The ISO/OSI (International Standards Organization/Open System Interconnection) model defines a networking framework for implementing protocols in seven layers. This ensures that each layer is functionally independent of the others. Control is passed from one layer to the next, starting at the top and proceeding to the bottom layer, over the channel to the other station and back up the layers. Although this information is not necessary to build a home network, it is a good idea to have a basic understanding of how your network works in order to troubleshoot future problems.

Application

The Application layer is the layer at which applications access network services. This layer represents the services that directly support applications such as software for file transfers, database access, email, and network games.

Presentation

The Presentation layer is the layer that translates data from the Application layer into a network format (and vice-versa). This layer also manages security issues by providing services such as data encryption and compression.

Session

The Session layer is the layer that allows applications on different computers to establish, use and end a session/connection. This layer establishes dialog control between the two computers in a session, regulating which side transmits, and when and how long it transmits.

Transport

The Transport layer is the layer that handles error recognition and recovery. It also repackages long messages when necessary into small packets for transmission and at the receiving end, rebuilds packets into the original message. The receiving Transport layer also sends receipt acknowledgements.

Network

The Network layer is the layer that addresses messages and translates logical addresses and names into physical addresses. It also determines the route from the source to the destination computer and manages traffic problems (flow control), such as switching, routing, and controlling the congestion of data packets.

Data Link

The Data Link layer is the layer that packages raw bits from the Physical layer into frames (logical, structures packets for data). This layer is responsible for transferring frames from one computer to another, without errors. After sending a frame, it waits for an acknowledgement from the receiving computer.

Physical

The Physical layer is the layer that transmits bits from one computer to another and regulates the transmission of a stream of bits over a physical medium. This layer defines how the cable is attached to the network adapter and what transmission technique is used to send data over the cable.