ARPANET

The ARPANET (American Research Project agency NET work), now called DARPA, owned by US Defense, doest not follow the OSI model at all. The IMP-IMP protocol really corresponds to mixture of the layer 2 and layer 3 protocols. Layer 3 also contains an elaborate routing mechanism. In addition, there is a mechanism that explicitly verifies the correct reception at the destination IMP of each and every of protocol sent by the source IMP.

The ARPANET does have protocols that roughly cover the same territory as the OSI network and transport protocols. The network protocols, called IP (Internet Protocol) is connectionless and was designed to handle the interconnection of the vast number of WAN and LAN. The ARPANET transport protocol is a connection-oriented protocol called TCP (Transmission Control Protocol). There is no session or presentation layer protocol in ARPANET.
The ARPANET services include files transfer, email and remote login. These services are supported by well-known protocols FTP, SMTP (Simple Mail Transfer protocols) and TELNET (remote login)