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 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 24 February 2023. Copyright Notice Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved. Sparks Expires 24 February 2023 [Page 1] Internet-Draft Multiple reasons August 2022 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 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. Sparks Expires 24 February 2023 [Page 2] Internet-Draft Multiple reasons August 2022 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, . [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, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Sparks Expires 24 February 2023 [Page 3] Internet-Draft Multiple reasons August 2022 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, . 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 Sparks Expires 24 February 2023 [Page 4]