Fluctuation-induced traffic congestion in heterogeneous networks

¹ School of Engineering and Applied Science, Aston University - Birmingham B4 7ET, UK, EU
² School of Physics and Astronomy, University of Birmingham - Birmingham B15 2TT, UK, EU
³ School of Electronic, Electrical and Computer Engineering, University of Birmingham Birmingham B15 2TT, UK, EU

Received: 7 September 2012
Accepted: 11 October 2012

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.