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Zero Checksum for the Stream Control Transmission Protocol
draft-tuexen-tsvwg-sctp-zero-checksum-00

Document Type Active Internet-Draft (individual)
Authors Michael Tüxen , Victor Boivie , Florent Castelli , Randell Jesup
Last updated 2022-10-24
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draft-tuexen-tsvwg-sctp-zero-checksum-00
Network Working Group                                           M. Tüxen
Internet-Draft                           Münster Univ. of Appl. Sciences
Intended status: Standards Track                               V. Boivie
Expires: 27 April 2023                                       F. Castelli
                                                                  Google
                                                                R. Jesup
                                                                 Mozilla
                                                         24 October 2022

       Zero Checksum for the Stream Control Transmission Protocol
                draft-tuexen-tsvwg-sctp-zero-checksum-00

Abstract

   The Stream Control Transmission Protocol (SCTP) uses a 32-bit
   checksum in the common header of each packet to provide some level of
   data integrity.  When the lower layer used by SCTP does already
   provide the same or a higher level of data integrity, computing this
   checksum does not provide any additional protection, but does require
   computing resources.  This document provides a simple extension to
   SCTP allowing to save these computing resources by using the constant
   0 as the checksum.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on 27 April 2023.

Copyright Notice

   Copyright (c) 2022 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/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  A New Chunk Parameter . . . . . . . . . . . . . . . . . . . .   3
   4.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Socket API Considerations . . . . . . . . . . . . . . . . . .   4
     5.1.  Get or Set Accepting a Zero Checksum
           (SCTP_ACCEPT_ZERO_CHECKSUM) . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   SCTP as specified in [RFC9260] uses a CRC32c to provide some level of
   data integrity.  When using, for example, Datagram Transport Layer
   Security (DTLS) as the lower layer for SCTP as specified in
   [RFC8261], using the CRC32c does not provide any additional
   protection over the one already provided by DTLS.  However, computing
   the CRC32c at the sender and receiver side does require computational
   resources for no benefit.  This is in particular important for
   computational limited end points using SCTP encapsulated in DTLS.

   The extension described in this document allows an SCTP end point to
   declare that it accepts SCTP packets with a checksum of zero.  This
   declaration happens during the setup of the SCTP association and
   allows end points supporting this extension to be interoperable with
   end points not supporting the extension described in this document.

   End points using this extension still need to implement the CRC32c
   checksum algorithms.

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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.  A New Chunk Parameter

   The Zero Checksum Acceptable Chunk Parameter is defined by the
   following figure.

    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 = 0x8001         |          Length = 4           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

             Figure 1: Zero Checksum Acceptable Chunk Parameter

   Type: 16 bits (unsigned integer)
      This field holds the IANA defined parameter type for the "Zero
      Checksum Acceptable" chunk parameter.  IANA is requested to assign
      the value 32769 (0x8001) for this parameter type.

   Length: 16 bits (unsigned integer)
      This field holds the length in bytes of the chunk parameter; the
      value MUST be 4.

   All transported integer numbers are in "network byte order" a.k.a.,
   Big Endian.

   The Zero Checksum Acceptable Chunk Parameter MAY appear in INIT and
   INIT ACK chunks.  It MUST NOT appear in any other chunk.

   If an end point not supporting the extension described in this
   document receives this parameter in an INIT or INIT ACK chunk, it
   skips it and continues to process further parameters in the chunk.
   This behaviour is REQUIRED by [RFC9260] because the highest-order 2
   bits of the Type are 10.

4.  Procedures

   An end point willing to accept SCTP packets with a checksum of zero,
   MAY include the Zero Checksum Acceptable Chunk Parameter in the INIT
   or INIT ACK chunk it sends.  An end point MUST do this consistently.

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   If an end point has sent the Zero Checksum Acceptable Chunk Parameter
   in an INIT or INIT ACK chunk, it MUST accept SCTP packets using a
   checksum value of zero for this association.  It MUST also accept
   SCTP packets containing the correct CRC32c checksum field.

   When an end point sends a packet containing an INIT chunk, it MUST
   include a CRC32c checksum in the packet containing the INIT chunk.

   When an end point receives an "Out of the Blue" (OOTB) SCTP packet
   and needs to send a response, it MUST include a CRC32c checksum in
   the response.

   If an end point has received an INIT or INIT ACK chunk from its peer
   during the association setup, it MAY use zero as the checksum for all
   packets sent in this association.

5.  Socket API Considerations

   This section describes how the socket API defined in [RFC6458] needs
   to be extended to provide a way for the application to control the
   UDP encapsulation.

   Please note that this section is informational only.

   A socket API implementation based on [RFC6458] is extended by
   supporting one new read/write IPPROTO_SCTP level socket option.

5.1.  Get or Set Accepting a Zero Checksum (SCTP_ACCEPT_ZERO_CHECKSUM)

   This socket option can be used to control the acceptance of a zero
   checksum.  It applies only to future SCTP associations on the socket.

   This option expects an integer boolean flag, where a non-zero value
   turns on the option, and a zero value turns off the option.

   This option is off by default.

6.  IANA Considerations

   [NOTE to RFC-Editor: "RFCXXXX" is to be replaced by the RFC number
   you assign this document.]

   [NOTE to RFC-Editor: The requested value for the parameter type is
   tentative and to be confirmed by IANA.]

   This document (RFCXXXX) is the reference for the registration
   described in this section.

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   A new chunk parameter type has to be assigned by IANA.  This requires
   an additional line in the "Chunk Parameter Types" registry for SCTP:

       +==========+===================================+===========+
       | ID Value | Chunk Parameter Type              | Reference |
       +==========+===================================+===========+
       | 32769    | Zero Checksum Acceptable (0x8001) | [RFCXXXX] |
       +----------+-----------------------------------+-----------+

          Table 1: New entry in "Chunk Parameter Types" registry

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>.

   [RFC8261]  Tuexen, M., Stewart, R., Jesup, R., and S. Loreto,
              "Datagram Transport Layer Security (DTLS) Encapsulation of
              SCTP Packets", RFC 8261, DOI 10.17487/RFC8261, November
              2017, <https://www.rfc-editor.org/info/rfc8261>.

   [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

   [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>.

Authors' Addresses

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

   Victor Boivie
   Google
   Kungsbron 2
   SE-11122 Stockholm
   Sweden
   Email: boivie@google.com

   Florent Castelli
   Google
   Kungsbron 2
   SE-11122 Stockholm
   Sweden
   Email: orphis@google.com

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

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