Some question about simulation(about fluid model)

[btlcmr0702]

hi, yi bo I try to use ns3 to verfiy the fluid model you come up in 'Congestion Control for Large-Scale RDMA Deployments'. Then i get some strange performance. For example, i change parameter BYTE_COUNTER to 10MB which comes from your paper, but the rate of host can't converge and queue length at bottleneck varies a lot. Then i found some parameters that i don't understand: CLAMP_TARGET_RATE CLAMP_TARGET_RATE_AFTER_TIMER If i set them both to 0, the rate of host can converge but it and queue length at bottleneck still oscillate a lot. I stick the figure of performance(2 flow) as below.

Thank you！

[bobzhuyb]

If you are referring to the straight, stable lines in the paper, they are the results of fluid model analysis.

The NS-3 simulation is packet-level. The random marking on switches can't keep the queue as stable as fluid model analysis. As long as your throughput is ~99% link rate and the queue length is mostly ~100KB or less, it is good enough in practice.

[btlcmr0702]

Ok, thank for your reply. But i still wonder what does these parameter used to? They are in file Qbb-net-device.cc/h CLAMP_TARGET_RATE CLAMP_TARGET_RATE_AFTER_TIMER Will they affect performance a lot?