1. A method for obtaining performance measurements for at least one selected resource in a computer network, said computer network containing a plurality of resources and executing a communication access program to control communication sessions between pairs of said plurality of resources, comprising the steps of: activating a performance exit interface in the communication access program to signal that performance data is to be collected for said at least one selected resource; requesting said communication access program to start the collection of performance data for each communication session between said pairs of plurality of resources having said at least one selected resource as one of said pairs of plurality of resources; collecting said performance data for said each communication session having said at least one selected resource as one of said pairs of plurality of resources without impairing any trace facilities of said communication access program and providing said performance data to said performance exit interface; processing said performance data to determine performance measurements for said at least one selected resource; and terminating said collection of performance data for said each communication session and deactivating said performance exit interface.