Network Working Group Q. Sun Internet-Draft L. Tian Expires: January 2, 2008 D. Ren Huawei Technologies July 2007 Multiple Reply in the Session Initiation Protocol (SIP) draft-sun-sipping-multiple-reply-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, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Sun, et al. Expires January 2, 2008 [Page 1] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 Abstract This document defines extensions to the Reply-To header field for MESSAGE so that it can be used to specify multiple addresses as the target of reply MESSAGE. These extensions include the use of pointers to Uniform Resource Identifier (URI)-lists in the Reply-To header field and the "multiple-reply" SIP option-tag. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. URI-List Document Format . . . . . . . . . . . . . . . . . . . 5 4. Option-tag . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5. Procedures at the Reply-Issuer . . . . . . . . . . . . . . . . 8 6. Procedures at the Reply-Recipient . . . . . . . . . . . . . . 9 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 7.1. Reply-Recipient use MESSAGE URI-List service to send reply MESSAGE requests . . . . . . . . . . . . . . . . . . 10 8. Security Considerations . . . . . . . . . . . . . . . . . . . 13 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 10. Acknowledges . . . . . . . . . . . . . . . . . . . . . . . . . 15 11. MIME Information . . . . . . . . . . . . . . . . . . . . . . . 16 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 12.1. Normative References . . . . . . . . . . . . . . . . . . . 17 12.2. Informative References . . . . . . . . . . . . . . . . . . 17 Appendix A. History of change . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 Intellectual Property and Copyright Statements . . . . . . . . . . 20 Sun, et al. Expires January 2, 2008 [Page 2] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 1. Introduction RFC 3261 [2] defines a Reply-To header field containing a logical return URI that may be different from the From header field. For example, the URI MAY be used to return missed calls or unestablished sessions. RFC 3428 [3] further defines the Reply-To as an optional header field that can be used and present in MESSAGE requests and responses. This allows the Reply-Issuer to provide Reply-Recipient with one User Agent (UA) as the target of reply MESSAGE. However in some scenarios, the Reply-Issuer may want the Reply- Recipient to send reply MESSAGE to a list of UAs. For example, a manager sends a message to notify the secretary to prepare a meeting. At the same time the manager provides the list of attendees in the message. Whenever the meeting is arranged the secretary can send meeting information in reply message to the list of attendees. Another use case may be that a scheduled reminder application sends a message to a user, the message informs the user should send some information, such as weekly project report, to a list of users while the notification itself is not meaningful for the intended recipients. This specification extends the above Reply-To mechanim to fullfil this requirement. The Reply-Issuer sends a MESSAGE request which contains the Reply-To header field pointing to a URI-List (Uniform Resource Identifier list) as the targets of reply MESSAGE to a Reply- Recipient. The Reply-Recipient may modify the provided list to add or remove recipients. The Reply-Recipient can create a reply MESSAGE request for each entry in the URI-List and send them respectively or send a reply MESSAGE to MESSAGE URI-list service [9] to distribute the reply MESSAGE requests. The requirements to support multiple reply may be summarized as follows: REQ-1: It MUST be possible for a Reply-Issuer to specify multiple reply targets in a MESSAGE request, where the identities of the reply targets are carried in the request itself. Sun, et al. Expires January 2, 2008 [Page 3] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 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 [1] This document defines the following new terms: Reply-Issuer: the user agent issuing the SIP request with Reply-To header field. Reply-Recipient: the user agent receiving the SIP request with Reply-To header field. Sun, et al. Expires January 2, 2008 [Page 4] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 3. URI-List Document Format As