A new Web proxy cooperation model is introduced and analyzed that preserves advantages of cooperative caching in the presence of proxy link capacity variations. The Restricted Broadcast Query (RBQ) cooperation model uses a score table containing dynamic information that describes proxy connectivity. This information is used to re-distribute load among proxies, thereby compensating for changes in link capacities. An analytic model was developed to evaluate network congestion effects on alternative Web proxy cooperation mechanisms (CMs). The model was applied to a system of identical, fully connected proxies, in order to compare the performance of two common CMs (Broadcasting and URL-hashing) with that of RBQ.