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rfc:rfc4820

Network Working Group M. Tuexen Request for Comments: 4820 Muenster Univ. of Applied Sciences Category: Standards Track R. Stewart

                                                                P. Lei
                                                   Cisco Systems, Inc.
                                                            March 2007
                    Padding Chunk and Parameter
        for the Stream Control Transmission Protocol (SCTP)

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The IETF Trust (2007).

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 a Stream Control Transmission Protocol (SCTP) packet
 to an arbitrary size.  The padding parameter is used to pad an SCTP
 INIT chunk to an arbitrary size.

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
 2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 2
 3.  Padding Chunk (PAD) . . . . . . . . . . . . . . . . . . . . . . 2
 4.  Padding Parameter (PAD) . . . . . . . . . . . . . . . . . . . . 3
 5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   5.1.  A New Chunk Type  . . . . . . . . . . . . . . . . . . . . . 4
   5.2.  A New Parameter Type  . . . . . . . . . . . . . . . . . . . 4
 6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
 7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 4
 8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
   8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
   8.2.  Informative References  . . . . . . . . . . . . . . . . . . 5

Tuexen, et al. Standards Track [Page 1] RFC 4820 Padding Chunk and Parameter for SCTP March 2007

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 [4].  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 RFC 2119 [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.

Tuexen, et al. Standards Track [Page 2] RFC 4820 Padding Chunk and Parameter for SCTP March 2007

 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.

Tuexen, et al. Standards Track [Page 3] RFC 4820 Padding Chunk and Parameter for SCTP March 2007

5. IANA Considerations

 This document is the reference for all registrations described in
 this section.  All registrations have been listed in the document
 available at sctp-parameters [3].  The changes are described below.

5.1. A New Chunk Type

 A chunk type for the PAD chunk has been assigned by IANA.  The value
 has been assigned as described in Figure 1.  The following has been
 added to the "CHUNK TYPES" table of sctp-parameters [3]:
 CHUNK TYPES
 ID Value    Chunk Type                                     Reference
 --------    ----------                                     ---------
 132(0x84)   Padding Chunk (PAD)                            [RFC4820]

5.2. A New Parameter Type

 A parameter type has been assigned for the PAD parameter by IANA.
 The value has been assigned as described in Figure 2.  The following
 has been added to the "CHUNK PARAMETER TYPES" table in sctp-
 parameters [3]:
 INIT Chunk Parameter Types
 Chunk Parameter Type                       Value
 --------------------                       -----
 Padding                            32773(0x8005)

6. Security Considerations

 This document does not add any additional security considerations to
 the ones given in RFC 2960 [2].

7. Acknowledgments

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

Tuexen, et al. Standards Track [Page 4] RFC 4820 Padding Chunk and Parameter for SCTP March 2007

8. References

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]  "IANA registry",
      <http://www.iana.org/assignments/sctp-parameters>.
 [4]  Mathis, M. and J. Heffner, "Packetization Layer Path MTU
      Discovery", RFC 4821, March 2007.

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
 Peter Lei
 Cisco Systems, Inc.
 955 Happfield Dr.
 Arlington Heights, IL  60004
 US
 Phone: +1 773 695-8201
 EMail: peterlei@cisco.com

Tuexen, et al. Standards Track [Page 5] RFC 4820 Padding Chunk and Parameter for SCTP March 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.

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 Intellectual Property Rights or other rights that might be claimed to
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Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Tuexen, et al. Standards Track [Page 6]

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