How do computers connect over the Internet?

Using the Internet, computers connect and communicate with one another, primarily using the TCP/IP (Transmission Control Protocol / Internet Protocol). Think of TCP/IP as a book of rules, a step-by-step guide that each computer uses to know how to talk to another computer. This book of rules dictates what each computer must do to transmit data, when to transmit data, how to transmit that data. It also states how to receive data in the same manner. If the rules are not followed, the computer can't connect to another computer, nor send and receive data between other computers.

To connect to the Internet and other computers on a network, a computer must have a NIC (network interface card) installed. A network cable plugged into the NIC on one end and plugged into a cable modem, DSL modem, router, or switch can allow a computer to access the Internet and connect to other computers.

ISPs (Internet service providers)

ISPs (Internet service providers), the companies that provide Internet service and connectivity, also follow these rules. The ISP provides a bridge between your computer and all the other computers in the world on the Internet. The ISP uses the TCP/IP protocols to make computer-to-computer connections possible and transmit data between them. An ISP assigns an IP address, a unique address given to your computer or network to communicate on the Internet.

Home network

If you have a home computer network, the computers are also using TCP/IP to connect. The TCP/IP protocol allows each computer to "see" the other computers on the network, and share files and printers.

When computers connect on the same network, it is called a local area network, or LAN (local area network). When multiple networks are connected, it is called a wide area network, or WAN (wide area network). With this type of network, your home has a network router that connects to your ISP. The router is given the IP address for your connection to the Internet and then assigns local IP addresses to each device in your network. These local addresses are often 192.168.1.2-255. When accessing a local computer in your network, your router sends your TCP/IP packets between the local IP addresses. However, when you want to connect to the Internet, your router uses the IP address assigned by the ISP. Your IP address is not a 192.168.x.x address because the ISP assigns that IP address and not your router.

When requesting information from a web page, such as Computer Hope, you enter a URL (uniform resource locator) that is easy to understand and remember. For your computer to access the computer containing the pages, that URL must be converted into an IP address, which is done with DNS (domain name system). Once DNS has converted the URL into an IP address, the routers on the Internet will know how to route your TCP/IP packet.

The illustration below helps explain the information in the previous sections about your computer communicates with others on the Internet.

Windows, macOS, and Linux computers use the TCP/IP protocol to connect to other computers on a LAN or WAN. Connecting to a LAN or WAN requires either a wired connection or a wireless connection. A wired connection is usually done using a network cable (Cat 5 or Cat 6 network cable). A wireless connection (Wi-Fi) uses an 802.11b, 802.11g or 802.11n wireless network card. With both connection types, a network router is usually required to connect to other computers. Connecting to the Internet at your home also requires either a cable modem or a DSL modem, depending on which ISP you use.