Supporting configurability and real time in RTD channels

Network communication services that can be configured to customize function ality provide significant advantages over monolithic versions, but can be d ifficult to construct if the services must also provide real-time guarantee s on message delivery. This paper describes how practical issues related to the combination of configurability and real time have been addressed in re al-time dependable (RTD) channels, a communication abstraction that has bee n prototyped using the Cactus system. The architecture and implementation o f RTD channels are described, including facilities for translating an appli cation's quality of service requirements into configuration-specific resour ce requirements, and an admission control architecture that uses system-wid e information to determine whether sufficient resources exist to create new channels. In addition, the results of experiments that demonstrate that th e desired channel properties-including real-time guarantees-are provided fo r various configurations are presented. Finally, practical problems and les sons learned from implementing RTD channels on the general-purpose MK 7.3 M ach operating system are discussed. Copyright (C) 2001 John Wiley & Sons, L td.