CURRENT_MEETING_REPORT_ Reported by Thane Frivold/SRI International and Ruth Lang/SRI International Minutes of the Multiparty Multimedia Session Control Working Group (MMUSIC) An on-line copy of the minutes and the accompanying PostScript slides are available from ftp://ftp.isi.edu/confctrl/minutes or ftp://ws11.std.sri.com/pub/confctrl/minutes in the files ietf.12.94 and slides.12.94.tar. The Multiparty Multimedia Session Control Working Group (MMUSIC) held a single two hour session at the IETF meeting in San Jose, California. The meeting was organized and led by Ruth Lang and Thane Frivold due to the limited availability of the chairs, Abel Weinrib and Eve Schooler. During the session, Abel raised the possibility that the working group consider concluding or refocusing, especially if the leadership of the group were to change. In an effort to make the working group aware of other standardization efforts, two brief presentations were given on ITU teleconferencing efforts by Ken Krechmer and Joerg Ott. Ted Ko gave an overview of both a centralized and a distributed implementation of the Shenker-Weinrib-Schooler agreement protocol -- the implementation experience gave rise to several interesting research issues concerning generality, dynamicity, and scalability. A summary of the responses from a survey of existing session control protocols was given by Thane Frivold, focusing on functional requirements for both session control protocols and session descriptions. Carsten Bormann presented an overview of inter-system (horizontal) and intra-system (vertical) session control requirements which left open questions on the transport and semantic requirements. A presentation was given by Mark Handley which identified additional requirements for the ``sd'' protocol and a discussion of proposed extensions followed. The current goals and milestones were reviewed by Ruth Lang and a list of potential working group documents was discussed. ITU-T Teleconferencing Overview The slides from this presentation (slides.12.94.a and slides.12.94.b) follow these minutes. Ken Krechmer, Technical Editor for Communications Standards Review, spoke briefly about the scope and goals of the ITU, and, in particular, about the ITU's three study groups looking at audio, video, and data teleconferencing issues and standardization. Ken also identified associated US Technical Advisory Groups (TAG) which provide input to the ITU. Joerg Ott gave a technical overview of the T.120 group, the ITU group whose work most closely resembles the MMUSIC charter. In particular, Joerg outlined the features of the Multipoint Communication Service (MCS) and the Generic Conference Control (GCC). MCS provides group transmission services atop a connection tree of TCP-like connections. GCC, which is built atop of MCS, provides multiparty session management. Like the MMUSIC architecture, GCC also makes the distinction between ``horizontal'' (conference state exchange) and ``vertical'' (media agent control) session control paths. These recommendations are still under development but are targeted for draft release in March 1995. Teleconferencing Session Management Engine The slides from this presentation (slides.12.94.c) follow these minutes. Abel Weinrib presented an overview of the agreement protocol described in ``Managing Shared Ephemeral Teleconferencing State: Policy and Mechanism'' by Scott Shenker, Abel Weinrib, and Eve Schooler (ftp://ftp.isi.edu:confctrl/docs/agree.ps). While teleconferencing has both policy and mechanism choices, a key to this algorithm is the separation between resolution policy and system specific decision mechanisms. Ted Ko then spoke about his master's thesis work on the implementation of this protocol. The core of his implementation is a generalized ``session engine'' that is to be used as a service by domain specific session managers. It is not hard-wried to understand media specific or session specific details, but rather, manipulates session control aspects expressed by variables, members, rules, and consistency designators. He described a session description language that he developed in order to characterize the state his ``session engine'' acts upon. Ted's initial implementation used a centralized model (one session manager for multiple applications) and he showed how it could be integrated into Bellcore's Touring Machine. The development of a distributed implementation is complete but requires more thorough testing. The implementation experience gave rise to several interesting research issues concerning generality, dynamicity, and scalability. In considering the generality required to support differing session management systems, questions of end-system heterogeneity, differing call models, and session policies arose. More study is required to determine the appropriate balance between developing an all-encompassing session engine and the associated cost of such a heavy-weight implementation. Source code for the session engine is available by contacting ted@mit.edu. Session Control Protocol Survey Report The slides from this presentation (slides.12.94.d) follow these minutes. In advance of the meeting, a survey of existing session control protocols was distributed on November 11 by Thane Frivold and Ruth Lang. Seven responses were received before this meeting on the following efforts: o AVCCP -- Kevin Lew, Janey Hoe (MIT) o CCCP -- Mark Handley, Ian Wakeman et al (UCL) o EXPANSE -- Howard Bussey, Steven Minzer (Bellcore) o GCC -- Joerg Ott, Carsten Bormann (from knowledge of ITU efforts) o SRI -- Ruth Lang, Thane Frivold (SRI) o Telescope -- Joerg Ott (Tech U. of Berlin), Carsten Bormann (U. of Bremen) o Touring Machine -- R. C. Sekar, Brian Coan (Bellcore) Thane described the goals of the survey which were to encourage documentation of existing session control protocols and subsequently use this information in developing a basis for session control protocol and session description functional requirements. He identified points of commonality among the systems described despite the variety of approaches to session management. He also summarized specific functional requirements gleaned from the responses with respect to both session control protocols and session descriptions. Service Interoperability The slides from this presentation (slides.12.94.e) follow these minutes. Carsten Bormann described conference services as consisting of communication and cooperation services. He then gave an overview of session control requirements focusing on both inter-system (horizontal) and intra-system (vertical) coordination. The horizontal protocol is used for propagating global state information (e.g., membership, policy, encoding formats, and applications). The vertical protocol implements local decisions (e.g., on local resource usage and device management) based on global state and presents this conference state to applications. Carsten also noted that the horizontal session protocol (in conjunction with the local vertical protocols) could be used to transport (some) horizontal application protocols. Although somewhat outside the scope of session control per se, the transport state maintained by the session control association could be used for low-volume application interaction. He wrapped up by posing open questions focusing on whether the transport and semantic requirements for the horizontal and vertical protocols share the same requirements and can be satisfied by the same protocol and implementation. Session Advertisement The slides from this presentation (slides.12.94.f) follow these minutes. Mark Handley gave an overview of the current sd packet payload format. Based on experience gained through implementing a clone of sd, he identified additional requirements for the sd session description and described proposed extensions to address them. In particular, he identified the need for extended contact information (beyond owner of the conference), expected bandwidth consumption, scheduling information for repeated events, and information required for PIM. Van Jacobson pointed out that information content is distinct from the distribution mechanism; other discussion focused on the utility of including RP for PIM. Working Group Goals and Milestones Review The slides from this presentation (slides.12.94.d) follow these minutes. Although the working group has produced an agreement protocol document and an implementation of the agreement protocol engine, many of the milestones in the original charter have passed. As a result, Ruth Lang presented a list of potential documents that might be appropriate output for the working group. Suggestions included producing session control protocol and session description functional requirement documents (as separate documents from the protocol specification itself), requirements and specification of the agreement protocol, and a document on session control architecture. Interest was expressed by Joerg Ott, Carsten Bormann, Eve Schooler, and Abel Weinrib in working on an architecture document. Abel Weinrib and Ted Ko offered support for producing needed documentation on the agreement protocol. Due to time constraints, little additional discussion took place on scope and direction of the working group. No action items were assigned as the Transport Area Director and working group chairs must consult before amending the charter.