Interactions Of Intelligent Route Control With Tcp Congestion Control

Intelligent Route Control (IRC) technologies allow multihomed networks to dynamically select egress links based on performance measurements. TCP congestion control, on the other hand, dynamically adjusts the send-window of a connection based on the current path's available bandwidth. Little is known about the complex interactions between IRC and TCP congestion control. In this paper, we consider a simple dual-feedback model in which both controllers react to packet losses, either by switching to a better path (IRC) or by reducing the offered load (TCP congestion control). We first explain that the IRC-TCP interactions can be synergistic as long as IRC operates on larger timescales than TCP ("separation of timescales"). We then examine the impact of sudden RTT changes on TCP, the behavior of congestion control upon path changes, the effect of IRC measurement delays, and the conditions under which IRC is beneficial under two path impairment models: short-term outages and random packet losses.