Though the most successful, the ARPANET was not the only packet data communications network under development. Other networks were being developed as well. In England, NPL Data Network had been developed at the National Physical Laboratories, Middlesex, in 1967. Michigan, Michigan State, and Wayne State Universities together established Merit Network (x.25 based) in 1969. ALOHAnet was developed in 1970 by Norman Abrahamson at the University of Hawaii; it was connected to the ARPANET in 1972. The development of these other networks (and the connection of ALOHAnet to the ARPANET) led to the realization that some mechanism was required for linking disparate networks as well as linking computer systems to an existing network. This led to ARPA research on internetworking -- the linking of separate networks -- culminating in the development, by Vinton Cerf and Bob Kanh, of their 1974 paper entitled "A Protocol for Packet Network Intercommunication." The ideas in this paper provide the substance of the internet protocols of today -- the Transmission Control Protocol (TCP) and Internet Protocol (IP).
The development of the Ethernet protocol by Bob Metcalfe occurred at roughly the same time as the recognition that interconnection of networks was necessary; refinement of this technology was to give rise to practical Local Area Networks (LANs), which would in turn fuel the need to interconnect networks. In the next few years, many other significant developments in networking were to be seen: the development of Telenet (1974) and Tymnet (1977), Usenet (1979), BITNET (1981), CSNet (1981), and the Defense Data Network (DDN, 1982).
Additional details on Internet and related developments in this period may be found here.[2]