Abstract: The increasing diversity of Internet appliances calls for an architecture for performance differentiation on information access. The World Wide Web is the dominant interface for information access today. Web proxy caching is the key performance accelerator in the web infrastructure. While many research efforts addressed performance differentiation in the network and on web servers, providing multiple levels of service in proxy caches has received much less attention. This paper has two main contributions. First, we describe, implement, and evaluate an architecture for differentiated content caching services as a key element of the Internet infrastructure. Second, we describe a control-theoretical approach that lays well-understood theoretical foundations for resource management to achieve performance differentiation in proxy caches. We describe our experiences with implementing the differentiated caching services scheme in Squid, a popular proxy cache used by many ISPs today. Experimental study and analyses prove that differentiated caching services provide significantly better performance to the premium content classes.