A P-Served-User Header Field Parameter for an Originating Call Diversion (CDIV) Session Case in the Session Initiation Protocol (SIP)
RFC 8498

Approval announcement
Draft of message to be sent after approval:

From: The IESG <iesg-secretary@ietf.org>
To: IETF-Announce <ietf-announce@ietf.org>
Cc: ben@nostrum.com, Jean Mahoney <mahoney@nostrum.com>, sipcore-chairs@ietf.org, sipcore@ietf.org, mahoney@nostrum.com, The IESG <iesg@ietf.org>, draft-ietf-sipcore-originating-cdiv-parameter@ietf.org, rfc-editor@rfc-editor.org
Subject: Document Action: 'A P-Served-User Header Field Parameter for Originating CDIV session case in Session Initiation Protocol (SIP)' to Informational RFC (draft-ietf-sipcore-originating-cdiv-parameter-08.txt)

The IESG has approved the following document:
- 'A P-Served-User Header Field Parameter for Originating CDIV session
   case in Session Initiation Protocol (SIP)'
  (draft-ietf-sipcore-originating-cdiv-parameter-08.txt) as Informational RFC

This document is the product of the Session Initiation Protocol Core Working
Group.

The IESG contact persons are Adam Roach, Alexey Melnikov and Ben Campbell.

A URL of this Internet Draft is:
https://datatracker.ietf.org/doc/draft-ietf-sipcore-originating-cdiv-parameter/


Technical Summary

Within 3GPP-specified mobile networks, the SIP header field P-Served-User [RFC5502] conveys the identity of the served user, his/her registration state, and the session case between a SIP proxy known as a Serving Call Session Control Function (S-CSCF) and a SIP Application Server (AS). Any calls that a user places (originates) or receives (terminates) pass through the user's assigned S-CSCF. Each user has a user profile that informs the S-CSCF of which action to perform depending on the session direction (originating or terminating) and the user state (registered or not). RFC 5502 covers basic originating and terminating session cases, but does not cover the case of call diversion services (CDIV) when the session is re-targeted. Without a session case for originating after CDIV, a S-CSCF cannot trigger an originating service for the diverting user nor can an AS execute the procedures for this particular session case.

This document defines a new P-Served-User header field parameter, "orig-cdiv", which conveys the session case of an originating session after CDIV services have been invoked. This document also fixes the ABNF in RFC5502 and provides more guidance for using the P-Served-User header field.

Working Group Summary

This document started out in the DISPATCH working group. During discussions on list, the DISPATCH working group found issues with RFC 5502's ABNF for the P-Served-User header field, so this draft captures that feedback. While this draft was being discussed in DISPATCH, the SIPCORE charter was expanded slightly, and the DISPATCH chairs felt that this document should go SIPCORE to see if the WG wanted to take it on (originally the draft was going to go the AD-sponsored route). The WG accepted the work with lots of +1s to adopt. It received thorough feedback from a few of the participants, all of which was included. 

Document Quality

This addition to the P-Served-User header field will be implemented in 3GPP mobile networks, so multiple vendors will be implementing this draft.  The document's Acknowledgments section thanks reviewers who had significant feedback, and all feedback was addressed. Since the document updates the Header Fields sub-registry of the SIP Parameters registry by adding a reference, the designated expert Adam Roach looked at it and had no issues. 

Personnel

Document Shepherd: Jean Mahoney
Responsible Area Director: Ben Campbell