dispatch R. Jesske Internet-Draft L. Liess Updates: 3326 (if approved) Deutsche Telekom Intended status: Standards Track March 31, 2011 Expires: October 2, 2011 Reason header filed in Session Initiation Protocol (SIP) responses draft-jesske-dispatch-update3326-reason-responses-02 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. 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 October 2, 2011. 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 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 Jesske & Liess Expires October 2, 2011 [Page 1] Internet-Draft Reason Header March 2011 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. 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 Jesske & Liess Expires October 2, 2011 [Page 2] Internet-Draft Reason Header March 2011 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 except 100 trying if it contains only a Q.850 Cause Code. 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. Jesske & Liess Expires October 2, 2011 [Page 3] Internet-Draft Reason Header March 2011 New Text: The Reason header field only 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 only 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 Elwell, 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. [Q.850] "Usage of cause and location in the Digital Jesske & Liess Expires October 2, 2011 [Page 4] Internet-Draft Reason Header March 2011 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 Jesske & Liess Expires October 2, 2011 [Page 5]