Below is an overview of the functions of each layer in the TCP/IP model.
Layer 5 – Application Layer
The application layer is where network applications reside. Examples of network applications include web browsers, chat clients, and email clients. Network applications at the application layer use their underlying layer, the Transport Layer, to connect to remote computers.
Layer 4 – Transport Layer
Two important protocols in the transport layer are TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). TCP is used to establish reliable connections, while UDP is used to establish fast streaming connections. The transport layer provides an addressing system for different applications, known as port numbers. The transport layer accurately delivers data to the corresponding application by assigning port numbers to applications.
Layer 3 – Network Layer
The network layer is responsible for transmitting data from one network to another. The main protocol of the network layer is the Internet Protocol (IP). The Internet Protocol (IP) uses IP addresses to identify the source and destination addresses of IP traffic. Routing functions are also associated with the network layer.
Layer 2 – Data Link Layer
Local area network standards (e.g., Ethernet) are associated with the data link layer. The data link layer creates data packets called frames, which encapsulate the IP datagrams of the Internet layer. The data link layer uses MAC addresses to identify the source and destination computers.
Layer 1 – Physical Layer
The physical layer is responsible for sending computer data from one device to another. The physical layer transmits data in the form of electrical signals, optical signals, or radio waves.