All the measurements presented so far have been made using grouped adaptive routing. In order to quantify the impact of this feature of the STC104 packet switch, deterministic routing and grouped adaptive routing have been compared on the Clos topology. With deterministic routing, routing channels are evenly spread across the centre stage links. Figure 6 shows the average network latency versus network throughput for a 256 node 3-stage Clos network under random traffic with 64 byte packets. The network load was increased until saturation occurred. Using grouped adaptive routing results in a nearly 20% higher saturation network throughput as well as lower average latencies. This is because the adaptive routing technique minimises the effects of load imbalance, thereby allowing a better utilisation of the links to the centre stage of the Clos network.
Figure 6: : Deterministic and grouped adaptive routing on a 256 node Clos network
under random traffic