OSI Networking Models

Study Material For Cisco Ccna Ccnp And Ccie Students

Study Material For Cisco Students

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The term networking model, or networking architecture, refers to an organized description of all the functions needed for useful communications to occur. Individual protocols and hardware specifications then are used to implement the functions described in the networking model. When multiple computers and other networking devices implement these protocols, which, in turn, implement the functions described by the networking model, the computers can successfully communicate.

You can think of a networking model like you think of a set of architectural plans for building a house. Sure, you can build a house without the architectural plans, but it will work better if you follow the plans. And because you probably have a lot of different people working on building your house, such as framers, electricians, bricklayers, painters, and so on, it helps if they can all reference the same plan. Similarly, you could build your own network, write your own software, build your own networking cards, and create a network without using any existing networking model. However, it is much easier to simply buy and use products that already conform to some well-known networking model. And because the products from different vendors conform to the same networking architectural model, the products should work well together.

The CCNA exams include detailed coverage of one networking model—the Transmission Control Protocol/Internet Protocol, or TCP/IP. TCP/IP is the most pervasive networking model in the history of data networking. You can find support for TCP/IP on practically every computer operating system in existence today, from mobile phones to mainframe computers. Almost every network built using Cisco products today supports TCP/IP. Not surprisingly, the CCNA exams focus on TCP/IP.

The INTRO exam, and the ICND exam to a small extent, also covers a second networking model, called the Open Systems Interconnection (OSI) model. Historically, OSI was the first large effort to create a vendor-neutral networking model that could be added to any and every computer in the world. Ironically, OSI might be the least-pervasive networking model deployed today. However, because OSI was the first major effort to create a vendor-neutral networking architectural model, many of the terms used in networking today come from the OSI model.

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