described in the Framework and Security Considerations for SIP URI-List Services [4] , specifications of individual URI-list services, need to specify a default format for 'recipient-list' bodies used within the particular service. The default format for 'recipient-list' bodies for multiple reply is XML Resource Lists [7] extended with Copy Control Attribute [8] . Reply-Issuer and Reply-Recipient MUST support both of these formats and MAY support other formats. As described in Copy Control Attribute [8] , each URI can be tagged with a 'copyControl' attribute set to either "to", "cc", or "bcc", indicating the role in which the recipient will get the MESSAGE request. Additionally, URIs can be tagged with the 'anonymize' attribute to prevent that the Reply-Recipient (UAS) discloses the target URI in a URI-list. In addition, the XML Resource Lists [7] defines a 'recipient-list- history' body that contains the list of recipients. The default format for 'recipient-list-history' bodies for UAs is also the XML Resource Lists [7] extended with the Copy Control Attribute [8] . If the Reply-Recipient sends the reply MESSAGE requests for each entry in the URI-List, it may provide 'recipient-list-history' body in the reply MESSAGE requests. In this case the Reply-Recipient MAY support these formats and MAY support others. If the Reply-Recipient sends the reply MESSAGE request to MESSAGE URI-list service [9] , it does not need to support these formats. UAs able to understand 'recipient-list-history' MUST support these formats and MAY support others. Nevertheless, the XML Resource Lists [7] provides features, such as hierarchical lists and the ability to include entries by reference relative to the XCAP root URI, that are not needed by the multiple reply mechanism defined in this document, which only needs to transfer a flat list of URIs between the Reply-Issuer and the Reply- Recipient. Therefore, when using the default resource list document, UAs SHOULD use flat lists (i.e., no hierarchical lists) and SHOULD NOT use elements. A Reply-Recipient receiving a URI-list with more information than what has just been described MAY discard all the extra information. Figure 1 shows an example of a flat list that follows XML Resource Lists [7] extended with Copy Control Attribute [8] ). Sun, et al. Expires January 2, 2008 [Page 5] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 Figure 1: Example for XML Resource List Document Sun, et al. Expires January 2, 2008 [Page 6] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 4. Option-tag This document defines a new SIP option-tag for the Require and Supported header fields: "multiple-reply". A UA including the "multiple-reply" option-tag in a Supported header field indicates compliance with this specification. A UA generating a MESSAGE request with a pointer to a URI-list in its Reply-To header field MUST include the "multiple-reply" option-tag in the Require header field of the MESSAGE request. Sun, et al. Expires January 2, 2008 [Page 7] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 5. Procedures at the Reply-Issuer A Reply-Issuer that wants to specify multiple reply addresses MUST be formatted according to Section 4 of RFC 3428 [3] . The Reply-Issuer populates the Request-URI with the SIP or SIPS URI of the Reply- Recipient. In addition to the regular MESSAGE body, the Reply-Issuer adds a recipient-list body whose Content-Disposition type is 'recipient-list' as defined in Framework and Security Considerations for SIP URI-List Services [4] . This body contains a URI-list with the recipients of the reply MESSAGE from the Reply-Recipient. Target URIs in this body MAY also be tagged with the 'copyControl' and 'anonymize' attributes specified in the Copy Control Attribute [8] . The Reply-Issuer MUST provide an appropriate Content-ID for the recipient-list body and populates the Reply-To with the value of Content-ID which identifies the list of intended recipient of reply message. The Reply-Issuer MUST also include the 'multiple-reply' option-tag, defined in Section 4, in a Require header field. the Reply-Issuer MAY use the "?" mechanism described in Section 19.1.1 of RFC 3261 [2] to encode extra information in any URI in the list. The following is an example of a URI that uses the "?" mechanism: sip:bob@example.com?Accept-Contact=*%3bmobility%3d%22mobile%22 The previous URI requests the