A Reliable Multicast Protocol for Distributed Mobile Systems: Design and Evaluation (extended version)

Reliable multicast is a powerful communication primitive for structuring distributed programs in which multiple processes must closely cooperate together. In this paper we propose a protocol for supporting reliable multicast in a distributed system that includes mobile hosts and evaluate the performance of our proposal through simulation. We consider a scenario in which mobile hosts communicate with a wired infrastructure by means of wireless technology. Our proposal provides several novel features. The sender of each multicast may select among three increasingly strong delivery ordering guarantees: FIFO, Causal, Total. Movements do not trigger the transmission of any message in the wired network as no notion of hand-off is used. The set of senders and receivers (group) may be dynamic. Size of data structures at mobile hosts, size of message headers, number of messages in the wired network for each multicast, are all independent on the number of group members. The wireless network is assumed to provide only incomplete spatial coverage and message losses could occur even within cells. Movements are not negotiated and a mobile host that leaves a cell may enter any other cell, perhaps after a potentially long disconnection. The simulation results show that the proposed protocol has good performance and good scalability properties.