Patterns of Congestion Collapse

In this paper we consider the potential for congestion collapse in a range of network scenarios. In particular, we are interested in the effect of the topology, the scheduling discipline (FIFO or FQ scheduling), the level of statistical multiplexing, the traffic characteristics, and other factors. We consider topologies more complex than a single congested link, or a single string of congested links. This paper first shows that it is possible to have high equilibrium loss rates with rational greedy senders sharing a FIFO link or with greedy senders sharing an FQ link with bursty cross-traffic. We then consider specific topologies with a range of senders to calculate steady-state packet loss rates and derive the goodput of the congested links. In particular, we find some scenarios where goodput is higher with FQ scheduling, and other scenarios where goodput is higher with FIFO scheduling.