Internet DRAFT - draft-sparks-sipcore-multiple-reasons
draft-sparks-sipcore-multiple-reasons
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
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Internet-Drafts are draft documents valid for a maximum of six months
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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
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document authors. All rights reserved.
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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 . . . . . . . . . . . . . . . . . . . . . . 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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