Hierarchical use of dedicated channels

Abstract

We consider efficient organizations for communication resources which are accessed by a large number of geographically distributed terminals. Developing a model for systems built with dedicated line channels, we answer the following questions: What is the role of hierarchies in organizing large communication nets? How should a large network be decomposed into smaller parts? What cost vs. performance gains can be achieved by such a decomposition? Assuming that the traffic to be carried and the mean response time are specified and that the goal is to minimize the necessary cost, we define burstiness and find the following: Dedicating channels is reasonable when the traffic is steady (i.e., not bursty) but when the traffic is bursty, the cost of simple dedicated-channel systems grows too fast with the number of terminals. By introducing regular hierarchical structures we show that the cost of bursty systems can significantly be reduced. The optimal structure must be balanced. The optimal number of levels and the ratio of the contribution of the different levels to both cost and delay is simply determined by a few key systems parameters.