“The performance of the xAMP protocol on Token-Bus and FDDI NAC's”

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Paulo Veríssimo, José Rufino, Henrique Fonseca, Luís Rodrigues

INESC, Tech. Rep. RT/101-91, Nov. 1991.

Abstract: There is an increasing number of distributed applications, some of them fault-tolerant, and it has been recognized that its construction may benefit from the existence of reliable broadcast protocols. Some systems are clock-driven, exhibiting tight synchrony: they rely on clock synchronization and space redundancy. Others, like the xAMp, an atomic multicast protocol for local area networks, are clock-less. This work deals with the performance implications of supporting soft real-time distributed applications, with clock-less reliable broadcast protocols. In particular it analyses the performance of the lower layers of the Delta-4 communication system, i.e. it studies the time domain behaviour of both Abstract Network and xAMp components. Throughout this report we will develop a generic model that allow us to predict protocol execution times in any architecture. Case studies concerning protocol execution on two target LANs - the 10Mbps Token-Bus and the 100 Mbps FDDI - will be presented, showing how protocol performance scales with the utilization of high-speed networks. Additionally a set of guidelines concerning the dimensioning of xAMp timers and performance optimizations, useful for both system configuration implementation, are presented.