Requirements for Conference Control

1
Requirements for Conference Control
Henning Schulzrinne

• Xiaotao Wu
• Petri Koskelainen
• Clayton C. Chen
• Columbia University/Nokia

2
Conference Control

• Focus on media-independent control (see Orit
  Levins talk for media issues)
• Conference models
• centralized lowest-hanging fruit
• centralized with replication seems similar
• fully meshed probably same mechanisms, but
  harder to coordinate (distributed system)
• multicast may also work for SSM
• Core property single media choke point

3
Taxonomy of functions (incomplete)

• Needed throughout conference life cycle
• Create new conference
• properties duration, media, user limit, ...
• mass-invitation
• but is this needed beyond the current ad-hoc
  conference creation (INVITE sipmy-new-conference_at_
  server)?
• Admit users
• similar to presence subscriber problem?
• proactive policy (dont admit .fbi.gov) ? CPL?
• individual decisions Alice wants to join
• Eject users (less important?)
• Shared resource access, aka floor control

4
Functions

• Not every conference needs all functions
• Web interface can be done, but hard to script
• Dont assume single person has multiple roles
• bouncer (sergeant-at-arms) vs. moderator
• Need to deal with moderator failure
• distributed leader election problem is hard
• may want to punt
• Provide mechanisms, avoid guessing at policy
• only admit Joe if fewer than 4 participants and
  if 65 of participants agree

5
Floor control

• General management of shared resources
• audio channel (typically, one)
• video (limited by bandwidth, screen)
• whiteboard and shared applications (one, but also
  multiple pointers)
• Managed by
• automated queuing
• policy can be messy (priority to speakers that
  have talked for less than 5 minutes)
• suggestion punt on policy
• one or more moderators

6
Floor control requirements

• Create a managed resource
• zero, one or multiple media
• Remove managed resource
• Change resource configuration
• moderator, users, concurrency
• Request resource
• Grant resource
• Revoke resource
• including pending requests
• Release resource
• Reorder resource claims

7
Commonalities across functionalities

• Functions are largely orthogonal
• But share communication needs
• asynchronous events
• Bob joined conference (sip-call-package)
• Carol has released floor
• David has requested floor
• commands to conference
• avoid commands directly to participants

8
Questions

• How hostile is the conference?
• If participants basically trust each other,
  moderator failure is much easier to deal with
• Define trusted subgroup?
• Panel discussion model panel vs. mob audience
• Scaling requirements?
• Primarily notifications are issue
• Centralized conference model imposes some
  limitations, but can still be hundreds
• REFER can provide some functionality (invite,
  eject)

9
Summary

• Conference control probably misnomer
• Keep media stream control separate may be
  needed for unicast just as much
• Dont require event subscription for
  participation (except maybe for moderator)
• Divide into components, possibly prioritize
• conference creation and deletion
• user admission
• resource management