Network Working Group A. Niemi Internet-Draft M. Garcia-Martin Expires: December 23, 2006 Nokia Research Center June 21, 2006 Multi-party Instant Message (IM) Sessions Using the Message Session Relay Protocol (MSRP) draft-niemi-simple-chat-05 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 December 23, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract The Message Session Relay Protocol (MSRP) defines a mechanism for sending instant messages within a peer-to-peer session, negotiated using the Session Initiation Protocol (SIP) and the Session Description Protocol (SDP). This document defines the necessary tools for establishing multi-party instant messaging (IM) sessions, or chat rooms, using the centralized conferencing model. Niemi & Garcia-Martin Expires December 23, 2006 [Page 1] Internet-Draft Multiparty MSRP June 2006 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Motivations and Requirements . . . . . . . . . . . . . . . . . 5 4. Overview of Operation . . . . . . . . . . . . . . . . . . . . 6 5. Creating, Joining, and Destroying a Chat Room . . . . . . . . 8 5.1. Creating a Chat Room . . . . . . . . . . . . . . . . . . . 8 5.2. Joining a Chat Room . . . . . . . . . . . . . . . . . . . 8 5.3. Destroying a Chat Room . . . . . . . . . . . . . . . . . . 8 6. Sending and Receiving Instant Messages . . . . . . . . . . . . 9 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 9. Security Considerations . . . . . . . . . . . . . . . . . . . 10 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 10.1. Normative References . . . . . . . . . . . . . . . . . . . 11 10.2. Informative References . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Intellectual Property and Copyright Statements . . . . . . . . . . 14 Niemi & Garcia-Martin Expires December 23, 2006 [Page 2] Internet-Draft Multiparty MSRP June 2006 1. Introduction The Message Session Relay Protocol (MSRP) [I-D.ietf-simple-message- sessions] defines a mechanism for sending a series of instant messages within a session. The Session Initiation Protocol (SIP) [RFC3261] in combination with the Session Description Protocol (SDP) [RFC3264] allows for two peers to establish and manage such sessions. In another application of SIP, a user agent can join in a multi-party session or conference that is hosted by a specialized user agent called a conference focus [RFC4353]. Such a conference can naturally involve an MSRP session as one of possibly many media components. It is the responsibility of an entity handling the media to relay instant messages received from one participant to the rest of the participants in the conference. Participants in a chat room can be identified with a pseudonym or nickname, and decide whether their real identity is disclosed to other participants. Participants can also use a rich set of features, such as the ability to send private instant messages to one or more participants, and the ability to establish sub-conferences with one or more of the participants within the existing conference. They also allow combining instant messaging with other media components, such as voice, video, whiteboarding, screen sharing, and file transfer. Such conferences are already available today with other technologies different than MSRP. For example, Internet Relay Chat (IRC) [RFC2810], Extensible Messaging and Presence Protocol [RFC3920] based chat rooms, and many other proprietary systems provide this kind of functionality. It makes sense to specify equivalent functionality for MSRP-based systems to both provide competitive features as well as enable interworking between the systems. The aim of this document is to define requirements, conventions and extensions for enabling features similar to many of these existing systems in the Internet, namely the Internet Relay Chat (IRC) [RFC2810] and Extensible Messaging and Presence Protocol [RFC3920] Multi-User Chat [JEP-0045]. This memo uses the SIP Conferencing Framework [RFC4353] as a design basis. It also aims to be compatible with the Centralized Conferencing Framework [I-D.ietf-xcon-framework]. Where appropriate, some features are specified generically to all conference types. This specification will discuss applying those generic mechanisms in the context of multiparty chats. Niemi & Garcia-Martin Expires December 23, 2006 [Page 3] Internet-Draft Multiparty MSRP June 2006 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, BCP 14 [RFC2119], and indicate requirement levels for compliant implementations. This memo deals with a particular case of tightly coupled SIP conferences where the media exchanged consist of session-based instant messaging. Unless otherwise noted, we use the terminology defined in the SIP Conferencing Framework [RFC4353] applied to the scope of this document. In addition to that terminology, we introduce some new terms: Session-based Instant Messaging Conference: an instance of a tightly coupled conference, in which the media exchanged between the participants consist of (among others) MSRP based instant messages. This term refers to all types of conferences: long- lasting as well as ad-hoc conferences. Also known as a chat room. Chat Room: a synonym for session-based instant messaging conference. Chat Room URI: a URI that identifies a particular chat room in a conference server. Since a chat room is a specialized conference of instant messages, in