Analysis of client/server transaction delay through a local area network switch

Abstract

Local area network (LAN) switches are increasingly being used to subdivide large LAN segments into multiple connected LAN "microsegments". A LAN switch is similar to a LAN bridge, but is typically higher in performance and has more ports. Communication between stations on different segments is through the LAN switch. A performance analysis is presented for a token ring LAN switch for the class of protocols known as request-response protocols. Request-response protocols are typical of many client/server applications including transaction processing. A performance model based on a detailed accounting of network delay components is presented. The performance model quantifies the importance of minimizing latency within a LAN switch. Two LAN switch frame forwarding architectures are described and evaluated. The architectures are store-and-forward and cut-through frame forwarding. The performance model demonstrates that the benefits of low delay in cut-through switching extend even to situations where attached token ring segments have a very high utilization.