dispatch R. Jesske Internet-Draft L. Liess Intended status: Informational Deutsche Telekom Expires: October 1, 2010 March 30, 2010 Reason header filed in Session Initiation Protocol (SIP) responses draft-jesske-dispatch-reason-in-responses-02 Abstract Although the use of the Reason header field in responses is considered in 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 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 reason codes for this and other purposes. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on October 1, 2010. Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. Jesske & Liess Expires October 1, 2010 [Page 1] Internet-Draft Reason Header March 2010 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 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. Jesske & Liess Expires October 1, 2010 [Page 2] Internet-Draft Reason Header March 2010 Table of Contents 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Overall Applicability . . . . . . . . . . . . . . . . . . . . . 4 4. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. Procedures at the UA . . . . . . . . . . . . . . . . . . . 4 4.2. Procedures at a SIP proxy . . . . . . . . . . . . . . . . . 5 4.3. Procedures at an application server . . . . . . . . . . . . 5 5. Procedures at an interworking point with ISUP . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 8. Normative References . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 Jesske & Liess Expires October 1, 2010 [Page 3] Internet-Draft Reason Header March 2010 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 Within [draft-jesske-dispatch-requirements-reason-in-responses-00] the reasoning and requirements for the use of the Reason Header within Responses is described. Based upon this document describes the procedures for the use of the Reason header within responses. 3. Overall Applicability The SIP procedures specified in this document are foreseen for networks providing simulation services and/or interworking to the PSTN/ISDN. The document is describing the use of the Reason header in SIP responses. These procedures are only valuable if the reason contained in the element "protocol" is "Q.850". A inclusion of a SIP reason (protocol="SIP") is not helpful due to the fact that the response already provides the SIP reason. The Release Causes are described within [Q.850]. (Note: The ETSI specifications can be downloaded under http://pda.etsi.org/pda/queryform.asp free of charge.) The appearance of the Reason header is applicable to final responses 3xx, 4xx, 5xx and 6xx and 18x and 199 provisional responses [I-D.ietf-sipcore-199]. 4. Procedures 4.1. Procedures at the UA A UA that supports the Reason header field can process the [Q.850] Cause Value and display it or an equivalent text. The inclusion of a Reason header field by UA is only for B2B UA interworking with the PSTN/ISDN or providing services foreseen. Jesske & Liess Expires October 1, 2010 [Page 4] Internet-Draft Reason Header March 2010 4.2. Procedures at a SIP proxy SIP proxies that receive a response containing a Reason header field is forwarding the response without changing the reason. A SIP proxy receiving a request that includes a Reason header field can route the request to an application server for further analysis and base services on it. Based on network policy a Proxy can remove a Reason header field send from a UAC. 4.3. Procedures at an application server An application server that receives a SIP request that contains a response including a Reason header MAY analyze the SIP Reason and base further procedures on this analyses. For Example the application server could use the reason for sending a announcement towards the originating entity of the session. As an example the Anonymous Communication Rejection (ACR) service defined by ETSI Telecommunications and Internet converged Services and Protocols for Advanced Networking (TISPAN) 5. Procedures at an interworking point with ISUP For interoperability reasons the Q.850 Cause Value of a Release shall be mapped to the Reason Header. 6. Security Considerations 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]. Jesske & Liess Expires October 1, 2010 [Page 5] Internet-Draft Reason Header March 2010 7. 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. 8. Normative References [I-D.ietf-sipcore-199] Holmberg, C., "Response Code for Indication of Terminated Dialog", draft-ietf-sipcore-199-00 (work in progress), April 2009. [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. [draft-jesske-dispatch-requirements-reason-in-responses-00] Jesske, R. and L. Liess, "Requirements for the use of the Reason header filed in Session Initiation Protocol (SIP) responses]", , March 2010. Jesske & Liess Expires October 1, 2010 [Page 6] Internet-Draft Reason Header March 2010 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 1, 2010 [Page 7]