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Versions: (RFC 3455) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 RFC 7315

Network Working Group                                           K. Drage
Internet-Draft                                       Lucent Technologies
Expires: April 20, 2006                                 October 17, 2005


   Update to RFC 3455: (Private Header (P-Header) Extensions to  the
 Session Initiation Protocol (SIP) for the 3rd-Generation  Partnership
                             Project (3GPP)
                   draft-drage-sipping-rfc3455bis-00

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   RFC3455 [3] describes a set of private Session Initiation Protocol
   (SIP) headers (P-headers) used by the 3rd-Generation Partnership
   Project (3GPP), along with their applicability, which is limited to
   particular environments.  Since RFC3455 [3] was approved in 2003, a
   number of minor corrections and extensions have arisen whose
   documentation would be convenient to 3GPP.  This proposed update to
   RFC3455 [3] provides those minor corrections and extensions.



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1.  Overall applicability

   While this document updates RFC3455 [3], it makes no changes to the
   overall applicability.















































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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, RFC2119 [1].














































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3.  Overview

   This document proposes a number of additions to RFC3455 [3] such as:

      further clarification on proxy procedures for the P-Associated-URI
      header.

      further clarification on the relationship between the History-Info
      header and the P-Called-Party-ID header.

      clarification on the UA procedures for the P-Charging-Vector and
      P-Charging-Function-Addresses header.

      definition of additional values of access technology in the
      P-Access-Network-Info header.

      clarification that additional parameters can be defined elsewhere
      for the P-Charging-Vector header.

































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4.  Issues

4.1.  Procedures for the P-Associated-URI header at a proxy

   RFC3455 [3] indicates that it defines no procedures for the
   P-Associated-URI header at a proxy.

   What is implicitly meant here is that the proxy does not add, read,
   modify or delete the header, and therefore RFC3261 [2] proxy
   procedures only apply to the header.

4.2.  P-Called-Party-ID header and the History-Info header

   At the time RFC3455 [3] was drafted, the History-Info header was a
   long way from specification; this header has now been specified and
   approved in draft-ietf-sip-history-info-06 [4].

   It is acknowledged that the History-Info header will provide
   equivalent coverage to that of the P-Called-Party-ID header.  However
   the P-Called-Party-ID header is used entirely within the 3GPP system
   and does not appear to SIP entities outside that of a single 3GPP
   operator.

   Additionally the P-Called-Party-ID header has been defined within
   3GPP systems since release 5, and therefore it is realistic to expect
   implementations to be already released to the field.

   It is therefore considered that replacement of the P-Called-Party-ID
   header within 3GPP systems causes more issues that it solves, and
   therefore the update of RFC3455 [3] to remove the P-Called-Party-ID
   header will not be addressed.  However it is recommended that any new
   usage of this type of functionality should use the History-Info
   header rather than the P-Called-Party-ID header.

4.3.  Procedures at the UA for the P-Charging-Function Addresses header

   The text in section 4.5.2.1 of RFC3455 [3] does not adequately take
   into account procedures for UAs located inside the private network,
   e.g. as gateways and suchlike which may play a full part in network
   charging procedures.  Section 4.5.2.1 is replaced with the following
   text:

      This document does not specify any procedure at a UA located
      outside the administrative domain of a private network, with
      regard to the P-Charging-Function-Addresses header.  Such UAs need
      not understand this header.





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      However, it might be possible that a UA is located within the
      administrative domain of a private network (e.g., a PSTN gateway,
      or conference mixer), and it may have access to the addresses of
      the charging entities.  In this cases, a UA MAY insert the
      P-Charging-Function-Addresses header in a SIP request or response
      when the next hop for the message is a proxy or UA located in the
      same administrative domain.  Similar such a UA may use the
      contents of the P-Charging-Function-Addresses header in
      communicating with the charging entities.

4.4.  Procedures at the UA for the P-Charging-Vector header

   The text in section 4.6.2.1 of RFC3455 [3] does not adequately take
   into account procedures for UAs located inside the private network,
   e.g. as gateways and suchlike which may play a full part in network
   charging procedures.  Section 4.6.2.1 is replaced with the following
   text:

      This document does not specify any procedure at a UA located
      outside the admininstrative domain of a private network, with
      regard to the P-Charging-Vector header.  UAs need not understand
      this header.

