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IPv4, which stands for Internet Protocol version 4, is a fundamental technology that enables the transmission of packages through the Internet by providing a unique identifier to each connected device. Developed in the early 1980s, the IPv4 address pool has a theoretical limit of 4.3 billion unique addresses. Nowadays, all IPv4 addresses are either in active use or are reserved for special purposes and cannot be used by the general public. An example IPv4 address would be

Whenever a client machine such as a PC, phone, tablet, or another smart device gets connected to the Internet, it is assigned an IP address. The assigning authority is usually the Internet Service Provider (ISP) which, in turn, is authorized by the local Regional Internet Registry (RIR). The ISP needs to be aware of the IP address of every connected device on their network so that when a remote server responds to the client’s query they can efficiently route all traffic to its intended destination.

IPv4 operates on a best-effort delivery model. This means that packet delivery is not guaranteed. Moreover, packets may be received out of order or the same packet may be delivered more than once. These data integrity issues are resolved by the Transmission Control Protocol (TCP) which is part of the next networking layer, namely the Transport Layer.

IPv4 is a cornerstone technology in the Internet layer of computer networking.
IPv4 is a cornerstone technology in the Internet layer of computer networking.

To learn even more about what an IPv4 address is and how it differs from IPv6, continue reading or jump to the section that interests you.

What Is an IP Address?

An IP address is a numeric identifier that gets assigned to every device that is connected to the Internet. You can think of the IP address as someone’s phone number – you can successfully communicate with that person only if both you and the person in question have valid phone numbers.

IP addresses are often hard to remember which is why they are commonly substituted for domain names in URLs. In fact, it is recommended that every website owner buys a memorable domain name to make their website easily accessible.

You can learn more about what IP addresses are and how they are used in web hosting in our dedicated article on the subject.

Where Are IPv4 Addresses Used?

IPv4 addresses are used throughout the Internet since they act as the connective tissue that binds all hosts into a world-wide web. Without IP addresses, you would not be able to connect to the web nor exchange data packets with remote hosts. In fact, during data packet transmission it is common for every packet to make several hops across third-party routers until it reaches its final destination, thus utilizing multiple IPv4 addresses in a single operation.