1. In a computer network having a plurality of links and a plurality of client computers, a method of determining which of the plurality of links are lossy, the method comprising: determining end-to-end packet loss rates at each of the plurality of clients; randomly choosing packet loss rates for one or more of the plurality of links such that in combination these match the packet loss rates determined for each of the plurality of clients; repeating the choosing step over a plurality of iterations; and statistically analyzing the randomly chosen packet link loss rates over the plurality of iterations for the one or more of the plurality of links.