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.