IP addresses and domain names

Just as a letter needs a postal address, every device on a network needs an address of its own. This is the IP address (Internet Protocol address). The most common IPv4 address has four numbers from 0 to 255 separated by dots: 192.168.1.10.

An IPv4 address is 32 bits long, so there are only about 4.3 billion (2^32) of them. When the number of devices exceeded that, the 128-bit IPv6 standard appeared; its addresses are written as groups of hexadecimal digits, for example 2001:db8::1. Home and school networks usually use private addresses (192.168.x.x, 10.x.x.x): they work only inside the local network, and traffic reaches the internet through the router’s shared address.

Numbers are hard to remember, so people use domain names, for example www.informatik.uz. A domain name is read from right to left: first the top-level domain (for example, uz for Uzbekistan, com, org), then the second-level domain (informatik), then the subdomain (www).

To find a website, the browser asks a DNS (Domain Name System) server. DNS turns the domain name into an IP address, which is why it is often called the “phone book” of the internet. Using that address, the browser connects to the server and requests the page.

Key takeaways

• An IP address identifies a device on a network: IPv4 has 32 bits, IPv6 has 128.
• An IPv4 address is written as four numbers (0–255) separated by dots.
• Local networks use private addresses and reach the internet through the router’s shared address.
• A domain name is convenient for people; DNS turns it into an IP address.