The Session Initiation Protocol (SIP) P-Refused-URI-List Private-Header (P-Header)
RFC 5318

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• 03

Network Working Group                                      J. Hautakorpi
Request for Comments: 5318                                  G. Camarillo
Category: Informational                                         Ericsson
                                                           December 2008

                 The Session Initiation Protocol (SIP)
              P-Refused-URI-List 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) 2008 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   license-info) in effect on the date of publication of this document.
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Abstract

   This document specifies the Session Initiation Protocol (SIP)
   P-Refused-URI-List Private-Header (P-Header).  This P-Header is used
   in the Open Mobile Alliance's (OMA) Push to talk over Cellular (PoC)
   system.  It enables URI-list servers to refuse the handling of
   incoming URI lists that have embedded URI lists.  This P-Header also
   makes it possible for the URI-list server to inform the client about
   the embedded URI list that caused the rejection and the individual
   URIs that form such a URI list.

Hautakorpi & Camarillo       Informational                      [Page 1]
RFC 5318            The P-Refused-URI-List P-Header        December 2008

Table of Contents

1. Introduction ....................................................2
2. Terminology .....................................................2
3. Usage Scenario ..................................................3
4. Overview of Operation ...........................................6
5. Syntax of P-Refused-URI-List Header Field .......................6
6. Response Generation .............................................7
7. Message Sequence Example ........................................7
8. Applicability ...................................................9
9. Security Considerations ........................................10
10. IANA Considerations ...........................................11
11. Acknowledgements ..............................................11
12. References ....................................................11
   12.1. Normative References .....................................11
   12.2. Informative References ...................................12

1.  Introduction

   The Open Mobile Alliance (OMA) has specified the Push to talk over
   Cellular (PoC) service, which uses the Session Initiation Protocol
   (SIP) [3] and Uniform Resource Identifier (URI)-list services [5]
   (more information about OMA PoC can be found at [8]).

   OMA PoC needs a mechanism for servers to refuse the handling of
   incoming URI lists when these have embedded URI lists.  Such a
   mechanism is intended to be used to establish a particular type of
   PoC session called an ad-hoc PoC group session.

   The remainder of this document is organized as follows.  Section 3
   describes the scenario where the mechanism will be used.  Section 4
   provides an overview of the mechanism, which includes a new P-Header
   called P-Refused-URI-List.  Section 5 defines the syntax of this new
   P-Header.  Section 6 specifies how to use the P-Header.  Section 7
   provides a usage example.  Section 8 describes the applicability of
   the P-Header.  Security considerations are discussed in Section 9
   and, finally, the IANA considerations are stated in Section 10.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [1].

Hautakorpi & Camarillo       Informational                      [Page 2]
RFC 5318            The P-Refused-URI-List P-Header        December 2008

3.  Usage Scenario

   An ad-hoc PoC group session is a type of multi-party PoC session.
   The originator of a particular ad-hoc PoC group session chooses in an
   ad-hoc manner (e.g., selecting from an address book) the set of
   desired participants.  In order to establish the ad-hoc PoC group
   session, the originator sends an INVITE request with a URI list that
   contains the URIs of those participants.

   The PoC network, following the procedures defined in [6], receives
   such an INVITE request and generates an individual INVITE request
   towards each of the URIs in the URI list.

   In previous versions of the OMA PoC service, the originator of an
   ad-hoc PoC group session was only allowed to populate the initial URI
   list with URIs identifying individual PoC users.  Later versions of