The Non-classified Internet Protocol Router Network (NIPRNet) is used to exchange sensitive but unclassified information between "internal" users as well as providing users access to the Internet. NIPRNet is composed of Internet Protocol routers owned by the United States Department of Defense (DOD). It was created by the Defense Information Systems Agency (DISA) to supersede the earlier MILNET.
NIPRNet is, by design, a parallel airgapped analogue to the SIPRNet, providing seamless interoperability for unclassified combat support applications, as well as providing a gateway to the public Internet. While the two networks are not intended to logically intersect, occasionally it is seen as necessary to tunnel the encrypted SIPRNet over NIPRNet (SIPR over NIPR).
SIPRNet and NIPRNet are referred to colloquially as sipper-net and nipper-net (or simply sipper and nipper), respectively.