Depending on the physical structuring of large distributed safety-critical real-time systems, one can distinguish federated and integrated system architectures. This paper investigates the communication services of an integrated system architecture, which combines the complexity management advantages of federated systems with the functional integration and hardware benefits of an integrated approach. A major challenge is the need to accommodate the communication services to the different types of integrated application subsystems that range from ultradependable control applications (e.g., an x-by-wire system) to non safety-critical applications such as multimedia or comfort systems. In particular, the encapsulation of the communication activities of different application subsystems is required not only to prevent error propagation from non safety-critical application subsystems to higher levels of criticality, but also to facilitate complexity management and permit independent development activities.