Broadcasting in unstructured peer-to-peer overlay networks

Peer-to-peer overlay networks present new opportunities and challenges for achieving enhanced network functionality at the application level. In this paper we study the impact of point-to-point network latency on flooding broadcast operations in peer-to-peer overlay networks. We show that two standard protocol mechanisms, used to control the amount of network resources used during flooding, can in combination, significantly reduce the reach of broadcast messages. We prove that these standard mechanisms, known as “time-to-live bounds” and “unique message identification”, can result in broadcast operations that only reach a vanishing fraction of the nodes. In addition, we provide empirical evidence that the trend suggested by our formal results are found in data obtained from the Gnutella network and through network simulations.