Performance evaluations of advanced communication subsystems and their applications are necessary methods to prove that a certain level of communication functionality demanded and a required minimal processing power of end-systems (workstations) and of intermediate systems (networks and routers) have been achieved. The communication middleware package Da CaPo++ provides a modern communication platform that supports flexible communication services, in particular for end-systems. Based on an implementation of Da CaPo++ on workstations (Sun SPARCStations and Sun UltraSPARCs) a performance evaluation has been carried out. Specifically, the performance for relevant communication tasks is identified and overhead required for providing various degrees of communication service flexibility is illustrated