Fluctuation-induced traffic congestion in heterogeneous networks

TL;DR

This paper models how rapid traffic reductions due to congestion in heterogeneous networks like the Internet can cause phase transitions and large fluctuations, leading to overreactions to initial congestion signs.

Contribution

It introduces a phase transition framework for understanding congestion onset in heterogeneous networks, emphasizing the role of non-Gaussian fluctuations and network heterogeneity.

Findings

Traffic losses exhibit phase transition behavior.

Heterogeneity amplifies fluctuation effects.

Networks overreact to initial congestion signals.

Abstract

In studies of complex heterogeneous networks, particularly of the Internet, significant attention was paid to analyzing network failures caused by hardware faults or overload, where the network reaction was modeled as rerouting of traffic away from failed or congested elements. Here we model another type of the network reaction to congestion -- a sharp reduction of the input traffic rate through congested routes which occurs on much shorter time scales. We consider the onset of congestion in the Internet where local mismatch between demand and capacity results in traffic losses and show that it can be described as a phase transition characterized by strong non-Gaussian loss fluctuations at a mesoscopic time scale. The fluctuations, caused by noise in input traffic, are exacerbated by the heterogeneous nature of the network manifested in a scale-free load distribution. They result in the network strongly overreacting to the first signs of congestion by significantly reducing input traffic along the communication paths where congestion is utterly negligible.