Congestion Management for Non-Blocking Clos Networks

The authors propose a distributed congestion management scheme for non-blocking, 3-stage Clos networks, comprising plain buffered crossbar switches. VOQ requests are routed using multipath routing to the switching elements of the 3rd-stage, and grants travel back to the linecards the other way around. The fabric elements contain independent single-resource schedulers, that serve requests and grants in a pipeline. As any other network with limited capacity, this scheduling network may suffer from oversubscribed links, hotspot contention, etc., which the authors identify and tackle. They also reduce the cost of internal buffers, by reducing the data RTT, and by allowing sub-RTT crosspoint buffers.