Payload Protocol Identifier based Fragmentation and Reassembly for the Stream Control Transmission Protocol
draft-tuexen-tsvwg-sctp-ppid-frag-00

Network Working Group                                           M. Tüxen
Internet-Draft                           Münster Univ. of Appl. Sciences
Intended status: Standards Track                                R. Jesup
Expires: 9 June 2024                                             Mozilla
                                                           H. Tschofenig
                                                         7 December 2023

 Payload Protocol Identifier based Fragmentation and Reassembly for the
                  Stream Control Transmission Protocol
                  draft-tuexen-tsvwg-sctp-ppid-frag-00

Abstract

   This document describes a method for the Stream Control Transmission
   Protocol (SCTP) allowing the upper layer to perform fragmentation,
   reassembly, and interleaving of large ordered user messages by using
   the payload protocol identifier (PPID).

   According to the base specification supporting fragmentation of large
   user messages is optional.  And even if an SCTP implementation
   supports fragmentation, interleaving of user messages is not
   supported by the base specification.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 9 June 2024.

Copyright Notice

   Copyright (c) 2023 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
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   Please review these documents carefully, as they describe your rights
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Sender Side Considerations  . . . . . . . . . . . . . . . . .   3
   4.  Receiver Side Considerations  . . . . . . . . . . . . . . . .   3
   5.  Socket API Considerations . . . . . . . . . . . . . . . . . .   3
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   This document specifies a method to use PPIDs for fragmenting ordered
   large user messages.  Using this method also allows the ability to
   interleave large user messages as provided by [RFC8260] in
   combination with using the SCTP_FRAGMENT_INTERLEAVE level_2 as
   described [RFC6458], Section 8.1.20.

   Reasons to use this method include:

   *  The fragmentation of large user messages is only an optional
      feature of SCTP implementations compliant [RFC9260].  Therefore,
      if an implementation does not support fragmentation, it is
      impossible to send large user messages requiring fragmentation.

   *  An SCTP implementation supporting [RFC9260], but not [RFC8260],
      does not allow the interleaving of large user messages.

   This method does not apply to user messages sent using partial
   reliability as described in [RFC3758].

   The idea described in this document was already described in
   [I-D.ietf-rtcweb-data-channel].  In the final specification
   [RFC8831], this method is declared deprecated.

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2.  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Sender Side Considerations

   An upper layer splits a user message in one or more user message
   fragments.  The upper layer SHOULD choose the size of the user
   message fragments such than SCTP level fragmentation is avoided.

   The upper layer uses two PPIDs.  It MUST use one PPID for all user
   messages fragments except the last one, and it MUST the other PPID
   for the last user message fragments.

   All user message fragments belonging to the same user message MUST be
   sent on the same stream, reliable, and ordered in the sequence they
   belong to the user message.  User message fragments sent on different
   stream MAY be sent in any order.  This allows the interleaving of
   user messages sent on different streams.

   User messages not requiring to be split into multiple user message
   fragments are sent as a single user message fragment with the PPID
   used for last user fragments.

4.  Receiver Side Considerations

   The upper layer MUST process user message fragments received on
   different streams independently.  All user message fragments are
   received by the upper layer in the correct ordering and the PPID MUST
   be used to reconstruct the user message boundaries.  A user message
   fragment with the PPID marking the last user message fragment is the
   last fragment of a use message.  The next received user message
   fragment on the stream is the first fragment of the next user
   message.

   An upper layer MUST deal with interleaving of user messages.

   Please note that notifications, if enabled, can be provided by the
   SCTP implementation at any time.

5.  Socket API Considerations

   This document does not require and changes or additions to the Socket
   API described in [RFC6458].

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6.  IANA Considerations

   This document does not make any requests for IANA.

7.  Security Considerations

   This document does not change the considerations given in [RFC9260].

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC9260]  Stewart, R., Tüxen, M., and K. Nielsen, "Stream Control
              Transmission Protocol", RFC 9260, DOI 10.17487/RFC9260,
              June 2022, <https://www.rfc-editor.org/info/rfc9260>.

8.2.  Informative References

   [I-D.ietf-rtcweb-data-channel]
              Jesup, R., Loreto, S., and M. Tüxen, "WebRTC Data
              Channels", Work in Progress, Internet-Draft, draft-ietf-
              rtcweb-data-channel-06, 4 January 2015,
              <https://datatracker.ietf.org/doc/html/draft-ietf-rtcweb-
              data-channel-06>.

   [RFC3758]  Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P.
              Conrad, "Stream Control Transmission Protocol (SCTP)
              Partial Reliability Extension", RFC 3758,
              DOI 10.17487/RFC3758, May 2004,
              <https://www.rfc-editor.org/info/rfc3758>.

   [RFC6458]  Stewart, R., Tuexen, M., Poon, K., Lei, P., and V.
              Yasevich, "Sockets API Extensions for the Stream Control
              Transmission Protocol (SCTP)", RFC 6458,
              DOI 10.17487/RFC6458, December 2011,
              <https://www.rfc-editor.org/info/rfc6458>.

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   [RFC8260]  Stewart, R., Tuexen, M., Loreto, S., and R. Seggelmann,
              "Stream Schedulers and User Message Interleaving for the
              Stream Control Transmission Protocol", RFC 8260,
              DOI 10.17487/RFC8260, November 2017,
              <https://www.rfc-editor.org/info/rfc8260>.

   [RFC8831]  Jesup, R., Loreto, S., and M. Tüxen, "WebRTC Data
              Channels", RFC 8831, DOI 10.17487/RFC8831, January 2021,
              <https://www.rfc-editor.org/info/rfc8831>.

Authors' Addresses

   Michael Tüxen
   Münster University of Applied Sciences
   Stegerwaldstrasse 39
   48565 Steinfurt
   Germany
   Email: tuexen@fh-muenster.de

   Randell Jesup
   Mozilla Corporation
   1835 Horse Shoe Trl
   Malvern, PA 19355
   United States of America
   Email: randell-ietf@jesup.org

   Hannes Tschofenig
   Email: hannes.tschofenig@gmx.net

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