the context of this document, a chat room URI is a synonym of a conference URI. Conference Server: a (possibly decomposed) server that provides multipart text conference services. It is also the combination of a conference focus and an MSRP switch. Sender: the conference participant that originally created an instant message and sent it to the chat room for delivery. Recipient: the destination conference participant(s). This defaults to the full conference participant list, minus the IM Sender. MSRP switch: a media level entity that receives MSRP messages and delivers them to the other conference participants. An MSRP switch has a similar role to a conference mixer with the exception that an MSRP switch does not actually "mix" together different input media streams; it merely relays the messages between participants. Niemi & Garcia-Martin Expires December 23, 2006 [Page 4] Internet-Draft Multiparty MSRP June 2006 3. Motivations and Requirements Although conference frameworks describing many types of conferencing applications already exist, such as the Framework and Data Model for Centralized Conferencing [I-D.ietf-xcon-framework] and the SIP Conferencing Framework [RFC4353], the exact details of session-based instant messaging conferences are not well-defined at the moment. To allow interoperable chat implementations, for both conference- aware, and conference-unaware user agents, certain conventions for MSRP conferences need to be defined. It also seems beneficial to provide a set of features that enhance the baseline multiparty MSRP in order to be able to create systems that have functionality on par with existing chat systems, as well as enable building interworking gateways to these existing chat systems. A number of requirements that enrich the session based messaging conferences have already been described in Requirements for Instant Messaging in 3GPP Wireless Systems [I-D.niemi-simple-im-wireless- reqs] or the Advanced Instant Messaging Requirements for the Session Initiation Protocol [I-D.rosenberg-simple-messaging-requirements]. In addition, we define the following requirements: Note that some of the requirements listed herein are not addressed by this document, but in other I-Ds possibly discussed in other working groups. REQ-1: The conference must have the ability to host other media in addition to MSRP, as well as multiple streams of MSRP. REQ-2: A conference participant must be able to determine the identities of the sender and recipient of the received IMs. For instance, the recipient of the message might be the entire conference, a conference sidebar or a single participant of the conference (i.e., a private message). REQ-3: It must be possible to send a message to a single participant, or a subset of the conference participants (i.e., a private instant message). REQ-4: It must be possible to set up a sidebar session with one or more participants of the chat room. REQ-5: A conference participant may have a nickname or pseudonym associated with their real identity. Niemi & Garcia-Martin Expires December 23, 2006 [Page 5] Internet-Draft Multiparty MSRP June 2006 REQ-6: It must be possible for a participant to change their nickname during the progress of the conference. REQ-7: It must be possible that a participant is only known by their nickname and not their real identity to the rest of the conference. REQ-8: It must be possible for the MSRP switch itself to send IMs to the conference (e.g., message of the day, welcome messages, server is shutting down, etc.) REQ-9: A chat room, or a chat room sidebar must be able to be characterized with a topic whose purpose is to identify the subject of conversation. REQ-10: A user with the appropriate privileges must be able to set and/or modify the topic of the chat room, or chat room sidebar. 4. Overview of Operation In order to set up a conference, one must first be created. Users wishing to host a conference themselves can of course do just that; their user agents simply morph from an ordinary user agent into a special purpose one called a conference focus. Another commonly used setup is one where a dedicated node in the network functions as a conference focus. Each chat room has an identity of its own: a SIP URI that participants use to join the conference, e.g., by sending an INVITE request. The conference focus processes the invitations, and as such, maintains SIP dialogs with each participant. In an instant messaging conference, or chat room, MSRP is one of the established media streams. Each conference participant establishes an MSRP session with an MSRP switch, which is a special purpose MSRP application. The MSRP switch is similar to a conference mixer in that it handles media sessions with each of the participants and bridges these streams together. However, unlike a conference mixer, the MSRP switch merely relays messages between participants but doesn't actually mix the streams in any way. The system is illustrated in Figure 1. Niemi & Garcia-Martin Expires December 23, 2006 [Page 6] Internet-Draft Multiparty MSRP June 2006 +------+ | MSRP | |Client| +------+ +--.---+ +------+ | MSRP | | | MSRP | |Client| | _|Client| +------._ | ,' +------+ `._ | ,' `.. +----------+ ,' `| |' | MSRP | | Switch | ,| |_ _,-'' +----------+ ``-._ +------.