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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 SIPCORE Working Group R. Sparks 3 Internet-Draft 12 November 2021 4 Updates: 3326 (if approved) 5 Intended status: Standards Track 6 Expires: 16 May 2022 8 Multiple SIP Reason Header Field Values 9 draft-sparks-sipcore-multiple-reasons-00 11 Abstract 13 The SIP Reason Header Field as defined in RFC 3326 allows only one 14 Reason value per protocol value. Practice shows it is useful to 15 allow multiple values with the same protocol value. This update to 16 RFC 3326 allows multiple values for an indicated registered protocol 17 when that protocol defines what the presence of multiple values 18 means. 20 Discussion Venues 22 This note is to be removed before publishing as an RFC. 24 Discussion of this document takes place on the Session Initiation 25 Protocol Core Working Group mailing list (sipcore@ietf.org), which is 26 archived at https://mailarchive.ietf.org/arch/browse/sipcore/. 28 Source for this draft and an issue tracker can be found at 29 https://github.com/rjsparks/draft-sparks-sipcore-multiple-reasons. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at https://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on 16 May 2022. 48 Copyright Notice 50 Copyright (c) 2021 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 55 license-info) in effect on the date of publication of this document. 56 Please review these documents carefully, as they describe your rights 57 and restrictions with respect to this document. Code Components 58 extracted from this document must include Simplified BSD License text 59 as described in Section 4.e of the Trust Legal Provisions and are 60 provided without warranty as described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 65 2. Conventions and Definitions . . . . . . . . . . . . . . . . . 2 66 3. Update to RFC3326 . . . . . . . . . . . . . . . . . . . . . . 2 67 4. Security Considerations . . . . . . . . . . . . . . . . . . . 3 68 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 69 6. Normative References . . . . . . . . . . . . . . . . . . . . 3 70 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 3 71 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4 73 1. Introduction 75 The SIP Reason Header Field as defined in RFC 3326 allows only one 76 Reason value per protocol value. Practice shows it is useful to 77 allow multiple values with the same protocol value. This update to 78 RFC 3326 allows multiple values for an indicated registered protocol 79 when that protocol defines what the presence of multiple values 80 means. 82 2. Conventions and Definitions 84 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 85 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 86 "OPTIONAL" in this document are to be interpreted as described in 87 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 88 capitals, as shown here. 90 3. Update to RFC3326 92 The last paragraph of section 2 of [RFC3326] is replaced as follows: 94 OLD: 96 A SIP message MAY contain more than one Reason value (i.e., multiple 97 Reason lines), but all of them MUST have different protocol values 98 (e.g., one SIP and another Q.850). An implementation is free to 99 ignore Reason values that it does not understand. 101 NEW: 103 A SIP message MAY contain more than one Reason value (i.e., multiple 104 Reason lines). If the registered protocol for the Reason value 105 specifies what it means for multiple values to occur in one message, 106 more than one value for that protocol MAY be present. Otherwise, 107 there MUST be only one value per protocol provided (e.g., one SIP and 108 another Q.850). An implementation is free to ignore Reason values 109 that it does not understand. 111 4. Security Considerations 113 This document adds no security considerations to the use of SIP. The 114 security considerations in [RFC3326] and those in any registered 115 protocols used in Reason header field values should be considered. 117 5. IANA Considerations 119 This document has no IANA actions. 121 6. Normative References 123 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 124 Requirement Levels", BCP 14, RFC 2119, 125 DOI 10.17487/RFC2119, March 1997, 126 . 128 [RFC3326] Schulzrinne, H., Oran, D., and G. Camarillo, "The Reason 129 Header Field for the Session Initiation Protocol (SIP)", 130 RFC 3326, DOI 10.17487/RFC3326, December 2002, 131 . 133 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 134 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 135 May 2017, . 137 Appendix A. Acknowledgments 139 This text is based on discussions at a STIR working group interim 140 meeting. Jean Mahoney and Russ Housley provided suggestions that 141 vastly improved the first attempts at assembling these words. 143 Author's Address 145 Robert Sparks 147 Email: rjsparks@nostrum.com