A Framework for Session Initiation Protocol (SIP) Session Policies
RFC 6794

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Internet Engineering Task Force (IETF)                           V. Hilt
Request for Comments: 6794                      Bell Labs/Alcatel-Lucent
Category: Standards Track                                   G. Camarillo
ISSN: 2070-1721                                                 Ericsson
                                                            J. Rosenberg
                                                             jdrosen.net
                                                           December 2012

   A Framework for Session Initiation Protocol (SIP) Session Policies

Abstract

   Proxy servers play a central role as an intermediary in the Session
   Initiation Protocol (SIP) as they define and impact policies on call
   routing, rendezvous, and other call features.  This document
   specifies a framework for SIP session policies that provides a
   standard mechanism by which a proxy can define or influence policies
   on sessions, such as the codecs or media types to be used.  It
   defines a model, an overall architecture and new protocol mechanisms
   for session policies.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6794.

Copyright Notice

   Copyright (c) 2012 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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must

Hilt, et al.                 Standards Track                    [Page 1]
RFC 6794                Session Policy Framework           December 2012

   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................5
   3. Session-Independent Policies ....................................5
      3.1. Architecture and Overview ..................................5
      3.2. Policy Subscription ........................................6
           3.2.1. User Agent Client (UAC) Behavior ....................6
           3.2.2. User Agent Server (UAS) Behavior ....................8
   4. Session-Specific Policies .......................................8
      4.1. Architecture ...............................................8
      4.2. Overview ...................................................9
      4.3. Examples ..................................................11
           4.3.1. Offer in Request ...................................11
           4.3.2. Offer in Response ..................................13
      4.4. UA/Policy Server Rendezvous ...............................15
           4.4.1. UAC Behavior .......................................15
           4.4.2. Proxy Behavior .....................................17
           4.4.3. UAS Behavior .......................................20
           4.4.4. Caching the Local Policy Server URI ................21
           4.4.5. Header Field Definition and Syntax .................22
      4.5. Policy Channel ............................................23
           4.5.1. Creation and Management ............................24
           4.5.2. Contacting the Policy Server .......................25
           4.5.3. Using Session Policies .............................26
   5. Security Considerations ........................................27
   6. IANA Considerations ............................................29
      6.1. Registration of the "Policy-ID" Header Field ..............29
      6.2. Registration of the "Policy-Contact" Header Field .........29
      6.3. Registration of the "non-cacheable" Policy-Contact
           Header Field Parameter ....................................29
      6.4. Registration of the "policy" SIP Option Tag ...............29
   7. References .....................................................30
      7.1. Normative References ......................................30
      7.2. Informative References ....................................31
   Appendix A. Acknowledgements ......................................32