Reply-Recipient to add the following header field to a reply MESSAGE request to be sent to bob@example.com: Accept-Contact: *;mobility="mobile" Sun, et al. Expires January 2, 2008 [Page 8] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 6. Procedures at the Reply-Recipient A Reply-Recipient that is able to receive and process MESSAGE requests with a Reply-To header field and 'recipient-list' body MUST include a 'multiple-reply' option-tag in a Supported header field when responding to OPTIONS requests. A Reply-Recipient that receives a MESSAGE request with a Reply-To header field and 'recipient-list' body processes it and responds following the precedure in section 7 of RFC 3428 [3] There are two possibilities for Reply-Recipient to send reply MESSAGE requests to intended recipients: o The Reply-Recipient creates a reply MESSAGE request for each entry in the URI-List and send them respectively. If it supports 'recipient-list-history' Content-Disposition type it MAY provide a 'recipient-list-history' body in the reply MESSAGE requests for each intended recipient following the procedure defined in Copy Control Attribute [8] . o The Reply-Recipient sends a reply MESSAGE request that includes the payload along with the URI-list to the MESSAGE URI-list service [9] to distribute the simliar reply MESSAGE requests to each of the URIs included in the list. The Reply-Recipient MAY modify the URI-list from Reply-Issuer to add or remove recipients. Sun, et al. Expires January 2, 2008 [Page 9] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 7. Examples 7.1. Reply-Recipient use MESSAGE URI-List service to send reply MESSAGE requests Figure 1 shows an example flow where a Reply-Issuer sends a MESSAGE request with Reply-To header field pointing to a URI list to a Reply- Recipient. The Reply-Recipient sends a reply MESSAGE with the URI list to MESSAGE URI-list service. +--------+ +--------+ +---------+ +--------+ +--------+ | Reply- | | Reply- | | MESSAGE | | reply | | reply | | Issuer | | Recip. | | URI-List| | target | | target | | | | | | server | | 1 | | 2 | +--------+ +--------+ +---------+ +--------+ +--------+ | | | | | | F1:MESSAGE with Reply-To pointing to a URI-List | |------------>| | | | | F2:200 OK | | | | |<------------| | | | | | F3:MESSAGE | | | | |-------------->| | | | | F4:202 Accepted | | | |<--------------| | | | | | F5:MESSAGE | | | | | --------------->| | | | | F6:MESSAGE | | | | | -------------------------->| | | | F8:200 OK | | | | |<--------------- | | | | | F9:200 OK | | | | |<-------------------------- | | | | | | Figure 1: Example flow for Reply-To pointing to multiple addresses Figure 2 shows an example of the MESSAGE request F1, which carries a 'multipart/mixed' body composed of two other bodies: o 'text/plain' body: contains the instant message payload; o 'application/resource-lists+xml' body: contains the intended recipients receving the reply MESSAGE request from Reply- Recipient. The Reply-To header field has the same value of Content-ID pointing to the URI-List which contains the intended recipients. Sun, et al. Expires January 2, 2008 [Page 10] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 MESSAGE sip:tom@example.com SIP/2.0 Via: SIP/2.0/TCP uac1.example.com ;branch=z9hG4bKhjhs8as34sc Max-Forwards: 70 To: From: Alice ;tag=210342 Call-ID: 39s02sdsl20d9sj2l CSeq: 1 MESSAGE Reply-To: Require: multiple-reply Content-Type: multipart/mixed;boundary="boundary1" Content-Length: xxx --boundary1 Content-Type: text/plain Please reply the deadline to the team! --boundary1 Content-Type: application/resource-lists+xml Content-Disposition: recipient-list Content-ID: --boundary1-- Figure 2: MESSAGE with Reply-To header field pointing to a URI list Figure 3 shows an example of the MESSAGE request F3, which carries a 'multipart/mixed' body composed of three other bodies: o 'text/plain' body: contains the instant message payload; Sun, et al. Expires January 2, 2008 [Page 11] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 o 'application/resource-lists+xml' body: contains the list of recipients. This list is the same with F1. MESSAGE sip:list-service.example.com SIP/2.0 Via: SIP/2.0/TCP uac1.example.com ;branch=z9hG4bKhjhs8as34sc Max-Forwards: 70 To: MESSAGE URI-list Service From: Alice ;tag=32331 Call-ID: d432fa84b4c76e66710 CSeq: 1 MESSAGE Require: multiple-reply, recipient-list-message Content-Type: