A dynamic congestion management system for InfiniBand networks

While the InfiniBand link-by-link flow control helps avoid packet loss, it unfortunately causes the effects of congestion to spread through a network. Even flows that do not pass through congested ports can suffer from reduced throughput. We propose a Dynamic Congestion Management System (DCMS) to address this problem. Without per-flow information, the DCMS leverages performance counters of switch ports to detect onset of congestion and determines whether-or-not victim flows are present. The DCMS then takes actions to cause an aggressive reduction in the sending rates of congestion-causing (contributor) flows, if victim flows are present. On the other hand, if there are no victim flows, the DCMS allows the contributor to maintain high sending rates and finish as quickly as possible. The value of dynamic management of a switch congestioncontrol parameter called Marking Rate, which is responsible for how quickly contributor flows can be throttled, is evaluated in an experimental testbed. Our results show that dynamic congestion management can enable a network to serve both contributor flows and victim flows effectively. The DCMS solution operates within the constraints of the InfiniBand Standard.