A P-Served-User Header Field Parameter for Originating CDIV session case in Session Initiation Protocol (SIP)
draft-ietf-sipcore-originating-cdiv-parameter-01

SIPCORE Working Group                                          M. Mohali
Internet-Draft                                                    Orange
Updates: 5502 (if approved)                           September 27, 2017
Intended status: Informational
Expires: March 31, 2018


A P-Served-User Header Field Parameter for Originating CDIV session case
                  in Session Initiation Protocol (SIP)
            draft-ietf-sipcore-originating-cdiv-parameter-01

Abstract

   This specification defines a new parameter of the P-Served-User
   header field in the Session Initiation Protocol (SIP).  This new
   "orig-cdiv" parameter defines the session case used by a proxy when
   handling an originating session after Call Diversion (CDIV) services
   has been invoked for the served user.  The P-Served-User header field
   is defined in RFC5502 to convey the identity of the served user and
   the session case that applies to this particular communication
   session and application invocation.  This document updates RFC5502 to
   add the "originating after CDIV" session case and to provide more
   guidance for using the P-Served-User header field in IP networks that
   were missing in RFC5502.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on March 31, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  General . . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.2.  Basic Use Case  . . . . . . . . . . . . . . . . . . . . .   3
     1.3.  Problem Statement . . . . . . . . . . . . . . . . . . . .   4
   2.  Proxy behavior and parameter handling . . . . . . . . . . . .   4
   3.  Applicability . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  General . . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.2.  ABNF  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   6.  Call Flow Examples  . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  Call diversion case . . . . . . . . . . . . . . . . . . .   8
     6.2.  Call diversion and privacy  . . . . . . . . . . . . . . .   9
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  12
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

1.1.  General

   The P-Served-User header field was defined in [RFC5502] to address an
   issue that was found in the 3rd Generation Partnership Project (3GPP)
   IMS (IP Multimedia Subsystem) between an S-CSCF (Serving Call Session
   Control Function) and an AS (Application Server) on the ISC (IMS
   Service Control) interface.  For more information on the IMS, a
   detailed description can be found in [TS.3GPP.24.229].

   The P-Served-User header field conveys the identity of the served
   user, his/her registration state and the session case that applies to
   this particular communication session and application invocation.





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   [RFC5502] defines the originating and terminating session cases for a
   registered or unregistered user.  This document extends the P-Served-
   User header field to include the session case for a forwarded leg
   when a call diversion service (CDIV) has been invoked and if an
   originating service of the diverting user has to be triggered.

   The sessioncase-param parameter of the P-Served-User header field is
   extended with the "orig-cdiv" parameter for this "originating after
   CDIV" session case.

   The following section defines usage of the "orig-cdiv" parameter of
   P-Served-User header field, Section 2 specifies the proxy behavior
   for handling the new header field parameter, and Section 3 discusses
   the applicability and scope of this new header field parameter.
   Section 4 describes the syntax and correct the syntax of [RFC5502],
   Section 5 registers the P-Served-User header field parameters with
   IANA, and Section 6 discusses the security properties of the
   environment where this new header field parameter is intended to be
   used.

1.2.  Basic Use Case

   In the 3GPP IMS (IP Multimedia Subsystem), the S-CSCF (Serving CSCF)
   is a SIP proxy that serves as a registrar and handles originating and
   terminating session states for users allocated to it.  This means
   that any call that is originated by a specific user or any call that
   is terminated to that specific user will pass through the S-CSCF that
   is allocated to that user.

   At the moment that an S-CSCF is allocated for a specific user, the
   user profile is downloaded from the HSS (Home Subscriber Server) to
   this S-CSCF, see [TS.3GPP.29.228].  The user profile contains the
   list of actions to be taken by the S-CSCF for the served user
   depending on the session direction (originating or terminating) and
   the user state (registered or not) in the IMS network.  With this
   user profile, the S-CSCF determines the current case and apply the
   corresponding actions such as forward the request to an AS.  At its
   turn, the AS has to go through a similar process of determining who
   is the current served user, what is his/her "registration state" and
   on which "session case" is the session.  [RFC5502] defines all those
   parameters and in particular the originating and terminating session
   cases.

   In basic call scenarios, the is no particular issue for the S-CSCF
   and AS to know which scenario needs to be realized but in case of
   call diversion services for which the session is re-targeted, the
   session cases defined in [RFC5502] poses some limitations as
   described in the following section.



