Network Working Group M. Garcia-Martin Internet-Draft Nokia Expires: January 2, 2006 July 1, 2005 Private Header (P-Header) Extensions to the Session Initiation Protocol (SIP) in support of the European Telecommunications Standards Institute (ETSI) Next Generation Networks (NGN) draft-garcia-sipping-etsi-ngn-p-headers-00 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of 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 January 2, 2006. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This document describes a private SIP header field (P-header) used by the European Telecommunications Standards Institte (ETSI) in Next Generation Networks (NGN). The P-header is used for triggering services. Garcia-Martin Expires January 2, 2006 [Page 1] Internet-Draft ETSI NGN SIP P- headers July 2005 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Overall Applicability . . . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. SIP Private Headers . . . . . . . . . . . . . . . . . . . . . 3 4.1 The SIP P-AoC header field . . . . . . . . . . . . . . . . 3 4.1.1 Applicability statement of the P-AoC header field . . 4 4.1.2 Usage of the SIP P-AoC header field . . . . . . . . . 4 4.1.3 Syntax of the P-AoC header field . . . . . . . . . . . 5 4.1.4 Table of methods . . . . . . . . . . . . . . . . . . . 6 4.2 Security Considerations . . . . . . . . . . . . . . . . . 6 4.3 IANA Considerations . . . . . . . . . . . . . . . . . . . 6 4.4 Acknowledgements . . . . . . . . . . . . . . . . . . . . . 7 5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.1 Normative References . . . . . . . . . . . . . . . . . . . 7 5.2 Informative References . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 8 Intellectual Property and Copyright Statements . . . . . . . . 9 Garcia-Martin Expires January 2, 2006 [Page 2] Internet-Draft ETSI NGN SIP P- headers July 2005 1. Introduction The European Telecommunication Standards Institute (ETSI) is defininig a Next Generation Network (NGN) where a substantial part of it is based on the IP Multimedia Subsystem (IMS) defined by the Third-Generation Partnership Project (3GPP). IMS is largely based on the Session Initiation Protocol [RFC3261]. ETSI has developed a number of requirements [I-D.jesske-sipping- tispan-requirements] to support the usage of SIP in Next Generation Networks that interoperate, at the service level, with the Public Switched Telephone Network (PSTN), the Integrated Services Digital Network (ISDN), the 3GPP IP Multimedia Subsystem (IMS), and SIP networks and terminals that implement the service logic. In order to provide full support in SIP of existing services, extensions to SIP are needed. This document defines a number of Private headers (P- headers) to support those services. 2. Overall Applicability The SIP extensions specified in this document make certain assumptions regarding network topology, linkage between SIP and lower layers, and the availability of transitive trust. These assumptions are generally NOT APPLICABLE in the Internet as a whole. The mechanisms specified here were designed to satisfy the requirements specified by ETSI NGN [I-D.jesske-sipping-tispan-requirements] for which either no general-purpose solution was planned, where insufficient operational experience was available to understand if a general solution is needed, or where a more general solution is not yet mature. An analysis of these requirements is documented in the ETSI NGN Analysis ID [I-D.jesske-sipping-tispan-analysis]. For more details about the assumptions made about these extensions, consult the Applicability subsection for each extension. 3. Terminology The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this document, are to be interpreted as described in RFC 2119 [RFC2119]. 4. SIP Private Headers 4.1 The SIP P-AoC header field This extension allows a User Agent Client (UAC) to request, at the time of sending a request, that an Application Server provides charging information related to the request where the header field is Garcia-Martin Expires January 2, 2006 [Page 3] Internet-Draft ETSI NGN SIP P- headers July 2005 included. The actual information to be delivered to the UAC is outside the scope of this specification, but in general, it is supposed to contain detailed information related to the session, subscription, messaging or any other SIP request that may incur charges to the user. The scope of this document is limited to defining the header field that provides a hint to an application server that the user is willing to receive advice of charge information. The actual mechanism and the contents of the advice of charging information delivered to the user are outside the scope of this document, but as an example, the application sender can send an instant message with the advice of charge information, or the instant message can contain a link to a web page that contains more detailed and accurate data. The actual information to be delivered to the UAC is supposed to contain detailed information related to the session, subscription, messaging or any other SIP request that may incur charges to the user, but once more, its acquisition and formatting is outside the scope of this document. The mechanism assumes that a SIP proxy is forwarding SIP requests that contain the P-AoC header field to an application server that is delivering the service. The application sever receives the request, analyzes and process it, and based on the available information produces the appropriate content and sends it in a separate request to the user. The application server also forwards the request to its destination. 4.1.1 Applicability statement of the P-AoC header field This mechanism is appropriate in environments where a service provider is collecting charging events related to the establishment of SIP sessions, subscriptions, messages, and other related SIP activities. Since SIP systems available in the public Internet will typically not be subjected to this type of charging, this SIP extension is not deemed to be of general interest. 