Cooperative caching systems

Cooperative Web caching is the most common solution for augmenting the low cache hit rates due to single proxies.

Many coordination schemes have been proposed to achieve effective and efficient cooperation. However, both purely hierarchical and flat architectures suffer from scalability problems due to cooperation protocol overheads.

We investigate new cooperation paradigms that aim to achieve better scalability in geographical environment by organizing cache servers in well connected clusters. We are also studying a novel cooperation model based on a two-tier lookup process.


Selected Papers

This page includes a selected list of publications since 1999. Publications not available online can be requested to the authors.

Testing of CDN performance

The largest Content Distribution Networks (CDN) provide an infrastructure of thousands of geographically distributed servers, which are placed at the edge of Internet that is, at the main ISP points of presence. A CDN includes a content-aware routing mechanism to dispatch the client requests to the "most convenient" edge server. There are several possible routing mechanisms, but the most used solution is based on a combination of dynamic URL rewriting at the origin server and DNS interposition. With respect to the traditional proxy caching, a CDN solution can achieve ery high cache hit rate. However, proxy caching is typically free, while CDN services are highly expensive.

Hence, it is of key importance to evaluate the real costs/benefits of this outsourcing solution. We propose a new tool called CDNperf that compares the user perceived response time of content delivery achieved with and without the use of CDNs.

Riccardo Lancellotti