address for each host on the ARPANET,4 which could be looked up by using the host’s one-word English language name, acronym, or abbreviation. The Network Information Center (NIC) at the Stanford Research Institute5 managed the registration of hosts and the distribution of the information needed to keep the HOSTS.TXT file current. The list of host names and their mapping to and from network addresses was maintained in the frequently updated HOSTS.TXT file, which was copied to and stored in each computer connected to the ARPANET. Thus, HOSTS.TXT6 was introduced to:

  • Simplify the identification of computers on the ARPANET. Simple and familiar names are much easier for humans to remember than lengthy (12-digit) numeric strings; and

  • Provide stability when addresses changed. Since addresses in the ARPANET were a function of network topology and routing,7 they often had to be changed when topology or routing changed. Names in the host table could remain unchanged even as addresses changed.

The HOSTS.TXT file had a very simple format. Each line in HOSTS.TXT included information about a single host, such as the network address, and when provided, system manufacturer and model number, operating system, and a listing of the protocols that were supported.

Because a copy of the host table was stored in every computer on the ARPANET, each time a new computer was added to the network, or an-


These network addresses could be represented using the Internet Protocol (IP) format or in the equivalent (now unused) ARPANET Network Control Protocol (NCP) format. The most widely used version (v4) of IP represents addresses using 32 bits, usually expressed as four integers in the range from 0 to 255, separated by dots. An example of an IP address is


Stanford Research Institute became known as SRI International in 1977.


For further discussion, see L. Peter Deutsch, “Host Names On-line,” Request for Comments (RFC) 606, December 1973; Ken Harrenstien, Vic White, and Elizabeth Feinler, “Hostnames Server,” RFC 811, March 1982; and Ken Harrenstien, M. Stahl, and Elizabeth Feinler, “DOD Internet Host Table Specification,” RFC 952, October 1985, all available at <>. RFCs are created to document technical and organizational aspects of the Internet. The Internet Engineering Task Force (IETF) manages the process for discussing, evaluating, and approving RFCs. See Box 3.3. For a discussion of the role of the DNS more generally, see John C. Klensin, “Role of the Domain Name System,” RFC 3467, February 2003.


Routing refers to the way data flowed on the ARPANET. Data transmitted from point A to point B might have traversed many different paths, or routes, on the ARPANET. Note that the ARPANET, as the original network to employ the Internet Protocol (IP), was often referred to as “the Internet,” although the term later formally encompassed the aggregate of interconnected IP-based networks.

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