Optimal Message Block Size for Computer Communications with Error Detection and Retransmission Strategies

Error detection and retransmission are used as error control in many computer communication systems. In these systems, random length messages are partitioned into fixed size blocks for ease in data handling and memory management. A mathematical model is developed in this paper to determine the optimal message block size that minimizes the expected waiting time in retransmission and acknowledgment delay and thus maximizes channel efficiency. The model considers two classes of error detection and retransmission strategies: 1) stop-and-wait and 2) continuous transmissions. Using the relationships among acknowledgment time, channel transmission rate, channel error characteristics (random error or burst error), average message length, optimal block size are computed from the model and presented in graphs. The model and the graphs should be useful as a guide in the selection of the optimal fixed message block size for computer communication systems.