ON DESIGING ENDUSER MULTICAST FOR MULTIPLE VIDEO SOURCES

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ON DESIGING END-USER MULTICAST FOR MULTIPLE
VIDEO SOURCES

• Y.Nakamura, H.Yamaguchi, A.Hiromori, K.Yasumoto,
  T.Higashino and K.Taniguchi
• Osaka University
• Nara Institute of Science and Technology

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Goal

• Realizing Multi-party video conferencing systems
• Many-to-many multicast application which consists
  of hundreds of users
• User hosts exchange multiple video streams in
  real-time
• Efficient use of bandwidth is required

Internet
3
Application Layer Multicast (ALM)

• ALM is multicast on overlay networks
• End users act as multicast routers
• Does not require special hardware such as IP
  multicast enable routers
• Application-specific routing protocols can be
  designed
• More efficient than Unicast because a sender does
  not need to send data to all receivers

Unicast
ALM
A
A
B
S
B
S
C
C
D
D
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Design Issues

• Each video uses some amount of bandwidth on
  overlay networks
• ?In delivering multiple video streams, they
  compete for bandwidth on overlay links
• Users may have priority requirements to video
  streams
• e.g. users may prefer the speakers video than
  audiences

Internet
5
End-user Multicast for Multi-party Application
(Emma)

• New ALM protocol for multi-party communication
  systems
• Users construct overlay networks
• Each user host sends its own video continuously
  and receives some of other user hosts video
  streams on overlay networks
• The sending and receiving video streams are
  controlled based on users priority requirement
  given to the video streams

Red
Red
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Users Join

• When a new user wants to join a session, the user
  gets the current users addresses from a central
  server
• The user measures delay with these users and
  establish overlay links with the closest two or
  three users to construct mesh-like overlay
  networks
• Existing routing trees are expanded so that they
  do not overlap each other as long as they can

E
C
A

• Routing tree can be expanded with
• small delay from each source
• less duplication

A133.1.xx.xx B129.3.yy.yy C
Address Management Server
B
D
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Priority-based Video Delivery

• Each user specifies a priority requirement as a
  priority value to each video stream.
• A request message with a priority value is
  forwarded to the video source user
• But there is no enough bandwidth on the path

C
A

A 8
B 5
C 6
D15
B
D
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Priority-based Video Delivery

• In forwarding the message, the followings are
  calculated step by step
• how to stop existing video streams
• how to minimize the loss of priority values
• If the loss of priority value lt the gain of
  priority value by accepting the request
• The existing streams are stopped and the new
  stream is delivered

C
A

A 8
The sum of the satisfied priority values becomes
larger than before
B 5
C 6
D15
B
D
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Users Leave and Failure

• Even if an user host leaves, trees can be
  recovered
• When a user leaves, the simplest way to recover
  tree is to let child nodes connect with the
  parent of the leaving user
• However, this may cause the concentration of
  overlay links to the parent user
• To prevent this, each user periodically collects
  the information of of overlay links of its
  descendant users
• When a user leaves, its parent can immediately
  suggest the children of the leaving user where to
  connect again

D,F,G
C,D
C
A
G
User E leaves
Recovery can be done quickly without
causing unbalanced trees
B
H
F
D
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Performance Evaluation

• We have developed a simulator for evaluating
  performance of Emma
• Written in an object oriented scripting language
  Ruby
• Network model
• Hierarchical topology model based on tiers
• 146 nodes, 66 users
• Users give priority values to video by Zipfs law

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Users Satisfaction

• The variation of average of satisfied priority
  value per user
• Compared with First-Come-First-Serve (FCFS)
  method which accepts user requests in a greedy
  manner
• Simulation Scenario
• Until 5 units of time, 66 users joined
• After 21 units of time, 1 user joins or leaves at
  one time

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Users Satisfaction

• Emma achieves 1.5 times higher values than FCFS
• Under the presence of users leave and join,
  priority values are kept high

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Routing Tree Duplication on Overlay Link

• of routing trees on an overlay link
• Less duplication is desirable
• Simple estimation of average duplication in the
  ideal case
• of users ( of users -1) / of total
  overlay links
• about 20
• ?Measure the of routing trees on each overlay
  link

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Routing Tree Duplication on Overlay Link

• 80 of overlay links have at most 10 routing trees

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Conclusion

• We have proposed new ALM protocol called Emma
• Avoiding resource competition
• From the experimental results
• Higher satisfaction of users than a simple method
• Even though some users leave from or join to a
  session, users satisfaction is kept high
• We have designed and implemented Java middleware
  based on Emma
• (http//www-tani.ist.osaka-u.ac.jp/software/s2.htm
  l)

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