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dispatch                                                       R. Jesske
Internet-Draft                                                  L. Liess
Intended status: Standards Track                        Deutsche Telekom
Expires: August 19, 2011                               February 15, 2011


   Reason header filed in Session Initiation Protocol (SIP) responses
          draft-jesske-dispatch-update3326-reason-responses-01

Abstract

   This document updates the Reason mechanism defined within RFC3326.

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 19, 2011.

Copyright Notice

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   document authors.  All rights reserved.

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   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this



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   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
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   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  RFC3326 1. Introduction . . . . . . . . . . . . . . . . . . . . 3
   4.  RFC3326 2. The Reason Header Field  . . . . . . . . . . . . . . 3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 4
   8.  Normative References  . . . . . . . . . . . . . . . . . . . . . 4
































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1.  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].

   This document uses terms from [RFC3261].

2.  Overview

   Although the use of the Reason header field in responses is
   considered in RFC3326[RFC3326], doing so is not specified for any
   existing response code.  Nonetheless, the Reason header field has
   been widely used in responses to carry Q.850 [Q.850]reason codes for
   failure responses to INVITEs that have been gatewayed to PSTN
   systems.  This document specifies and formally permits the use of the
   Reason header field in SIP responses to carry Q.850 [Q.850]reason
   codes for this and other purposes.

3.  RFC3326 1. Introduction

   Original Text:

   Initially, the Reason header field defined here appears to be most
   useful for BYE and CANCEL requests, but it can appear in any request
   within a dialog, in any CANCEL request and in any response whose
   status code explicitly allows the presence of this header field.

   Note that the Reason header field is usually not needed in responses
   because the status code and the reason phrase already provide
   sufficient information.

   New Text:

   Initially, the Reason header field defined here appears to be most
   useful for BYE and CANCEL requests, but it can appear in any request
   within a dialog, in any CANCEL request independent of the protocol
   value used and in any response, if it contains a Q.850 Cause Code,
   except the 100 trying response.

4.  RFC3326 2. The Reason Header Field

   Original Text

   The Reason header field MAY appear in any request within a dialog, in
   any CANCEL request and in any response whose status code explicitly
   allows the presence of this header field.




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   New Text:

   The Reason header field containing a Q.850 Cause Code MAY appear in
   any request within a dialog, in any CANCEL request .  The appearance
   of the Reason header field containing a Q.850 Cause Code is
   applicable to final responses 3xx, 4xx, 5xx and 6xx and 18x and 199
   provisional responses [I-D.ietf-sipcore-199].

   The Reason header field containing any other reason value MAY appear
   in any request within a dialog, in any CANCEL request and in any
   response whose status code explicitly allows the presence of this
   header field.

5.  Security Considerations

   The Update allows the presence of the Reason in Responses.  The
   presence of the Reason header in a response does not affect the
   treatment of the response.

   Including such a header by an untrusted entity could adulterate the
   reactions of the originating entities.  E.G. sending back a cause
   value "87" can cause an announcement within the PSTN/ISDN saying that
   the call was rejected due to the Closed User Group service.

   Therefore it is RECOMMENDED to include the Reason header information
   in Responses only by trusted entities as it is described within
   [RFC3325].

6.  IANA Considerations

   This document describes the use of the Reason header field described
   within [RFC3326] .  No additional SIP elements are defined within
   this document.  Therefore, this document does not provide any action
   to IANA.

7.  Acknowledgments

   Thanks to Paul Kyzivat, Mary Barnes, John Ellwell, Keith Drage,
   Thomas Belling which provided helpful comments, feedback and
   suggestions.

8.  Normative References

   [I-D.ietf-sipcore-199]  Holmberg, C., "Session Initiation Protocol
                           (SIP) Response Code for Indication of
                           Terminated Dialog", draft-ietf-sipcore-199-03
                           (work in progress), December 2010.




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   [Q.850]                 "Usage of cause and location in the Digital
                           Subscriber Signalling System No. 1 and the
                           Signalling System No. 7 ISDN User Part [ITU-T
                           Recommendation Q.850]", ITU Recommendation
                           Q.850, April 1998.

   [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.

   [RFC3325]               Jennings, C., Peterson, J., and M. Watson,
                           "Private Extensions to the Session Initiation
                           Protocol (SIP) for Asserted Identity within
                           Trusted Networks", RFC 3325, November 2002.

   [RFC3326]               Schulzrinne, H., Oran, D., and G. Camarillo,
                           "The Reason Header Field for the Session
                           Initiation Protocol (SIP)", RFC 3326,
                           December 2002.

Authors' Addresses

   Roland Jesske
   Deutsche Telekom
   Heinrich-Hertz-Strasse 3-7
   Darmstadt,   64307
   Germany

   Phone: +4961516282766
   EMail: r.jesske@telekom.de


   Laura Liess
   Deutsche Telekom
   Heinrich-Hertz-Strasse 3-7
   Darmstadt,   64307
   Germany

   Phone: +4961516282761
   EMail: Laura.Liess@telekom.de






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