Effects of ensemble-TCP

TCP currently recalculates the state of each connection from a fixed set of initial parameters; this recalculation occurs over several round trips, du ring which the connection can be less than efficient. TCP control block sha ring is a technique for reusing information among connections in series and aggregating it among connections in parallel. This paper explores the desi gn space of a modified TCP stack that utilizes these two ideas, and one pos sible design (E-TCP) is presented in detail. E-TCP has been designed so tha t the network transmission behavior of group of parallel E-TCP connections closely resembles that of a single TCP/Reno connection. Simulated web acces ses using HTTP/1.0 over E-TCP show a significant performance improvement co mpared to TCP/Reno connection bundles. This paper is first to evaluate perf ormance using four different intra-ensemble schedulers for different worklo ads. In one scenario simulating a common case, E-TCP is 4-75% faster than R eno for transmitting the HTML parts of various pages, and 17-61% faster tra nsmitting the whole pages. In the same scenario, reusing cached state speed s up repeated E-TCP page accesses by 17-53% for the HTML parts and 10-28% f or the whole pages, compared to the initial access. E-TCP can also be integ rated with other proposed TCP extensions (such as TCP/Vegas or TCP/SACK), t o further improve performance.