TRANSPORT LAYER STATISTICAL MULTICAST BASED ON THE XTP BUCKET ALGORITHM

Multicast or point-to-multipoint transmission is becoming a major issu e for supporting distributed multimedia applications. In this paper, w e analyze the service provided by the XTP reliable multicast. We disco ver several problems and drawbacks, such as multiple retransmission of the same data packets or the protocol inefficiency when performing wi th large group size and non-broadcast networks. To overcome some of th ese problems, we introduce new constraints at the sender side to preve nt any unnecessary retransmissions. We introduce the service semantic called statistical reliable to cope with large group size while keepin g a high level of reliability (related to error recovery issues). The quality of service provided by this modified protocol is assessed by s imulation experiments for two different network environments : FDDI an d ATM. We show that the reliability is almost binary, i.e. all reliabl e or unreliable at all. If the parameters are correctly sized, we can expect to get an all reliable semantic while using the statistical rel iable protocol with the benefit of low protocol overhead. We are now w orking on a modified version of the proposed protocol to specifically adress ATM based networks.