TCP/IP Addressing

From http://www.w3schools.com (Copyright Refsnes Data)

# TCP/IP Addressing

TCP/IP uses 32 bits, or four numbers between 0 and 255, to address a computer.

## IP Addresses

Each computer must have an IP address before it can connect to the Internet.

Each IP packet must have an address before it can be sent to another computer.

This is an IP address: 192.68.20.50
This might be the same IP address: www.w3schools.com

## An IP Address Contains 4 Numbers.

Each computer must have a unique IP address.

This is your IP address: 123.19.56.205

TCP/IP uses four numbers to address a computer. The numbers are always between 0 and 255.

IP addresses are normally written as four numbers separated by a period, like this: 192.168.1.50.

## 32 Bits = 4 Bytes

TCP/IP uses 32 bits addressing. One computer byte is 8 bits. So TCP/IP uses 4 computer bytes.

A computer byte can contain 256 different values:

00000000, 00000001, 00000010, 00000011, 00000100, 00000101, 00000110, 00000111, 00001000 .......and all the way up to 11111111.

Now you know why a TCP/IP address is four numbers between 0 and 255.

## Domain Names

A name is much easier to remember than a 12 digit number.

Names used for TCP/IP addresses are called domain names.

w3schools.com is a domain name.

When you address a web site, like http://www.w3schools.com, the name is translated to a number by a Domain Name Server (DNS).

All over the world, DNS servers are connected to the Internet. DNS servers are responsible for translating domain names into TCP/IP addresses.

When a new domain name is registered together with a TCP/IP address, DNS servers all over the world are updated with this information.

From http://www.w3schools.com (Copyright Refsnes Data)