On the effectiveness of measurement reuse for performance-based detouring

For both technological and economic reasons, the default path between two end systems in the wide-area Internet can be suboptimal. This observation has motivated a number of systems that attempt to improve reliability and performance by routing over one or more hops in an overlay. Most of the proposed solutions, however, fall at an extreme in the cost-performance trade-off. While some provide near-optimal performance with an unscalable measurement overhead, others avoid measurement when selecting routes around network failures but make no attempt to optimize performance. This paper presents an experimental evaluation of an alternative approach to scalable, performance detouring based on the strategic reuse of measurements from other large distributed systems, namely content distribution networks (CDNs). By relying on CDN redirections as hints on network conditions, higher performance paths are readily found with little overhead and no active network measurement. We report results from a study of more than 13,700 paths between 170 widely-distributed hosts over a three-week period, showing the benefits of this approach. We demonstrate that it is practical by implementing an FTP suite that uses our publicly available SideStep library to take advantage of these alternative Internet routes.