1 © NOKIA IPTel2001.PPT/ 04-03-2001 / DOT Scalable Floor Control in Conferencing Environments : The RBone Approach Dirk Trossen Nokia Research Center Boston.

1 © NOKIA IPTel2001.PPT/ 04-03-2001 / DOT

Scalable Floor Control inScalable Floor Control inConferencing Environments :Conferencing Environments :

The RBone ApproachThe RBone Approach

Dirk TrossenNokia Research Center Boston

IP Telephony Workshop 2001


Outline

• Motivation

• Services

• Approach

• Protocol• However, no detailed protocol description (see

paper)

• Conclusion and Outlook


What Scenarios ?

• Enterprise scenarios

• Shared lectures

Why Floor Control ?

• Regulating access to resources in conference scenarios, e.g.,

• Right to speak• Right to send video to common MC group• Right to control shared application

Motivation

Map Social Protocols onto distributed environments (tight control)

Connecting few multicast-capable LANs withpossibly larger number of participants

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What’s provided ?

• Provision of floors, identified by unique name• Decimal naming recommended• No temporary inconsistencies

• Provided services :• Grab floor (exclusive use)• Inhibit floor (non-exclusive use)• Release floor• Test floor status• Ask current holder for floor• Give floor to other user• Query floor holder list

very similar to T.122 services (except floor holder list)


ApproachRelated Work

• Tree-based approaches

• Multicast-based approaches

Users are routing requests

Multicast-routing is used

• Stars as simplest form• Shortest-path routing (SCCS)• Routing to topmost (ITU T.122)

• Tree of inter-connected users(not necessarily binary)

• Multicast each request reliably• Large response time

• Temporary inconsistency (e.g., NTE)• Resolve inconsistency on application level


FloorControlIsland

ConferenceManagementGroup

• Use multicast on local level

Combine tree- and multicast-based approaches

ApproachIdea

• Use floor-control-specific unicast routing on global level• Choose dedicated users to route requests

RBone

RBone provider


Assumptions

• Different multicast groups are known• Using SDP for description• Using SAP or similar for announcement

• Unicast Transport• Connection failure indication provided

• Multicast transport• Globally ordered messages• Reliability• Using local multicast scope only

• Each user maintains local floor context, i.e., name, status, and local holders for each floor


Protocol Functionality

Environment Maintenance

Global:• Establish RBone• Extend RBone• Repair Rbone

Local:• Join FCI• Heartbeat

Service Requests

• Grab• Inhibit• Release• Test• Ask• Give• Holder List

Routing of service requests:• First, send request to local FCI• if necessary, local RBone provider forwards request using Rbone decision based on local floor context• if necessary, local RBone provider relays RBone messages on FCI


Example: Floor Asking

CheckFloor Context

Send out locally

Forward globally

Relay locally


Failure Recovery

• RBone connection fails• Both RBone providers start RBone extend operation

• Local RBone provider quits• First, selection of new local RBone provider• Second, new RBone provider starts RBone extend

operation• Local RBone provider fails

• Detected by heartbeat• Selection of new RBone provider depending on age of

local users• New RBone provider starts RBone extend operation

Service requests are handled appropriately during repair

• Floor holder fails (or quits without releasing)• Currently not covered, but local heartbeat might be

used


Conclusions

Presented floor control protocol for conference course control

• Related approaches based on either unicast or multicast schemes

Idea: Use multicast on local, unicast on global level

Scenarios:

Several MC-capable islands, e.g.,– Enterprise meetings– Shared lectures

• Protocol includes maintenance & service request functionality

• Failure recovery also addressed


Future Work

• Naming scheme for floors• Decimal numbers recommended

• Other failure modes• Include floor holder failure• …

• Protocol prototyping, simulations,…


Thank You !

For further information:

[email protected]

1 © NOKIA IPTel2001.PPT/ 04-03-2001 / DOT Scalable Floor Control in Conferencing Environments : The RBone Approach Dirk Trossen Nokia Research Center Boston.

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