SIPCORE Working Group                                          R. Sparks
Internet-Draft                                          12 November 2021
Updates: 3326 (if approved)
Intended status: Standards Track
Expires: 16 May 2022


                Multiple SIP Reason Header Field Values
                draft-sparks-sipcore-multiple-reasons-00

Abstract

   The SIP Reason Header Field as defined in RFC 3326 allows only one
   Reason value per protocol value.  Practice 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.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Discussion of this document takes place on the Session Initiation
   Protocol Core Working Group mailing list (sipcore@ietf.org), which is
   archived at https://mailarchive.ietf.org/arch/browse/sipcore/.

   Source for this draft and an issue tracker can be found at
   https://github.com/rjsparks/draft-sparks-sipcore-multiple-reasons.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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 16 May 2022.





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Copyright Notice

   Copyright (c) 2021 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
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   extracted from this document must include Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   2
   3.  Update to RFC3326 . . . . . . . . . . . . . . . . . . . . . .   2
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   3
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .   3
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   The SIP Reason Header Field as defined in RFC 3326 allows only one
   Reason value per protocol value.  Practice 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.

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.

3.  Update to RFC3326

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

   OLD:




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   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.  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>.

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.





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Author's Address

   Robert Sparks

   Email: rjsparks@nostrum.com














































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