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Dispatch                                                       R. Jesske
Internet-Draft                                          Deutsche Telekom
Updates: RFC6442 (if approved)                         February 10, 2017
Intended status: Standards Track
Expires: August 14, 2017


           Location Parameter for the SIP Reason Header Field
              draft-jesske-dispatch-reason-loc-q850-00.txt

Abstract

   The SIP Reason header field is defined for Q.850 cause values.  Some
   services in SIP networks may need to know the location where the call
   was released in the PSTN network to correctly interpret the reason of
   release.

Status of This Memo

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

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   This Internet-Draft will expire on August 14, 2017.

Copyright Notice

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Rationale . . . . . . . . . . . . . . . . . . . . . . . . . .   2
   4.  Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   6.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .   4
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
     8.1.  Registration of resp-location Parameter for reason header
           field . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   5
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   5
     10.2.  Informative References . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   The SIP Reason header field specification [RFC3326] describes a SIP
   header field that is used to indicate that a SIP request or response
   is carrying the reason of release.  The location information
   identifies the part of the ISUP network where the call was released.

   This document adds a location value parameter to the reason-extension
   parameter in [RFC3326] so that the location value can be interworked
   from the PSTN.  The interworking from PTSN needs only to include the
   location received by the interworking gateway.

2.  Terminology

   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 [RFC2119].

3.  Rationale

   The primary intent of the parameter defined in this specification is
   for use in IMS networks defined by 3GPP but also open to be used by
   any other network.  The purpose of this parameter is to transport the
   location of call release from the originating PSTN entity to the SIP
   entity receiving the response or BYE message containing the location
   of the call release.  The ISDN location is defined in [Q.850].







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4.  Mechanism

   As defined by [RFC3326] a Reason header field MAY appear in any
   request in a dialog, in any CANCEL request and in any response whose
   status code explicitly allows the presence of this header field.  The
   syntax of the header field follows the standard SIP parameter syntax.

   The mechanism employed adds a parameter with the location value
   defined in [Q.850] to the Reason header field that identifies the
   location of the call release in ISUP as defined in [Q.850] . The
   Augmented BNF (ABNF) [RFC5234] for this parameter is shown in
   Figure 1.


                  reason-extension  =/ resp-location
                  resp-location    =  "location" EQUAL string


                The values to be used as location are:
                U               for user
                LPN             for private network serving the local user
                LN              for public network serving the local user
                TN              for transit network
                RLN             for public network serving the remote user
                RPN             for private network serving the remote user
                INTL    for international network
                BI              for network beyond interworking point


                          Figure 1: resp-location

   Depending on the direction the UAC or UAS shall include the resp-
   location when setting up the Reason header field with a Q.850 cause.
   This approach is only valid in cases when the ISUP Q.850 location is
   available.

5.  Example

   The following example shows a SIP 404 response message containing a
   Reason header field with a Q.850 cause value and a resp-location
   value.  The 404 Response will be set up when a gateway receives an
   ISUP Release with a Q.850 cause set to 1 meaning "Unallocated
   (unassigned) number", i.e. the number is not known in the PSTN.








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     404 Not Found

      SIP/2.0 404 Not Found

      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Reason: Q.850;cause=1;text="Unallocated (unassigned) number"; location=LN
      Content-Length: 0


            Figure 2: Example Location in Reason header field.

6.  Privacy Considerations

   This document doesn't change any of the privacy considerations
   described in [RFC3326].  While the addition of the resp-location
   parameter does provide an indicator of the entity that added the
   location in the signaling path this provides little more exposure
   than the Q.850 cause itself.

7.  Security Considerations

   This document doesn't change any of the security considerations
   described in [RFC3326].  The addition of the resp-location parameter
   does provide an indicator of the location where the call was release
   within the PSTN.  This information my be used for specific location
   driven services but does not create any additional security
   constrains.  But since the location is very imprecise the location
   value itself will not add any major security constrain.  The use of
   this parameter is not restricted to a specific architecture.

8.  IANA Considerations

8.1.  Registration of resp-location Parameter for reason header field

   This document calls for IANA to register a new SIP header parameter
   as per the guidelines in [RFC3261], which will be added to header
   sub-registry under http://www.iana.org/assignments/sip-parameters.

   Header Field:  Reason

   Parameter Name:  resp-location







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9.  Acknowledgments

   Thanks to Michael Kreipel for his comments and review.

10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [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,
              <http://www.rfc-editor.org/info/rfc3261>.

   [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>.

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

10.2.  Informative References

   [Q.850]    INTERNATIONAL TELECOMMUNICATION UNION, "Usage of cause and
              location in the Digital Subscriber Signalling System No. 1
              and the Signalling System No. 7 ISDN User Part", Q 850,
              May 1998.

Author's Address

   Roland Jesske
   Deutsche Telekom
   Heinrich-Hertz Str, 3-7
   Darmstadt  64295
   Germany

   Email: r.jesske@telekom.de
   URI:   www.telekom.de





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