TCP/IP (short for Transmission Control/Internet Protocol) is a framework for a set of Internet protocols created in 1970 by DARPA, an agency of the United States Department of Defense.

The TCP/IP model describes a set of general design principles and implementations of specific Internet protocols that allow computers to communicate with each other over a network. TCP/IP provides end-to-end connectivity that specifies how data should be formatted, addressed, transmitted, routed, and received.

TCP/IP has several layers:

• Physical
• Link
• Internet
• Transport
• Application

The physical layer refers to the actual hardware in any network infrastructure.

The link layer (or also Network Access Layer/Network Layer) is used to move packets between two user interfaces of two different hosts on the same link.

The Internet layer solves the problem of sending packets across one or more networks.

The Transport Layer is responsible for the capabilities to transfer messages between end clients, independent of the network. The transport layer also takes care of error control, segmentation, flow control, congestion control, and application addressing.

The application layer takes care of the protocols that most applications use for network communication. Examples of these applications include FTP (File Transfer Protocol), or SMTP (Simple Mail Transfer Protocol).