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supported by a multiple description codec (MDC), in which a server provides
several different stripes of video with different quality. A key feature in this
streaming environment is that during each streaming session, multiple mul-
ticast trees are used, each of which is for sending different stripes of video.
This is illustrated in Figure 5.13. With such a streaming structure, a peer
can logically join different trees simultaneously at a different position in each
tree. Specifically, when a peer joins a certain multicast tree at a higher level
(e.g., peer A in the tree for stripe II), it needs to provide a larger uploading
bandwidth to serve the lower level peers in the same tree. On the other hand,
a peer can also join a tree as a leaf so that it becomes a pure recipient in the
tree.
Source
Peer A
Peer B
Peer C
Others
Stripe I
Stripe
II
Stripe
III
Internal
nodes
Leaf
nodes
FIGURE 5.13: Layered video streaming using multiple multicast trees [hua
Chu and Zhang, 2004].
With this model, Chu and Zhang [hua Chu and Zhang, 2004] then studied
the effects of different degrees of altruism. They used a parameter K = f /r,
where f is the total uploading bandwidth provided by a peer and r is its
total downloading bandwidth. Thus, a larger value of K indicates a higher
degree of altruism for the peer. Similar to many other P2P sharing systems
described above in this chapter, a peer with a higher value of K can enjoy a
better performance (in terms of media quality in the streaming application).
Simulation results indicate that a small average value of K (e.g., 1.5) can
already improve the overall performance of the whole system.
Shrivastava and Banerjee [vivek Shrivastava and Banerjee, 2005] demon-
strated that streaming based on a multicast structure could be a result of
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