MediaWorm: a QoS capable router architecture for clusters

With the increasing use of clusters in real-time applications, it has become essential to design high-performance networks with quality-of-service (QoS) guarantees. We explore the feasibility of providing QoS in wormhole switched routers, which are widely used in designing scalable, high-performance cluster interconnects. In particular, we are interested in supporting multimedia video streams with CBR and VBR traffic, in addition to the conventional best-effort traffic. The proposed MediaWorm router uses a rate-based bandwidth allocation mechanism, called Fine-Grained VirtualClock (FGVC), to schedule network resources for different traffic classes. Our simulation results on an 8-port router indicate that it is possible to provide jitter-free delivery to VBR/CBR traffic up to an input load of 70-80 percent of link bandwidth and the presence of best-effort traffic has no adverse effect on real-time traffic. Although the MediaWorm router shows a slightly lower performance than a pipelined circuit switched (PCS) router, commercial success of wormhole switching, coupled with simpler and cheaper design, makes it an attractive alternative. Simulation of a (2×2) fat-mesh using this router shows performance comparable to that of a single switch and suggests that clusters designed with appropriate bandwidth balance between links can provide required performance for different types of traffic.