From ARPANET to SDN: How the Internet Evolved Over 60 Years

Editor’s Note

“Those who cannot remember the past are doomed to repeat it.” – George Santayana, 1905.

Since 2006, SDN has evolved from narrow OpenFlow concepts to today’s fully programmable P4 networks, a journey worth revisiting to understand the original goals and future direction of networking.

Cold War Background

After World War II, the United States and the Soviet Union entered a decades‑long Cold War, competing via proxy wars, technology races, and space exploration while avoiding direct military conflict.

APRA Formation

In response to Sputnik I (1957) and the perceived Soviet lead, the U.S. created the Advanced Research Projects Agency (ARPA) in 1958 to explore high‑risk, high‑payoff technologies, including distributed command systems to survive nuclear attacks.

ARPANET Project Launch

ARPA’s IPTO office, led by Robert Taylor in 1966, advocated a universal communication protocol, resulting in the ARPANET project. Key contributors included Lawrence G. Roberts (MIT), Paul Baran (RAND), and Leonard Kleinrock (UCLA).

Baran’s distributed communication theory proposed two ideas: fully decentralized network control and packet switching instead of circuit switching.

Roberts designed the Interface Message Processor (IMP) as a small, cheap computer to handle routing, effectively the first router.

ARPANET Birth

In 1969, BBN won the $1 million contract to build the first four‑node ARPANET using IMPs with 50 kbps links between UCLA, Stanford, UCSB, and the University of Utah.

Key milestones include the first login test (CHARLEY KLINE) and the transition to TCP/IP in 1982.

TCP/IP and the Internet

Early ARPANET used the Network Control Protocol (NCP). In 1973, Bob Kahn and Vint Cerf designed TCP, later split into TCP (transport) and IP (network) layers, forming TCP/IP.

TCP/IP replaced NCP in 1982, and by 1984 it became the dominant standard, leading to the modern Internet.

HTTP and the Web

In 1989, Tim Berners‑Lee at CERN proposed three core Web components: URI, HTML, and HTTP. The first HTTP server and client were demonstrated in December 1990, and the first website went live in August 1991.

REST Architecture and API Economy

Roy Thomas Fielding’s 2000 PhD thesis introduced REST, emphasizing resource representation, statelessness, and uniform interfaces. RESTful APIs became the backbone of modern cloud services.

Accept: Application/json
Content-Type: Application/json

# Client
GET /resource
Accept: text/html

# Server
Content-Type: text/html;charset=utf-8
Response code: 200

Future Internet Concepts

Early 2000s research split into “evolutionary” (patch‑based) and “revolutionary” (clean‑slate) approaches. NSF funded GENI and FIND projects to explore new architectures with better security, manageability, and QoS.

OpenFlow and SDN Birth

In 2006, Martin Casado’s Ethane project introduced a centralized controller for network security. This led to the creation of Nicira (later acquired by VMware) and the OpenFlow protocol, first described in a 2008 SIGCOMM paper.

SDN Turbulence

Open Networking Foundation (ONF)

Founded in 2011 by academia and industry leaders to promote SDN and OpenFlow.

OpenDaylight

Launched in 2013 under the Linux Foundation, OpenDaylight emphasized multi‑southbound protocols and distributed controllers, expanding SDN beyond OpenFlow.

Overlay Virtual Networks

Standardized overlay technologies (VXLAN, NVGRE, STT) emerged to provide virtual L2 networks over L3, widely adopted in data‑center clouds.

P4 Programmable Networks

In 2014, the P4 language and Barefoot’s Tofino ASIC enabled protocol‑independent, reconfigurable data‑plane processing, overcoming the limitations of OpenFlow.

Future: Fully Programmable Networks

Intel’s 2019 acquisition of Barefoot and Nick McKeown’s roadmap outline three phases: (2010‑2020) control‑plane separation via OpenFlow, (2015‑2025) data‑plane programmability with P4, and (2020‑2030) end‑to‑end programmable NICs, switches, and protocol stacks.