Internet Core Protocols: The Definitive Guide

A Brief History of the Internet

Before you can understand how TCP/IP works—or why it works the way it does—you first have to understand the origins of the networking protocols and the history of the Internet. These subjects provide a foundation for understanding the basic design principles behind TCP/IP, which in turn dictate how it is used today.

TCP/IP presented a radical departure from the traditional computer networking services in use during its development. In the early days of commercial computing (the late 1960s), most companies bought a single large system for all of their data processing needs. These systems used proprietary networking architectures and protocols, which primarily consisted of plugging dumb terminals or line printers into an intelligent communications controller, each of which used proprietary networking protocols to communicate with the central hosts.

Most of the early computer networks used this hierarchical design for their proprietary network protocols and services. As users’ computing requirements expanded, they rarely bought a different system from a different vendor, but instead added new components to their existing platforms or replaced the existing system with a newer, larger model. Cross-platform connectivity was essentially unheard of, and was not expected. To this day, you still can’t plug an IBM terminal into a DEC system and expect it to work. The protocols in use by those devices are completely different from each other.

As the use of computers ...