   This appendix is non-normative.  It is present to give the reader a
   concise mathematical definition of an SCTP endpoint.  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 a 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



Stewart, et al.         Expires December 14, 2007              [Page 35]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


               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.

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.




Stewart, et al.         Expires December 14, 2007              [Page 36]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   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.

A.4.  Relationship with RFC 4960

   SCTP-BIS [I-D.ietf-tsvwg-2960bis] defines the notion of an endpoint.
   This subsection will show that these endpoints are also (special)
   generalized endpoints.

   SCTP-BIS [I-D.ietf-tsvwg-2960bis] 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.





Stewart, et al.         Expires December 14, 2007              [Page 37]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


Authors' Addresses

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

   Phone:
   Email: rrs@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


   Shin Maruyama
   Kyoto University
   Yoshida-Honmachi
   Sakyo-ku
   Kyoto, Kyoto  606-8501
   JAPAN

   Phone: +81-75-753-7468
   Email: mail@marushin.gr.jp










Stewart, et al.         Expires December 14, 2007              [Page 38]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


   Masahiro Kozuka
   Kyoto University
   Yoshida-Honmachi
   Sakyo-ku
   Kyoto, Kyoto  606-8501
   JAPAN

   Phone: +81-75-753-7468
   Email: ma-kun@kozuka.jp










































Stewart, et al.         Expires December 14, 2007              [Page 39]

Internet-Draft    SCTP Dynamic Address Reconfiguration         June 2007


Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.


Acknowledgment

   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).





Stewart, et al.         Expires December 14, 2007              [Page 40]


Html markup produced by rfcmarkup 1.109, available from https://tools.ietf.org/tools/rfcmarkup/