TCP/IP Layers: Description

TCP/IP (Transmission Control Protocol/Internet Protocol) was developed by scientists of the Defense Advanced Research Projects Agency (DARPA) of the Department of Defense in the 1970s and was officially adopted by the ARPANET (the world's first public packet-switched computer network and the grandparent of the Internet) in 1983. The four layers of TCP/IP are:

1. Application Layer: combines the Application, Presentation, and Session layers of OSI. Hands over data received from TCP to the application and makes sure the app is able to interpret the received data.
2. Transmission Control Protocol (TCP) Layer: delivers data from the client to the server without errors or loss. Overlaps the functionality of Transport Layer of OSI reference model. TCP ensures that, if a segment of data is lost in transmission, it is resent again until all the data arrives nominally.
3. Internet Protocol (IP) Layer: forwards the data segments received from the TCP, referred to as packets, from one node (= device on the network) to the destination node based on the IP address. Overlaps OSI's Network Layer.
4. Network Access Layer: Combines the functions of the Data Link and the Physical Layers of OSI. creating data 'frames' for transmitting and receiving data from the physical layer. This function is implemented by a hardware and software Network Interface Card (NIC), an adapter connected to the computer through physical wires or optical fiber cables.