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in video communication systems where a packet level FEC is used. The use of
FEC enables the receiver to recover the lost packets caused by corrupted paths.
To take advantage of path diversity in a multisource P2P streaming system,
a child peer could select parents located in different places so as to receive
video packets from different parents and network paths in hope of reducing
the impact of path failures. For example, the topology-aware parent selec-
tion algorithm used in PROMISE [37] uses connection conditions to select
parents. In CoopNet [45] and SplitStream [35], video packets are transmit-
ted on multiple distribution trees to provide path redundancy. In summary,
multisource structures provide a way to achieve source level diversity and
the topology-aware parent selection algorithms provide methods to achieve
path level diversity.
1.6 Conclusion
In this chapter, we covered different architectures for delivering multimedia
content to users. We pointed out the potential problems in the traditional uni-
cast architecture. After introducing the multicast technologies and how they
would be applied to solve the problems in traditional architecture, we pro-
ceeded to describing P2P streaming systems and how they can help reduce
server load and network bottlenecks. Finally, we analyzed the theoretical
peer behavior and estimated the affect of employing a packet level FEC on
robustness. Even though P2P streaming systems seem very promising, there
are still some open issues.
First, there are still a lot of open QoS issues. Marfia et al., 2007 [6] com-
pares the performance of different P2P schemes and the results show that
the startup delay of current P2P live streaming systems are still very high
(see Figure 1.38; Table 1.1) [51-53].
Second, current P2P live streaming technologies are most suitable for deliv-
ering popular video channels where a newly joining peer can easily find
User Click Play
Video playback
Buffering time
Start-Up delay
Figure 1.38
Illustration of startup delay.
