IPv4 - what is it and what does it consist of?
For business
14 June 2025
IPv4 is a name that says nothing to most Internet users. Without this protocol, however, it would be impossible to use the Internet. Importantly, the history of its development shows how technology has changed over the years. What is IPv4 and how does it affect communication on the Web? Read on!
What is the IPv4 protocol?
Today, almost every electronic device allows access to the internet. Whatever it is (e.g. a computer, smartphone or tablet), it has a unique identifier. This is the Internet Protocol (IP). It makes communication between devices possible. IP addresses are also assigned to websites. This allows equipment to communicate with them and exchange data.
In practice, communication via IP addresses is unnoticeable to the user. Without them, however, it would be impossible to exchange messages in instant messengers, browse websites or download files from them. The standard used by devices and websites is IPv4, i.e. Internet Protocol version 4. It is a sequence of digits stored in the bit system.
The billions of addresses created in this system were intended to provide the ability to assign unique identifiers to new sites and devices for decades. However, developments in technology and the global network have meant that they have become scarce over time. The reason for this is the now distant history of the creation of the IPv4 protocol. 
History of IPv4
The IPv4 protocol was created in the 1980s. Responsible for this is the Internet Assigned Numbers Authority (IANA), an informal association for the assignment of Internet addresses. The members of the IANA were and are the outstanding minds who laid the foundations of the modern internet. One of them was Jon Postel, the creator of, among other things, the structure of site addresses, the email communication protocol (SMTP) and the hierarchical domain system (DNS).
Both Jon Postel, as president of IANA, and others in the association could not have foreseen everything. The creation of 32-bit IPv4 addresses allowed the creation of more than 4 billion addresses. In the 1980s, this amount seemed sufficient. Mobile devices such as smartphones did not yet exist. The computer, on the other hand, was a rare sight in private homes. The internet itself was only in its infancy. Suffice it to say that the first web server was created in 1989 and a browser a year later.
The demand for more IPv4 addresses increased rapidly in the 1990s. To ensure that they did not run out too quickly, many parties and devices were assigned identifiers by IANA that had not been used for years. In the meantime, new names were also assigned. The last of these were used in 2019.
From now on, only old, unused addresses are assigned. However, these too will sooner or later run out. The IANA members were aware that this would happen. For this reason, they proposed the implementation of a new communication protocol - IPv6 - as early as the end of the 20th century. To understand the innovations it brings, however, it is necessary to know the operation and components of the older standard.
IPv4 protocol components
The structure of an IPv4 address is 32-bit. The address is divided into four bytes. Due to their 8-bit structure, they are called octets. Each octet is stored as a number from 0 to 255. An example IPv4 address can therefore take the form 0.0.0.0., 1.2.3.4., 33.44.55.66., 444.555.666.777. etc. The whole is called the header. Its individual components indicate the version of the protocol used, its sender, receiver, etc.
Due to the difficulty of remembering long strings of numbers, IANA decided to fragment them. This is why consecutive bits are divided by dots. Importantly, IPv4 addresses are always composed of digits only.
For many years, consecutive IPv4 addresses have been assigned randomly. Until 1997, however, this was not the case. At the time, there was a division into IPv4 network classes. The highest of these - Class A - was given to networks consisting of many computers. These tended to be held by the largest corporations. Class B IPv4 header was given to medium-sized networks and C was given to the smallest ones. Class D included group names, i.e. addresses that allowed data transfer to multiple devices simultaneously. In addition to this, there was also Class E. It was never made available to users, remaining an experimental category of the IPv4 protocol. 
An IPv4 datagram is used to transfer data under this protocol. This technology enables data packets to be transmitted. By using routing, the individual parts of the packet arrive at the recipient via different paths. This allows them to be sent more quickly than if they were sent in their entirety as a bit stream. This advantage is not exclusive to IPv4. It is also a feature of IPv6. Unlike the older standard, it has several other advantages.
IPv4 and IPv6 - differences and similarities
The rapidly depleting stock of IPv4 addresses has necessitated a new method of name combination. The newer IPv6 standard is not just composed of numbers. The string also contains the basic letters of the Latin alphabet. Parts of the address are also not separated by a dot, but by a colon. An example of an IPv6 protocol might take the form 1234:ab567:8901:2345:6c7d:8e90:1234:5678. How many bits an IP version 4 address has and how many bits it has in version 6 has a colossal impact on the number of available addresses. The new system has increased their pool from 4.3 billion to 340 sextillion.
The increase in the number of addresses in IPv6 would not have been possible without doubling their length. Each header consists of eight 16-bit parts. Extended headers can be simplified by removing strings of zeros. In the IPv4 protocol, this is not allowed. For example, the address 1234:ab567:0000:0000:0000:0000:0000:1234:5678 is equivalent to 1234:ab567:0:0:0:0:1234:5678.
It is possible to shorten it further. Getting rid of the last two zeros gives the form 1234:ab567:0:0::1234:5678. In this case, a separator in the form of a double colon is required. This notation is also valid for subsequent simplifications. The same as the original address is, for example, 1234:ab567::1234:5678. Importantly, the double colon can only be used once in an address.
The IPv4 protocol has proved to be a necessary but insufficient tool for communication on the internet. Although its time is passing, it undoubtedly proved to be one of the milestones in the development of the global network. Its history shows what a remarkable journey the technology has gone through, for which a few billion addresses proved to be too few after only about 30 years.
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