Internet Engineering Task Force P. Koskelainen Internet Draft Nokia draft-koskelainen-mmusic-floor-req-01.txt H. Schulzrinne October 31, 2002 Columbia U. Expires: May 2003 J. Ott Universitaet Bremen Requirements for Floor Control 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 To view the list Internet-Draft Shadow Directories, see http://www.ietf.org/shadow.html. Abstract This document defines the requirements for floor control. 1 Introduction Multimedia conferences often contain shared resources such as the right to talk, input access to a limited-bandwidth video channel, or a pointer or input focus in a shared application. In many cases, it is desirable to be able to control who can provide input (send/write/control, depending on the application) to the shared resource. Floor control enables applications or users to gain safe and mutually exclusive or non-exclusive input access to the shared object or P. Koskelainen/H. Schulzrinne/J. Ott [Page 1]
Internet Draft Floor control reqs. October 31, 2002 resource. We define a floor as the temporary permission for a conference participant to access or manipulate a specific shared resource or group of resources [2]. Floor control is an optional feature of conferences. SIP [4] conferencing applications may decide not to support this feature at all. Some applications of floor control, such as write access to a shared document, are useful even for "conferences" with two members, while other resources, such as an audio channel, may only make floor control worthwhile for larger groups. Earlier work on this topic (e.g., [3], [5], [6], [2]) can serve as useful input for the SIP standardization efforts. In general, floor control is closely related to the management of shared resources in operating systems and distributed systems. Synchronization, mutual exclusion and the reader-writer problem have become standard tools in those areas. However, floor control differs in that it generally involves managing access by human participants, with a much stronger emphasis on policies. This work supports on-going SIPPING conferencing work [1], and [7]. 2 Conventions of This Document In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALLNOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in RFC 2119 [8]. 3 Definitions Focus: The focus is a SIP user agent that is addressed by a conference URI. The focus maintains a SIP signaling relationship with each participant in the conference. The focus is responsible for ensuring, in some way, that each participant receives the media that make up the conference. The focus also implements conference policies. The focus is a logical role. Floor: A floor is a set of shared resources within a conference. A single conference may have multiple floors. Conference members: A conference member or participant that has a signaling relationship with the conference focus and receives one or more of the media streams that are part of the conference. Conference owner: A conference owner is a privileged user who P. Koskelainen/H. Schulzrinne/J. Ott [Page 2]
Internet Draft Floor control reqs. October 31, 2002 defines rules for running the conference. By default, the conference creator becomes the owner, but the role can be delegated to another entity. Among other roles, the conference owner also establishes rules for floor control, by creating floors, assigning and removing floor chairs. The conference owner may delegate some of these responsibilities to another party. The conference owner does not have to be a member in the conference. Chair: A user (or an entity) who manages one floor by granting, denying or revoking access privileges. The chair does not have to be a member of the conference. The chair is sometimes also referred to as the moderator. Different floors within a conference may have different chairs. Chairs may change during a conference. Floor control: Floor control is a mechanism that enables applications or users to gain safe and mutually exclusive or non-exclusive access to the shared object or resource. Floor controller: A floor controller is a logical entity that manages floors. It receives requests from conference participants, the conference owner and the floor chair and issues protocol requests to affect conference and floor status. Depending on floor policy, the floor controller may ask the chair to approve decisions. Floor policy: The floor policy is the set of rules and attributes governing operation of the floor controller. The floor policy is defined upon creation of a floor and may be modified by an authorized participant. 4 Model A floor control protocol is used to convey the floor control messages among the floor chairs (moderators) of the conference, the floor controller, the focus and the participants of the conference. Floor control can operate at the origin of data, at a redistribution point or at the destination. At the origin of data, floor control can ask the sender, via signaling, to surpress the generation of data. At the redistribution point, the floor controller can modify the mixing matrix, so that only media streams from certain participants are delivered to other participants. At the destination, floor control can filter incoming media or messages, so that only floor holders can affect the state of the shared resource. We can also distinguish cooperative and coercive floor control. P. Koskelainen/H. Schulzrinne/J. Ott [Page 3]
