Layered architectures and the architectures of computer networks. The ISO Open System Interconnection Reference Model and the TCP/IP architecture. Formal methods for the definition of communication protocols. Application of the numerical Petri nets to the definition of layer protocols and interface (service) protocols. Verification and validation of protocols. Local networks and its architectures. Medium access control protocols for the local networks. The transport level interface service protocol and its applications. Connectionless (datagram) and connection oriented communication. Models of the client server communication. The protocols and distributed data bases of the internet layer of the TCP/IP architecture. Standard network applications and its protocols.