development of a user-network protocol that has become the standard interface between users and packet switched networks; namely, ITU-T (formerly CCITT) Recommendation X.25. This "standard" interface encouraged BBN to start Telenet, a commercial packet-switched data service, in 1974; after much renaming, Telenet is now a part of Sprint's X.25 service. The initial host-to-host communications protocol introduced in the ARPANET was called the Network Control Protocol (NCP). Over time, however, NCP proved to be incapable of keeping up with the growing network traffic load. In 1974, a new, more robust suite of communications protocols was proposed and implemented throughout the ARPANET, based upon the Transmission Control Protocol (TCP) and Internet Protocol (IP). TCP and IP were originally envisioned functionally as a single protocol, thus the protocol suite, which actually refers to a large collection of protocols and applications, is usually referred to simply as TCP/IP. The original versions of both TCP and IP that are in common use today were written in September 1981, although both have had several modifications applied to them (in addition, the IP version 6, or IPv6, specification was released in December 1995). In 1983, the DoD mandated that all of their computer systems would use the TCP/IP protocol suite for long-haul communications, further enhancing the scope and importance of the ARPANET. In 1983, the ARPANET was split into two components. One component, still called ARPANET, was used to interconnect research/development and academic sites; the other, called MILNET, was used to carry military traffic and became part of the Defense Data Network. That year also saw a huge boost in the popularity of TCP/IP with its inclusion in the communications kernel for the University of California s UNIX implementation, 4.2BSD (Berkeley Software Distribution) UNIX. In 1986, the National Science Foundation (NSF) built a backbone network to inte...
