The Session Initiation Protocol (SIP) P-User-Database Private-Header (P-Header)
RFC 4457

Document Type RFC - Informational (April 2006; No errata)
Was draft-camarillo-sipping-user-database (individual in rai area)
Last updated 2013-03-02
Stream IETF
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Stream WG state (None)
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IESG IESG state RFC 4457 (Informational)
Telechat date
Responsible AD Allison Mankin
Send notices to gonzalo.camarillo@ericsson.com, german.blanco@ericsson.com
Network Working Group                                       G. Camarillo
Request for Comments: 4457                                     G. Blanco
Category: Informational                                         Ericsson
                                                              April 2006

                 The Session Initiation Protocol (SIP)
               P-User-Database Private-Header (P-Header)

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.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This document specifies the Session Initiation Protocol (SIP)
   P-User-Database Private-Header (P-header).  This header field is used
   in the 3rd-Generation Partnership Project (3GPP) IMS (IP Multimedia
   Subsystem) to provide SIP registrars and SIP proxy servers with the
   address of the database that contains the user profile of the user
   that generated a particular request.

Table of Contents

   1. Introduction ....................................................2
   2. Scenarios .......................................................2
      2.1. User Registering to the IMS ................................2
      2.2. Incoming Request for an Unregistered User ..................3
   3. Requirements ....................................................4
   4. P-User-Database Header Field Definition .........................4
   5. Applicability ...................................................5
   6. IANA Considerations .............................................5
   7. Security Considerations .........................................5
   8. Acknowledgements ................................................6
   9. References ......................................................6
      9.1. Normative References .......................................6
      9.2. Informative References .....................................6

Camarillo & Blanco           Informational                      [Page 1]
RFC 4457              The P-User-Database P-Header            April 2006

1.  Introduction

   The 3rd-Generation Partnership Project (3GPP) IMS (IP Multimedia
   Subsystem) uses the Session Initiation Protocol (SIP) [2] as its main
   signalling protocol.  (For more information on the IMS, a detailed
   description can be found in 3GPP TS 23.228 [5] and 3GPP TS 24.229
   [6].) 3GPP has identified a set of requirements that can be met,
   according to the procedures in RFC 3427 [3], by defining a new SIP
   Private-Header (P-header).

   The remainder of this document is organized as follows.  Section 2
   describes the scenarios considered by 3GPP and Section 3 discusses
   the requirements derived from these scenarios.  Section 4 defines the
   P-User-Database header field, which meets those requirements, and
   Section 5 discusses the applicability and scope of this new header
   field.  Section 6 registers the P-User-Database header field with the
   IANA and Section 7 discusses the security properties of the
   environment where this header field is intended to be used.

2.  Scenarios

   In the 3GPP IMS, there are two scenarios where a set of proxies
   handling a request need to consult the same user database.  These
   scenarios consist of a user registering to the IMS network and an
   unregistered user receiving an incoming request that triggers a
   service (e.g., a voice mail service).

2.1.  User Registering to the IMS

   In the 3GPP IMS, SIP REGISTER requests generated by a User Agent (UA)
   traverse a set of SIP proxy servers before reaching the SIP
   registrar.  A REGISTER request sent by a UA is routed to the outbound
   proxy of the UA, which is referred to as the P-CSCF (Proxy-
   Call/Session Control Function).

   The P-CSCF routes the REGISTER request to another proxy, which is
   referred to as the I-CSCF (Interrogating-CSCF) and is always located
   in the home domain of the user.  The I-CSCF consults the user
   database of the domain, which is referred to as the Home Subscriber
   Server (HSS), in order to choose the registrar that will process the
   REGISTER request.

   With the information received from the HSS, the I-CSCF routes the
   REGISTER request to the appropriate registrar, which is referred to
   as the S-CSCF (Serving-CSCF).  At this point, the S-CSCF needs to
   contact the same HSS that was previously contacted by the I-CSCF in
   order to fetch the user profile of the user that generated the
   REGISTER request.

Camarillo & Blanco           Informational                      [Page 2]
RFC 4457              The P-User-Database P-Header            April 2006
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