What is TCP/IP?

TCP/IP stands for Transmission Control Protocol/Internet Protocol, the language governing communications between all computers on the Internet. TCP/IP is a set of instructions that dictates how packets of information are sent across multiple networks. It also includes a built-in error-checking capability to ensure that data packets arrive at their final destination in the proper order.

The basic TCP/IP model has five layers of interaction:

- Physical or Data Transport Layer : This most basic layer moves data over cables based on the physical address of each Network Interface Card (NIC). The most common types are ethernet and token ring.

- Data Link Layer : This layer frames the packets of data that are sent through the network. PPP, frame relay, and X.25 operate at this layer. Bridges connect local networks at this layer.

- Network or Internet Protocol Layer : This layer puts an Internet Protocol wrapper around the data with source and destination addresses in its header. Routers, which connect networks together, operate at this layer.

- Transport Layer : This layer governs the setting of suitable packet sizes, segmenting and reassembling data, detection of errors, and flow control.

- Application Layer : This layer provides for standard interfaces for such functions as message handling and file transfer and remote login. It allows, for example, for different e-mail programs to be used, as long as they conform to the standard interface. This layer in TCP/IP corresponds to the session, presentation, and application layers in the OSI model.