Transport Area H. Schulzrinne Internet-Draft X. Wu Expires: July 8, 2004 Columbia University P. Koskelainen Nokia J. Ott Uni Bremen TZI January 8, 2004 Requirements for Floor Control Protocol draft-ietf-xcon-floor-control-req-00 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 July 8, 2004. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This document defines the requirements for floor control in a multi-party conference environment. Schulzrinne, et al. Expires July 8, 2004 [Page 1] Internet-Draft fcp-req January 2004 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions Used in This Document . . . . . . . . . . . . . . 4 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5. Integration with Conferencing . . . . . . . . . . . . . . . . 7 6. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 8 7. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 10 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 Normative References . . . . . . . . . . . . . . . . . . . . . 12 Informative References . . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 13 Intellectual Property and Copyright Statements . . . . . . . . 15 Schulzrinne, et al. Expires July 8, 2004 [Page 2] Internet-Draft fcp-req January 2004 1. Introduction Conference applications often have 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 resource. The floor is an individual temporary access or manipulation permission for a specific shared resource (or group of resources) [7]. Floor control is an optional feature for conferencing applications. SIP [2] conferencing applications may also decide not to support this feature at all. Two-party applications may use floor control outside conferencing, although the usefulness of this kind of scenario is limited. Floor control may be used together with conference policy control protocol (CPCP) [8], or it may be used as independent standalone protocol, e.g. with SIP but without CPCP. Floor control has been studied extensively over the years, (e.g. [9], [7], [6]) therefore earlier work can be leveraged here. The present document describes the requirements for a floor control protocol. As a requirements specification, the document makes no assumptions about the later implementation of the respective requirements as parts of one or more protocols and about the entities implementing it/them and their roles. This document may be used in conjunction with other documents, such as the Conferencing framework document [3]. In particular, when speaking about a floor control server, this entity may be identical to or co-located with the focus or a conference policy server defined in the framework document, while participants and floor chairs referred to in this specificiation may be regular participants as introduced in the conferencing framework document. The term "floor control protocol" is used in an abstract sense in this specification and may ultimately be mapped to any of the existing conference control or other signaling protocols (including CPCP and SIP). But defining those relationships is left to a concrete floor control protocol specification. Schulzrinne, et al. Expires July 8, 2004 [Page 3] Internet-Draft fcp-req January 2004 2. Conventions Used in This Document 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. Schulzrinne, et al. Expires July 8, 2004 [Page 4] Internet-Draft fcp-req January 2004 3. Terminology This document uses the definitions from [3]. Additional definitions: Floor: A permission to temporarily access or manipulate a specific shared resource or set of resources. Conference owner: A privileged user who controls the conference, creates floors and assigns and deassigns floor chairs. The conference owner does not have to be a member in a conference. Floor chair: A user (or an entity) who manages one floor (grants, denies or revokes a floor). The floor chair does not have to be a member in a conference. Floor control: A mechanism that enables applications or users to gain safe and mutually exclusive or non-exclusive input access to the shared object or resource. Floor control server: A logical entity that maintains the state of the floor(s) including which floors exists, who the floor chairs are, who holds a floor, etc. Requests to manipulate a floor are directed at the floor control server. Floor request set: A logical data structure holding all requests for a particular floor at a given point in time. Floor holder set: A logical data structure identifying all participants who currently hold the floor. Schulzrinne, et al. Expires July 8, 2004 [Page 5] Internet-Draft fcp-req January 2004 4. Model The model for floor control comprises three logical entities: a single floor control server, one or more floor chairs (moderators), and any number of regular conference participants. A floor control protocol is used to convey the floor control messages among the floor chairs (moderators) of the conference, the floor control server, and the participants of the conference. A centralized architecture is assumed in which all messages go via one point, the floor control server. Processing (granting or rejecting) floor control requests is done by the one or more floor chairs or by the server itself, depending on the policy. Floor requests from the participants are received by the floor