Trimming the Multipath for Efficient Dynamic Routing

TL;DR

This paper proposes a limited-path multipath routing approach that achieves load balancing comparable to or better than ECMP by selecting a few optimal end-to-end paths, reducing complexity while maintaining performance.

Contribution

It introduces an algorithm for selecting a small set of paths per source-destination pair to balance network load effectively, outperforming traditional ECMP in some scenarios.

Findings

Limited-path routing achieves load balancing similar to ECMP.

Selected paths can outperform ECMP when shortest path constraints are relaxed.

Few end-to-end tunnels suffice for effective traffic load balancing.

Abstract

Multipath routing is a trivial way to exploit the path diversity to leverage the network throughput. Technologies such as OSPF ECMP use all the available paths in the network to forward traffic, however, we argue that is not necessary to do so to load balance the network. In this paper, we consider multipath routing with only a limited number of end-to-end paths for each source and destination, and found that this can still load balance the traffic. We devised an algorithm to select a few paths for each source-destination pair so that when all traffic are forwarded over these paths, we can achieve a balanced load in the sense that the maximum link utilization is comparable to that of ECMP forwarding. When the constraint of only shortest paths (i.e. equal paths) are relaxed, we can even outperform ECMP in certain cases. As a result, we can use a few end-to-end tunnels between each source and destination nodes to achieve the load balancing of traffic.