Information Technology Reference
In-Depth Information
Playback Pointer
Tree-Push Pointer
Time
Mesh-Pull Window
Figure 1.32
Push-Pull switching buffer in mTreebone. (From Wang, F., Xiong, Y., and Liu, J., Proceedings of
International Conference on Distributed Computing Systems, Toronto, Ontario, Canada, June
2007. With permission.)
the tracker. With this mechanism, the new peer should quickly identify good
peers and shorten the time for exchanging video chunks.
1.4.3.2 mTreebone
The idea of mTreebone is to design a protocol that combines the advantages of
both tree-push and mesh-pull methods. A tree-push based backbone (called
a treebone) is built from identified stable nodes in the network. A mesh over-
lay is built upon all the other nodes. The stable node identification is based
on observing user behavior so that the nodes with a higher age tend to stay
in the network longer. The media data is delivered through the treebone, and
the lost packets are recovered by the mesh structure (see Figure 1.32).
1.5 Dynamic Behavior of Peers in Peer-to-Peer Systems
The dynamic behavior of peers in P2P systems is one of the major challenges.
Since peers are transient in nature, once a parent peer departs from the system,
the receivers receiving streaming content from that parent peer might suffer
from temporarily unstable transmission. In P2P streaming systems that orga-
nize peers into a specific topology (e.g., tree-based topology), this temporarily
unstable transmission could lead to burst packet loss [57,58,67]. To reduce the
impact of parent departure, many researchers [35,37,45,65,66] focus on detect-
ing the failure and locating a new parent as quickly as possible. However, even
if the peer failure can be detected and quickly recovered from, the associated
child peers still suffer burst packet losses before locating a new parent peer.
Moreover, in a tree-based P2P system, once an ancestor peer loses packets, all of
its descendant peers have no way to receive the missing packets. Subsequently,
the packet losses accumulate along the forwarding path. Addressing the above
problems, we first discuss the dynamic behavior of parents in P2P systems
and then describe a multisource structure with
Forward Error Correction
(FEC),
which can be used to overcome the burst packet loss problem.
