In this chapter of the journey to learn computer networking technology we explain the OSI Reference Model in simple terms, and expand on the different layers of the OSI model.
The OSI model defines the basic building blocks of computer networking, and is an essential part of a complete understanding of modern TCI/IP networks. The theoretical OSI Reference Model is the creation of the European based International Organization for Standardization (ISO), an independent, non-governmental membership organization that creates standards in numerous areas of technology and industry.
Why is the OSI Reference Model important?
An understanding of the concepts of the OSI Reference Model is absolutely necessary for someone learning the role of the Network Administrator or the System Administrator. The OSI model is important because many certification tests use it to determine your understanding of computer networking concepts.
The Open Systems Interconnection Reference Model (OSI Reference Model or OSI Model) was originally created as the basis for designing a universal set of protocols called the OSI Protocol Suite. This suite never achieved widespread success, but the model became a very useful tool for both education and development. The model defines a set of layers and a number of concepts for their use that make understanding networks easier.
The Internet and the TCP/IP family of protocols evolved separately from the OSI model. Often you find teachers, and websites, making direct comparison of the different models. Don't spend too much time trying to compare one versus the other. The two models were developed independently of each other to describe the standards of computer networking.
The TCP/IP Reference Model is not merely a reduced version of the OSI Reference Model with a straight line comparison of the four layers of the TCP/IP model to seven layers of the OSI model. The TCP/IP Reference Model does NOT always line up neatly against the OSI model. People try too hard to make neat comparisons of one model versus the other when there is not always a neat one to one correlation of each aspect.
Simply put the OSI Reference Model is a THEORETICAL model describing a standard of computer networking. The TCP/IP Reference model is based on the ACTUAL standards of the internet which are defined in the collection of Request for Comments (RFC) documents started by Steve Crocker in 1969 to help record unofficial notes on the development of ARPANET. RFCs have since become official documents of Internet specifications, as discussed in the article What is the difference between the Internet and OSI reference model.
If are looking for something less technical that focuses more on using a computer network, rather than understand the core concepts of how it works, please visit our companion website The Guru 42 Universe where we discuss managing technology from the perspective of a business owner or department manager.