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Versions: 00 01                                                         
Transport Area                                            H. Schulzrinne
Internet-Draft                                                     X. Wu
Expires: November 30, 2003                           Columbia University
                                                          P. Koskelainen
                                                                  J. Ott
                                                          Uni Bremen TZI
                                                               June 2003

                Requirements for Floor Control Protocol

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
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   This Internet-Draft will expire on November 30, 2003.

Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.


   This document defines the requirements for floor control in a
   multi-party conference environment.

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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

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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)

   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 standalone separate
   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 utilized here.

   This document can be used with other documents, such as Conferencing
   framework document [3].

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2. Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119.

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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.

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4. Model

   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 centralized conference server controls the floors at least in the
   signaling level. Controlling also the actual (physical) media
   resources (e.g. audio mixer) is highly recommended, but beyond the
   scope of this document.

   Note that the floor is a concept coupled with one or more media
   streams.  The creation of the media session itself is defined
   elsewhere.  A participant with appropriate privileges may create a
   floor by defining that one or more existing media sessions are now
   floor- controlled, and apppoint a floor chair.

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5. Integration with Conferencing

   Floor control itself does not support privileges such as handing over
   chair privileges to another users (or taking them away). Instead,
   some external mechanism, such as conference management (e.g. CPCP or
   internal web-interface for policy manipulation) is used for that.

   The conference policy (and 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 also the conference policy that defiens 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 conference policy server. Therefore,
   communication mechanisms between floor control server and other
   central conferencing entities are not defined at this point.

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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 and where requests for the floor should be addressed

   (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 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 authorize other
   entities, via the conference policy.

   REQ-4: 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 the chair.

   REQ-5: 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-6: A floor holder MUST be able to release a floor.

   REQ-7: The chair or controller MUST be able to revoke a floor from
   its current holder.

   REQ-8: It MUST be possible to grant a floor to a participant.

   REQ-9: 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

   - whether "no floor control" is applied (free for all policy)

   - what is the floor control policy (such as chair-controlled, first-
   come first-served, random);

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   - the number of simultaneous floor holders.

   REQ-10: Floor policies MAY support time limits that automatically
   pass the floor (e.g. to the next-in-line) or revoke the floor after a
   preset time interval.

   REQ-11: It MUST be possible for a user with appropriate conference
   privileges to change the chair for a floor.

   REQ-12: Bandwidth and terminal limitations SHOULD be taken into
   account in order to ensure that floor control can be efficiently used
   in mobile environments.

   REQ-13: 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-14: 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.)

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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

   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

   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.

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8. Acknowledgements

   The authors would like to thank IETF conferencing design team and
   Sanjoy Sen, Eric Burger, Brian Rosen, and Nermeen Ismail for their

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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.

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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

   [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

   EMail: hgs@cs.columbia.edu

   Xiaotao Wu
   Columbia University
   1214 Amsterdam Avenue
   New York  10027

   EMail: xiaotaow@cs.columbia.edu

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   Petri Koskelainen
   P.O. Box 100 (Visiokatu 1)
   Tampere  FIN-33721

   EMail: petri.koskelainen@nokia.com

   Joerg Ott
   Uni Bremen TZI


   EMail: jo@tzi.uni-bremen.de

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