Hop-by-hop Flow Control in Ethernet Networks : Implementation and Simulationbased Analysis of Performance

Abstract

This thesis addresses flow control in backpressured hop-by-hop packet networks. Our work evaluates the properties of a proposed flow control protocol, P, claimed to be lossless and free of both deadlocks and livelocks.

The evaluation is done through simulationbased analysis using the J-Sim network simulator. Specifically, this thesis looks at how Protocol P behaves compared to IEEE 802.3x and to the no flow control scenario with respect to performance (throughput and latency), backpressure, packetloss, deadlocks and livelocks in the Gigabit Ethernet context. And, we have searched for differences in control message overhead, buffer occupancy and bottleneck link utilization between Protocol P and IEEE 802.3x.

Using a irregular spanning tree with 16 switches and 64 hosts, our findings are very internally coherent, and show a very small or none significant difference between the two flow control schemes. We have shown that protocol P in fact exhibits all the promised properties, with the limitation of deadlocks to store-and-forward deadlocks. The surprisingly low variance when comparing the two flow control schemes are mainly attributed to using the same network components, and in particular pause scheme, buffer thresholds and link scheduling. We conclude that in the current Ethernet context, protocol P does not give additional performance, and has the drawback of higher buffer management cost.