Microsoft is producing high-quality documentation for Windows client-server and server-server protocols. Our group in the Windows organization is responsible for verifying the documentation to ensure it is of the highest quality. We are applying various test-driven methods including, when appropriate, a model-based approach. This paper describes certain aspects of the quality assurance process we put in place, and specifically focuses on model-based testing (MBT). Our experiences so far confirm that MBTworks and that it scales, provided it is accompanied by sound tool support and clear methodological guidance.