NSFNET was the network that succeeded ARPANET as the principal U.S. Internet backbone.
The National Science Foundation created NSFNET in 1985 to connect the country’s new supercomputing centers with universities and regional research networks. Its backbone used the TCP/IP protocols that had already proven successful on ARPANET, allowing many separate networks to exchange data through a growing national infrastructure.
NSFNET became the principal Internet backbone in 1986, after its first regional connection became operational. The original backbone operated at much lower speeds than today’s Internet, but it expanded rapidly. An upgraded 45-megabit-per-second T-3 backbone was deployed in 1991 and connected a broad collection of academic, government, and international research networks.
CSNET and BITNET were important earlier academic networks, but they did not replace ARPANET as the central backbone. Internet2 is a much later advanced research network. ARPANET was phased out around 1990, while NSFNET continued serving as a crucial transitional backbone until its backbone service was decommissioned on April 30, 1995, as commercial Internet providers took over.