Feedback-based Dynamic Traffic Balancing for Multipath Routing in ISP Networks

Abstract

In recent years, it has become increasingly important to utilize the entire network links more effectively to avoid traffic congestion for Internet Service Providers (ISPs), where link installation costs are high. As a promising approach to address this issue, multipath routing, which distributes traffic across multiple reachable paths to the destination, has getting attention. In multipath routing, congestion can be avoided by using other paths and balancing path loads even if a path is congested. Conventionally, realizing load-aware multipath routing has required both the collection of load metrics to track dynamically changing path loads and the distribution of traffic at an appropriate ratio with fine-grained traffic units such as flowlets. However, in ISP networks, existing methods may fail to balance path loads due to the large path delay and the variation in flow bit rates. In this paper, we propose a novel traffic balancing method suitable for ISP networks. In the proposed method, we first derive a target bandwidth for each path to equalize congestion levels of all paths in multipath, and then decide the distribution ratio by feedback control. In addition to this, the proposed method adopts modified flow-level traffic distribution, which makes flows reselect their paths at a certain time intervals. These approaches enable to balance traffic more evenly in ISP networks than conventional methods. Through network simulations using network topologies assuming ISP networks, including SINET6, we demonstrated that the proposed method can reduce the average flow completion time (FCT) by 16.0%, 44.5%, and 58.4% compared to ECMP, which performs naive traffic distribution, CONGA and W-ECMP, which achieve advanced traffic distribution.