SIPCORE Working Group                                          R. Sparks
Internet-Draft                                            23 August 2022
Updates: 3326 (if approved)
Intended status: Standards Track
Expires: 24 February 2023


                Multiple SIP Reason Header Field Values
                 draft-ietf-sipcore-multiple-reasons-01

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 update to RFC 3326 allows multiple
   values for an indicated registered protocol when that protocol
   defines what the presence of multiple values means.

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
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   This Internet-Draft will expire on 24 February 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
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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 and Definitions . . . . . . . . . . . . . . . . .   2
   3.  Update to RFC3326 . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   3
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .   4
   Appendix B.  Changelog  . . . . . . . . . . . . . . . . . . . . .   4
     B.1.  00  . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     B.2.  01  . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   4

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 update to RFC 3326
   allows 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 and Definitions

   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.







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3.  Update to RFC3326

   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/rfc/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/rfc/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/rfc/rfc8174>.



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6.2.  Informative References

   [STIRREASONS]
              Wendt, C., "Identity Header Errors Handling", Work in
              Progress, Internet-Draft, draft-ietf-stir-identity-header-
              errors-handling-03, 19 August 2022,
              <https://datatracker.ietf.org/doc/html/draft-ietf-stir-
              identity-header-errors-handling-03>.

Appendix A.  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.

Appendix B.  Changelog

   (This section to be removed by the RFC editor.)

B.1.  00

   *  rename draft-sparks to draft-ietf.  Add changelog.

B.2.  01

   *  expand a little on "Practice shows", referring to [STIRREASONS]

Author's Address

   Robert Sparks
   Email: rjsparks@nostrum.com

















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