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1.3.  Problem Statement

   In case of a call diversion service, the received request is first
   considered as a terminating session case and the terminating filter
   criteria configured in the S-CSCF are performed.  Receiving the call
   initiation request, the Application Server is able to determine the
   served user and the session case (here "term") from the received P-
   Served-User header field content and to execute terminating services.
   When the call diversion service is executed (as a terminating
   service), the Application Server changes the target (Request-URI) of
   the session and a new call leg is created.  This new call leg could
   be considered as an originating call leg from the diverting user but
   this is not the case.  Indeed, the originating user remains the same
   and some of the diverting user's originating services should not be
   triggered as if it was an originating call.  For instance, the
   originating user identity should not be restricted because the
   diverting user has a privacy service for his/her own identity.  The
   privacy of the diverting user should apply to information related to
   this user (eg. in the Histroy-Info header field).  In the same
   manner, some specific services will need to be specifically triggered
   on the outgoing leg after a call diversion.  Without a dedicated
   session case for originating after CDIV, there is no possiblity for a
   proxy to trigger an originating service for the diverting user or for
   an Application Server to execute the procedures for this particular
   session case.

   For this use case, this document creates a new parameter for the
   originating after CDIV session case to be embedded in the P-Served-
   User header field.

2.  Proxy behavior and parameter handling

   The "orig-cdiv" header field parameter can be used inside a trust
   domain of the P-Served-User header field by proxies that are
   processing call diversion services.  The following section
   illustrates how this header field parameter can be used in a 3GPP
   network.

   For a terminating call, when receiving the initial INVITE request,
   the S-CSCF will determine that the session case is for a terminating
   user as described in [RFC5502], then it determines the served user by
   looking at the Request-URI and saves this Request-URI.  After that,
   the S-CSCF starts the analysis of filter criteria and triggers the
   served user Application Server for the terminating services to be
   executed including in the INVITE request the P-Served-User header
   field with the "sescase" parameter set to "term" and the regstate to
   the corresponding value.




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   Based on some criteria, the Application Server concludes that the
   request has to be diverted to another target user or application.
   The received Request-URI is then replaced with the new diverted-to
   address.  The Application Server stores the successive Request-URI(s)
   values by adding one or two History-Info header field entry(ies)
   [RFC7044] in the outgoing INVITE.  In the History-Info header field,
   the served user address is tagged thanks to the mp-param header field
   parameter added in entry associated to the diverted-to address
   created.

   In the next step, the Application Server forwards the INVITE request
   back to the S-CSCF.  When receiving back the INVITE request, the
   S-CSCF can see that the topmost Route header field contains its own
   hostname but the Request-URI does not match the saved Request-URI.
   In this case, the S-CSCF updates the P-Served-User header field
   content by replacing the "sescase" parameter by the "orig-cdiv"
   parameter.  The PServedUser-value remains unchanged.

   Then the procedure continues by forwarding the INVITE request over to
   an AS that hosts the originating services of the served user
   (diverting user) that specifically need to be executed on the
   forwarded leg after a call diversion service.

   When the Application Server receives the INVITE request, it
   determines that the session case is for "orig-cdiv" session case and
   will perform the originating services to be executed after
   retargeting for the diverting user (i.e. served user).

   This document also provides the following guidance that reminds or
   clarifies the P-Served-User handling that are missing in [RFC5502]:

   o  This header is forbidden to be repeated within a request for a
      particular session at a particular time for the reason that
      session cases are mutually exclusive.  This document updates
      [RFC5502] to clearly state that P-Served-User header field MUST
      not contain different values either comma-separated or header-
      separated.  This documents also updates the syntax of the header
      as defined in [RFC5502] to reflect this uniqueness of parameters
      values.

   o  Whether the "regstate" parameter is removed or not by the S-CSCF
      when processing the orginating after CDIV session case is out of
      the scope of this document.  In one hand, it can either be
      considered that the S-CSCF is able to store the previous regstate
      value and that the same value applies or that the "regstate" is
      not relevant after a diverting service.  On the other hand, the
      regstate can be combined to the orig-cdiv session case to provide




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      different services if the served user is registered or
      unregistered.  These choices are implementation dependent.