multipart/mixed;boundary="boundary1" Content-Length: xxx --boundary1 Content-Type: text/plain The deadline is 14:00 GMT Octobor 10, 2007. --boundary1 Content-Type: application/resource-lists+xml Content-Disposition: recipient-list --boundary1-- MESSAGE request received at the MESSAGE URI-list server Sun, et al. Expires January 2, 2008 [Page 12] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 8. Security Considerations URI-lists may contain private information, such as SIP URIs. It is therefore not desirable that these URI-lists are known by third parties. Eavesdroppers are able to watch URI-lists contained in SIP requests unless the SIP message is sent over a secured channel, by using any of the available SIP mechanisms, such as Transport Layer Security (TLS) [5] , or unless the URI-list body itself is encrypted with, e.g., S/MIME [6] . Therefore, it is RECOMMENDED that URI-list bodies are encrypted with S/MIME [6] or that the SIP request is encrypted with TLS [5] or any other suitable encryption mechanism. Sun, et al. Expires January 2, 2008 [Page 13] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 9. IANA Considerations This document defines the 'multiple-reply' SIP option-tag. It should be registered in the Option Tags subregistry under the SIP parameter registry. The following is the description to be used in the registration. +------------------------+------------------------------+-----------+ | Name | Description | Reference | +------------------------+------------------------------+-----------+ | multiple-reply | The body contains the | [RFC XXXX]| | | inten contains the intended | | | | recipients receving the | | | | reply MESSAGE request from | | | | Reply-Recipient. | | +------------------------+------------------------------+-----------+ Figure 4: Registration of the 'multiple-reply' Option-Tag in SIP. Sun, et al. Expires January 2, 2008 [Page 14] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 10. Acknowledges TBD Sun, et al. Expires January 2, 2008 [Page 15] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 11. MIME Information TBD Sun, et al. Expires January 2, 2008 [Page 16] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 12. References 12.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, March 1997. [2] 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. [3] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C., and D. Gurle, "Session Initiation Protocol (SIP) Extension for Instant Messaging", RFC 3428, December 2002. [4] Camarillo, G. and A. Roach, "Framework and Security Considerations for Session Initiation Protocol (SIP) Uniform Resource Identifier (URI)-List Services", draft-ietf-sipping-uri-services-06 (work in progress), September 2006. [5] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.1", RFC 4346, April 2006. [6] Ramsdell, B., "Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Message Specification", RFC 4346, January 1999. [7] Rosenberg, J., "Extensible Markup Language (XML) Formats for Representing Resource Lists", RFC 4826, May 2007. [8] Garcia-Martin, M. and G. Camarillo, "Extensible Markup Language (XML) Format Extension for Representing Copy Control Attributes in Resource Lists", draft-ietf-sipping-capacity-attribute-04.txt (work in progress), December 2006. 12.2. Informative References [9] Garcia-Martin, M. and G. Camarillo, "Multiple-Recipient MESSAGE Requests in the Session Initiation Protocol (SIP)", draft-ietf-sip-uri-list-message-01.txt (work in progress), January 2007. Sun, et al. Expires January 2, 2008 [Page 17] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 Appendix A. History of change This is the first version of this draft. Sun, et al. Expires January 2, 2008 [Page 18] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 Authors' Addresses Qian Sun Huawei Technologies Bantian Longgang Shenzhen, Guandong 518129 P.R China Phone: +86 755 28780808 Email: sunqian@huawei.com Linyi Tian Huawei Technologies Bantian Longgang Shenzhen, Guandong 518129 P.R China Phone: +86 755 28780808 Email: tianlinyi@huawei.com Daqi Ren Huawei Technologies Bantian Longgang Shenzhen, Guandong 518129 P.R China Phone: +86 755 28780808 Email: rendaqi@huawei.com Sun, et al. Expires January 2, 2008 [Page 19] Internet-Draft Multiple Reply in SIP MESSAGE July 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Sun, et al. Expires January 2, 2008 [Page 20]