-' | `--+------+ | MSRP | | | MSRP | |Client| | |Client| +------+ | +------+ +---'--+ | MSRP | |Client| +------+ Figure 1: Multiparty MSRP in a Centralized Conference Typically conference participants also subscribe to the conference event package [I-D.ietf-sipping-conference-package] to gather information about the conference roster in the form of conference state notifications. For example, participants can learn about other participants' identities. All messages in the chat room use the 'multipart/mixed' MIME type to accommodate a 'Message/CPIM' wrapper content type [RFC3862] .When a participant wants to send an instant message to the conference, it constructs an MSRP SEND request and submits it to the MSRP switch including a regular payload (e.g., a Message/CPIM message that contains a text, html, an image, etc.). The Message/CPIM To header is set to the chat room URI. The switch then fans out the SEND request to all of the other participants using their existing MSRP sessions. A participant can also send a private instant message addressed to one or more conference participants whose identities have been learnt, e.g., via a notification from the conference event package [I-D.ietf-sipping-conference-package]. Procedures for private messaging are described in separate documents. Naturally, when a participant wishes to leave a chat room, it sends a Niemi & Garcia-Martin Expires December 23, 2006 [Page 7] Internet-Draft Multiparty MSRP June 2006 SIP BYE request to the conference focus and disconnects. 5. Creating, Joining, and Destroying a Chat Room 5.1. Creating a Chat Room Since we consider a chat room a particular type of conference where one of the offered media happens to be MSRP, the methods defined by the SIP Conference Framework [RFC4353] for creating conferences are directly applicable to a chat room. Once a chat room is created, it is identified by a SIP URI, like any other conference. 5.2. Joining a Chat Room Participants usually join the conference by sending an INVITE request to the conference URI. As long as the conference policy allows, the INVITE request is accepted by the focus and the user is brought into the conference. Participants are aware that the peer is a focus due to the presence of the "isfocus" feature tag [RFC3840] in the Contact header field of the 200-class response to the INVITE request. Participants are also aware that the mixer is an MSRP switch due to the presence of an additional 'message' media type and either TCP/ MSRP or TCP/TLS/MSRP as the protocol field in the SDP [RFC2327] media-line. The conference focus of a chat room MUST include support for a Message/CPIM [RFC3862] top-level wrapper for the MSRP messages by setting the 'accept-types' MSRP media line attribute in the SDP offer or answer to include 'Message/CPIM'. Note that the 'Message/CPIM' wrapper is used to carry the sender information that, otherwise, it will not be available to the recipient. Additionally, 'Message/CPIM' wrapper carries the recipient information (e.g., To and Cc: headers). 5.3. Destroying a Chat Room As with creating a conference, the methods defined by the SIP Conference Framework [RFC4353] for destroying a conference are directly applicable to a chat room. Destroying a chat room is an action that heavily depends on the policy of the chat room. The policy can determine that the chat room is destroyed when the creator leaves the conference, or with any out of band mechanism. Niemi & Garcia-Martin Expires December 23, 2006 [Page 8] Internet-Draft Multiparty MSRP June 2006 6. Sending and Receiving Instant Messages This section describes the conventions used to send and receive instant messages that are addressed to all the participants in the chat room. These are sent over a regular MSRP SEND request that contains a Message/CPIM wrapper [RFC3862] and the desired payload (e.g., text, image, video-clip, etc.). When a chat room participant wishes to send an instant message to all the other participants in the chat room, he constructs an MSRP SEND request that MUST contain a top-level wrapper of type 'Message/CPIM' [RFC3862]. The actual instant message payload inside 'Message/CPIM' MAY be of any type negotiated in the SDP 'accept-types' attribute according to the MSRP rules. The sender SHOULD populate the From header of the Message/CPIM wrapper with a proper identity by which the user is recognized in the conference. Identities that can be used (among others) are: o A SIP URI [RFC3261] representing the sender's address-of-record o A tel URI [RFC3966] representing the sender's telephone number o An IM URI [RFC3860] representing the sender's instant messaging address If the sender of the message wants to remain anonymous to the rest of the participants, and providing that the policy of the conference allows anonymous participation, the creator SHOULD populate the From header of the Message/CPIM body with an anonymous identity, e.g., using the "anonymous" SIP URI as described in RFC 3261 [RFC3261] Section 8.1.1.3. The sender MUST populate the To header field of the Message/CPIM body with the chat room URI. An MSRP switch that receives a SEND request from a participant SHOULD first verify that the From header field of the Message/CPIM wrapper is correctly populated with a valid URI as indicated earlier. If the URI included in the From header field of the Message/CPIM wrapper is not valid (e.g, because it does not "belong" to the user), then the MSRP switch MUST generate a 403 