The origins of the TCP protocol lie with ARPA (Advanced Research Projects Agency, renamed "DARPA" in 1972), which launched the ARPANET project in 1966. The first ARPANET segment went live in October 1969, interconnecting UCLA and Stanford universities. The aim was to link research centers through a packet-switched network that could keep communications running even in the event of partial infrastructure failure.

As part of this dynamic, ARPA financed the University of Berkeley to integrate the first TCP/IP protocols into its BSD Unix system. This played a major role in spreading and standardizing the protocol, first in the academic world, and later in industry.

Note: at that time, computer scientists didn't yet have Linux (which wouldn't appear until the early 1990s), nor Minix, the educational system designed by Andrew Tanenbaum. The main options were Unix, or, sometimes, proprietary mainframes like OpenVMS. Thanks to its flexibility and openness, Unix was instrumental in spreading the first networking concepts.

Strictly speaking, TCP/IP is not a single protocol but a suite of protocols built around TCP and IP. It rose to prominence because it provided a standardized programming interface for exchanging data between machines on the same network. This interface, based on primitives called "sockets", made it possible to create reliable and flexible connections while integrating essential application protocols.

ARPANET is therefore the historical foundation of today's Internet. Indeed, the Internet is a global network based on the principle of packet switching, where information circulates using a set of standardized protocols that ensure compatibility and interoperability between heterogeneous systems. This open architecture has enabled the development and deployment of countless services and applications, including:

The governance and evolution of these protocols are overseen by the Internet Architecture Board (IAB). This organization coordinates technical directions through two main structures:

The distribution of network resources (IP address ranges, autonomous system numbers, root domain names, etc.) is coordinated internationally by IANA/ICANN. Operational management relies on: RIR (Regional Internet Registries): RIPE NCC (Europe, Middle East, Central Asia), ARIN, APNIC, LACNIC and AFRINIC.

All TCP/IP protocol specifications are recorded in documents called RFC (Request For Comments), which serve as authoritative technical references. RFCs are continually updated and numbered to reflect the ongoing evolution of the protocol suite.

The TCP/IP stack is often represented as a stack of four functional layers, often compared to the seven-layer OSI (Open Systems Interconnection) model developed by the ISO (International Standards Organization), which serves as a conceptual reference for networking.

The four layers of the TCP/IP model are:

Today, the most widely used version of IP is IPv4, but its 32-bit address space has clear limitations. This led to the creation of IPv6, which uses 128-bit addressing and offers virtually unlimited capacity: essential for supporting the explosive growth of connected devices and meeting the challenges of the Internet of Things, mobility, and security.

Each layer of the TCP/IP stack provides specific services, making it possible to address different networking needs in a modular way: physical transmission, logical addressing, data integrity, and application-level services.