ECRIT Working Group M. Patel Internet-Draft Nortel Intended status: Standards Track October 26, 2009 Expires: April 29, 2010 SOS Uniform Resource Identifier (URI) Parameter for Marking of Session Initiation Protocol (SIP) Requests related to Emergency Services draft-patel-ecrit-sos-parameter-07.txt 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 April 29, 2010. Copyright Notice Copyright (c) 2009 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 in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract This document defines a new Session Initiation Protocol (SIP) Uniform Resource Identifier (URI) parameter intended for marking SIP Patel Expires April 29, 2010 [Page 1] Internet-Draft SOS URI Parameter for SIP Emergency October 2009 registration requests related to emergency services. The URI parameter is extensible to allow future values to be defined if required by other use cases that require specific SIP registrations to be distinctly identified. The usage of this new URI parameter complements the usage of the Service Uniform Resource Name (URN) and is not intended to replace it. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. The "reg-type" URI Parameter . . . . . . . . . . . . . . . . . 4 4.1. REGISTER Request . . . . . . . . . . . . . . . . . . . . . 4 4.2. 2xx Response to REGISTER Request . . . . . . . . . . . . . 5 4.3. Backwards compatibility issues . . . . . . . . . . . . . . 5 5. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 9.1. Normative References . . . . . . . . . . . . . . . . . . . 7 9.2. Informative References . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 Patel Expires April 29, 2010 [Page 2] Internet-Draft SOS URI Parameter for SIP Emergency October 2009 1. Introduction One way to differentiate a SIP-based emergency call from an ordinary call is by the presence of the Service URN as defined in RFC 5031 [RFC5031] (and used in the IETF emergency services architecture described in PhoneBCP[I-D.ietf-ecrit-phonebcp]). The 3GPP IP Multimedia Subsystem (IMS) emergency services architecture, illustrated in 3GPP TS 23.167 [3GPP.23.167], specifies that the User Equipment (UE) performs emergency registration prior to or during the initiation of an emergency call. The circumstances where such an emergency registration is beneficial are listed below: - the UE is not registered with its home network; - the UE is currently registered but roaming (to ensure that the emergency call is handled in the visited network, as required by some jurisdictions). Emergency registration is possible only when the UE has sufficient credentials to register with its home network and can detect that an emergency session is initiated. Unfortunately, marking of the emergency registration can not be fulfilled by the use of the Service URN. In some countries, it is a regulatory requirement that devices be able to place emegency calls in circumstances where other calls may not be permitted. When a UAC issues an emergency marked REGISTER request it informs the registrar that the contact address and the address-of-record being registered are to be used for emergency calls, and roaming and barring restrictions should not be applied for the registered address-of-record. This document concentrates on a use case defined by 3GPP as described above. However, the solution proposed does not preclude other systems that require emergency registration to occur prior to placing an emergency call. This document proposes a way to mark a REGISTER request as an emergency registration. 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 RFC 2119 [RFC2119] Patel Expires April 29, 2010 [Page 3] Internet-Draft SOS URI Parameter for SIP Emergency October 2009 3. Requirements Req: Where emergency registration is required prior to placing an emergency call, it shall be possible to distinguish emergency registration from non-emergency registration. 4. The "reg-type" URI Parameter This section provides an overview of the proposed new URI parameter to be used for marking REGISTER requests related to emergency services. A new URI parameter "reg-type" is defined in this document. The "reg-type" parameter is appended to a URI consistent with RFC 3261 [RFC3261]. It is proposed that use of this URI parameter is restricted to the Contact header included in the REGISTER request (and the 2xx response to the REGISTER request) related to an emergency call only. The "reg-type" URI parameter SHALL take a value of "sos" to indicate that the REGISTER request pertains to emergency registration. The "reg-type" URI parameter with value "sos" MUST NOT be considered as a replacement for the Service URN for emergency calls originated by a UA. Other use cases where specific instances of SIP registration need to be identified are also possible. One such case may be by an end-user registering their address-of-record with the specific purpose of making "test" calls within a network. Such cases not specific to the use case identified in this draft for identifying emergency registration are not dealt with in this document. However the "reg- type" URI parameter is extensible to allow other "reg-type" values to be defined in the future. 