Rearrange Broadcast Schedules on DHT-Based Peer-to-Peer Networks

In peer-to-peer (P2P) networks, broadcast is a basic service for many operations. For DHT-based P2P networks, several approaches have been proposed. They explicitly or implicitly maintain a spanning tree so that each non-leaf peer forwards broadcast messages to its children along the spanning tree. When peers are uniformly distributed, it is highly expected that the broadcast message will reach all peers by at most O(log N) hops where N is the network size. We study fast broadcast on DHT-based P2P networks in finer time granularity. In a round, an activated peer - that has received the broadcast message - can unicast the message to a non-activated peer - that has not yet received the message. We try to rearrange the forwardings in an existing spanning tree. A non-activated peer finds an activated peer in a bottom-up approach. When the search is restricted to on the path from a peer to the root, we present an algorithm, denoted as BSR (Broadcast Schedule Rearranger), to rearrange the forwardings. Simulation results show that when there are enough peers in the network, the number of rounds of the resultant broadcast schedule is close to log₂N.