LARS: Keeping Local Traffic Local with Latency-Aware Route Servers at IXPs

Internet Exchange Points facilitate traffic exchange through Route Servers that use BGP for path selection without considering latency. This paper presents LARS, the first system to enable latency-aware path optimization at IXP route servers. It requires no changes to BGP and no bilateral coordination among members, thus directly enabling latency-aware routing for all IXP members. LARS continuously probes the route-server RIB, annotates routes with RTT-derived BGP communities, and enables members to (i) enforce a configurable latency radius that suppresses high-latency routes and (ii) prefer lower-latency alternatives when multiple paths exist. We evaluate LARS at a very large IXP using a production-level prototype that demonstrates stable latency estimation, effective tail-latency control via selective redistribution, and potential to optimize BGP best paths.