1.1 History of the Concept
2. The OSI Reference Model
2.1 OSI Layer 1: The Physical Layer
2.2 OSI Layer 2: The Data Link Layer
2.3 OSI Layer 3: The Network Layer
2.4 OSI Layer 4: The Transport Layer
2.5 OSI Layer 5: The Session Layer
2.6 OSI Layer 6: The Presentation Layer
2.7 OSI Layer 7: The Application Layer
3. Summary of the OSI reference model
Over the past forty years computer networks have dramatically changed the way that we work, play, and communicate. In more ways than ever thought possible, we now have information and personal communication literally at our fingertips. The technology has become so evolved and integrated into every area of our lives that most people are not even aware of their lifestyle's significant reliance on computer networks. Television, cellular and landline phones, the Internet, our national military forces, and even the electricity received through the walls of homes would all fail if computer network technology was to vanish from the earth. This document will cover the history, workings, and modern day implementations of computer networks and the most common data communication protocols they utilize.
1.1 History of the Concept
The Oxford American Dictionary primarily defines the word network as "An arrangement of intersecting horizontal and vertical lines; A group of interconnected people or things". One of the simplest concepts developed by man, a network is the infrastructure that allows the efficient linking of multiple points. This term was not coined with the dawn of the computer, but rather closer to the dawn of time. Some well-known examples of networks before the digital age are interconnected irrigation canals, automobile highway systems, and utility delivery lines. Though not commonly called networks, all of these systems can be defined as networks and are excellent examples of a concept that is not new, but rather has found startling new applications in the past four to six decades. The first computers were extremely expensive, room sized machines which required a team of people to operate and performed what, by today's standards, would seem trivial computations. Despite the computer's start being so primitive, it did not take long for the first computer scientists to begin envisioning the potential power of applying the concept of networking to the new world of digital processing. In 1962, a man by the name of Licklider conceived an idea he called the "Galactic Network", and specifically exampled how it could be used for social interactions. Though his concepts were slightly ahead of their time, over the next few decades the idea that he drafted would come into reality.