  Given the respective advantages of the two complimentary techniques for
peer-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 hybrid
system usually consists of backbone trees formed by the stable peers and other
overlay structures in the second tier to accommodate the remaining peers. In
this paper, we embrace the hybrid push-pull structure for peer-to-peer media
streaming. Our protocol is dominated by a multi-tree push mechanism to minimize
the delay in the backbone and is complemented by other overlay structures to
cope with peer dynamics. What mainly distinguishes our multi-tree pushing from
the conventional ones is an unbalanced tree design guided by the so called
snow-ball streaming, which has a provable minimum delay and can be smoothly
"melded" with virtually any other existing overlay structures lying in the
second tier. We design algorithms to construct and maintain our SNowbAll
multi-tree Pushing (SNAP) overlay, and we also illustrate how to smoothly weld
the SNAP backbone with the second tier. Finally, we perform simulations in
ns-2; the results indicate that our approach outperforms a recently proposed
hybrid streaming system.