3.  Applicability

   The use of the P-Served-User header field extensions is only
   applicable inside a Trust Domain for P-Served-User.  Nodes in such a
   Trust Domain explicitly trust each other to convey the served user
   and to be responsible for withholding that information outside of the
   Trust Domain.  The means by which the network determines the served
   user and the policies that are executed for a specific served user is
   outside the scope of this document.

4.  Syntax

4.1.  General

   [RFC5502] defines the P-Served-User header field with the
   sessioncase-param parameter "sescase" which is specified as having
   "orig" and "term" predefined values.  This document defines an
   additional parameter for the sessioncase-param: "orig-cdiv".

   Because this document extends the existing sessioncase-param
   parameter in a special way and that it has been identified errors in
   the syntax of the P-Served-User header field as defined in [RFC5502],
   this document corrects and extends the header at the same time.

   The extension of the sessioncase-param parameter to add the "orig-
   cdiv" session case is done in a way to fit the parameter format
   introduced in release 11 of the 3GPP [TS.3GPP.24.229] and keep a
   backward compatibility.

   "EQUAL", "HCOLON", "SEMI", "name-addr", "addr-spec", and "generic-
   param" are defined in [RFC3261].

4.2.  ABNF

   The augmented Backus-Naur Form (ABNF) [RFC5234] syntax of the P-
   Served-User header field is described in [RFC5502].

   This document updates [RFC5502] to correct the P-Served-User header
   field ABNF syntax and extend it as following:









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 P-Served-User            = "P-Served-User" HCOLON PServedUser-value
                            *(SEMI served-user-param)
 served-user-param        = sessioncase-param
                            / registration-state-param
                            / generic-param
 PServedUser-value        = name-addr / addr-spec
 sessioncase-param        = 1("sescase" EQUAL 1("orig" / "term")/ orig-cdiv)
 registration-state-param = "regstate" EQUAL 1("unreg" / "reg")
 orig-cdiv                = "orig-cdiv"


   Examples of possible P-Served-User header field:

   P-Served-User: <sip:user@example.com>; orig-cdiv; regstate=reg
   or
   P-Served-User: <sip:user@example.com>; orig-cdiv
   or
   P-Served-User: <sip:user@example.com>; sescase=term; regstate=unreg


5.  IANA Considerations

   The syntax of the P-Served-User header field is defined in [RFC5502]
   and updated in Section 4 of this document.

   This document requests IANA to update the existing row for the P-
   Served-User header field in the "Header Fields" sub-registry:

   Header Name        Compact Form        Reference
  -------------       ------------     ----------------
  P-Served-User         none          [RFC5502][RFCXXXX]

Note to RFC Editor: Please replace XXXX with the RFC number of this document.


   This document requests IANA to add new rows for the P-Served-User
   header field parameters in the "Header Field Parameters and Parameter
   Values" sub-registry as per the registry created by [RFC3968]:

 Header Field   Parameter Name     Predefined Values       Reference
--------------  ----------------   -----------------   -----------------
P-Served-User     sescase               Yes            [RFC5502][RFCXXXX]
P-Served-User     regstate              Yes            [RFC5502][RFCXXXX]
P-Served-User     orig-cdiv             No             [RFCXXXX]

Note to RFC Editor: Please replace XXXX with the RFC number of this     document.





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6.  Call Flow Examples

6.1.  Call diversion case

   The following call flow shows a session establishement for Alice
   calls Bob which has a call diversion when busy towards Carol.

                  proxy           server            UA
Alice    Bob's...S-CSCF-B..........AS-B.............Bob             Carol
  |                |                |                |                |
  |   INVITE F1    |                |                |                |
  |--------------->|   INVITE F2    |                |                |
  |                |--------------->|                |                |
  |                |   INVITE F3    |                |                |
  |                |<---------------|  INVITE F4     |                |
  |                |-------------------------------->|                |
  |                |                486   F5         |                |
  |                |<--------------------------------|                |
  |                |    486   F6    |                |                |
  |                |--------------->|                |                |
  |                |   INVITE F7    |                |                |
  |                |<---------------|                |                |
  |                |   INVITE F8    |                |                |
  |                |--------------->|                |                |
  |                |   INVITE F9    |                |                |
  |                |<---------------|      INVITE F10                 |
  |                |------------------------------------------------->|
  |                |                |                |                |
  |                |                |                |    180   F11   |
  |                |                |    180   F12   |<---------------|
  |                |    180   F13   |<---------------|                |
  |    180   F14   |<---------------|                |                |
  |<---------------|                |                |                |
  |                |                |                |                |

