Defense Information Systems Network
Providing the transmission infrastructure for a variety of routed military networks, the Defense Information Systems Network (DISN) was also an incremental replacement of transmission systems built from point-to-point digital multiplexers. Its current deployment, using Asynchronous Transfer Mode (ATM), began in 1991.
As opposed to the transportable and mobile transmission systems in Warfighter Information Network-Tactical, it interconnects fixed locations that connect to WIN-T and its predecessors. Military satellite communications systems complement the ATM backbone.
Some of the major routed networks that run over it include NIPRNET, SIPRNET and JWICS, at, respectively, the unclassified but government-only extranet, the SECRET, and TOP SECRET/compartmented control levels. Circuit-switched and bridged classified networks, however, can interconnect with the ATM backbone without routing, via TSEC/KG-75 FASTLANE ATM encryption devices, although the trend is away from these technologies and toward routing.