Reusing CDN Monitoring Information

Motivation and approach

To enhance web browsing experiences, content distribution networks (CDNs) move web content "closer" to clients by caching copies of web objects on thousands of servers worldwide. Additionally, to minimize client download times, such systems perform extensive network and server measurements, and use them to redirect clients to different servers over short time scales. We are exploring techniques for inferring and exploiting network measurements performed by the largest CDN, Akamai; our objective is to locate and utilize quality Internet paths without performing extensive path probing or monitoring.

We have conducted a broad measurement study of Akamai's CDN, probing Akamai's network from 140 PlanetLab vantage points for two months. We have found that Akamai redirection times, while slightly higher than advertised, are sufficiently low to be useful for network control. We have empirically shown that Akamai redirections overwhelmingly correlate with network latencies on the paths between clients and the Akamai servers. Finally, we have illustrated how large-scale overlay networks can exploit Akamai redirections to identify the best detouring nodes for one-hop source routing. Our research shows that in more than 50% of investigated scenarios, it is better to route through the nodes "recommended" by Akamai, than to use the direct paths.