Internet Draft Floor control reqs. October 31, 2002 Cooperative floor control relies on the cooperation of the data source, while coercive floor control does not; it can function even if a participant is malicious or malfunctioning. Among the three locations of floor control, floor control at the redistribution point and at the receiver can be made coercive, while floor control at the sender is by necessity cooperative. A floor is always coupled to one or more media sessions. The manner of creating a media session itself is defined elsewhere. A participant with appropriate privileges may create a floor by defining that one or more media sessions are now floor-controlled. As part of the creation of a floor, a chair needs to be appointed. (In some cases, the chair is an automaton, rather than a human participant.) 5 Integration with Conferencing We assume that the ability of users to create floors is governed by the conference policy. For simplicity, we assume that a chair can delegate his or her responsibility to any other member of the conference. The conference policy and thus, indirectly, the conference owner defines whether or not floor control is in use and for which resources. If floor control is enabled for a particular resource or set of resources, the conference policy also defines for which resources the use of floor control is mandatory and for which it is optional. [TBD: Not clear what mandatory and optional means.] Typically, the conference owner creates a floor using a yet-to-be- defined mechanism and appoints the floor chair. The conference owner can remove the floor at any time (so that the resources are no longer floor-controlled), change the chair or the floor parameters. The chair just controls the access to the floor, according to the conference policy. Figure 1 depicts how floor control integrates into the overall conferencing architecture. 6 Requirements REQ-1: It MUST be possible to announce to participants that a particular media session (or group of media session) is floor-controlled and where requests for the floor should be addressed to. P. Koskelainen/H. Schulzrinne/J. Ott [Page 4]
Internet Draft Floor control reqs. October 31, 2002 +------------------------+ | | +-------+ | +------------------+ | |Floor | | | Conference Policy| | |Control| --- | | Server | | |Server | ------ | +------------------+ | +-------+ ----- | | . . . ---+-- +-------------+ | . . .. | --- | Media Policy| | . .. .. | | Server | | . . . | +-------------+ | . . .. | | Floor . . .. | +---------+ +-----+ | Control . .. . | |Focus | |Mixer| | Protocols. . .. | +---------+ +-----+ | (SUB/NOT & . . .. +-----/-----------------+ controls) . . .---- / | . . ----.. / | . ---- ./ dialogs . ---- . /. | . ---- . / .. | --- / .. | +-------+ +-------+ . +-------+ | | | | .. | | | Client| | Client| .. | Client| | | | | . | | | | | | | | | | | | | | +-------+ +-------+ +-------+ Figure 1: Floor control integration into Conferencing SDP's "a" line offers one possible indication. REQ-2: It MUST be possible to group more than one media sessions together so that one floor applies to the group. The SDP "fid" extension may serve this purpose. REQ-3: It MUST be possible to define who is allowed to create, change and remove a floor in a conference. We assume that the conference owner always has this privilege and may also P. Koskelainen/H. Schulzrinne/J. Ott [Page 5]
Internet Draft Floor control reqs. October 31, 2002 authorize other entities, via conference policy. REQ-4: A participant with appropriate privileges MUST be able to create a floor with specific parameters, such as how many simultaneous users are allowed to access the resource. It MUST be possible to modify these parameters during the lifetime of a floor. REQ-5: It MUST be possible to use a chair-controlled floor policy in which the floor controller notifies the floor chair and waits for the chair to make a decision. This enables the chair to fully control who has the floor. The server MAY forward all requests immediately to chair, or it may do filtering and send only occasional notifications to chair. REQ-6: Participants MUST be able to request (claim) a floor and give additional information about the request, such as the topic of the question for an audio floor. REQ-7: A floor holder MUST be able to release a floor. REQ-8: The chair or controller MUST be able to revoke a floor from its current holder. REQ-9: It MUST be possible to grant a floor to a participant. REQ-10: It MUST be possible to get and set at least the following floor parameters: - who is floor control chair (this does not have to be the conference owner); - floor control policy (such as chair-controlled, first- come first-served, random); - the number of simultaneous floor holders. REQ-11: Floor policies MAY support time limits that automatically pass the floor to the next-in-line after a preset time interval. REQ-12: It MUST be possible for a user with appropriate conference privileges to change the chair for a floor. REQ-13: It MAY be possible for a user to request that a media session should be floor-controlled. The requestor does not necessarily become the floor chair. (For example, a P. Koskelainen/H. Schulzrinne/J. Ott [Page 6]
