Borg

Multicast avoids sending repeated packets over the same network links and thus offers the promise of supporting multimedia streaming over wide-area networks. Previously, two opposite multicast schemes -- forward-path forwarding and reverse-path forwarding -- have been proposed on top of structured peer-to-peer (p2p) overlay networks. This paper presents Borg, a new scalable application-level multicast system built on top of p2p overlay networks. Borg is a hybrid protocol that exploits the asymmetry in p2p routing and leverages the reverse-path multicast scheme for its low link stress on the physical networks. Borg has been implemented on top of Pastry, a generic, structured p2p routing substrate. Simulation results based on a realistic network topology model shows that Borg induces significantly lower routing delay penalty than both forward-path and reverse-path multicast schemes while retaining the low link stress of the reverse-path multicast scheme.