4.1. REGISTER Request In networks where the UA sends a REGISTER request for emergency registration prior to placing an emergency call, the "reg-type" URI parameter with value "sos" MUST be appended to the URI in the Contact header. This serves as an indication to the registrar that the request is for emergency registration. Example: Contact: "Alice" ;q=0.7; expires=3600 Patel Expires April 29, 2010 [Page 4] Internet-Draft SOS URI Parameter for SIP Emergency October 2009 In the event that more than one Contact header field is included in the REGISTER request, only the contact addresses that include the "reg-type" URI parameter with value "sos" shall be considered as emergency registered contact addresses. The "reg-type" URI parameter with value "sos" MUST NOT be included in non-REGISTER requests, and MUST NOT be included in REGISTER requests that do not pertain to emergency calls. 4.2. 2xx Response to REGISTER Request If the registrar receives a REGISTER request that includes the "reg- type" URI parameter with value "sos" in the Contact heade field, the registrar MUST include the "reg-type" URI parameter with value "sos" in the Contact header field in the 200 (OK) response sent by the registrar upon successful registration. The "reg-type" URI parameter with value "sos" is appended to the URI included in the Contact header, thus indicating to the UA that it needs to include this contact address in the Contact header of an INVITE for emergency call initiation. 4.3. Backwards compatibility issues The backwards compatibility scenario considered in this document is where a legacy registrar does not support the "reg-type" URI parameter with value "sos". In this case, if the registrar receives a REGISTER request that includes the "reg-type" URI parameter with value "sos" in the Contact header field, the registrar proceeds with registration procedures and silently ignores the URI-parameter in accordance with RFC 3261[RFC3261]. This ensures the user is registered and thus can successfully initiate an emergency call. The drawback of proceeding with registration is if the address-of- record is for example barred or has roaming restrictions applied, then these restrictions will not be lifted and thus registration will be unsuccessful. This can limit the UAC's ability to successfully place an emergency call. If registration is successful, the 200 (OK) response from a legacy registrar is unlikely to include the "reg-type" URI parameter in the Contact header field since this registration is treated as a non- emergency registration. 5. Formal Syntax The following syntax specification uses the augmented Backus-Naur Form (BNF) as described in RFC 5234 [RFC5234]. Patel Expires April 29, 2010 [Page 5] Internet-Draft SOS URI Parameter for SIP Emergency October 2009 The "reg-type" URI parameter is a "uri-parameter", as defined by RFC 3261[RFC3261]. uri-parameter =/ reg-type-param reg-type-param = "reg-type=" ("sos" / genvalue) genvalue = 1*(alphanum / "-" / "." ) 6. IANA Considerations This specification defines one new SIP URI parameter, as per the registry created by RFC 3969 [RFC3969] Parameter Name: reg-type Predefined Values: sos Reference: [RFCXXXX] [NOTE TO IANA: Please replace XXXX with the RFC number of this specification.] 7. Security Considerations As an identifier, the "reg-type" parameter itself does not raise any particular security issues. The semantic described by the "reg-type" parameter are meant to be well-known so privacy considerations do not apply to the URI parameter. The main possibility of attack involves use of the "reg-type" parameter to bypass the normal procedures in order to achieve fraudulent use of services or to bypass security procedures. The usage of this parameter as described in this document is purely for the purpose of the REGISTER request and hence in presence of user authentication it is ensured that the respective user can be held accountable. It is RECOMMENDED to log events of misuse of the "reg-type" URI parameter with value "sos", for example by including it in a request or response not related to an emergency call. 8. Acknowledgements The author would like to thank Keith Drage, Milo Orsic, Deb Barclay, John-Luc Bakker, Andrew Allen, Hiroshi Ishikawa, Sean Schneyer, Peter Leis, Georg Mayer, Marvin Bienn, Ricky Kaura, Steve Norreys, Laura Patel Expires April 29, 2010 [Page 6] Internet-Draft SOS URI Parameter for SIP Emergency October 2009 Liess, AC Mahendran, Roozbeh Atarius, Ramachandran Subramanian and Sandeep Sharma, Brian Rosen, Hannes Tschofenig, Christer Holmberg and Henning Schulzrinne for the discussions and contributions that led to this work. 9. References 9.1. Normative References [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. [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. [RFC3969] Camarillo, G., "The Internet Assigned Number Authority (IANA) Uniform Resource Identifier (URI) Parameter Registry for the Session Initiation Protocol (SIP)", BCP 99, RFC 3969, December 2004. 9.2. Informative References [I-D.ietf-ecrit-phonebcp] Rosen, B. and J. Polk, "Best Current Practice for Communications Services in support of Emergency Calling", draft-ietf-ecrit-phonebcp-13 (work in progress), July 2009. [RFC5031] Schulzrinne, H., "A Uniform Resource Name (URN) for Emergency and Other Well-Known Services", RFC 5031, January 2008. [3GPP.23.167] 3GPP, "IP Multimedia Subsystem (IMS) emergency sessions", 3GPP TS 23.167 7.11.0, December 2008. Patel Expires April 29, 2010 [Page 7] Internet-Draft SOS URI Parameter for SIP Emergency October 2009 Author's Address Milan Patel Nortel Maidenhead Office Park, Westacott Way Maidenhead, Berkshire, UK Email: milanpa@nortel.com Patel Expires April 29, 2010 [Page 8]