Sebastien Soudan, Romaric Guillier and Pascale Primet
Keywords: Grid networks, flow scheduling, bulk data transfers, rate limitation, pacing.In Grids, transfer jobs and network resources need to be managed in a more deterministic way than in the Internet. New approaches like flow scheduling are proposed and studied as alternatives to traditional QoS and reservation proposals. To enable such flow scheduling approaches, run-time mechanisms controlling flow sending time and rate have to be implemented in the data plane.
In this work we have quantified and compared, end-host based mechanisms combined with transport protocols to instantiate different scheduling strategies. A simple scenario has been deeply explored in a range of latency conditions. We have shown that, in high speed network, a single-rate scheduling strategy implemented by TCP-variant protocol like BIC with packet pacing mechanism offers predictable performance and is insensitive to latency (deficiency of mean completion time ranging from 4% at 0.1 ms RTT to 4.7% at 100 ms RTT). This work also highlights the limits of other strategies and rate limitation mechanisms like token bucket which may present unpredictability and other drawbacks. Future work will concentrate on larger experiments on the Grid5000 testbed and will examine the scalability of the flow scheduling approach in real grid context, multirate allocations schemes and transfers preemption issues.