This memorandum presents a solution to one of the most basic optimization problems which arose from the adoption of the HDLC (High level Data Link Control) procedure in the IIASA data communication network data link control protocol. Strictly, the problem discussed here is finding out the optimal HDLC Information-frame structure in order to maximize the throughput, so that the solution states the optimal length of the information part of the Information-frame is 5, 16, 57, 190, 610 and 1800 bytes corresponding to the line quality of 10^(-2), 10^(-3), 10^(-4), 10^(-5), 10^(-6), and 10^(-7) in bit error probability, where the HDLC half duplex normal response mode and the case of file-transfer are assumed. Some other related results and remarks are also given in this memorandum
