The OSI Network Model

The Open Systems Interconnect (OSI) model was developed by the International

Standards Organization (ISO) to provide a guideline for the development of standards

for interconnecting computing devices. The OSI model is a framework for developing

these standards rather than a standard itself—the task of networking is too complex to

be handled by a single standard.

The OSI model breaks down device to device connection, or more correctly

application to application connection, into seven so-called layers of logically related tasks

(see Table 2.1 ). An example will show how these layers combine to achieve a task such as

sending and receiving an e-mail between two computers on separate local area networks

(LANs) that are connected via the Internet.