      However, it might be possible that a UA is located within the
      administrative domain of a private network (e.g., a PSTN gateway,
      or conference mixer), and it may it may interact with the charging
      entities.  In this cases, a UA MAY insert the P-Charging-Vector
      header in a SIP request or response when the next hop for the
      message is a proxy or UA located in the same administrative
      domain.  Similar such a UA may use the contents of the P-Charging-
      Voector header in communicating with the charging entities.

4.5.  Recognition of additional values of access technology in the
      P-Access-Network-Info header

   A number of new access technologies are contemplated in 3GPP, and the
   reuse of IMS to support Next Generation Networks (NGN) is also
   resulting in new access technologies.  Values for access technologies
   are defined explicitly in RFC3455 [3] and no IANA procedures are
   defined to maintain a separate registry.

   Input is sought on whether the appropriate extension mechanism for
   the P-Access-Network-Info header is to create an IANA registry.  In
   the meanwhile, the proposed modification to the syntax is given
   below.

   It is therefore proposed that section 5.4 of RFC3455 [3] is enhanced
   as follows:



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      The syntax of the P-Access-Network-Info header is described as
      follows:

      P-Access-Network-Info = "P-Access-Network-Info" HCOLON access-net-
         spec

      access-net-spec = access-type *(SEMI access-info)

      access-type = "IEEE-802.11a" / "IEEE-802.11b" / "IEEE-802.11e" /
         "IEEE-802.11g" / "3GPP-GERAN" / "3GPP-UTRAN-FDD" / "3GPP-UTRAN-
         TDD" / "3GPP-CDMA2000" / token

      access-info = cgi-3gpp / utran-cell-id-3gpp / extension-access-
         info

      extension-access-info = gen-value

      cgi-3gpp = "cgi-3gpp" EQUAL (token / quoted-string)

      utran-cell-id-3gpp = "utran-cell-id-3gpp" EQUAL (token / quoted-
         string)

      The access-info may contain additional information relating to the
      access network.  The values for "cgi-3gpp" and "utran-cell-id-
      3gpp" are defined in 3GPP TS 24.229 [15].

   There are ongoing discussions within 3GPP that may result in
   additional values being added to this section, e.g.  XDSL and WiMax,
   and there may also be associated parameters to add.

   It appears additional values have also been defined by 3GPP2, and
   there is ongoing discussions within 3GPP2 that may result in further
   additional values being added to this section, and there may also be
   associated parameters to add.

4.6.  Definition of additional parameters to the P-Charging-Vector
      header

   Section 5.6 of RFC3455 [3] defines the syntax of the P-Charging-
   Vector header.

   Additional parameters were considered too application specific for
   specification in RFC3455 [3], but it was acknowledged that they would
   exist, and indeed additional specification of such parameters,
   relating to specific access technologies, has occurred in 3GPP.

   This update therefore defines that applications using the P-Charging-
   Vector header within their own applicability are allowed to define



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   generic-param extensions without further reference to the IETF
   specification process.

















































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5.  Security considerations

   This document makes a number of small changes to some headers defined
   in RFC3455 [3].  It is not considered that these changes impact the
   initial security analysis performed in RFC3455 [3].














































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6.  IANA considerations

   This document requires no action by IANA.

7.  References

   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", March 1997.

   [2]  Rosenberg, J., "SIP: Session Initiation Protocol", June 2002.

   [3]  Garcia-Martin, M., "Private Header (P-Header) Extensions  to the
        Session Initiation Protocol (SIP) for the 3rd-Generation
        Partnership Project (3GPP)", January 2003.

   [4]  Barnes, M., "An Extension to the Session Initiation Protocol for
        Request History  Information", January 2005.


































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Author's Address

   Keith Drage
   Lucent Technologies
   Optimus, Windmill Hill Business Park
   Swindon, Wilts
   UK

   Email: drage@lucent.com










































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