TCP/IP

TCIP/IP forms the backbone of the Internet: Without these protocols, we wouldn’t be able to surf the Web. The term TCP/IP actually refers to several sets of rules for transferring data packets in a Local Area Network (LAN) or Wide Area Network (WAN). These networks include the World Wide Web, or Internet.

TCP/IP is named after the two protocols that are crucial for Internet communications: the Transmission Control Protocol (TCP) and Internet Protocol (IP). The term TCIP/IP suite actually encompasses even more protocols: The Internet Control Message Protocol (ICMP) and the User Datagram Protocol (UDP) are also part of this suite. In other words, TCP/IP is not a specific protocol in itself, but a group of distinct protocols. What they all have in common is that they have become standards for network communications.

The protocols of the TCP/IP model have a significant advantage: They operate independently of the hardware and the underlying software. The protocols are standardized to work in any context, no matter which operating system you use or which device you use to communicate over the network.

The protocols comprise layers 3 and 4 of the OSI model. The transport and link layer are directly responsible for connecting two devices in a network. For example, the IP address and the Internet Protocol are used to send the data packet to the correct recipient. TCP, on the other hand, is responsible for establishing a connection between the two devices and maintaining the connection for data transmission. If the data packet transmission is unsuccessful, the protocol will attempt to resend the packets.

Since TCP/IP is just an umbrella term for the most important Internet protocols, the term is also used in other instances. That’s why there's also a reference model that governs TCP/IP. Similar to the OSI model, the model is designed to map all aspects of network communication. However, the TCP/IP model consists of four different layers, unlike the OSI model, which has seven layers. The layers in the TCP/IP model are assigned various tasks and therefore protocols.

• Network access layer: This layer is included in the reference model, but no specific protocol is defined. In practice, Ethernet (wired) and IEEE 802.11 (wireless) protocols are mainly used. The network access layer is used to link different subnets for applications such as connecting a home Wi-Fi network to the Internet via a router.
• Internet layer: The Internet Protocol operates on this layer and ensures that the transmitted data reaches the correct destination. The data packets are routed through the network via the IP address.
• Transport layer: TCP is used for transport in the reference model. The protocol allows end-to-end communication, meaning it’s responsible for the connection between two devices. Along with TCP, UDP is also part of this layer.
• Application layer: The top layer controls communication between applications across the network. Protocols such as HTTP and FTP are crucial for the application layer. Email communication protocols (such POP or SMTP) also operate on this layer.