Internet Protocol version 4 (IPv4) is the fourth edition of the Internet Protocol. It is a system of identifying individual computers and digital devices on the Internet by assigning each one with a unique address.

IPv4 address consists of a set of four numbers separated by a period character (“.”), often referred to as a “dot.” Each number can be from 0 to 254. Some addresses may not be assigned because they are reserved for special uses. IPv4 can accommodate up to 4 billion unique addresses, but these have already been used up as the Internet continues to grow.

You can think of IPv4 as the unique ID which a computer, smartphone, or game console displays to communicate with similar devices.

Other interesting terms…

Read More about “IPv4”

IPv4 was first used in 1983 for the Advanced Research and Project Agency Network (ARPANET). The ARPANET, of course, was the first connected network used by the U.S. Department of Defense for communication. IPv4 and the ARPANET can be considered the technical foundation of the Internet.

How does IPv4 Work?

IPv4 is one of the major protocols in the Transmission Control Protocol (TCP)/IP suite. The TCP/IP, in the simplest terms, is the protocol that allows devices to communicate over the Internet.

IPv4 is responsible for identifying hosts (computers) based on their logical addresses (IPv4 addresses) and routing data among them over the underlying network (Internet). As such, IPv4 provides a way to identify hosts using an IP addressing scheme uniquely. Note, however, that IPv4 uses best-effort delivery. It means that delivery to the desired host is not guaranteed but the protocol will do its best to reach the destination. IPv4 uses 32-bit logical addresses, more commonly known as “IP addresses.”

3 IPv4 Addressing Modes

Sending data over the Internet can happen in several ways. IPv4 supports three of these addressing modes, which are:

1. Unicast addressing mode

In this mode, the data gets sent to only one host. The destination address field contains only the IPv4 address of the destination host. A computer sends data to a target server. It is a one-to-one transmission. It is what happens when a user sends an email to a single recipient.

2. Broadcast addressing mode

In this mode, the data gets sent to all of the hosts connected to a network. The destination address field contains a special broadcast address. Any host that sees the packet will process it. It is a one-to-all transmission. It is how mass mailers get sent to all connected recipients.

3. Multicast addressing mode

This is a combination of the unicast and broadcast addressing modes. It can be one-to-many or many-to-many transmission. In this mode, the destination address includes a unique address that begins with 224.x.x.x, which can be accommodated by more than one host. 

Think of it this way, if marketers use broadcast addressing mode to reach as many potential customers as possible (likely the entire Internet population), targeted marketing campaigns would use multicast addressing mode to only reach desired audiences (for example, a specific country).

What Are the Limitations of IPv4?

There are some constraints in using IPv4. We identified two major ones below.

  • Scarcity: There are 4,294,967,296 IPv4 addresses, but not all of them can be used since many are allocated to specific companies and cannot be used by the public. In fact, the last IPv4 blocks have already been allocated. The projection, reflected in the chart below, shows that the IPv4 addresses are close to depletion.
limitations of IPv4

Projection of consumption of remaining regional Internet registry (RIR) address pools taken from

  • Security concerns: Rules and standards governing IPv4 are old, published in 1981. They don’t take into account modern security threats. While Internet Protocol Security (IPSec) can protect IPv4 packets, it is only optional, and some companies may not implement it.

At present, the Internet has run out of IPv4 addresses, which led to the creation of IPv6.