A loss-free connection control protocol for the Thunder and Lightning network

Abstract

The ready-to-go virtual circuit protocol (or RGVC) is a novel connection control protocol for gigabit networks that is designed to ensure lossless transmission for delay-sensitive traffic and for traffic whose rate changes with time. The RGVC protocol is one of the two connection control protocols that will be used in the 40 Gbit/s fiber-optic ATM-based Thunder and Lightning network, currently being developed at UCSB. We introduce the RGVC protocol, discuss its main features, and indicate its lossless character. The RGVC protocol can be viewed as a reservation protocol where the reservation and the data transmission phases overlap. The source need not wait for an end-to-end round-trip delay for reservations to be made before transmitting the data. Instead the data packets follow the setup packet after a short offset-interval, which is much smaller than the round-trip delay. As a result, the protocol does considerably better than wait-for reservation protocols in terms of minimizing pre-transmission delay, and is useful for connection establishment for traffic with strict delay requirements. If the setup packet is unsuccessful in reserving the required capacity, or if the rate of the session changes without there being sufficient capacity to accommodate the change, the packets are buffered at intermediate nodes and back-pressure is exercised to the upstream nodes to control the source transmission rate. The back-pressure mechanism uses the concept of freezing of capacity to ensure that the protocol is lossless.