Given the respective advantages of the two complimentary techniques forpeer-to-peer media streaming (namely tree-based push and mesh-based pull),there is a strong trend of combining them into a hybrid streaming system.Backed by recently proposed mechanisms to identify stable peers, such a hybridsystem usually consists of backbone trees formed by the stable peers and otheroverlay structures in the second tier to accommodate the remaining peers. Inthis paper, we embrace the hybrid push-pull structure for peer-to-peer mediastreaming. Our protocol is dominated by a multi-tree push mechanism to minimizethe delay in the backbone and is complemented by other overlay structures tocope with peer dynamics. What mainly distinguishes our multi-tree pushing fromthe conventional ones is an unbalanced tree design guided by the so calledsnow-ball streaming, which has a provable minimum delay and can be smoothly"melded" with virtually any other existing overlay structures lying in thesecond tier. We design algorithms to construct and maintain our SNowbAllmulti-tree Pushing (SNAP) overlay, and we also illustrate how to smoothly weldthe SNAP backbone with the second tier. Finally, we perform simulations inns-2; the results indicate that our approach outperforms a recently proposedhybrid streaming system.
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