This thesis addresses flow control in backpressured hop-by-hop packetnetworks. Our work evaluates the properties of a proposed flow controlprotocol, P, claimed to be lossless and free of both deadlocks andlivelocks.
The evaluation is done through simulationbased analysis using theJ-Sim network simulator. Specifically, this thesis looks at howProtocol P behaves compared to IEEE 802.3x and to the no flow controlscenario with respect to performance (throughput and latency),backpressure, packetloss, deadlocks and livelocks in the GigabitEthernet context. And, we have searched for differences in controlmessage overhead, buffer occupancy and bottleneck link utilizationbetween Protocol P and IEEE 802.3x.
Using a irregular spanning tree with 16 switches and 64 hosts, ourfindings are very internally coherent, and show a very small or nonesignificant difference between the two flow control schemes. We haveshown that protocol P in fact exhibits all the promised properties,with the limitation of deadlocks to store-and-forward deadlocks. Thesurprisingly low variance when comparing the two flow control schemesare mainly attributed to using the same network components, and inparticular pause scheme, buffer thresholds and link scheduling. Weconclude that in the current Ethernet context, protocol P does notgive additional performance, and has the drawback of higher buffermanagement cost.