Session Initiation Protocol (SIP) Cause URI parameter for Service Number translation
draft-mohali-dispatch-cause-for-service-number-06

Network Working Group                                          M. Mohali
Internet-Draft                                                    Orange
Updates: RFC4458 (if approved)                                 M. Barnes
Intended status: Informational               MLB@Realtime Communications
Expires: September 22, 2016                               March 21, 2016

Session Initiation Protocol (SIP) Cause URI parameter for Service Number
                              translation
           draft-mohali-dispatch-cause-for-service-number-06

Abstract

   [RFC4458] defines a "cause" URI parameter as having predefined values
   for Redirecting reasons as a mapping from ITU-T Q.732.2-5 Redirecting
   Reasons.  The "cause" URI parameter is to be used in SIP or SIPs URI.
   In particular, it may appear in the Request-URI of a SIP request.
   This specification creates a new predefined value for the "cause" URI
   parameter for cases when the retargeting is due to specific service
   action leading to a called service access number translation.
   This document updates [RFC4458].

Status of This Memo

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   This Internet-Draft will expire on September 22, 2016.

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   carefully, as they describe your rights and restrictions with respect
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Table of Contents

   1.  Introduction, Terminology and Overview  . . . . . . . . . . .   2
   2.  Solution  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Interaction with Request History Information  . . . . . .   4
     2.2.  Handling and Processing the Service Number Translation
           "cause" URI parameter value . . . . . . . . . . . . . . .   5
   3.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction, Terminology and Overview

   A mechanism has been defined in [RFC4458] to add a "cause" URI
   parameter in the target URI to be able to identify retargeting due to
   the call forwarding supplementary services from other retargetings.
   This "cause" URI parameter has defined values equivalent to the TDM
   (Time Division Multiplexing) Redirecting reasons.

   In the Public Switched Telephone Network (PSTN)/ Integrated Services
   Digital Network (ISDN), there is another kind of retargeting
   introduced by the Intelligent Network (IN) services in
   [ITU-T_I.312_Q.1201].  IN aims to ease the introduction of new
   services (i.e.  Universal Personal Telecommunication (UPT), Virtual
   Private Network (VPN), Freephone, etc.) based on greater flexibility
   and new capabilities.  For these IN services, it was introduced in
   ISUP the "called IN number" and the "original called IN number"
   parameters that enable to keep the information of the service access
   number requested prior its translation.

   The term "service access number" is used in this specification to
   refer to the dialable number by which a specific service is reached.
   This special number is not a globally routable number and therefore
   needs to be translated into a routable SIP or tel URI to process the
   session establishment.

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   This specification proposes a solution to allow the identification of
   well-known services such as premium or toll free services that are
   doing service access number translation.

   A mechanism is required to identify URIs that are issued from a
   retargeting or number translation by a specific service similar to
   PSTN/ISDN IN services.

   The mechanism covers the IN services that can be identified in the
   ISUP signaling in the "called IN number" and "original called IN
   number" optional parameters defined in [ITU-T_Q.763] and used in
   ISUP/INAP interworking as described in [ITU-T_Q.1600].

2.  Solution

   A new value for the "cause" URI parameter of the 'sip:' or 'sips:'
   URI schemes is defined.  This value may be used in a 'sip:' or
   'sips:' URI inserted in the Request-URI and in the History-Info
   header field [RFC7044] when the "mp" or "rc" tag is present and the
   URI is issued from a retargeting or an service access number
   translation by a specific service similar to PSTN/ISDN IN services
   that is not a call forwarding service.
   As defined in [RFC4458], the cause URI parameter must be encoded in
   the new target URI when generated by the service.

   The ABNF grammar [RFC5234] for the cause-param and target-param
   parameters is summarized below as it has been subject to Errata [ID:
   1409] in [RFC4458].  The Status-Code is defined in [RFC3261].

   target-param = "target=" pvalue

   cause-param = "cause=" Status-Code

   The following value for this URI parameter is added to the existing
   ones:

                   +---------------------------------+-------+
                   | Service Type                    | Value |
                   +---------------------------------+-------+
                   | Service number translation      | 380   |
                   +---------------------------------+-------+

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2.1.  Interaction with Request History Information

   The History-Info header field defined in [RFC7044] specifies a means
   of providing the UAS and UAC with information about the retargeting
   of a request.  This information includes the initial Request-URI and
   any retargeted URIs.  This information is placed in History-Info
   headers as the request is retargeted and, upon reaching the UAS, is
   returned in certain responses.  The History-Info header field enables
   many enhanced services by providing the information as to how and why
   a SIP request arrives at a specific application or user and to keep
   this information throughout the signaling path even when successive
   applications are involved.

