Information Technology Reference
In-Depth Information
Web server
Tracker
(4)
(1)
(2)
(3)
New leecher
A Swarm of Seeds and Leechers
Figure 1.24
BitTorrent for file sharing.
(a)
Whole file
(b)
Sliding window
Playback Point
Figure 1.25
Buffer snapshots of (a) BitTorrent and (b) CoolStreaming. (From Liu, J., Rao, S., Li, B., and Zhang,
H.,
Proceedings of the IEEE,
96, 11-24, 2008. With permission.)
BitTorrent and mesh-pull P2P streaming systems like CoolStreaming dif-
fer mainly in their buffer management. Figure 1.25 shows the buffer snap-
shots of BitTorrent and CoolStreaming.
1.4.2.1 CoolStreaming (DONet)
CoolStreaming, developed by Hong Kong University of Science and
Technology, is one of the earliest P2P streaming systems. The first version of
CoolStreaming uses a mesh-pull mechanism to collect video chunks from
peers. Each video chunk contains about one second of content. A peer keeps
about 120 video chunks in the buffer. A buffer map with a 2-byte offset and
120 bits for identifying the video chunks is used to exchange existing video
c hu n k s a mong p e er s. Pe er s t r y to ide nt i f y t he v ide o c hu n k s t hey wa nt ba s e d on
the buffer maps and send out requests for the video chunks once identified.
