You can connect to the Internet from any device: computer, laptop, tablet, smartphone, etc. This is possible because their software executes network protocols, i.e. sets of rules that dictate how devices exchange data across networks. One of these important protocols is IP.

This topic will give you an understanding of what this protocol is and why it is needed. You will also learn about IP versions, IP addresses, and what helps programmers check the speed of devices and test programs and web applications.

IP and IP addresses

It can be said that the Internet as we know it exists thanks to the IP, because it became the link between different computer networks around the world. IP (Internet Protocol) defines the addressing of information as it is transmitted over the network and ensures the organization of the transport of this information to specific destinations. It specifies the way, time, and place of its forwarding.

In order to correctly determine to which address deliver the information on the Internet, there is an IP address. When a computer connects to the Internet, it is assigned a unique number called an IP address.

It's not just computers that have IP addresses. Every site on the Internet has its own IP address. It is equivalent to the IP address of the server hosting the site. Knowing the IP addresses of the sites you are interested in, you can visit them by typing IP addresses into the address bar. True, it's quite inconvenient. People find it difficult to remember IP addresses because of their specific format, and even more difficult to associate these addresses with sites. That's why IP addresses of sites are assigned domain names like hyperskill.org (opens new window).

There are two versions of the IP protocol: IPv4 and IPv6. An IP address on the Internet can be represented in one of the two formats depending on which of these two versions of the IP protocol is used.

IPv4

We will start with IPv4, as this is the most common version of the protocol on the Internet at the moment. Any address following this format consists of four numbers from 0 to 255 separated by dots. Here is an example of an IP address:

132.245.4.216

This is a human-readable version of an IP address. In computers, such an address is represented with 44 sequences of 88 bits that equal to 3232 bits in total. One sequence of 88 bits of information is usually called an octet. Here is the same example of an Internet address written in the binary format:

IP addresses at IPv4 are short and relatively easy to remember, but there is one inconvenience with them. The number of IP addresses is very limited, and many of them are reserved for technical needs. As the IPv4 uses a 32-bit value for its Internet addresses, it means that the protocol can provide support for 2^{32}232 IP addresses in total that is equal to around 4.294.29 billion various addresses. Despite being quite large, even this value isn't enough to provide addresses for all the possible users in the near future.

IPv6

For all its simplicity and convenience, there is a major problem that prevents the continued use of IPv4 — the depletion of the address range. IPv6 was developed to solve this problem.

This version of the IP protocol uses 128128 bits to represent an address that allows for 2^{128}2128 different addresses. In this version, an address consists of eight groups of four hexadecimal digits separated by colons.

Here is an example of an IPv6 address:

0de2:041a:7d43:65ab:9a63:a63e:aa78:34c2

To shorten an IPv6 address we can omit leading zeros. For example, the address 0000:0000:0000:0000:0000:0000:0000:0001 can be simplified to 0:0:0:0:0:0:0:1. After this procedure you can shorten the address again. To do this, select the longest row of consecutive hexadecimal zeros and replace it with two colons (::). Thus, 0:0:0:0:0:0:0:1 converts to ::1.

Despite the fact that this new format allows storing an immense number of addresses, it has one significant drawback: this version isn't backward compatible with IPv4. It is still possible to start using IPv6 though, so if you decide to use this protocol within a network, you need to upgrade your infrastructure and all your devices to support this IPv6 version.

Loopback addresses

There are special IP addresses that point to the local computer, that is, the computer you are using right now. They are called loopback addresses. They are useful when you want to connect to a server on your computer.

Loopback addresses are commonly used for testing purposes. They may be used for speed testing of devices, or to reduce the load on network resources. You can use loopback addresses to test your programs and web applications, to make sure that everything works as it should before you publish them on the Internet.

The most commonly used IP addresses to connect to a server on your local computer are 127.0.0.1 for IPv4 and ::1 for IPv6.

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Interestingly, no website on the Internet can have an IP address that starts with 127. That's because the first part of the address, 127, is reserved only for when you want to connect to your own computer.

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In addition to loopback addresses, there are other reserved addresses that are useful to know. For example, addresses starting with 192.168 are reserved for local networks. Usually, the IP address of your router is 192.168.1.1. It is used to control the router's settings.

Conclusion

So, as you know now, IP is a protocol that defines the address of the information as it is transmitted over a network. It also arranges the transport of this information to its destinations. In this topic, you've learned about the two versions of this protocol, depending on the format of the IP address representation. You've also learned about loopback addresses which are used to connect to a server on your own computer. Now let's put this knowledge into practice.