   When a proxy inserts a URI containing the "cause" URI parameter
   defined in [RFC4458] into the Request-URI of a forwarded request, per
   [RFC7044], the proxy must also copy this new Request-URI within a
   History-Info header field entry into the forwarded request, and so
   the URI in that entry includes the "cause" URI parameter.  Therefore,
   even if the Request-URI is replaced as a result of rerouting by a
   downstream proxy, the History-Info header field will still contain
   these parameters, which can be of use to the UAS.  Note that if a
   proxy does not support generation of the History-Info header field or
   if a downstream proxy removes the History-Info header fields, an
   application will only have access to the "cause" URI parameter if the
   request is not subsequently retargeted (i.e., it will be contained
   only in the Request-URI in the incoming request).  The implications
   of this are further discussed in section Section 2.2.

   In order to be able to filter specific entries among the history
   information, tags have been defined in [RFC7044].  In particular, the
   "mp" and "rc" tags having the following definitions: The "mp" tag is
   added when the new target was determined based on a mapping to a user
   other than the target user associated with the Request-URI being
   retargeted.  This allows identifying retargets that are the result of
   a decision made by a particular type of application or that an
   initial request has been retargeted as a result of an application
   decision in a general manner.  The "rc" tag is added when the new
   target represents a change in Request-URI, while the target user
   remains the same.  These tags can be used in conjunction with the new
   "cause" URI parameter for certain applications, an example of which
   is provided in section Section 3.

   When using the History-Info header field in conjunction with the
   "cause" URI parameter in a Request-URI, it is important to consider
   that the "cause" URI parameter is not the same parameter as the
   "cause" header field parameter included in the Reason header
   [RFC3326].  The "cause" header field parameter of the Reason header

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   should be added to a History-Info entry only when the retargeting is
   due to a received SIP response.

2.2.  Handling and Processing the Service Number Translation "cause" URI
      parameter value

   At the application:

      When an application receiving a request that is addressed to a
      service access number changes the Request-URI into a routable
      number it should insert within this new Request-URI a "cause" URI
      parameter value set to 380.  Following the process described in
      [RFC7044], the application must add a new History-Info header
      field entry including the new Request-URI value including the
      "cause" URI parameter.  It is also possible for an application to
      add a "target" URI parameter as defined in [RFC4458] with the
      initial value of the Request-URI received by the application.

   Note that if the new Request-URI is further replaced by a downstream
   proxy for any reason and if the History-Info header field is not
   supported, the information of the service access number initially
   requested would be lost.  Thus, it is strongly recommended to support
   the History-Info header field all along the signaling path.

   At the UAS:

      When the UAS receiving the request wants to retrieve the service
      access number by which it has been reached, first it should look
      for the "cause" URI parameter value 380 in the History-Info header
      field.  This History-Info entry should also contain an "mp" or
      "rc" tag and then the UAS can find the requested service number in
      the History-Info entry having an index parameter value that match
      this "mp" or "rc" tag value.  If for any reason, there is no "mp"
      or "rc" tag in the identified History-Info entry, the UAS can find
      the requested service number in the preceding History-Info entry.

   If the History-Info header is not supported or has been removed by a
   proxy for any reason, the UAS might be able to find the requested
   service access number before translation in either of the following
   ways, but there is no guarantee:

   o  If the UAS is the direct target of the request coming from the
      application, the UAS ought to be able to find the service access
      number in the "target" URI parameter of the Request-URI if there
      is also a "cause" URI parameter set to 380 in this Request-URI.

   o  If there is no "cause" URI parameter set to 380 in the Request-URI
      and there is no Histroy-Info header field, the UAS might find the

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      service access number before translation in the To header only if
      the To header has not been changed when the request was
      retargeted.

3.  Example

   In this section an example is provided to illustrate the application
   of the new cause-param value.

   In this example, Alice calls her bank customer care.  John is the
   person at the call center that answers the call.  John is in a call
   center that manages several toll-free services and he needs to know
   for which service Alice is calling to provide the appropriate welcome
   speech.

  Alice      Toll-Free Service   Atlanta.com          John
    |                |              |                   |
    |    INVITE F1   |              |                   |
    |----------- --->|   INVITE F2  |                   |
    |                |------------->|                   |
    |                |              |  INVITE F3        |
    |                |              |------------------>|

                    * Rest of flow not shown *

          Figure 1: Service Access Number Translation Example

Message Details

   F1 INVITE 192.0.2.1 -> Toll-Free Service

      In the initial request, the Request-URI contains the Toll-Free
      number dialed by Alice.

      INVITE sip:+18005551002@example.com;user=phone  SIP/2.0
      Via: SIP/2.0/TCP 192.0.2.1:5060;branch=z9hG4bK74bf
      From: Alice <sip:+15551001@example.com;user=phone>;tag=9fxced76sl
      To: <sip:+18005551002@example.com;user=phone>
      Call-ID: c3x842276298220188511
      CSeq: 1 INVITE
      Max-Forwards: 70
      Contact: <sip:alice@192.0.2.1>
      Content-Type: application/sdp
      Content-Length: <appropriate value>

      [SDP Not Shown]

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   F2 INVITE Toll-Free Service -> Atlanta.com

      The Toll-Free application receives the request and translates
      the service number into a routable number toward the call center.
      The Request-URI is changed and, in the new Request-URI, the
      "cause" URI parameter set to 380 is added. As there was no
      History-Info header field in the received request,
      the application creates a History-Info header with two entries:
      one for the received Request-URI and one for the new Request-URI.

