Title: Dynamic Membership Protocol for Epidemic ProtocolsSpeaker: Byung K. Choi, Assistant Professor, Michigan TechDate: Tuesday, July 22, 10:30am~11:30am, 2008Place: ICP lecture room, Science library (과도관 6층 ICP 강의실)Abstract:Epidemic protocols have two fundamental assumptions. One is the availability of a mechanism that provides each node with a set of log(N) (fanout) nodes to gossip with at each cycle. The other is that the network size N is known to all member nodes. While it may be trivial to support these assumptions in small systems, it is a challenge to realize them in large open dynamic systems, such as peer-to-peer (P2P) systems. Since the most fundamental parameter of epidemic protocols is log(N), without knowing the system size, the protocols will be limited. Further, the problem of network churn of P2P systems due to frequent and rapid membership change makes it difficult to provide a different node set of log(N) at each different cycle. In order to support the assumptions, the fanout nodes should be selected randomly and uniformly from the entire membership even with network churn.This talk introduces one possible solution which addresses both problems providing at each cycle a different set of log(N) nodes selected randomly and uniformly from the entire network under churn, and estimating the dynamic network size in the number of nodes. This solution improves the previously developed distributed algorithm called Shuffle to deal with churn, and utilizes the Shuffle infrastructure to estimate the dynamic network size. The effectiveness of the proposedsolution is evaluated by imulation. According to the simulation results, the proposed algorithms successfully handle network churn to rovide random log(N) fanout nodes, and accurately estimate the network size for practical purposes.Bio:Byung K. Choi received PhD in Computer Science from Texas A&M University in 2002. He is currently an Assistant Professor in the Department of Computer Science at Michigan Technological University. Recently he has investigated dynamic membership management for large scale peer-to-peer systems and epidemic protocols which rely on such membership management. His research interests include anonymous communication, peer-to-peer systems, network security, and QoS issues.Prior to his graduate studies he was a team leader for LG Information and Communications (LGIC) R&D Center in Korea, where he worked on various switching system designs which have been widely used in Korea.