1. A method for determining which of a plurality of links of a computer network are lossy, the network comprising a plurality of clients that communicate with a server over one or more of the plurality of links, the method comprising: establishing a system of equations that describes the relationship between the packet loss rates at the links and the packet loss rates at the clients; setting up constraints on the possible solutions to the system of equations; linearizing the constraints; deriving an objective function that represents both an aggregation of the packet loss rates for the plurality of links and an aggregate slack in the constraints; and calculating loss rates that solve the system of equations and give a minimum possible value for the function.