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Transport Area                                            P. Koskelainen
Internet-Draft                                                     Nokia
Expires: December 22, 2003                                H. Schulzrinne
                                                     Columbia University
                                                                  J. Ott
                                                            Bremen Univ.
                                                           June 23, 2003

                     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
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   This Internet-Draft will expire on December 22, 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. 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.  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). 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. 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 existing media session(s) is 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.

   Conference policy (and conference owner or creator) decides whether
   floor control is in use or not. Actual conference media enforcing
   (e.g. controlling audio bridge) are beyond the scope of this
   document. Floor control itself does not define media enforcing. It is
   also conference policy about what media streams can be in a
   conference, and which ones are floor controlled.

   Typically, conference owner creates the floor(s) using floor control
   protocol (or some other mechanism) and appoints the floor chair.
   Conference owner can remove the floor anytime (so that media is not
   floor controlled anymore), or change floor chair or floor parameters.

   Floor chair just controls the access to the floor(s), according to
   the conference policy.

   Floor control server is a separate logical entity, typically
   co-located with focus and conference policy server. Therefore,
   communication between floor control server and other conferencing
   entities (except with the client) does not need to be defined.

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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 session) 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 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 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
   and terminate 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 the 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

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   - what is the 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 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.

   OPEN ISSUE: Is this needed?

   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 have the capability to
   learn who has the floor and who has requested the floor. (Note:
   Conference policy may prevent members seeing this.)

   REQ-17: 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-18: 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

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7. Open Issues

   - separation of floor creation and floor granting

   - support for privacy (esp. REQ-16)

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8. Acknowledgements

   The author would like to thank IETF conferencing design team and
   Xiaotao Wu, Sanjoy Sen, Eric Burger, Brian Rosen, and Nermeen Ismail
   for their feedback.

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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-00
        (work in progress), June 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

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

   EMail: petri.koskelainen@nokia.com

   Henning Schulzrinne
   Columbia University
   1214 Amsterdam Avenue
   New York  10027

   EMail: hgs@columbia.edu

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   Joerg Ott
   Bremen Univ.


   EMail: jo@tzi.uni-bremen.de

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