The SIP P-Served-User Private-Header (P-Header) for the 3GPP IP Multimedia (IM) Core Network (CN) Subsystem
RFC 5502

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Network Working Group                                      J. van Elburg
Request for Comments: 5502                Ericsson Telecommunicatie B.V.
Category: Informational                                       April 2009

            The SIP P-Served-User Private-Header (P-Header)
      for the 3GPP IP Multimedia (IM) Core Network (CN) Subsystem

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

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Abstract

   This document specifies the SIP P-Served-User P-header.  This header
   field addresses an issue that was found in the 3rd Generation
   Partnership Project (3GPP) IMS (IP Multimedia Subsystem) between an
   S-CSCF (Serving Call Session Control Function) and an AS (Application
   Server) on the ISC (IMS Service Control) interface.  This header
   field conveys the identity of the served user and the session case
   that applies to this particular communication session and application
   invocation.

van Elburg                   Informational                      [Page 1]
RFC 5502               The P-Served-User P-Header             April 2009

Table of Contents

   1. Introduction ....................................................3
   2. Conventions .....................................................3
   3. Definitions .....................................................3
      3.1. Identity, Network Asserted Identity, Trust Domain,
           and Spec(T) ................................................3
      3.2. Served User ................................................3
   4. Scenarios .......................................................4
      4.1. General ....................................................4
      4.2. Diversion: Continue on Terminating Leg, but Finish
           Subsequent Terminating iFC First ...........................5
      4.3. Diversion: Create New Originating Leg and Provide
           Originating iFC Processing .................................6
      4.4. Call Out of the Blue: on Behalf of User B, but
           Service Profile of Service Identity C.......................8
   5. Requirements ....................................................8
   6. P-Served-User Header Field Definition ...........................9
   7. Proxy Behavior ..................................................9
      7.1. Generating the P-Served-User Header ........................9
      7.2. Consuming the P-Served-User Header ........................10
   8. Applicability ..................................................10
   9. IANA Considerations ............................................11
   10. Security Considerations .......................................11
   11. Acknowledgments ...............................................11
   12. References ....................................................12
      12.1. Normative References .....................................12
      12.2. Informative References ...................................12
   Appendix A.  Why the History-Info Header Is Not Suitable to
                Convey the Served User Information on the ISC
                Interface ............................................13
     A.1.  Semantics  ................................................13
     A.2.  Additional Observations  ..................................13
     A.3.  Conclusion ................................................14

van Elburg                   Informational                      [Page 2]
RFC 5502               The P-Served-User P-Header             April 2009

1.  Introduction

   The 3rd Generation Partnership Project (3GPP) IMS (IP Multimedia
   Subsystem) uses SIP (RFC 3261 [2]) as its main signaling protocol.
   (For more information on the IMS, a detailed description can be found