4.1.2 Usage of the SIP P-AoC header field When a User Agent (UA) generates a non-mid dialog request, and the user wants to receive information about the potential charges incurred by the SIP event, the UAC inserts a P-AoC header field in the SIP request with the value set to 'inform'. The presence of this header field in the request allows the network SIP proxies to route the SIP request through an application server that can be analyzing the request, collecting charging information, and generating some sort of feedback to the user. Garcia-Martin Expires January 2, 2006 [Page 4] Internet-Draft ETSI NGN SIP P- headers July 2005 4.1.2.1 Procedures at the UA A UAC that supports this extension and is willing to receive advice of charge information related to the request MAY insert a P-AoC header in a non mid-dialog request (e.g., initial INVITE, initial SUBSCRIBE, MESSAGE outside a dialog, etc.). The presence of this header is a request to the network to provide charging information, if available, although there is not guarantee that the network nodes are able or willing to honor the request for this information. In general a User Agent Server (UAS) will not receive requests containing a P-AoC header field. However, if the service is not supported by the caller's network, then it is possible that the UAS receives a SIP request containing a P-AoC header filed. User Agent Servers that support this extension and receive a request that contains a P-AoC header field SHOULD ignore the header field. 4.1.2.2 Procedures at a SIP proxy Generally speaking, SIP proxies that receive a request containing a P-AoC header field should include the header when the request is forwarded downstream. Note that this is also the default proxy behaviour for unknown header fields. A SIP proxy that receives a request that includes a P-AoC header field can route the request to an application server for further analysis and generation of advice of charging information. Besides that, SIP proxies do not do any other action on the header field. 4.1.2.3 Procedures at an application server An application server that receives a SIP request that contains a P-AoC header field MAY analyze the SIP request for the purpose of collecting charging data. If the service is provided, the application server SHOULD remove the P-AoC header field from the request before forwarding downstream. But no matter whether the service is provided or not the application server MUST forward the request downstream. Additionally, the application server can deliver the charging information to the user, however, the nature and procedures of this information is outside the scope of this memo. 4.1.3 Syntax of the P-AoC header field The syntax of the P-AoC header field is described according to the Augmented Backus-Naur Form (BNF) defined in RFC 2234 [RFC2234] and extended by RFC 3261 [RFC3261]. Garcia-Martin Expires January 2, 2006 [Page 5] Internet-Draft ETSI NGN SIP P- headers July 2005 P-Advice-of-Charge = "P-AoC" HCOLON p-aoc-spec *(COMMA p-aoc-spec) p-aoc-spec = "inform" / token *(SEMI aoc-param) aoc-param = generic-param The 'inform' value requests an application server to deliver information of the potential charges associated with the request, and at the same time request the application server to proceed processing the request downstream. Other values or parameters can be added in the future as needed. 4.1.4 Table of methods Table 1 shows the occurance of the P-AoC header field in different SIP methods. Header field where proxy ACK BYE CAN INV OPT REG ___________________________________________________________ P-AoC R dr - - - o o o Header field SUB NOT PRA INF UPD MSG REF ___________________________________________________________ P-AoC R o - - - - o o Table 1: Summary of methods 4.2 Security Considerations The presence of the P-AoC header in a request does not affect the treatment of the request, and thus, the actions of rogue proxies that deliberately insert or remove this header in SIP requests do not have an action on the session, subscription, message, etc. itself. 4.3 IANA Considerations This memo requests IANA to include a new P-AoC header field in the Header Fields subregistry of the Session Initiation Protocol (SIP) Parameters registry, as follows: Header Name compact Reference ----------------- ------- --------- P-AoC [RFCXXXX] Note to IANA and the RFC Editor: Please replace RFCXXXX with the RFC number of this memo. Garcia-Martin Expires January 2, 2006 [Page 6] Internet-Draft ETSI NGN SIP P- headers July 2005 4.4 Acknowledgements The author would like to thank the members of the ETSI TISPAN WG3 for their comments to this memo. 5. References 5.1 Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 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. 5.2 Informative References [I-D.jesske-sipping-tispan-requirements] Jesske, R., "Input Requirements for the Session Initiation Protocol (SIP) in support for the European Telecommunications Standards Institute (ETSI) Next Generation Network (NGN) simulation services", draft-jesske-sipping-tispan-requirements-01 (work in progress), June 2005. [I-D.jesske-sipping-tispan-analysis] Jesske, R., "Analysis of the Input Requirements for the Session Initiation Protocol (SIP) in support for the European Telecommunications Standards Institute (ETSI) Next Generation Networks (NGN) simulation service", draft-jesske-sipping-tispan-analysis-00 (work in progress), June 2005. Garcia-Martin Expires January 2, 2006 [Page 7] Internet-Draft ETSI NGN SIP P- headers July 2005 Author's Address Miguel A. Garcia-Martin Nokia P.O. Box 407 NOKIA GROUP, FIN 00045 Finland Phone: +358 50 480 4586 Email: miguel.an.garcia@nokia.com Garcia-Martin Expires January 2, 2006 [Page 8] Internet-Draft ETSI NGN SIP P- headers July 2005 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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