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Versions: (draft-tuexen-tsvwg-sctp-padding) 00 01 02 RFC 4820

Network Working Group                                          M. Tuexen
Internet-Draft                        Muenster Univ. of Applied Sciences
Intended status: Standards Track                              R. Stewart
Expires: April 19, 2007                                           P. Lei
                                                     Cisco Systems, Inc.
                                                        October 16, 2006


                  Padding Chunk and Parameter for SCTP
                  draft-ietf-tsvwg-sctp-padding-02.txt

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Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This document defines a padding chunk and a padding parameter and
   describes the required receiver side procedures.  The padding chunk
   is used to pad an SCTP packet to an arbitrary size.  The padding
   parameter is used to pad an SCTP INIT chunk to an arbitrary size.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Padding Chunk (PAD) . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Padding Parameter (PAD) . . . . . . . . . . . . . . . . . . . . 4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
     5.1.  A New Chunk Type  . . . . . . . . . . . . . . . . . . . . . 5
     5.2.  A New Parameter Type  . . . . . . . . . . . . . . . . . . . 5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 6
   Intellectual Property and Copyright Statements  . . . . . . . . . . 8



































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1.  Introduction

   This document defines a padding chunk and a padding parameter and
   describes the required receiver side procedures.  The padding chunk
   is used to pad an SCTP packet to an arbitrary size.  The padding
   parameter is used to pad an SCTP INIT chunk to an arbitrary size.
   The usage of the PAD chunk for path MTU discovery is described in
   PMTU [3].  The inappropriate usage of the PAD parameter or PAD chunk
   can result in wasted bandwidth.


2.  Conventions

   The key words "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 [1].


3.  Padding Chunk (PAD)

   This chunk is used to pad an SCTP packet.  A PAD chunk can be used to
   enlarge the packet by 4 to 65536 bytes in steps of 4 bytes.  An SCTP
   packet MAY contain multiple PAD chunks.

    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 = 0x84   |   Flags=0     |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   \                         Padding Data                          /
   /                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 1

   Type: 1 byte (unsigned integer)
      This value MUST be set to 0x84 for all PAD-chunks.

   Flags: 1 byte (unsigned integer)
      This value SHOULD be set to zero on transmit and MUST be ignored
      on receipt.

   Length: 2 bytes (unsigned integer)
      This value holds the length of the Padding Data plus 4.





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   Padding Data: n bytes (unsigned integer)
      This holds the Padding Data.  The Padding Data MUST be ignored by
      the receiver.

   The receiver of the PAD chunk MUST discard this chunk and continue
   processing the rest of the chunks in the packet.  Please note that
   this is also the required processing behavior for any unknown chunk
   having the same highest order two bits of the type as the PAD chunk.


4.  Padding Parameter (PAD)

   This parameter is used to pad an INIT chunk.  A PAD parameter can be
   used to enlarge the INIT chunk by 4 bytes as the minimum to the
   maximum size of the INIT chunk in steps of 4 bytes.  An INIT chunk
   MAY contain multiple PAD parameters.

    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 = 0x8005   |       Parameter Length        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                                                               /
   \                          Padding Data                         \
   /                                                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 2

   Parameter Type: 2 bytes (unsigned integer)
      This value MUST be set to 0x8005.

   Parameter Length: 2 bytes (unsigned integer)
      This value holds the length of the Padding Data plus 4.

   The PAD parameter MAY be included only in the INIT chunk.  It MUST
   NOT be included in any other chunk.  The receiver of the PAD
   parameter MUST silently discard this parameter and continue
   processing the rest of the INIT chunk.  This means that the size of
   the generated COOKIE parameter in the INIT-ACK MUST NOT depend on the
   existence of the PAD parameter in the INIT chunk.  A receiver of a
   PAD parameter MUST NOT include the PAD parameter within any State
   Cookie parameter it generates.


5.  IANA Considerations

   [NOTE to RFC-Editor:



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      "RFCXXXX" is to be replaced by the RFC number you assign this
      document.

   ]

   This document (RFCXXX) is the reference for all registrations
   described in this section.  All registrations need to be listed in
   the document available at sctp-parameters [4].  The suggested changes
   are described below.

5.1.  A New Chunk Type

   A chunk type for the PAD chunk has to be assigned by IANA.  It is
   suggested to use the value given in Figure 1.  This requires an
   additional line in the "CHUNK TYPES" table of sctp-parameters [4]:

   CHUNK TYPES

   ID Value    Chunk Type                                     Reference
   --------    ----------                                     ---------
   132(0x84)   Padding Chunk (PAD)                            [RFCXXXX]

5.2.  A New Parameter Type

   A parameter type has to be assigned for the PAD parameter by IANA.
   It is suggested to use the values given in Figure 2.  This requires a
   modification in the "CHUNK PARAMETER TYPES" table in sctp-
   parameters [4]: Add a new line to the "INIT Chunk Parameter Types"
   table:

   Chunk Parameter Type                       Value
   --------------------                       -----
   Padding                            32773(0x8005)


6.  Security Considerations

   This document does not add any additional security considerations in
   addition to the ones given in RFC2960 [2].


7.  Acknowledgments

   The authors wish to thank Matthew J. Zekauskas, and Lars Eggert for
   his invaluable comments.


8.  References



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8.1.  Normative References

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

   [2]  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.

8.2.  Informative References

   [3]  Mathis, M. and J. Heffner, "Packetization Layer Path MTU
        Discovery", draft-ietf-pmtud-method-10 (work in progress),
        September 2006.

URIs

   [4]  <http://www.iana.org/assignments/sctp-parameters>


Authors' Addresses

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

   Email: tuexen@fh-muenster.de


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

   Email: rrs@cisco.com












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   Peter Lei
   Cisco Systems, Inc.
   955 Happfield Dr.
   Arlington Heights, IL  60004
   US

   Phone: +1 773 695-8201
   Email: peterlei@cisco.com











































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