SIPPING Working Group G. Camarillo Internet-Draft Ericsson Expires: August 6, 2004 February 6, 2004 Requirements and Framework for Session Initiation Protocol (SIP) Exploder Invocation draft-camarillo-sipping-exploders-02.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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 August 6, 2004. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This document describes the need for SIP exploders and provides requirements for their invocation. Additionaly, it defines a framework which includes all the SIP extensions needed to meet these requirements. Camarillo Expires August 6, 2004 [Page 1] Internet-Draft Reqs and Framework for SIP Exploders February 2004 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Framework . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1 Carrying URI Lists in SIP . . . . . . . . . . . . . . . . . . 5 4.2 Managing Ad-Hoc URI Lists . . . . . . . . . . . . . . . . . . 5 4.3 Transaction State Information . . . . . . . . . . . . . . . . 5 4.4 Multiple REFER Targets . . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 6. Acknowledges . . . . . . . . . . . . . . . . . . . . . . . . . 6 Normative References . . . . . . . . . . . . . . . . . . . . . 6 Informational References . . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 7 Intellectual Property and Copyright Statements . . . . . . . . 8 Camarillo Expires August 6, 2004 [Page 2] Internet-Draft Reqs and Framework for SIP Exploders February 2004 1. Introduction Some applications require that, at a given moment, a SIP UA performs a similar transaction with a number of remote UAs. For example, an instant messaging application that needs to send a particular message (e.g., "Hello folks") to n receivers needs to send n MESSAGE requests; one to each receiver. When the transacton that needs to be repeated consists of a large request, or the number of recipients is high, or both, the access network of the UA needs to carry a considerable amount of traffic. Completing all the transactions on a low-bandwidth access would require a long time. This is unacceptable for a number of applications. A solution to this problem consists of introducing exploders in the network. The task of an exploder is to receive a request from a UA and send a number of similar requests to a number of destinations. Once the requests are sent, the exploder needs to inform the UA about their status. Effectively, the exploder behaves as a B2BUA. Note that resource lists, as described in [2], already use SIP exploders for SUBSCRIBE transactions. Still, the set of destinations needs to be preconfigured using out-of-band mechanisms (e.g., XCAP). The Advanced Instant Messaging Requirements for SIP [3] also mentions the need for exploders for MESSAGE transactions: "REQ-GROUP-3: It MUST be possible for a user to send to an ad-hoc group, where the identities of the recipients are carried in the message itself." The remainder of this document provides requirements to invoke exploders in an efficient manner and a framework that meets these requirements. 2. Terminology In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119 [1] and indicate requirement levels for compliant implementations. 3. Requirements This section contains the requirements: Camarillo Expires August 6, 2004 [Page 3] Internet-Draft Reqs and Framework for SIP Exploders February 2004 1. The invocation mechanism MUST allow the invoker to provide a list of destination URIs to the exploder. This URI list MAY consist of one or more URIs. 2. It MUST be possible to send URI list "deltas" to update the list of URIs handled by the exploder. 3. The invocation mechanism MUST NOT be request specific. 4. The invocation mechanism SHOULD NOT require more than one RTT. 5. An exploder MAY provide services beyond request explosion. That is, exploders can be modelled as application servers. For example, an exploder handling INVITE requests may behave as a conference server and perform media mixing for all the participants. 6. The interpretation of the meaning of the URI list sent by the invoker MUST be at the discretion of the application to which the list is sent. 7. It MUST be possible for the invoker to find out about the result of the operations performed by the application with the URI list. An invoker may, for instance, be interested in the status of the transactions initiated by the exploder. 8. It MUST be possible for the application that makes use of a list of URIs to convey the list of URIs to any recipients of messages created by the application from that list. OPEN ISSUE: do we really need this requirement? 9. Exploders MUST NOT perform any request explosion without authenticating the invoker. 