The animated TECHTip tutorial available here.

OSI [Open Systems Interconnection] is a universal model for communications and computing but does not necessarily encompass all standards.

The OSI model provides means for interoperability between systems and allows manufacturers to enhance their own systems. It is a framework for data communications at each layer and outlines the what, not the how, of the work at each layer. Not all seven layers are used, for example; only five layers are used for Internet communications. Layers one through four are considered transport and Layer five and above are considered applications or software.

The “open” comes from the open process through which forums to debate protocols such as: IEEE, Frame Relay Forum, and Internet Engineering Task Force. Let’s see all the layers and relative functions with various types of equipment. Many manufacturers are combining specific Layer functions together simplifying use and applications. In this, one of many thousands of everyday Internet applications, we show how voice is processed and how voice is encapsulated into packages or packets with headers (address, routing, types of service, error checking, controls) and data (voice, data, video, etc.)