Hash-based internet traffic load balancing

Abstract

High bandwidth scalable router port aggregates multiple physical links due to its scalability, reliability and cost-effectiveness. When IP packets are distributed over such multiple physical links, load unbalancing and packet reordering may occur. A good traffic distribution method plays a key role to maximize the efficiency of multiple links reducing the amount of packet reordering. Sending a flow over a unique link by hashing the packet header is a simple solution to keep the packet order. However, hashing does not guarantee an even distribution of the traffic amount among the links, which could lead to packet loss under heavy load. We have analyzed the actual Internet packet trace data collected on OC-12 links and observed that such an unbalancing is quite common. We have enhanced the hashing algorithm by measuring the flow volume periodically to detect high-bandwidth flows and by moving them to lightly loaded links. In simulation, this method shows a significant performance improvement with little packet loss and reordering.