  As traffic patterns and network topologies become more and more complicated
in current enterprise data centers and TOP500 supercomputers, the probability
of network congestion increases. If no countermeasures are taken, network
congestion causes long communication delays and degrades network performance. A
congestion control mechanism is often provided to reduce the consequences of
congestion. However, it is usually difficult to configure and activate a
congestion control mechanism in production clusters and supercomputers due to
concerns that it may negatively impact jobs if the mechanism is not
appropriately configured. Therefore, simulations for these situations are
necessary to identify congestion points and sources, and more importantly, to
determine optimal settings that can be utilized to reduce congestion in those
complicated networks. In this paper, we use OMNeT++ to implement the IEEE
802.1Qbb Priority-based Flow Control (PFC) and RoCEv2 Congestion Management
(RCM) in order to simulate clusters with RoCEv2 interconnects.
