This paper describes RTC, a set of software layers based on the ISO/OSI standard that implements a complete real-time communication platform on a cluster running under realtime Linux. A modi ed TDMA protocol is implemented as Media Access Control (MAC) discipline, and at the application level the communication approach is channel-oriented. The RTC platform guarantees a bandwidth for each channel, which makes it attractive for multimedia applications, which currently is the main application considered. RTC also supports non-real-time tra c among the nodes using TCP/IP, for instance. The platform, with the exception of some parts of the non-real-time capabilities, is implemented as modules of the Linux/RTAI operating system. As underlying communication network currently SCI is used. SCI has been selected due to its low latency, low jitter and high bandwidth. RTC, however has been designed to support other network technologies as well. The paper also shows performance evaluation results that demonstrate the real-time properties of RTC.