OPTIMIZATION OF TCP SEGMENT SIZE FOR FILE TRANSFER

In this paper, we study the problem of optimal Transmission Control Pr otocol (TCP) segment size for file transfer from hosts to clients, The criterion of optimality is the minimization of the amount of TCP and IP (Internet Protocol) processing by the sender, The parameters that g overn the host-processing cost include the cost for processing both th e outgoing TCP segments and incoming TCP acknowledgments, the TCP wind ow size, the maximum transferable unit (MTU) size of the network, and the network reliability factor, We study the variations of the sender processing cost as a function of the TCP segment size and the network reliability factor, We show that there exists a network reliability fa ctor gamma(0) such that 1) for all network reliability factors gamma l ess than or equal to gamma(0), the optimal TCP segment size equals the MTU size less the sizes of the TCP and IP headers (the sender process ing cost increases with the TCP segment size in this case); and 2) for each gamma > gamma(0), there exists an optimal TCP segment size that is greater than the MTU site, Moreover, the optimal TCP segment size i s an increasing function of the network reliability factor, We also de rive a sufficient condition for the optimal TCP segment size to be gre ater than the MTU size. In this case, a lower bound for the optimal TC P segment size can be obtained as a simple function of the network rel iability factor.