Join Timothy Pintello for an in-depth discussion in this video Introducing the OSI model, part of Foundations of Networking: Networking Basics.
- The next major topic I want to discuss is the OSI Model. The OSI Model stands for Open Systems Interconnection Reference Model. The OSI Model was created initially as a reference model and teaching aid to help students and other people learn how protocols in networks all work together to carry out the job of moving data from one end to the other of the network. It was never intended to actually reflect any actual networking architectures.
Aside from being a device to teach people how protocols and networks work together, the OSI Model was also a model that was intended as a reference for organizations to use when creating new protocols. By using the model to create new protocols, organizations could be assured that the new protocols that they create would fit into an overall architecture without having to basically reinvent the wheel each time they did it. The OSI Model looks like this.
The OSI Model has seven layers, and each one of these layers has a unique specific job, which we'll get into in more detail in following videos. Now, starting at top to bottom, we have the Application, Presentation, Session, Transport, Network, Data Link, and Physical layers. A way to memorize these layers in the proper order is to use a mnemonic. A mnemonic is a memory device that helps you learn each layer by using a word, or a common word, that is the first character of the layer that you're trying to memorize.
So, a mnemonic commonly used to learn the OSI Model from top to bottom, is this: All People Seem To Need Data Processing. Another mnemonic that is commonly used to learn the layers of the OSI Model from bottom to top is: Please Do Not Throw Sausage Pizza Away. Either one of these mnemonics, or one you create for yourself, will help you memorize the proper order that the layers of the OSI Model should be in.
The OSI Model when it was first created came out in two parts. The first part was the abstract model that we just looked at. This model had the seven layers as we've just discussed it. The second part of the OSI Model was actually a specifically created set of protocols that was designed to illustrate how the protocols would fit inside this abstract model that was created to help teach how networking and protocols work together.
The protocols that were created are not actually used in any network systems, and were not really intended to be used in network systems. They were strictly intended to be reference protocols that other people could use to create protocols in the future. Two organizations published the OSI Model back in 1984. One of the organizations that helped publish the model was International Standards Organization. The International Standards Organization published the model as the ISO 7498 standard.
The other organization that helped publish the OSI Model was the Telecommunications Standardization Sector of the International Telecommunications Union, or ITU-T. ITU-T published the OSI Model under the ITU standard X.200. A good place to get additional information on the OSI Model is this website right here, that is part of Microsoft's support web page.
- Topologies: mesh, bus, ring, star, and more
- Point-to-point vs. point-to-multipoint networks
- Exploring LANs, WLANs, and PANs
- Understanding the seven layers of the OSI model
- Exploring layers in the TCP/IP model
- Working with NICs, hubs, switches, and routers