control server and kept in an -- at the level of the floor control protocol -- "unordered" floor request set. The current floor holders are reflected in a current floor holder set. Floor chairs are capable of manipulating both sets to e.g. grant, revoke, reject, and pass the floor. The order in which requests are processed, whether they are granted or rejected, how many participants obtain a floor simultaneously, is determined by a higher layer application operating on these sets and is not confined by the floor control protocol. A floor is associated with one or more media sessions. The centralized conference server manages the floors and thus controls access to the media sessions. There are two aspects to this: 1) The server maintains and distributes consistent state information about who has a certain floor at a certain point in time and does so following some rule set. This provides all participants with the necessary information about who is allowed to e.g. speak, but relies on a cooperative behavior among all participants. 2) In addition, to prevent individuals from ignoring the "hints" given by the floor control server, the latter may -- e.g. in cooperation with other functional entities -- enforce compliance with floor status, e.g. by blocking media streams from participants not entitled to speak. The floor control server controls the floors at least at the signaling level (1); actively controlling also the actual (physical) media resources (2) is highly recommended, but beyond the scope of this document. As noted in the introduction, an actual protocol specification fulfilling the requirements defined in this memo may map the components of the above model onto the conferencing components defined in the conferencing framework document. Some of these aspects are discussed briefly in the next subsection. Schulzrinne, et al. Expires July 8, 2004 [Page 6] Internet-Draft fcp-req January 2004 5. Integration with Conferencing Floor control itself does not support privileges such as creating floors and appointing floor chairs, handing over chair privileges to other users (or taking them away). Instead, some external mechanism, such as conference management (e.g. CPCP or web interface for policy manipulation) is used for that. The conference policy (and thus the conference owner or creator) defines whether floor control is in use or not. Actually enforcing conference media distribution in line with the respective media's floor status (e.g. controlling an audio bridge) is beyond the scope of this document. Floor control itself does not define media enforcement. It is up to the conference and media policies to define which media streams may be used in a conference and which ones are floor controlled. Typically, the conference owner creates the floor(s) using conference policy control protocol (or some other mechanism) and appoints the floor chair. The conference owner can remove the floor anytime (so that a media session is not floor-controlled anymore) or change floor chair or floor parameters. The floor chair just controls the access to the floor(s), according to the conference policy. A floor control server is a separate logical entity, typically co-located with focus and/or conference policy server. Therefore, the floor control server can interact with focus, conference Policy Server and media servers as needed. Communication mechanisms between floor control server and other central conferencing entities are not defined at this point. Schulzrinne, et al. Expires July 8, 2004 [Page 7] Internet-Draft fcp-req January 2004 6. Requirements REQ-1: It MUST be possible to announce to participants that a particular media session (or group of media sessions) is floor-controlled. (This is a requirement for session protocol, i.e. SIP. SDP's "a" line offers one possible indication.) REQ-2: It MUST be possible to group several media sessions in a conference together so that one floor applies to the group. 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 authorize other entities, via the conference policy. (This is a requirement for CPCP rather than an FCP requirement.) REQ-4: It MUST be possible to use a chair-controlled floor policy in which the floor control server 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 the floor chair, or it may do filtering and send only occasional notifications to the chair. REQ-5: Participants MUST be able to request (claim) a floor. REQ-6: It SHOULD be possible for a user requesting a floor to give additional information about the request, such as the topic of the question for an audio floor. In some scenarios, the floor chair may use this information when granting the floor to the user, or when making manipulation to the floor sets at the server. REQ-7: It MUST be possible to grant a floor to a participant. REQ-8: A participant MUST be informed that she has been granted the floor. REQ-9: It MUST be possible to reject a participant's floor request. REQ-10: A participant MUST be informed that his floor request has been rejected. REQ-11: The floor chair or moderator MUST be able to revoke a floor from (one of) its current holder(s). REQ-12: A participant MUST be informed that the floor was revoked Schulzrinne, et al. Expires July 8, 2004 [Page 8] Internet-Draft fcp-req January 2004 