Reliable Adaptive Multicast Protocol (RAMP)

Abstract

RAMP [BZ93][KZ96] is a transport-level protocol for multicast applications. It is designed for relatively error-free networks, such as, alloptical circuit-switched networks with bit error rate of 10–12 or better, switched virtual circuit ATM networks, or for networks with QOS guarantees in the switches. Since the network is mostly error-free, it does not make sense for the receivers to send acknowledgements (ACKs) indicating successful reception of packets. Therefore, receivers send Negative-acknowledgements (NACKs) to the sender when packets are lost which is a rather rare event. In addition, the bottleneck in an error-free network is at the end-points which may lose packets because of buffer overflow. Therefore, the sender in RAMP retransmits lost packets using unicast as opposed to using multicast. RAMP can thus be summarized as an immediate receiver-initiated NACK-based multicast protocol with sender-based unicast retransmission.