This PhD work aims at proposing a methodology and tools for the evaluation of transport protocols in the context of large scale computing environment based on high speed networks. The goal is to define and validate a benchmark for comparing different transport and congestion control approaches. Our contribution concerns the definition of metrics, scenarios, experiments and pilot demonstrations for high demanding distributed applications. After stating the problem of evaluating transport protocols in high speed networks, we present existing methodologies for this purpose. We introduce our proposal of a tool to help users performing network experiments. We illustrate our approach with a few examples of results obtained from experiments in our Grid'5000 testbed which complements other existing approaches.

We consider wireless LANs such as IEEE 802.11 operating in the unlicensed radio spectrum. While their nominal bit rates have increased considerably, the MAC layer remains practically unchanged despite much research effort spent on improving its performance. We observe that most proposals for tuning the access method focus on a single aspect and disregard others. Our objective is to define an access method optimized for throughput and fairness, able to dynamically adapt to physical channel conditions, to operate near optimum for a wide range of error rates, and to provide equal time shares when hosts use different bit rates.We propose a novel access method derived from 802.11 DCF [2] (Distributed Coordination Function) in which all hosts use similar values of the contention window CW to benefit from good short-term access fairness. We call our method Idle Sense, because each host observes the mean number of idle slots between transmission attempts to dynamically control its contention window. Unlike other proposals, Idle Sense enables each host to estimate its frame error rate, which can be used for switching to the right bit rate. We present simulations showing how the method leads to high throughput, low collision overhead, and low delay. The method also features fast reactivity and time-fair channel allocation.