Topology aware overlay networks

Abstract

Recently, overlay networks have emerged as a means to enhance end-to-end application performance and availability. Overlay networks attempt to leverage the inherent redundancy of the Internet's underlying routing infrastructure to detour packets along an alternate path when the given primary path becomes unavailable or suffers from congestion. However, the effectiveness of these overlay networks depends on the natural diversity of overlay paths between two endhosts in terms of physical links, routing infrastructure, administrative control, and geographical distribution. Several recent studies realized that a measurable number of path outages were unavoidable even with use of such overlay networks. This stems from the fact that overlay paths might overlap with each other when overlay nodes are selected without considering the underlying topology. An overlay network's ability to quickly recover from path outages and congestion is limited unless we ensure path independence at the IP layer. This paper proposes a novel framework for topology-aware overlay networks. In this framework, we expressly design overlay networks, aiming to maximize path independence without degrading performance. We develop measurement-based heuristics for 1) placement of overlay nodes inside an ISP and 2) selection of a set of ISPs. We base our analysis on extensive data collection from 232 points in 10 ISPs, and 100 PlanetLab nodes. On top of node placement, we present measurement-based verification to conclude that single-hop overlay routing performs as well as multi-hop routing with respect to both availability and performance. Our analysis results show that a single-hop overlay path provides the same degree of path diversity as the multi-hop overlay path for more than 90% of source and destination pairs. Finally, we validate the proposed framework using real Internet outages to show that our architecture is able to provide a significant amount of resilience to real-world failures.