Performance Analysis of a Multicast Protocol for Wireless Environments

This paper presents a performance study, using both analytical modeling and simulation techniques, of a new end-to-end reliable multicast protocol for use in environments with wireless access. The proposed protocol, known as the reliable mobile multicast protocol (RM2), divides a multicast tree into sub-trees where subcasting is applied within these relatively smaller regions using a hierarchical tree of retransmission servers (RSs). RM2 is receiver oriented [Pingali, 94] in that the transmitter does not need to know its receivers, hence offering better scalability. The Internet Group Management Protocol (IGMP) is used to manage group membership whereas the IETF’s Mobile IP offers support to user mobility through a care-of address (temporary IP address). Each RS has a retransmission subcast address shared by its members and which may be dynamically configured using allocation schemes such as the IETF’s MADCAP (Multicast Address Dynamic Client Allocation Protocol) [MADCAP, 99]. More importantly, RM2 uses a dynamic retransmission strategy to switch between multicast and unicast retransmission modes according to the amount of extra load generated both in the network and in the wireless interfaces by packet retransmissions. It is shown through both analytical modeling and simulation that RM2’s dynamic adaptation is not only important but also necessary when considering mobile wireless access.