10. The UA MUST be able to provide credentials to the exploder so that the exploder can use them to prove to the destinations that it is sending requests on behalf of the UA. 4. Framework Although Section 3 contains specific requirements for SIP exploders, this framework is not restricted to application servers that only provide request explosion services. We also deal with application servers that provide a particular service that includes a request explosion (e.g., a conference server that INVITEs several participants which are chosen by a user agent). Camarillo Expires August 6, 2004 [Page 4] Internet-Draft Reqs and Framework for SIP Exploders February 2004 We need to use several SIP extensions to meet the requirements in Section 3. We list these extensions in the following sections and explain which role they play within the framework. 4.1 Carrying URI Lists in SIP User agents can send a list of URIs to an application server using the list SIP and SIPS URI parameter defined in (draft-camarillo-sipping-uri-list-01). The user agent adds a list parameter to the Request-URI of the SIP request sent to the application server. This parameter contains a pointer to a URI list, which can be carried in the SIP request itself or can be stored in an external server (e.g., an http URI pointing to an XCAP resource list). The way the application server interprets the URI list received in the request is service specific. 4.2 Managing Ad-Hoc URI Lists An application server that receives a request with a URI list (or a pointer to it) creates a so called ad-hoc list, whose lifetime depends on the service provided by the server. Services that involve ad-hoc lists that are valid for a period of time need to allow user agents to modify these lists. A user agent can manage ad-hoc lists at a server in two ways, as described in (draft-camarillo-sipping-adhoc-management-00): using SIP or using an external means (e.g., XCAP). User agents using SIP to manage ad-hoc lists send a new SIP request with a pointer to a new list that will substitute the old list. User agents using an external means to manage ad-hoc lists need to obtain from the server a URI that allows them to manipulate the list (e.g., an http URI pointing to an XCAP resource list). The server provides such a URI in an Associated-List-Manipulation header field in the response to the request that created the ad-hoc list. 4.3 Transaction State Information User agents may be interested in the results of the message explosion at the application server. That is, user agents may want to know the result of the transactions that the application server initiated towards the URIs in the URI list provided by the user agent. The transaction state event package defined in (draft-camarillo-sipping-transac-package-00) provides this information to the user agent subscribing to this package. Still, in order to subscribe to the transaction state event package, Camarillo Expires August 6, 2004 [Page 5] Internet-Draft Reqs and Framework for SIP Exploders February 2004 the user agent needs a URI to subscribe to. The application server provides such a URI in an Associated-Transactions-State header field in the response to the request that triggered the new transactions, as defined in (draft-camarillo-sipping-transac-package-00). 4.4 Multiple REFER Targets Building REFER requests with multiple REFER targets requires special considerations, as described in (draft-camarillo-sipping-multiple-refer-00). The Refer-To header field carries a pointer to a URI list, and the NOTIFIES carry transaction state information using the transaction state event package. User agents may use bodies whose disposition type is template to describe the messages to be sent by the application server. A conferencing application is an example of an application that may use REFERs with multiple REFER targets. A user agent may send a REFER to the conferencing server so that the server BYEs a set of users. 5. Security Considerations Requirements related to security are considered in Section 3. TBD: this section should be expanded considerably. 6. Acknowledges Duncan Mills and Miguel A. Garcia-Martin supported the idea of 1 to n MESSAGEs. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Informational References [2] Roach, A., Rosenberg, J. and B. Campbell, "A Session Initiation Protocol (SIP) Event Notification Extension for Resource Lists", draft-ietf-simple-event-list-04 (work in progress), June 2003. [3] Rosenberg, J., "Advanced Instant Messaging Requirements for the Session Initiation Protocol (SIP)", draft-rosenberg-simple-messaging-requirements-00 (work in progress), December 2002. Camarillo Expires August 6, 2004 [Page 6] Internet-Draft Reqs and Framework for SIP Exploders February 2004 Author's Address Gonzalo Camarillo Ericsson Hirsalantie 11 Jorvas 02420 Finland EMail: Gonzalo.Camarillo@ericsson.com Camarillo Expires August 6, 2004 [Page 7] Internet-Draft Reqs and Framework for SIP Exploders February 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property 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; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. 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