response and MUST NOT forward the SEND request to any of the participants. Otherwise, the MSRP switch SHOULD generate a 200 response according to the MSRP rules for response generation. Then the MSRP switch should inspect the To header field of the Message/CPIM wrapper. If the To header field of the Message/CPIM Niemi & Garcia-Martin Expires December 23, 2006 [Page 9] Internet-Draft Multiparty MSRP June 2006 wrapper contains the chat room URI, the MSRP switch generates a copy of the SEND request to each of the participants in the conference except the sender. The MSRP switch MUST NOT modify any of the bodies included in the received SEND request. Note that the MSRP switch does not need to wait for the reception of the complete MSRP chunk or MSRP message before it starts the distribution to the rest of the participants. Instead, once the MSRP switch has received the headers of the Message/CPIM body it is able to start the distribution process. The MSRP switch is required to examine the To header field of the Message/CPIM wrapper in order to determine whether the message is addressed to the whole roster (i.e., it is the chat room URI) or to a subset of it (e.g., a sidebar or a private message). An MSRP endpoint that receives a SEND request from an MSRP switch containing a Message/CPIM wrapper SHOULD first inspect the To header field of the Message/CPIM body. If the To header field is set to the chat room URI, then it is a regular message that has been distributed to all the participants in the conference. Then the MSRP endpoint SHOULD inspect the From header field of the Message/CPIM body to identify the sender. The From header field will include a URI that identifies the sender. The endpoint might have also received further identity information through a subscription to the SIP conference event package [I-D.ietf-sipping-conference-package]. 7. Examples TBD. 8. IANA Considerations None. 9. Security Considerations This document proposes extensions to the Message Session Relay Protocol [I-D.ietf-simple-message-sessions]. Therefore, the security considerations of such document apply to this document as well. In general, messages sent to a multi-party session based messaging focus are not deem to expose any security threat. Nevertheless, if a participant wants to avoid eavesdropping from non authorized entities, it should send those messages a TLS [RFC2246] transport connection, as allowed by MSRP. Niemi & Garcia-Martin Expires December 23, 2006 [Page 10] Internet-Draft Multiparty MSRP June 2006 10. References 10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC 2246, January 1999. [RFC2327] Handley, M. and V. Jacobson, "SDP: Session Description Protocol", RFC 2327, April 1998. [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. [RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, "Indicating User Agent Capabilities in the Session Initiation Protocol (SIP)", RFC 3840, August 2004. [RFC3860] Peterson, J., "Common Profile for Instant Messaging (CPIM)", RFC 3860, August 2004. [RFC3862] Klyne, G. and D. Atkins, "Common Presence and Instant Messaging (CPIM): Message Format", RFC 3862, August 2004. [RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966, December 2004. [RFC4353] Rosenberg, J., "A Framework for Conferencing with the Session Initiation Protocol (SIP)", RFC 4353, February 2006. [I-D.ietf-xcon-framework] Barnes, M., "A Framework and Data Model for Centralized Conferencing", draft-ietf-xcon-framework-04 (work in progress), June 2006. [I-D.ietf-simple-message-sessions] Campbell, B., "The Message Session Relay Protocol", draft-ietf-simple-message-sessions-14 (work in progress), February 2006. Niemi & Garcia-Martin Expires December 23, 2006 [Page 11] Internet-Draft Multiparty MSRP June 2006 10.2. Informative References [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with Session Description Protocol (SDP)", RFC 3264, June 2002. [JEP-0045] Saint-Andre, P., "Multi-User Chat", JSF JEP 0045, September 2005. [RFC3920] Saint-Andre, P., Ed., "Extensible Messaging and Presence Protocol (XMPP): Core", RFC 3920, October 2004. [RFC2810] Kalt, C., "Internet Relay Chat: Architecture", RFC 2810, April 2000. [I-D.niemi-simple-im-wireless-reqs] Niemi, A., "Requirements for Instant Messaging in 3GPP Wireless Systems", draft-niemi-simple-im-wireless-reqs-02 (work in progress), October 2003. [I-D.rosenberg-simple-messaging-requirements] Rosenberg, J., "Advanced Instant Messaging Requirements for the Session Initiation Protocol (SIP)", draft-rosenberg-simple-messaging-requirements-01 (work in progress), February 2004. [I-D.ietf-sipping-conference-package] Rosenberg, J., "A Session Initiation Protocol (SIP) Event Package for Conference State", draft-ietf-sipping-conference-package-12 (work in progress), July 2005. Niemi & Garcia-Martin Expires December 23, 2006 [Page 12] Internet-Draft Multiparty MSRP June 2006 Authors' Addresses Aki Niemi Nokia Research Center P.O. Box 407 NOKIA GROUP, FIN 00045 Finland Phone: +358 50 389 1644 Email: aki.niemi@nokia.com Miguel A. Garcia-Martin Nokia Research Center P.O. Box 407 NOKIA GROUP, FIN 00045 Finland Phone: +358 50 480 4586 Email: miguel.an.garcia@nokia.com Niemi & Garcia-Martin Expires December 23, 2006 [Page 13] Internet-Draft Multiparty MSRP June 2006 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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