Slide 12 of 32

“Dotted Octet” Notation

Every computer connected to the Internet requires a unique number to be associated with it. This number is commonly referred to as an IP address . One or more names may be associated with the computer as well. This name is commonly referred to as the domain name of a computer.

An IP address is a 32-digit binary number. For example,

  1000 0010 . 1101 1011 . 0000 0100 . 0110 0100

Notice the period (or "dot") placed between each group of eight digits above. This convention gave rise to the term "dotted octet notation."

To improve readability, each group of eight binary digits ("bits") grouped above may be converted to decimal; viz:

  130 . 219 . 4 . 100

Both sets of numbers above represent an IP address of a computer connected to the Internet.

In this case, the domain name associated with this IP address is shown below:

  rwja.umdnj.edu

Notice that the periods (or "dots") are retained in the domain name. Unlike the binary to decimal number conversion, there is no mathematical algorithm used to derive a domain name from an IP address: instead domain names are assigned to correspond to particular IP addresses.

Domain names follow a naming convention. This convention is described on this web page: http://www.isi.edu/in-notes/rfc1591.txt