Error control in the Xpress transfer protocol

The error-control mechanisms used in the Xpress transfer protocol (XTP) are presented. Policies for the use of these mechanisms are proposed and simulated. A potential failure mode on contention-oriented media under high utilization is identified, and two proposals are made to prevent its occurrence. It is found that even for bit error rates as high as 10^-5, the loss in performance is only about 25% for large packets, and about 5% for small packets. The delays introduced by error-recovery actions being prematurely triggered by variation in the round trip time (RTT), even on a single-segment Ethernet, are found to contribute more to the overall delay than the delay due to copying and checksumming. Two ways of reducing this effect are proposed, i.e., more careful RTT estimation, and less aggressive use of XTP´s synchronizing handshake