The Open Systems Interconnection (OSI) layer model is a way of describing communications by computer systems over networks. The goal is to set a standard for how communicating over a network should look. The OSI model is not protocol specific, but instead different protocols belong in different layers.
The layering of communication protocols allows for an abstract way of thinking and describing how different protocols interact with one another.
The OSI layers are:
| Layer | example |
|---|---|
| Application | HTTP |
| Presentation | SSL |
| Session | Logical port |
| Transport | TCP |
| Network | IP |
| Data Link | MAC |
| Physical | DSL |
In terms of networking, the bottom four layers are the most widely referenced. A network engineer will just as often refer to Layer 3 as they will to the IP protocol.
For a beginner, especially one studying for an exam such as the CCNA the order of the OSI layer may be difficult to remember. Some helpful mnemonics may make it easier to remember the OSI layer model order. Find one you like and use it to make the memorization easier.
All Pros Search Top Notch Donut Places
All People Seem To Need Data Processing
All People Should Try New Dr Pepper
A Priest Slapped The Nun During Prayer
And a couple OSI layer mnemonics which work from the bottom up:
Please Do Not Throw Sausage Pizza Away
Please Do Not Touch Sally’s Pretty Ass
Please Do Not Touch Steve’s Pet Alligator
Good luck with your OSI model memorization!
