The architecture that makes 'network is the computer' possible is the protocol architecture shown in the figure. This protocol architecture is used in the Internet. Above the Internet Protocol, the Transmission Control Protocol runs. Above TCP, the application layers software runs which is different for different applications. The SMTP (Simple Mail Transfer Protocol) is used for mail, above which the Multimedia Internet Mail Extension (MIME) protocol is used for multimedia mail transfer. File Transfer Protocol (FTP) is used for file transfer. TELNET protocol is used for remote log in. Hypertext Transfer Protocol (HTTP) is the protocol used for web access. The Simple Network Management Protocol (SNMP) is used for network management. SNMP runs on UDP, the User Datagram Protocol. TCP is a connection-oriented protocol whereas the UDP is connectionless. BGP, Border Gateway Protocol, is used for routing.
IP has to run on every end system and router. TCP has to run on every end system.