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Versions: 00 01 02 03 04 draft-ietf-sipcore-proxy-feature

SIPCORE Working Group                                        C. Holmberg
Internet-Draft                                               I. Sedlacek
Intended status: Standards Track                                Ericsson
Expires: March 28, 2011                               September 24, 2010


               Indication of features supported by proxy
              draft-holmberg-sipcore-proxy-feature-00.txt

Abstract

   The Session Initiation Protocol (SIP) "Caller Preferences" extension
   defined in RFC 3840 provides a mechanism that allows a SIP message to
   convey information relating to the originator's capabilities.  This
   document makes it possible for SIP proxies to convey similar
   information, by extending the rr-param rule defined in RFC 3261, so
   that the header field parameter can be used to convey feature tags
   that indicate features supported by the proxy.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 28, 2011.

Copyright Notice

   Copyright (c) 2010 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
   include Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Use-case: IMS Service Continuity  . . . . . . . . . . . . . 3
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   4.  User Agent behavior . . . . . . . . . . . . . . . . . . . . . . 4
   5.  Proxy behavior  . . . . . . . . . . . . . . . . . . . . . . . . 4
   6.  Feature tag semantics . . . . . . . . . . . . . . . . . . . . . 4
   7.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     7.1.  Example name  . . . . . . . . . . . . . . . . . . . . . . . 5
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   9.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 5
   11. Change Log  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     12.1. Normative References  . . . . . . . . . . . . . . . . . . . 6
     12.2. Informative References  . . . . . . . . . . . . . . . . . . 6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 6




























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1.  Introduction

   The SIP "Caller Preferences" extension defined in RFC 3840 [RFC3840]
   provides a mechanism that allows a SIP message to convey information,
   using feature tags, relating to the originator's capabilities.

   Feature information can be useful for other SIP entities, that might
   trigger actions and enable functions based on features supported by
   other SIP entities.

   This document extends the rr-param rule defined in RFC 3261
   [RFC3261], so that it can be used to convey feature tags indicating
   support of features in SIP proxies.  The rr-param rule is used in the
   SIP Path, Route, Record-Route and Service-Route header fields.

1.1.  Use-case: IMS Service Continuity

   The 3rd Generation Partnership Project (3GPP) defines a IP Multimedia
   Subsystem (IMS) Service Continuity mechanism [3GPP.23.237] for
   handover of Packet Switched (PS) sessions to Circuit Switched (CS).
   The handover can be performed by a Service Centralization and
   Continuity Application Server (SCC AS), or by a SCC AS together with
   an Access Transfer Control Function (ATCF), that acts as a SIP proxy.
   Delegating part of the session handover functionality to an ATCF
   provides advantages related to voice interruption during session
   handover etc, since it is located in the same network as the user.

   In order for a SCC AS to delegate part of the session handover
   functionality to an ATCF, when it receives a SIP REGISTER request, it
   needs to be informed whether there is a proxy that provides ATCF
   functionality in the registration path.


2.  Conventions

   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 BCP 14, RFC 2119
   [RFC2119].


3.  Definitions

   The rr-param rule defined in RFC 3261 [RFC3261]:

   rr-param = generic-param

   is extended to:



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   rr-param = generic-param / feature-param

   where feature-param is defined in Section 9 of RFC 3840 [RFC3840].


4.  User Agent behavior

   This specification does not specify any new User Agent behavior.


5.  Proxy behavior

   When a proxy inserts a Path header field (during registration), a
   Service-Route header field (during registration) or a Record-Route
   header field (during a dialog establishment), it MAY insert a feature
   tag in the header field.

   If a feature tag is inserted in a Path or Service-Route header field
   during registration, the resource identified by the URI in the header
   field MUST provide support for the associated feature for all dialogs
   associated with the registration, until the registration is
   terminated or re-freshed.

   If a feature tag is inserted in a Record-Route header field during a
   dialog establishment, the resource identified by the URI in the
   header field MUST provide support for the associated feature until
   the dialog is terminated.


6.  Feature tag semantics

   The feature tag in a header field constructed using rr-param rule
   indicates support of the feature in the resource identified by the
   URI in the header field.

   In order to insert a feature tag in a SIP header field constructed by
   using rr-param rule, the feature specification MUST specify the
   semantics of the feature tag when inserted in that specific header
   field.  Unless the feature specification defines such semantics, a
   the feature tag MUST NOT be included in that specific header field.

   NOTE: If a route set is built using Path, Record-Route or Service-
   Route header fields, any inserted feature tag will be copied into the
   associated Route header fields, together with other header field
   parameters.  This specification does not define any specific meaning
   of the feature tags present in Route header fields in such cases.





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7.  Examples

7.1.  Example name

   TBD

     Alice                         P1                      REGISTRAR
       |                           |                           |
       |--- REGISTER-------------->|                           |
       |                           |                           |
       |                           |--- REGISTER-------------->|
       |                           |    Path: P1;+g.3gpp.srvcc |
       |                           |                           |
       |                           |                           |
       |                           |<-- 200 OK ----------------|
       |                           |    Path: P1;+g.3gpp.srvcc |
       |                           |    Service-Route: REG     |
       |<-- 200 OK ----------------|                           |
       |    Path: P1;+g.3gpp.srvcc |                           |
       |    Service-Route: REG     |                           |
       |                           |                           |


                        Figure 1: Example call flow


8.  IANA Considerations

   TBD


9.  Security Considerations

   Feature tags can provide sensitive information about a SIP entity.
   RFC 3840 cautions against providing sensitive information to another
   party.  Once this information is given out, any use may be made of
   it.


10.  Acknowledgements

   Thanks to Paul Kyzivat for his comments and guidance on the mailing
   list.


11.  Change Log

   [RFC EDITOR NOTE: Please remove this section when publishing]



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   Changes from draft-holmberg-sipcore-proxy-feature-00
   o  To be added when the -01 version is submitted


12.  References

12.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              June 2002.

   [RFC3840]  Rosenberg, J., Schulzrinne, H., and P. Kyzivat,
              "Indicating User Agent Capabilities in the Session
              Initiation Protocol (SIP)", RFC 3840, August 2004.

12.2.  Informative References

   [3GPP.23.237]
              3GPP, "IP Multimedia Subsystem (IMS) Service Continuity;
              Stage 2", 3GPP TS 23.237 10.2.0, June 2010.


Authors' Addresses

   Christer Holmberg
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   Email: christer.holmberg@ericsson.com


   Ivo Sedlacek
   Ericsson
   Scheelevaegen 19C
   Lund  22363
   Sweden

   Email: ivo.sedlacek@ericsson.com






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