Topologies and routing in gigabit switching fabrics
Sven-Arne Reinemo · 2000
The ever increasing demand for bandwidth in computer networking has led us from the 3Mbps Ethernet of 1976 to todays 1Gbps Ethernet. This evolution in Ethernet bandwidth has presented the network vendors with an increasing range of challenges when producing high capacity Ethernet switches. In this thesis we look at the problems related to throughput, scalability and fairness when designing switching fabrics suitable for Gigabit Ethernet switches. We study three different topologies, the Butterfly, the Double Butterfly and the Hierarchical Clos together with several routing strategies in our quest to find a viable solution. The study is performed using two IEEE-1355 based test-beds to build the actual topologies and do measurements. We draw the conclusion that the Butterfly is the topology that has the best price/performance ratio while the Double Butterfly is the winner when price is not an issue. Universal routing is necessary to achieve fairness in the network. This combined with grouped adaptive routing gives us high throughput without sacrificing fairness. Finally, over capacity in the network means a lot for the performance and drastically reduces the differences between the different routing schemes. When a high level of link utilization is necessary a high degree of over capacity should be considered.