We consider a computer communication network in which users communicate with each other via a central node. The available channel is divided into the up- and downlink subchannels. Users contend for the uplink according to the pure ALOHA protocol. The central node is capable of recognizing erroneous packets, rejecting duplicate packets, and storing error-free packets. Given that the total available channel capacity is the limiting resource, the system throughput and the average packet delay are derived. Aiming at the improvement of system performance, we found the channel capacity divisions that maximize the throughput and minimize the average packet delay (numerically). In order to obtain the above-mentioned performance characteristics, we have assumed the infinite users' population model.