The effect of retransmitted packet size preservation property on TCP goodput over links with Bernoulli bit-errors

In this paper, we investigate the effect of the retransmitted packet size preservation (RPSP) property on TCP performance over links with Bernoulli bit-errors, where RPSP means that the sizes of all packets transferred over datalinks (referred to as transferred packets) with the same sequence-number at retransmissions are equal to the size of a packet generated from a message at the original transmission (namely, generated packet). To achieve this, we present a Markov model for size-sequences of the generated and transferred packets, in which the TCP message-segmentation and error-recovery functions with RPSP are taken into account, respectively. Furthermore, we derive the round-trip time and the transferred packet corruption probability, which are the main parameters of TCP performance. Applying them to the conventional TCP-Reno send-rate formula, we discuss the effect of RPSP on TCP-Reno goodput. The key findings from the numerical results include that RPSP cannot be negligible for networks that suffer from a high bit-error rate (e.g., 1 × 10^-4, which is the mean bit-error rate of a wireless link in an industrial environment), when the message-segmentation occurrence probability is relatively small.