DISPATCH                                                       R. Jesske
Internet-Draft                                                  L. Liess
Intended status: Standards Track                        Deutsche Telekom
Expires: February 12, 2012                               August 11, 2011


Carrying Q.850 Codes in Reason Header Fields in SIP (Session Initiation
                          Protocol) Responses
          draft-jesske-dispatch-update3326-reason-responses-05

Abstract

   Although the use of the Reason header field in responses is
   considered in general in RFC3326, its use is not specified for any
   particular response code.  Nonetheless, existing deployments have
   been using Reason header fields in responses to carry Q.850 cause
   codes for failure responses to INVITE requests that have been
   gatewayed to PSTN systems.  This document normatively describes the
   use of the Reason header field in SIP responses to carry Q.850 cause
   codes.

Status of This Memo

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   to this document.  Code Components extracted from this document must
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Table of Contents

   1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Applicability . . . . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 4
   7.  Normative References  . . . . . . . . . . . . . . . . . . . . . 4

























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.  Overview

   Although the use of the Reason header field in responses is
   considered in general in RFC3326[RFC3326], its use is not specified
   for any particular response code.  Nonetheless, existing deployments
   have been using Reason header fields in responses to carry Q.850
   [Q.850] cause codes for failure responses to INVITE requests that
   have been gatewayed to PSTN systems.  This document normatively
   describes the use of the Reason header field in SIP responses to
   carry Q.850 [Q.850] cause codes.

.  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].

.  Applicability

   This document allows SIP responses to carry Reason header fields as
   follows:

   Any SIP Response message, with the exception of a 100 (Trying) MAY
   contain a Reason header field with a Q.850 [Q.850] cause code.

   The Reason header field is not needed in the the 100 (Trying)
   responses since they are transmitted hop-by-hop, not end-to-end.  SIP
   responses with Reason header fields carrying values other than Q.850
   [Q.850] cause code are outside of the scope of this document.

.  Security Considerations

   This specification allows the presence of the Reason containing Q.850
   [Q.850] cause codes in responses.  The presence of the Reason header
   field in a response does not affect the treatment of the response.
   Nevertheless, there could be situations where a wrong Q.850 [Q.850]
   cause code could, for example, cause an announcement system to play
   the wrong information.  To avoid such situations, it is RECOMMENDED
   that this header field is protected by a suitable integrity
   mechanism.  The use of transport or network layer hop-by-hop security
   mechanisms, such as TLS or IPSec with appropriate cipher suites, can
   satisfy this requirement.







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.  IANA Considerations

   No IANA actions are required

.  Acknowledgments

   Thanks to Gonzalo Camarillo and Mary Barnes for the detailed review
   of this document.

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

.  Normative References

   [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.

   [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: +4961515812766
   EMail: r.jesske@telekom.de










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

   Phone: +4961515812761
   EMail: Laura.Liess@telekom.de











































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