IP address

When two devices exchange data over the internet, they need to be able to find each other. For this, every device gets its own identifier made of numbers, the IP address. It serves the same purpose as a postal address on a letter: it says where something should be delivered. An example of such an address is 93.184.216.34. Your laptop has one, your phone has one, and every computer that serves up a website has one too. The abbreviation IP stands for Internet Protocol, meaning the set of rules by which devices communicate with each other on the internet.

Why no data packet arrives without addresses

The internet doesn’t send complete videos or web pages all at once. It breaks everything down into small data packets. Each individual packet carries a sender address and a recipient address. Without this information, a packet would be like a letter without an address: it would simply be discarded.

IP addresses have also become economically important. The older version, IPv4, allows for around 4.3 billion different addresses. In 1981, that sounded like an almost infinite number, but today it’s nowhere near enough. Free IPv4 address blocks are therefore traded, often for several dozen euros per address. Large cloud providers now charge extra when a server needs its own public address.

A second reason for their importance is data protection. An IP address can be used to roughly deduce which region someone is in and which provider operates the connection. German courts therefore treat IP addresses as personal data. Anyone who stores them is subject to the rules of the General Data Protection Regulation.

From name to number and back again

People remember names better than strings of numbers. That’s why you type in tagesschau.de rather than a sequence of digits. In the background, your device asks a name server which IP address belongs to this name. This lookup system is called DNS. Only after that does the actual data exchange begin.

Most devices don’t get their address permanently assigned, but rather borrowed. Your router at home assigns internal addresses to your phone, TV, and laptop. Externally, though, the entire household often appears under just a single address. This process is called address translation, or Network Address Translation in English. It’s one of the reasons the scarce IPv4 addresses still suffice at all.

The newer version, IPv6, solves the problem more thoroughly. It uses longer addresses with letters and numbers, such as 2001:0db8:85a3::8a2e:0370:7334. This provides a practically unlimited number of addresses. Both versions have been running in parallel for years, because old technology can’t be switched over all at once.

Where you notice your own address

You notice IP addresses most clearly when a service classifies you based on your location. Streaming providers show a different program lineup abroad. Search engines deliver results from your region. Both work via the address under which your connection appears on the network.

In the news, IP addresses usually come up in the context of security topics. After an attack on a company, it’s often said that the attack originated from certain addresses. However, this is a common misconception: an IP address identifies a connection, not a person. Attackers almost always use someone else’s or rented computers as an intermediary station.

A VPN shifts exactly this point. The service reroutes your traffic through its own server, so that its address becomes visible to the outside world. Only the VPN provider then knows your real address. You shouldn’t confuse the IP address with the MAC address, though: the latter is permanently built into the network hardware and only applies within the local network.