An efficient multicast protocol using de Bruijn structure for mobile computing

Abstract

In this paper, we design a protocol to efficiently deliver multicast messages to mobile computers. The main concern in the design of such a protocol is to ensure that each message is delivered exactly once to each mobile host in a multicast group. However, the requirements of avoiding multiple delivery of a message, and of a host not missing a message are not easy to efficiently satisfy in a mobile environment. To satisfy these requirements, an earlier work had to actually broadcast a multicast message. The novelty of our approach is that we satisfy the multicast requirements without broadcasting a message, which is central to the efficiency of our protocol. We structure the mobile support stations (MSS) as a de Bruijn network, and define a multicast tree on the network. A multicast message is routed on a multicast tree on a de Bruijn network. Assuming that there are N MSS's in a network, a multicast group of mobile hosts belong to the cells of N MSS's, τ is the maximum of the time to route a message between two adjacent MSS's, Λ is the sum of the mobility rates of all mobiles in a multicast group, λ is the maximum among the mobility rates, and ψ is the cell cross-over time of a mobile, our protocol runs with a message complexity of O(min(N log N, N) + Λ log N) and a communication delay of O(τ log N + λmaxψ). Thus, our protocol is very efficient when a message is multicast to a small number of mobile hosts. To show the practicability of structuring a set of MSS's as a de Bruijn network, we have demonstrated how a de Bruijn network can be emulated as a collection of virtual paths on an arbitrarily connected ATM network.