Internet-Draft Multiple reasons November 2021
Sparks Expires 16 May 2022 [Page]
Workgroup:
SIPCORE Working Group
Internet-Draft:
draft-sparks-sipcore-multiple-reasons-00
Updates:
3326 (if approved)
Published:
Intended Status:
Standards Track
Expires:
Author:
R. Sparks

Multiple SIP Reason Header Field Values

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 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 16 May 2022.

Table of Contents

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:

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, , <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, , <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, , <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.

Author's Address

Robert Sparks