Avoiding Oscillations Due to Intelligent Route Control Systems
Rui Qiang Gao, Constantine Dovrolis, Ellen Witte Zegura · 2006
Abstract — Intelligent Route Control (IRC) systems are increasingly deployed in multihomed networks. IRC systems aim to optimize the cost and performance of outgoing traffic, based on measurement-driven dynamic path switching techniques. In this paper, we first show that IRC systems can introduce sustained traffic oscillations, causing significant performance degradation instead of improvement. This happens, first, when IRC systems do not take into account the self-load effect, i.e., when they ignore that the performance of a path can change after additional traffic is switched to that path. Second, oscillations can take place when different IRC systems get synchronized due to significant overlap of their measurement time windows. We then propose measurement methodologies and path switching algorithms that can effectively deal with the previous two issues. The proposed IRC techniques use available bandwidth estimation to avoid the self-load effect, and they introduce a random component in the path switching decision or time scale. We evaluate the proposed techniques under diverse traffic conditions. When the background traffic is stationary, IRC systems should switch paths conservatively, only upon major traffic fluctuations. With nonstationary background traffic and congestion periods that last for a time scale ¢¡, IRC systems improve performance only if they can detect congestion and switch paths much faster than ¡; otherwise, they cause oscillations and hurt performance. We also show that the gradual deployment of randomized IRC systems, in the presence of traffic from deterministic IRC systems, can play a stabilizing role and benefits early adopters.