This paper presents experiences gained from the verification of a large-scale real-world embedded system by means of formal methods. This industrial verification project was performed for a fault-tolerant system designed and implemented by DaimlerChrysler Aerospace for the International Space Station ISS. The verification involved various aspects of system correctness, like deadlock and livelock analysis, correct protocol implementation, etc. The approach is based on CSP specifications and uses the model-checking tool FDR. It is realized by combining methods for the development as well as for the analysis. It is illustrated by examples and results obtained during the verification of the Byzantine agreement protocol implementation, where the combination of different abstraction methods is required.