IP addresses in detail
Introduction
Every computer on the Internet is given an IP addresses which is unique. This IP address is different to other computers on the Internet. How is an IP address formatted and how is it used? Computers on networks connected to the Internet use a protocol (a set of rules for communication) called TCP/IP to send and receive packets of information. Information such as a web page is broken down into packets of data, each of which is a fixed size and contains the IP address of the target computer (as well as other information). Because the IP address is unique, the packets will constantly be forwarded from the sending computer ever closer to the target computer by routers, going from network to network, until eventually, all the packets arrive, are reassembled and displayed.
The format of an IP address
An IP address using a system called IPv4 is made up of 4 bytes separated by dots, a total of 32 bits. A typical IP might look like this: 01110000.11010100.11111111.11111111 which is slightly problematic for humans to work with! We therefore usually display the IP address as 4 numbers between 0 and 255. The example just given would therefore be expressed as 112.212.255.255 which is much easier for us to talk about. Each number can range from 0 to 255.
Two parts to an IP address
An IP address has two parts. The first part identifies the network. The second part identifies the computer on the network. There are five kinds of networks, called 'classes'.
Class A networks
The binary address starts with a 0. The first 8 bits identify the network. The last 24 bits identify the host (a computer, a networked printer or any other piece of equipment that needs an address) on the network. Because the first 8 bits begin with a 0, the first decimal number can go from 0 to 127, while the other 3 numbers can go from 0 to 255. This network is designed to support huge networks, with 16 million hosts!
Class B networks
The binary address starts with a 10. The first 16 bits identify the network. The last 16 bits identify the host on the network. Because the first 8 bits begin with a 10, the first decimal number can go from 128 to 191, while the other 3 numbers can go from 0 to 255. This network is designed to support 16000 networks, each with 65000 hosts!
Class C networks
The binary address starts with a 110. The first 24 bits identify the network. The last 8 bits identify the host on the network. Because the first 8 bits begin with a 110, the first decimal number can go from 192 to 223, while the other 3 numbers can go from 0 to 255. This network is designed to support 2 million networks, each with 254 hosts!
Class D networks
The binary address starts with a 1110. All the bits are used for multi-casting. Because the first 8 bits begin with a 1110, the first decimal number can go from 224 to 239, while the other 3 numbers can go from 0 to 255.
Class E networks
The binary address starts with a 1111. All the bits are used for experimenting with. Because the first 8 bits begin with a 1111, the first decimal number can go from 240 to 254, while the other 3 numbers can go from 0 to 255.
Examples of IP address
When you write down an IP address, you are allowed to use hyphens and wildcards in a range. There are also a number of different ways you can write the same range of IP addresses. Here are some examples:
108.18.19.20 = a specific IP address for a specific host computer on a network
108.18.19.* = all IP addresses beginning 108.18.19
123.18.19.0-255 = a range of IP addresses from 123.18.19.0 to 121.18.19.255 inclusive
123.18.* = all IP addresses beginning 123.18
123.18.0-255. = all IP addresses in the range 123.18.0-255
123.18.0-255.0-255 = all IP addresses beginning 123.18
123.* = all IP addresses beginning 123
123.0-255.0-255.0-255 = all IP addresses beginning 123
The different classes are used to accommodate different sized networks. Class A is good for defining a few networks with a lot of hosts each. Class B network addresses use the first two numbers (the remainder of the first, and all of the second) to define the network and the last two to define the hosts on each network. Class C network addresses use the first three numbers to define the network and the last one to define hosts within that network.
Who hands out the public IP addresses?
ISPs (Internet Service Providers), for example, are assigned public IP addresses by organisations set-up to distribute and manage public IP addresses. The Network Information Center (NIC) and the Internet Assigned Numbers Authority (IANA) are two such orgnaisations.
IPv6
Most computer networks use the IPv4 system but because of the growth of the Internet, available network addresses are running out. A newer system called IPv6 is being introduced. This has 128 bits and is typically written as five hex numbers separated by colons, for example: 22A3:4338:FA23:324D:AC4B
What is your IP address?
If you type 'What is my IP address' into Google, it will tell you. You can also go into a terminal window in Windows (click on the start button and then in the search area, type in Command prompt). Then type in ipconfig and see what you get.