      INVITE sip:+15555551002@atlanta.com;cause=380;user=phone SIP/2.0
      Via: SIP/2.0/TCP 192.0.2.4:5060;branch=z9hG4bK-ik8
      Via: SIP/2.0/TCP 192.0.2.1:5060;branch=z9hG4bK74bf
      From: Alice <sip:+15551001@example.com;user=phone>;tag=9fxced76sl
      To: <sip:+18005551002@example.com;user=phone>
      Call-ID: c3x842276298220188511
      CSeq: 1 INVITE
      Max-Forwards: 69
      Supported: histinfo
      History-Info: <sip:+18005551002@example.com;user=phone>;index=1
      History-Info: <sip:+15555551002@atlanta.com;cause=380;user=phone>;
                    index=1.1;mp=1
      Contact: <sip:alice@192.0.2.1>
      Content-Type: application/sdp
      Content-Length: <appropriate value>

      [SDP Not Shown]

   F3 INVITE Atlanta.com -> John

      The call center proxy routes the received request to John's
      IP address by changing the Request-URI. When changing the
      Request-URI, the proxy adds a new entry in the History-Info
      header field.

      INVITE sip:john@198.51.100.2 SIP/2.0
      Via: SIP/2.0/TCP 198.51.100.1:5060;branch=z9hG4bKpxk7g
      Via: SIP/2.0/TCP 192.0.2.4:5060;branch=z9hG4bK-ik8
      Via: SIP/2.0/TCP 192.0.2.1:5060;branch=z9hG4bK74bf
      From: Alice <sip:+15551001@example.com;user=phone>;tag=9fxced76sl
      To: <sip:+18005551002@example.com;user=phone>
      Call-ID: c3x842276298220188511
      CSeq: 1 INVITE
      Max-Forwards: 68
      Supported: histinfo
      History-Info: <sip:+18005551002@example.com;user=phone>;index=1
      History-Info: <sip:+15555551002@atlanta.com;cause=380;user=phone>;

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                    index=1.1;mp=1
      History-Info: <sip:john@198.51.100.2>;index=1.1.1;rc=1.1
      Contact: <sip:alice@192.0.2.1>
      Content-Type: application/sdp
      Content-Length: <appropriate value>

      [SDP Not Shown]

4.  IANA Considerations

   [RFC4458] defines a "cause" parameter specified as having predefined
   values.  This RFC defines a new value for the "cause" parameter: 380.
   This RFC has been added to the references listed for the "cause" the
   "SIP/SIPS URI Parameters" sub-registry in
   <http:/www.iana.org/assignments/sip-parameters> for the "cause"
   parameter.

     Parameter Name         Predefined Values            References
     --------------         -----------------        ------------------
       cause                      Yes                [RFC4458][RFCxxxx]

5.  Security Considerations

   The security considerations in [RFC4458] apply.

   A privacy service that performs the "Privacy: header" Service
   [RFC3323] must remove the cause URI parameter from the URI.  Privacy
   of the parameters, when they form part of a URI within the History-
   Info header field, is covered in [RFC7044].

6.  References

6.1.  Normative References

   [RFC3261]  "SIP: Session Initiation Protocol", RFC 3261, June 2002.

   [RFC3323]  "A Privacy Mechanism for the Session Initiation Protocol
              (SIP)", RFC 3323, November 2002.

   [RFC3326]  Schulzrinne, H., Oran, D., and G. Camarillo, "The Reason
              Header Field for the Session Initiation Protocol (SIP)",
              RFC 3326, DOI 10.17487/RFC3326, December 2002,
              <http://www.rfc-editor.org/info/rfc3326>.

   [RFC7044]  "An Extension to the Session Initiation Protocol (SIP) for
              Request History Information", RFC 7044, February 2014.

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6.2.  Informative References

   [ITU-T_I.312_Q.1201]
              ITU-T Recommendation I312/Q.1201, "Principles of
              Intelligent Network Architecture", October 1992.

   [ITU-T_Q.1600]
              ITU-T Recommendation Q.1600, "Signalling System No. 7 -
              Interaction between ISUP and INAP", September 1997.

   [ITU-T_Q.763]
              ITU-T Recommendation Q.763, "Signalling System No. 7 -
              ISDN User Part formats and codes.", December 1999.

   [RFC4458]  "Session Initiation Protocol (SIP) URIs for Applications
              such as Voicemail and Interactive Voice Response (IVR)",
              RFC 4458, April 2006.

   [RFC5234]  "Augmented BNF for Syntax Specifications: ABNF", RFC 5234,
              January 2008.

Authors' Addresses

   Marianne Mohali
   Orange
   38-40 rue du General Leclerc
   Issy-Les-Moulineaux Cedex 9  92794
   France

   Phone: +33 1 45 29 45 14
   Email: marianne.mohali@orange.com

   Mary Barnes
   MLB@Realtime Communications
   TX
   US

   Email: mary.ietf.barnes@gmail.com

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