Switching Techniques for Broadband ISDN

The properties of switching techniques suitable for use in broadband networks have beeninvestigated. Methods for evaluating the performance of such switches have beenreviewed. A notation has been introduced to describe a class of binary self-routingnetworks. Hence a technique has been developed for determining the nature o f theequivalence between two networks drawn from this class. The necessary and sufficientcondition for two packets not to collide in a binary self-routing network has beenobtained. This has been used to prove the non-blocking property of the Batcher-banyanswitch. A condition for a three-stage network with channel grouping and link speed-up tobe nonblocking has been obtained, of which previous conditions are special cases.A new three-stage switch architecture has been proposed, based upon a novel cell-levelalgorithm for path allocation in the intermediate stage of the switch. The algorithm issuited to hardware implementation using parallelism to achieve a very short executiontime. An array of processors is required to implement the algorithm The processor hasbeen shown to be of simple design. It must be initialised with a count representing thenumber of cells requesting a given output module. A fast method has been described forperforming the request counting using a non-blocking binary self-routing network.Hardware is also required to forward routing tags from the processors to the appropriatedata cells, when they have been allocated a path through the intermediate stage. A methodo f distributing these routing tags by means of a non-blocking copy network has beenpresented.The performance of the new path allocation algorithm has been determined by simulation.The rate of cell loss can increase substantially in a three-stage switch when the outputmodules are non-uniformly loaded. It has been shown that the appropriate use of channelgrouping in the intermediate stage of the switch can reduce the effect of non-uniformloading on performance. 1. SWITCHING IN BROADBAND ISDN. 1.