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

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

Outline

• Motivation

• Services

• Approach

• Protocol• However, no detailed protocol description (see

paper)

• Conclusion and Outlook

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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)

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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

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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

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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

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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

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Example: Floor Asking

CheckFloor Context

Send out locally

Forward globally

Relay locally

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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

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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

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Future Work

• Naming scheme for floors• Decimal numbers recommended

• Other failure modes• Include floor holder failure• …

• Protocol prototyping, simulations,…

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Thank You !

For further information:

dirk.trossen@nokia.com