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. In this paper, 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 tra c, in addition to the conventional beste ort tra c. The proposed MediaWorm router uses a rate-based bandwidth allocation mechanism, called Fine-Grained VirtualClock (FGVC), to schedule network resources for di erent tra c classes. Our simulation results on an 8-port router indicate that it is possible to provide jitter-free delivery to VBR/CBR tra c up to an input load of 70-80% of link bandwidth, and the presence of best-e ort tra c has no adverse e ect on real-time tra c. 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 di erent types of tra c.