The modeling of message switches in store-and-forward computer communication networks

A network approach is developed for constructing a message switch model from which the message processing delay can be determined as a function of the input traffic statistics. The model requires a knowledge of computer service times which are determined by modeling a multicomputer, multichannel, multidisk system, based upon the assumption that the service times consist primarily of cumulative disk accessing times. Model parameters of interest are determined using analytic and approximate queuing theory techniques. A new channel waiting model is introduced to account for disks competing for a smaller number of channels, causing the disk queue service times to be traffic rate-dependent. A method for determining computer service times is formulated, and techniques are developed for approximating the disk access per message distribution and an overlap factor which accounts for simultaneous disk accesses over more than one channel.