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
draft-koskelainen-xcon-floor-control-req-00
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Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
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)
[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 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",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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
to.
(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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owner);
- 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
messages.)
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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
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-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
Nokia
P.O. Box 100 (Visiokatu 1)
Tampere FIN-33721
Finland
EMail: petri.koskelainen@nokia.com
Henning Schulzrinne
Columbia University
1214 Amsterdam Avenue
New York 10027
USA
EMail: hgs@columbia.edu
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Joerg Ott
Bremen Univ.
Germany
EMail: jo@tzi.uni-bremen.de
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