Internet Draft Floor control reqs. October 31, 2002 conference creator may designate a set of media as a latent floor that automatically becomes floor controlled as soon as a member requests it.) REQ-14: Different floors may have different chairs. REQ-15: Bandwidth and terminal limitations SHOULD be taken into account in order to ensure that floor control can be efficiently used in mobile environments. REQ-16: Conference members and the chair MUST be able to determine who has the floor and who has requested the floor. REQ-17: Conference members and the chair MUST be able to be notified when the floorholder changes and when a new floor request is being made. REQ-18: It should be possible to name custom floor control policies, both with local meaning only and global registration. REQ-19: It may be desirable to support a floor control mechanism where users without specialized software can request the floor. (For example, a floor control mechanism could utilize specific instant messages.) 7 Open Issues o Support multiple simultaneous chairs for one floor? o Support for privacy (especially for REQ-16) 8 Acknowledgements The authors would like to thank Xiaotao Wu, Sanjoy Sen, Jonathan Rosenberg, Brian Rosen, Nermeen Ismail, Rohan Mahy, and Orit Levin for their comments. 9 Authors' Addresses Petri Koskelainen Nokia Visiokatu 1, 33720 Tampere Finland electronic mail: petri.koskelainen@nokia.com P. Koskelainen/H. Schulzrinne/J. Ott [Page 7]
Internet Draft Floor control reqs. October 31, 2002 Henning Schulzrinne Dept. of Computer Science Columbia University 1214 Amsterdam Avenue, MC 0401 New York, NY 10027 USA electronic mail: hgs@cs.columbia.edu Joerg Ott <jo@tzi.org> Universitaet Bremen MZH 5180 Bibliothekstr. 1 D-28359 Bremen Germany tel:+49-421-201-7028 sip:jo@tzi.org 10 Bibliography [1] J. Rosenberg, "A Framework for Conferencing with the Session Initiation Protocol, " Internet Draft, Internet Engineering Task Force, Oct 2002, Work in progress. [2] Dommel, H.-P., and Garcia-Luna-Aceves, J., "Floor control for activity coordination in networked multimedia applications.," In Proc. of 2nd Asian-Pacific Conference on Communications (APCC (Osaka, Japan, June 1995). [3] P. Koskelainen, H. Schulzrinne, and X. Wu, "A sip-based conference control framework," in The 12nd International Workshop on Network and Operating System Support for Digital Audio and Video (NOSSDAV) , (Miami Beach, Florida), May 2002. [4] J. Rosenberg, H. Schulzrinne, G. Camarillo, A. Johnston, J. Peterson, R. Sparks, M. Handley, and E. Schooler, "SIP: session initiation protocol," RFC 3261, Internet Engineering Task Force, June 2002. [5] C. Bormann, D. Kutscher, J. Ott, and D. Trossen, "Simple conference control protocol service specification," Internet Draft, Internet Engineering Task Force, Mar. 2001. Work in progress. [6] X. Wu, P. Koskelainen, H. Schulzrinne, and C. Chen, "Use SIP and SOAP for conference floor control," Internet Draft, Internet Engineering Task Force, Apr. 2002. Work in progress. [7] O. Levin et al. , "Requirements for tightly coupled SIP conferencing," Internet Draft, Internet Engineering Task Force, July P. Koskelainen/H. Schulzrinne/J. Ott [Page 8]
Internet Draft Floor control reqs. October 31, 2002 2002. Work in progress. [8] S. Bradner, "Key words for use in RFCs to indicate requirement levels," RFC 2119, Internet Engineering Task Force, Mar. 1997. Full Copyright Statement Copyright (c) The Internet Society (2002). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Table of Contents 1 Introduction ........................................ 1 2 Conventions of This Document ........................ 2 3 Definitions ......................................... 2 4 Model ............................................... 3 5 Integration with Conferencing ....................... 4 6 Requirements ........................................ 4 7 Open Issues ......................................... 7 P. Koskelainen/H. Schulzrinne/J. Ott [Page 9]
Internet Draft Floor control reqs. October 31, 2002 8 Acknowledgements .................................... 7 9 Authors' Addresses .................................. 7 10 Bibliography ........................................ 8 P. Koskelainen/H. Schulzrinne/J. Ott [Page 10]