Using preemptive campon to establish connections in a network of cascaded crossbar switches

Abstract

We consider a high bandwidth connection oriented network formed by cascading crossbar switches. Such a network could be used to implement Class 1 service of the Fibre Channel Standard, which is an emerging standard for local computer communications. Connections are full duplex and are established by forwarding a connection request from the source to the destination, reserving the entire link bandwidth of all the links as it advances. Three types of campon strategies for connection establishment are examined. Using a no-campon strategy, a connection request is rejected as soon as it is blocked, and it is retried later. Using a campon strategy, a blocked connection request waits at a blocking switch until it can be forwarded. We introduce a preemptive campon strategy in which a blocked connection request waits at a blocking switch but can be rejected if one of its reserved links can be used to forward another connection request. We demonstrate by simulation that preemptive campon performs better than the other two strategies in a variety of situations.