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file sharing protocol. When joining the network, a peer first connects to a
tracker to get the channel list. After deciding what channel to watch, the
peer then registers its information with the tracker server and downloads an
initial peer list. While trying to connect to peers in the initial peer list, it also
exchanges peer list information with other peers, so as to collect more peers
for best parent selection.
PPLive divides the streamed video into smaller video chunks. A buffer
map records the existing video chunks in a peer. Peers then exchange buffer
map information before pulling data from other peers. Figure 1.28 shows a
conceptual diagram of the buffer map.
Figure 1.29 shows a more detailed working mechanism of PPLive. It shows
that the protocol used in PPLive is very similar to BitTorrent with the differ-
ence being the time constraint of the buffer data. That is, the P2P streaming
Tracker
server
1) Channel list download
2) Peer registration
3) Peer list download
PC
1
2
PC
PC
PC
Figure 1.27
Channel and peer discovery in PPLive. (From Hei, X., Liang, C., Liang, J., Liu, Y., and Ross, K.,
Multimedia, IEEE Transactions , 9, 1672-87, 2007. With permission.)
BM width
Offset
111111 10 00
11
000
1
. . .
. . .
0
Time
BM
playable
video
Gap
Figure 1.28
Buffer Map. (From Hei, X., Liang, C., Liang, J., Liu, Y., and Ross, K., Multimedia, IEEE Transactions ,
9, 1672-87, 2007. With permission.)
 
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