Providing Full QoS Support in Clusters Using Only Two VCs at the Switches

Current interconnect standards providing hardware support for quality of service (QoS) consider up to 16 virtual channels (VCs) for this purpose. However, most implementations do not offer so many VCs because they increase the complexity of the switch and the scheduling delays. In this paper, we show that this number of VCs can be significantly reduced. Some of the scheduling decisions made at network interfaces can be easily reused at switches without significantly altering the global behavior. Specifically, we show that it is enough to use two VCs for QoS purposes at each switch port, thereby simplifying the design and reducing its cost.