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 stand­ard­ised 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.