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Technology Infrastructure: The Internet and the World Wide Web

in networking applications, an 8-bit number is often called an octet. In binary, an octet
can have values from 00000000 to 11111111; the decimal equivalents of these binary
numbers are 0 and 255, respectively. 71
Because each of the four parts of a dotted decimal number can range from 0 to 255,
IP addresses range from 0.0.0.0 (written in binary as 32 zeros) to 255.255.255.255
(written in binary as 32 ones). Although some people find dotted decimal notation to be
confusing at first, most do agree that writing, reading, and remembering a computer’s
address as 216.115.108.245 is easier than 11011000011100110110110011110101, or its
full decimal equivalent, which is 3,631,433,189.
Today, IP addresses are assigned by three not-for-profit organizations: the American
Registry for Internet Numbers (ARIN), the Reséaux IP Européens (RIPE), and the Asia-Pacific
Network Information Center (APNIC). These registries assign and manage IP addresses for
various parts of the world: ARIN for North America, South America, the Caribbean, and
sub-Saharan Africa; RIPE for Europe, the Middle East, and the rest of Africa; and APNIC
for countries in the Asia-Pacific area.
You can use the ARIN Whois page at the ARIN Web site to search the IP addresses
owned by organizations in North America. Enter an organization name into the search
box on the page, then click the Search WHOIS button, and the Whois server returns a list
of the IP addresses owned by that organization. For example, performing a search on the
word Carnegie displays the IP address blocks owned by Carnegie Bank, Carnegie Mellon
University, and a number of other organizations whose names begin with Carnegie. You
can also enter an IP address and find out who owns that IP address. If you enter “3.0.0.0”
(without the quotation marks), you will find that General Electric owns the entire block of
IP addresses from 3.0.0.0 to 3.255.255.255. General Electric can use these addresses,
which number approximately 16.7 million, for its own computers, or it can lease them to
other companies or individuals to whom it provides Internet access services.
In the early days of the Internet, the 4 billion addresses provided by the IPv4 rules
certainly seemed to be more addresses than an experimental research network would ever
need. However, about 2 billion of those addresses today are either in use or unavailable
for use because of the way blocks of addresses were assigned to organizations. The new
kinds of devices on the Internet’s many networks, such as wireless personal digital
assistants and smartphones, promise to keep demand high for IP addresses.
Network engineers have devised a number of stopgap techniques to stretch the supply
of IP addresses. One of the most popular techniques is subnetting, which is the use of
reserved private IP addresses within LANs and WANs to provide additional address space.
Private IP addresses are a series of IP numbers that are not permitted on packets that
travel on the Internet. In subnetting, a computer called a Network Address Translation
(NAT) device converts those private IP addresses into normal IP addresses when it
forwards packets from those computers to the Internet.
The Internet Engineering Task Force (IETF) worked on several new protocols that could
solve the limited addressing capacity of IPv4, and in 1997, approved Internet Protocol
version 6 (IPv6) as the protocol that will replace IPv4. The new IP had to be implemented
gradually because the two protocols are not directly compatible. The process of switching
the Internet completely over to IPv6 is taking many years; however, network engineers
have devised ways to run both protocols in parallel on interconnected networks.

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