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High Performance Networking
For example, TCP can penalize the overall performance of high performance flows to a much higher degree than the lower performance ones. In addition, in order to fully exploit high link capacity, the congestion avoidance algorithms of TCP, which depend on the congestion window size, have to be properly tuned. However, large window sizes produce bursts of output traffic, which, if the router queues are nosufficiently large to handle these bursts, may cause packet loss and a consequent poor user-perceived performance.
Although some ad-hoc approaches such as striped ftp allow to partly circumvent
the problem of large window sizes, it is far from clear that these solutions
will scale to Gigabit per second file transfer. It is also doubtful that
existing TCP congestion avoidance approaches (i.e. Reno/Newreno) are well
suited in a high-speed environment. Therefore, a number of different aspects
need to be investigated such as:
There are a number of ongoing projects, e.g. Web100, which are directly tackling the issue of poor file transfer performance over very high speed long distance networks, as well as better instrumentation of TCP/IP, in order to ease the tuning or even allow self-tuning of the applications. Activities will be carried out in collaboration with such projects, if possible, and will be based on relevant results achieved by the whole community, which includes among the others researchers from the University of Illinois Chicago (Electronic Visualization Lab), iCAIR (international Centre for Advanced Internet Research) & NorthWestern University.
End-to-end inter-domain QoS
From the point of view of the Grid, however, end-to-end QoS integrated across a WAN comprising of multiple independent administrative domains has not yet been demonstrated routinely. At each domain boundary a common service level specification (SLS) has to be agreed upon, so that all the Grid domains can support a consistent end-to-end service despite the fact that each domain can choose a service implementation completely independent from the one adopted by other domains. Several research networks like GÉANT, Abilene, GARR, UKERNA and others are already in the process of defining or offering pilot services. Cooperation with the Internet Service Providers who provide testbed connectivity will be fundamental to speeding up the introduction of QoS features into production networks and to provide help with the definition of services and their validation. Thus the entire sector of moving QoS onto the heterogeneous WAN is highly innovative at this time. This project provides an ideal context in which to integrate these pilot QoS services into the middleware, and test them using different traffic classes.