RELIABLE MULTICAST TRANSPORT PROTOCOL (RMTP)

This paper presents the design, implementation, and performance of a r eliable multicast transport protocol (RMTP). RMTP is based on a hierar chical structure in which receivers are grouped into local regions or domains and in each domain there is a special receiver called a design ated receiver (DR) which is responsible for sending acknowledgments pe riodically to the sender, for processing acknowledgment from receivers in its domain, and for retransmitting lost packets to the correspondi ng receivers. Since lost packets are recovered by local retransmission s as opposed to retransmissions from the original sender, end-to-end l atency is significantly reduced, and the overall throughput is improve d as well. Also, since only the DR's send their acknowledgments to the sender, instead of all receivers sending their acknowledgments to the sender, a single acknowledgment is generated per local region, and th is prevents acknowledgment implosion. Receivers in RMTP send their ack nowledgments to the DR's periodically, thereby simplifying error recov ery. In addition, lost packets are recovered by selective repeat retra nsmissions, leading to improved throughput at the cost of minimal addi tional buffering at the receivers. This paper also describes the imple mentation of RMTP and its performance on the Internet.