1. A computer-readable storage medium containing instructions for controlling interceptors to track context of a service provider, the interceptors being layered from a highest level to a lowest level interceptor between a client and the service provider, by a method comprising: providing by the highest level interceptor to the client of the service provider modified service provider context information which has been modified to reference interceptor context information associated with the client, the service provider context information being modified by the lowest level interceptor by retaining a copy of a portion of the service provider context information prior to modification by the lowest level interceptor and replacing that portion of the service provider context information with a reference to the interceptor context information of the lowest level interceptor, the modified service provider context information provided by each interceptor except the highest level interceptor being modified by the next higher level interceptor by retaining a copy of a portion of the modified service provider context information provided by the interceptor prior to modification by that next higher level interceptor and replacing that portion of the modified service provider context information with a reference to the interceptor context information of that next higher level interceptor; upon receiving from the client a request for a service of the service provider, for each interceptor from the highest level to the lowest level, receiving the request by the interceptor; using modified service provider context information of the request to retrieve interceptor context information by retrieving from the modified service provider context information the reference to the interceptor context information of the interceptor and retrieving the interceptor context information referenced by the retrieved reference; restoring the modified service provider context information to before modification by the interceptor by replacing the portion that was replaced with the retained copy; and forwarding to the next lower level interceptor or the service provider the request along with the restored service provider context information wherein the lowest level interceptor replaces the portion of the service provider context information that was replaced with the retained copy of the portion of the service provider context information; and upon receiving from the service provider a response to the request for service, modifying by each interceptor the service provider context information to reference the interceptor context information; and forwarding to the client the response along with the modified service provider context information.