I will use ARPANET to refer to the Defense Department’s network from its conception in the late 1960s until 1992, whereas the Internet refers to the commercial network that began in 1992 when the National Science Foundation partnered with a group of commercial ISPs to interconnect at MAE-East, the first Internet Exchange Point (IXP) intended to support commercial traffic. Notably, MAE-East predated the National Infrastructure Plan, which later formalized the establishment of IXPs across the U.S.
The development of modern networked computing involved multiple parallel efforts, including a pre-TCP/IP protocol, a pre-UNIX operating system, and a pre-ARPANET network.
During the ARPANET period, various other networks existed because ARPANET did not allow commercial traffic, yet businesses had an increasing need to transport data. As a result, commercial common carrier networks like Tymnet and Telenet, government-funded X.25 networks such as TRANSPAC, Datapac, and Euronet, and commercial proprietary networks by companies like GE and IBM emerged to fill this gap. These networks eventually faded away when the Internet became commercial in 1992.
The project to develop what would become ARPANET began in 1966, when Bob Taylor was named Director of Information Processing Techniques Office (IPTO) and initiated the first funding for the project by convincing Charles Hertzfield to transfer one million dollars from a ballistic missile defense fund to ARPA for the purpose.
Before TCP/IP, the first protocol used on ARPANET was Network Control Protocol (NCP), which played a foundational networking role and drove the transition to TCP/IP. NCP didn’t vanish—it evolved. It became the foundation for both the proprietary Tymnet protocol and CCITT X.25, two distinct networking approaches often conflated.
Tymnet, in particular, was not an X.25 network. It was a separate, packet-switched system that incorporated many features later found in TCP and predated ARPANET. Initial development efforts began in early 1968, when La Roy Tymes left Berkeley Lawrence Laboratory to join Tymshare. Tymes had been eager to build a working network, and was chafing at ARPA’s slow pace. He moved to Tymshare to build the network.
Tymnet went live with production traffic in late 1968, a full year before the first ARPANET nodes came online. By November 1971, the network had reached 50 operational nodes with an international footprint. Tymnet’s management then decided to commercialize the network, officially opening it to third-party connections and paying customers in February 1972—a full 20 years before the Internet’s commercialization at MAE-East in 1992. While the MAE-East contract was signed in late 1992, actual traffic-bearing connections began appearing in early 1993.
MAE-East was created by a team of network engineers at MFS Datanet, a company founded by Tymnet alumni. This establishes a direct, linear connection between the founding of Tymnet in 1968 and the birth of the commercial Internet in 1992.
In response to Tymnet’s commercial success, Bolt, Beranek, and Newman (BBN)—a major ARPANET contractor—leveraged government-funded ARPA technology to launch Telenet in 1974, an X.25-based commercial network.
The focus on UNIX as the backbone of early Internet systems also overlooks an important reality: the first computers connected to the Internet were not UNIX-based. In fact, UNIX was a latecomer, first arriving as BSD 4.2 in 1983. The first ARPANET connection, established in late October 1969, linked an SDS-940 at Stanford to another SDS system at UCLA. These systems ran an operating system called BTSS, derived from Project Genie, an influential time-sharing OS developed at UC Berkeley long before UNIX existed.
Tymshare, the company behind Tymnet, further enhanced the BTSS system developed at UC Berkeley and named their variation Tymcom. Tymshare also convinced Scientific Data Systems (SDS) to create a time-sharing optimized hardware platform, known as the SDS-940. This combination of the enhanced BTSS OS and the SDS-940 hardware became the first true network operating system and computer.
Understanding this broader history provides valuable context for how the Internet evolved—not just through TCP/IP and UNIX, but through competing technologies and commercial forces that shaped the networking landscape.
For a deeper dive into this overlooked history, I suggest The Tym Before (ISBN: 979-8333665959) and Securing the Network (ISBN: 978-1520155586).
Liked this, really helped me with my cybersecurity project.💯