On the resource utilization and traffic distribution of multipath transmission control

There is growing interest in the development and deployment of multipath rate and route control mechanisms for the Internet, due to their ability to exploit bandwidth resources, alleviate network congestion, and provide robustness against failures. However, two performance issues have been uncovered: low link utilization when the number of flows is small, and route flappiness, namely the traffic of a flow tends to concentrate on one path and then another. In this paper we study these issues with respect to several variations of multipath rate and route control algorithms. We demonstrate the qualitatively different impacts that the couplings of the increase and decrease phases have on link utilization. We also demonstrate how the coupling strength affects both the long-term and short-term traffic distributions among different paths. In particular, we show that the flappy behavior is prominent only when there is strong coupling in both the increase and decrease phases, and when the number of good paths is small.