Congestion Control Safety via Comparative Statics

Abstract

When congestion control algorithms compete on shared links, unfair outcomes can result, especially between algorithms that aim to prioritize different objectives. For example, a throughput-maximizing application could make the link completely unusable for a latency-sensitive application. In order to study these outcomes formally, we model the congestion control problem as a game in which applications have heterogeneous utility functions. We draw on the comparative statics literature in economics to derive simple and practically useful conditions under which all applications achieve at least ε utility at equilibrium, a minimal safety condition for the network to be useful for any application. Compared to prior analyses of similar games, we show that our framework supports a more realistic class of utility functions that includes highly latency-sensitive applications such as teleconferencing and online gaming.