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 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 Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on February 12, 2012. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect Jesske & Liess Expires February 12, 2012 [Page 1] Internet-Draft Reason Header August 2011 to this document. Code Components extracted from this document must 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. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this 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 not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. 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 Jesske & Liess Expires February 12, 2012 [Page 2] Internet-Draft Reason Header August 2011 1. 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. 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]. This document uses terms from [RFC3261]. 3. 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. 4. 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. Jesske & Liess Expires February 12, 2012 [Page 3] Internet-Draft Reason Header August 2011 5. IANA Considerations No IANA actions are required 6. 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. 7. 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 Jesske & Liess Expires February 12, 2012 [Page 4] Internet-Draft Reason Header August 2011 Laura Liess Deutsche Telekom Heinrich-Hertz-Strasse 3-7 Darmstadt, 64307 Germany Phone: +4961515812761 EMail: Laura.Liess@telekom.de Jesske & Liess Expires February 12, 2012 [Page 5]