from her. REQ-13: A participant SHOULD be informed that her floor request is pending and will be processed later. REQ-14: A floor holder MUST be able to release a floor. REQ-15: It SHOULD be possible to get and set various floor related parameters. Note that not all parameters maintained for a floor are also interpreted by the floor control protocol (e.g. floor policy descriptions may be stored associated with a floor but may be interpreted by a higher layer application. (For example, it may be useful to see who the floor chair is, what kind of policy is in use, time limits, number of simultanous floor holders and current floor holder.) REQ-16: It MUST be possible for a user with appropriate conference privileges to change the chair for a floor. (This is rather a requirement for the conference policy control protocol than for the floor control protocol.) REQ-17: Bandwidth and terminal limitations SHOULD be taken into account in order to ensure that floor control can be efficiently used in mobile environments. It should be noted that efficient communication by means of minimal sized messages may contradict the desire to express reasons for requesting a floor (as per REQ-6) along with other information. Therefore, a floor control protocol SHOULD be designed in a way that it allow for expressive as well as minimal messaging, as (negotiable) configuration option and/or selectable on a per-message basis. REQ-18: Conference members and the chair MUST have the capability to learn who has the floor and who has requested the floor. (Note: Conference policy may prevent members seeing this.) REQ-19: It MUST be possible to notify conference members and chair about the floorholder changes and when a new floor request is being made. (Note: Conference policy may prevent members seeing this.) REQ-20: There MAY be operations to manipulate the request set available for floor chair(s). Schulzrinne, et al. Expires July 8, 2004 [Page 9] Internet-Draft fcp-req January 2004 7. Open Issues - Support for privacy, e.g. the following: floor claimer must be able to indicate privacy preference, and the ability to hide floor chair's identity. Preliminary proposal: RRQ-a: It MUST be possible for the floor requester to indicate her privacy preference. The privacy preferences MUST include the following options: anonymous: the participants (including the floor chair) cannot see the floor requester's identity. The floor chair grant the floor based on the claim id and the topic of the claim. known to the floor chair: only the floor chair is able to see the floor requester's identity; all other participants do not obtain this information. public: all the participants can see the floor requester's identity. RRQ-b: It MUST be possible to hide the identity of a floor chair from a subset or all participants of a conference. Schulzrinne, et al. Expires July 8, 2004 [Page 10] Internet-Draft fcp-req January 2004 8. Acknowledgements The authors would like to thank IETF conferencing design team and Marcus Brunner, Keith Drage, Sanjoy Sen, Eric Burger, Brian Rosen, and Nermeen Ismail for their feedback. Schulzrinne, et al. Expires July 8, 2004 [Page 11] Internet-Draft fcp-req January 2004 Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, BCD 14, March 1997. [2] Rosenberg et al., J., "SIP: Session Initiation Protocol", RFC 3261, June 2002. [3] Rosenberg, J., "A Framework for Conferencing with the Session Initiation Protocol", draft-rosenberg-sipping-conferencing-framework-01 (work in progress), February 2003. Schulzrinne, et al. Expires July 8, 2004 [Page 12] Internet-Draft fcp-req January 2004 Informative References [4] Koskelainen, P., Schulzrinne, H. and X. Wu, "Additional Requirements to Conferencing", October 2002. [5] Wu, X., Schulzrinne, H. and P. Koskelainen, "Use of SIP and SOAP for conference floor control", January 2003. [6] Koskelainen, P., Schulzrinne, H. and X. Wu, "A sip-based conference control framework", Nossdav'2002 Miami Beach, May 2002. [7] Dommel, H. and J. Garcia-Luna-Aceves, "Floor control for activity coordination in networked multimedia applications", Proc. of 2nd Asian-pacific Conference on Communications APPC, Osaka Japan, June 1995. [8] Koskelainen, P. and H. Khartabil, "An Extensible Markup Language (XML) Configuration Access Protocol (XCAP) Usage for Conference Policy Manipulation", draft-koskelainen-xcon-xcap-cpcp-usage-01 (work in progress), October 2003. [9] Borman, C., Kutchner, D., Ott, J. and D. Trossen, "Simple conference control protocol service specification", draft-ietf-mmusic-sccp-00 (work in progress), March 2001. Authors' Addresses Henning Schulzrinne Columbia University 1214 Amsterdam Avenue New York 10027 USA EMail: hgs@cs.columbia.edu Xiaotao Wu Columbia University 1214 Amsterdam Avenue New York 10027 USA EMail: xiaotaow@cs.columbia.edu Schulzrinne, et al. Expires July 8, 2004 [Page 13] Internet-Draft fcp-req January 2004 Petri Koskelainen Nokia P.O. Box 100 (Visiokatu 1) Tampere FIN-33721 Finland EMail: petri.koskelainen@nokia.com Joerg Ott Uni Bremen TZI Bibliothekstr. 1 Bremen D-28359 Germany EMail: jo@tzi.uni-bremen.de Schulzrinne, et al. Expires July 8, 2004 [Page 14] Internet-Draft fcp-req January 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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