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IP Address Size, Address Space and "Dotted Decimal" Notation
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IP Address "Dotted Decimal" Notation
Most people still find hexadecimal
a bit difficult to work with. So IP addresses are normally expressed
with each octet of 8 bits converted to a decimal number and the octets
separated by a period (a “dot”). Thus, the example above would
become 227.82.157.177, as shown in Figure 56.
This is usually called dotted decimal notation for rather obvious
reasons. Each of the octets in an IP address can take on the values
from 0 to 255 (not 1 to 256, note!) so the lowest value is theoretically
0.0.0.0 and the highest is 255.255.255.255.
 Key Concept: IP addresses are 32-bit binary numbers, which can be expressed in binary, hexadecimal or decimal form. Most commonly, they are expressed by dividing the 32 bits into four bytes and converting each to decimal, then separating these numbers with dots to create dotted decimal notation.
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Dotted decimal notation provides
a convenient way to work with IP addresses when communicating amongst
humans. Never forget that to the computers, the IP address is always
a 32-bit binary number; the importance of this will come in when we
look at how the
IP address is logically divided into components
in the next topic, as well as when we examine techniques that manipulate
IP addresses, such as subnetting.
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