   F1 INVITE Alice -> S-CSCF-B
   INVITE sip:bob@example.com SIP/2.0
        From: Alice <sip:alice@domaina.com>;tag=1928301774
        To: Bob <sip:bob@example.com>

   F2 INVITE S-CSCF-B -> AS-B
   INVITE sip:bob@example.com SIP/2.0
        From: Alice <sip:alice@domaina.com>;tag=1928301774
        To: Bob <sip:bob@example.com>
        P-Served-User: <sip:bob@example.com>; term; regstate=reg

   F3 INVITE AS-B -> S-CSCF-B
   INVITE sip:bob@example.com SIP/2.0



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        From: Alice <sip:alice@domaina.com>;tag=1928301774
        To: Bob <sip:bob@example.com>
        P-Served-User: <sip:bob@example.com>; term; regstate=reg

   F4 INVITE S-CSCF-B -> Bob
   INVITE sip:bob@192.0.2.4 SIP/2.0
        From: Alice <sip:alice@domaina.com>;tag=1928301774
        To: Bob <sip:bob@example.com>
        P-Served-User: <sip:bob@example.com>; term; regstate=reg

   F5-F6 486 BUSY Bob -> S-CSCF-B  -> AS-B
   486 BUSY
    From: Alice <sip:alice@domaina.com>;tag=1928301774
        To: Bob <sip:bob@example.com>;tag=es43sd

   F7 INVITE AS-B -> S-CSCF-B
   INVITE sip:Carol@domainc.com SIP/2.0
        From: Alice <sip:alice@domaina.com>;tag=1928301774
        To: Bob <sip:bob@example.com>
        P-Served-User: <sip:bob@example.com>; term; regstate=reg

   F8 INVITE S-CSCF-B -> AS-B
   INVITE sip:Carol@domainc.com SIP/2.0
        From: Alice <sip:alice@domaina.com>;tag=1928301774
        To: Bob <sip:bob@example.com>
        P-Served-User: <sip:bob@example.com>; orig-cdiv; regstate=reg

   F9 INVITE AS-B -> S-CSCF-B
   INVITE sip:carol@domainc.com SIP/2.0
        From: Alice <sip:alice@domaina.com>;tag=1928301774
        To: Bob <sip:bob@example.com>
        P-Served-User: <sip:bob@example.com>; orig-cdiv; regstate=reg

   F10 INVITE S-CSCF-B -> Carol
   INVITE sip:carol@192.0.2.7 SIP/2.0
        From: Alice <sip:alice@domaina.com>;tag=1928301774
        To: Bob <sip:bob@example.com>

             Figure 1: P-Served-User during call diversion service


6.2.  Call diversion and privacy

   The following call flow shows a call diversion use case for which
   Alice has no identity restriction service and Bob has an
   unconditional call diversion service towards Carol and an identity
   presentation restriction service.




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                  proxy           server            UA
Alice    Bob's...S-CSCF-B..........AS-B.............Bob             Carol
  |                |                |                |                |
  |   INVITE F1    |                |                |                |
  |--------------->|   INVITE F2    |                |                |
  |                |--------------->|                |                |
  |                |   INVITE F3    |                |                |
  |                |<---------------|                |                |
  |                |   INVITE F4    |                |                |
  |                |--------------->|                |                |
  |                |   INVITE F5    |                |                |
  |                |<---------------|      INVITE F6 |                |
  |                |------------------------------------------------->|
  |                |                |                |                |
  |                |                |                |    180   F7    |
  |                |                |    180   F8    |<---------------|
  |                |    180   F9    |<---------------|                |
  |    180   F10   |<---------------|                |                |
  |<---------------|                |                |                |
  |                |                |                |                |

   F1 INVITE Alice -> S-CSCF-B
   INVITE sip:bob@example.com SIP/2.0
        From: Alice <sip:alice@domaina.com>;tag=1928301774
        To: Bob <sip:bob@example.com>
        Supported: histinfo

   F2 INVITE S-CSCF-B -> AS-B
   INVITE sip:bob@example.com SIP/2.0
        From: Alice <sip:alice@domaina.com>;tag=1928301774
        To: Bob <sip:bob@example.com>
        P-Served-User: <sip:bob@example.com>; term; regstate=reg

