Internet Engineering Task Force (IETF)                         R. Sparks
Request for Comments: 9366                                    March 2023
Updates: 3326
Category: Standards Track
ISSN: 2070-1721


               Multiple SIP Reason Header Field Values

Abstract

  The SIP Reason header field as defined in RFC 3326 allows only one
  Reason value per protocol value.  Experience with more recently
  defined protocols shows it is useful to allow multiple values with
  the same protocol value.  This document updates RFC 3326 to allow
  multiple values for an indicated registered protocol when that
  protocol defines what the presence of multiple values means.

Status of This Memo

  This is an Internet Standards Track document.

  This document is a product of the Internet Engineering Task Force
  (IETF).  It represents the consensus of the IETF community.  It has
  received public review and has been approved for publication by the
  Internet Engineering Steering Group (IESG).  Further information on
  Internet Standards is available in Section 2 of RFC 7841.

  Information about the current status of this document, any errata,
  and how to provide feedback on it may be obtained at
  https://www.rfc-editor.org/info/rfc9366.

Copyright Notice

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

  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.  Conventions
  3.  Update to RFC 3326
  4.  Security Considerations
  5.  IANA Considerations
  6.  References
    6.1.  Normative References
    6.2.  Informative References
  Acknowledgments
  Author's Address

1.  Introduction

  The SIP Reason header field as defined in RFC 3326 allows only one
  Reason value per protocol value.  Experience with more recently
  defined protocols shows it is useful to allow multiple values with
  the same protocol value [STIRREASONS].  This document updates RFC
  3326 to allow multiple values for an indicated registered protocol
  when that protocol defines what the presence of multiple values
  means.  It does not change the requirement in RFC 3326 restricting
  the header field contents to one value per protocol for those
  protocols that do not define what multiple values mean.

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.  Update to RFC 3326

  The last paragraph of Section 2 of [RFC3326] is replaced as follows:

  OLD:

  |  A SIP message MAY contain more than one Reason value (i.e.,
  |  multiple Reason lines), but all of them MUST have different
  |  protocol values (e.g., one SIP and another Q.850).  An
  |  implementation is free to ignore Reason values that it does not
  |  understand.

  NEW:

  |  A SIP message MAY contain more than one Reason value (i.e.,
  |  multiple Reason lines).  If the registered protocol for the Reason
  |  value specifies what it means for multiple values to occur in one
  |  message, more than one value for that protocol MAY be present.
  |  Otherwise, there MUST be only one value per protocol provided
  |  (e.g., one SIP and another Q.850).  An implementation is free to
  |  ignore Reason values that it does not understand.

4.  Security Considerations

  This document adds no security considerations to the use of SIP.  The
  security considerations in [RFC3326] and those in any registered
  protocols used in Reason header field values should be considered.

5.  IANA Considerations

  This document has no IANA actions.

6.  References

6.1.  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>.

  [RFC3326]  Schulzrinne, H., Oran, D., and G. Camarillo, "The Reason
             Header Field for the Session Initiation Protocol (SIP)",
             RFC 3326, DOI 10.17487/RFC3326, December 2002,
             <https://www.rfc-editor.org/info/rfc3326>.

  [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>.

6.2.  Informative References

  [STIRREASONS]
             Wendt, C., "Identity Header Errors Handling for STIR",
             Work in Progress, Internet-Draft, draft-ietf-stir-
             identity-header-errors-handling-08, 25 February 2023,
             <https://datatracker.ietf.org/doc/html/draft-ietf-stir-
             identity-header-errors-handling-08>.

Acknowledgments

  This text is based on discussions at a STIR Working Group interim
  meeting.  Jean Mahoney and Russ Housley provided suggestions that
  vastly improved the first attempts at assembling these words.
  Christer Holmberg, Dale Worley, Brian Rosen, Chris Wendt, and Paul
  Kyzivat provided constructive discussion during SIPCORE Working Group
  adoption.

Author's Address

  Robert Sparks
  Email: [email protected]

You are viewing proxied material from gopher.fnord.one. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.