The book "Principles of Protocol Design" offers a comprehensive introduction to the fundamental principles used in the construction of modern data communication protocols. The author, Robin Sharp, takes a formal approach based on the description of protocols in CSP notation. This method allows for a concise representation of protocols and the analysis of their interesting properties, as well as the formal proof of certain aspects of their correctness with respect to appropriate specifications. After discussing the basic principles, specific protocols that utilize these principles are examined. This fully revised edition of the book, first published in 1994, reflects the developments in computer networking technology and distributed systems in recent years. The terms and concepts from the OSI reference model used in the book remain crucial for a systematic analysis of data communication systems.