   F3 INVITE AS-B -> S-CSCF-B
   INVITE sip:carol@domainc.com SIP/2.0
        From: Alice <sip:alice@domaina.com>;tag=1928301774
        To: Carol <sip:carol@domainc.com>
        P-Served-User: <sip:bob@example.com>; term; regstate=reg
        History-Info:
                <sip:bob@example.com>;index=1,
                <sip:carol@domainc.com;cause=302>;index=1.1;mp=1

   F4 INVITE S-CSCF-B -> AS-B
   INVITE sip:carol@domainc.com SIP/2.0
        From: Alice <sip:alice@domaina.com>;tag=1928301774
        To: Carol <sip:carol@domainc.com>
        P-Served-User: <sip:bob@example.com>; orig-cdiv; regstate=reg
        History-Info:



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                <sip:bob@example.com>;index=1,
                <sip:carol@domainc.com;cause=302>;index=1.1;mp=1

   F5 INVITE AS-B -> S-CSCF-B
   INVITE sip:carol@domainc.com SIP/2.0
        From: Alice <sip:alice@domaina.com>;tag=1928301774
        To: Carol <sip:carol@domainc.com>
        P-Served-User: <sip:bob@example.com>; orig-cdiv; regstate=reg
        History-Info:
                <sip:bob@example.com?privacy=history>;index=1,
                <sip:carol@domainc.com;cause=302>;index=1.1;mp=1

   F6 INVITE S-CSCF-B -> Carol
   INVITE sip:carol@192.0.2.7 SIP/2.0
        From: Alice <sip:alice@domaina.com>;tag=1928301774
        To: Carol <sip:carol@domainc.com>
        History-Info:
                <sip:bob@example.com?privacy=history>;index=1,
                <sip:carol@domainc.com;cause=302>;index=1.1;mp=1
                <sip:carol@192.0.2.7>;index=1.1.1;rc=1.1

            Figure 2: P-Served-User when privacy requested


7.  Security Considerations

   The security considerations in [RFC5502] apply.

   As the "orig-cdiv" parameter of P-Served-User header field can be
   used to trigger applications, it is important to ensure that the
   parameter has not been added to the SIP message by an unauthorized
   SIP entity.

8.  Acknowledgments

   The author wishes to thank the 3GPP community for providing guidance,
   input, and comments on the document.  Thanks also to Dale Worley for
   his careful review of the document.  A special thanks to Christer
   Holmberg.

9.  References

9.1.  Normative References








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   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,
              <https://www.rfc-editor.org/info/rfc3261>.

   [RFC3968]  Camarillo, G., "The Internet Assigned Number Authority
              (IANA) Header Field Parameter Registry for the Session
              Initiation Protocol (SIP)", BCP 98, RFC 3968,
              DOI 10.17487/RFC3968, December 2004,
              <https://www.rfc-editor.org/info/rfc3968>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <https://www.rfc-editor.org/info/rfc5234>.

   [RFC7044]  Barnes, M., Audet, F., Schubert, S., van Elburg, J., and
              C. Holmberg, "An Extension to the Session Initiation
              Protocol (SIP) for Request History Information", RFC 7044,
              DOI 10.17487/RFC7044, February 2014,
              <https://www.rfc-editor.org/info/rfc7044>.

9.2.  Informative References

   [RFC5502]  van Elburg, J., "The SIP P-Served-User Private-Header
              (P-Header) for the 3GPP IP Multimedia (IM) Core Network
              (CN) Subsystem", RFC 5502, DOI 10.17487/RFC5502, April
              2009, <https://www.rfc-editor.org/info/rfc5502>.

   [TS.3GPP.24.229]
              3GPP, "IP multimedia call control protocol based on
              Session Initiation Protocol (SIP) and Session Description
              Protocol (SDP);Stage 3", 3GPP TS 24.229 v11.

   [TS.3GPP.29.228]
              3GPP, "IP Multimedia (IM) Subsystem Cx and Dx interfaces;
              Signalling flows and message contents", 3GPP TS 29.228
              v11.

Author's Address










Mohali                   Expires March 31, 2018                [Page 12]


Internet-Draft      P-Served-User parameter orig-cdiv     September 2017


   Marianne Mohali
   Orange
   Orange Gardens, 44 avenue de la Republique
   Chatillon  92326
   France

   Email: marianne.mohali@orange.com












































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