Networking basics

The most common way of describing a network is the International Standards Organization's Open Systems Interconnection (OSI) Reference Model, also referred to as the OSI seven-layer model. The seven layers of the OSI model areas follows:

7 Application
6 Presentation
5 Session
4 Transport
3 Network
2 Data Link
1 Physical

Levels 1 through 3 are network specific, and will differ depending on what physical network you are using. Levels 4 through 7 comprise network-independent, higher level functions. Each layer describes a particular function (instead of a specific protocol) that occurs in data communications.