MILNET (Military Network) was the acronym given to that part of the Advanced Research Projects Agency Network (ARPANET) assigned to unclassified traffic from the United States Department of Defense. ARPANET was the name given to the computer network topography that would later become what is today known popularly as the internet. In 1983, the ARPANET and MILNET were split so that henceforth the former would be dedicated to academic research while the latter would be used for the transmission of U.S military data. The system that dictates the ascription of domain names to websites –- the domain name system (DNS) -– assigned the top level domain (TLD).mil for use by the U.S military.
The provenance of today’s internet lies in what was in its early stages a research project that researchers entitled ARPANET; this network was originally a minute version of the massive interconnected network we know today as The Net. In 1969, the ARPANET network connected the universities of California, Stanford and Utah and provided for the simple packet switching of data around these sites, or nodes.
In 1983, the number of ARPANET’s nodes, or points of connection, numbered 113. Subsequent to the ARPANET/MILNET split, however, the MILNET part of the network sequestered 65 nodes that it would dedicate to military data and which it could better safeguard. This left the ARPANET with 68 nodes. The ARPANET and MILNET networks retained a certain number of connection points, known as gateways, but these were few and easily uncoupled, affording the MILNET network with a security provision that could be invoked if the network was attacked or compromised.
As the potential for massive interconnectedness was realized in the advances that saw the advent of the internet, military agencies were also aware of the potential for MILNET. Initially providing Internet Protocol (IP) connectivity among the various United States military bases at home and abroad, the MILNET split again in the 1990s into several networks that are today known as the Non-Classified Internet Protocol Router Network (NIPRNET), the Secret, formerly secure, Internet Protocol Router Network (SIPRNET) and the Joint Worldwide Intelligence Communications System (JWICS).
Today what was known as the MILNET network has been subsumed by the Defense Data Network (DDN), and the section that was once known as MILNET is now known as NIPRNET, the network the United States military to use to exchange sensitive but unclassified data among internal users.