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Technology Infrastructure: The Internet and the World Wide Web

of private networks; however, organizations today can create secure intranets using VPN
technologies. If security is not an issue, they can even build intranets using public
networks. Similarly, an extranet was originally defined as an intranet that had been 69
extended to include specific entities outside the boundaries of the organization, such as
business partners, customers, or suppliers. Extranets were used to save money and
increase efficiency by replacing traditional communication tools such as fax, telephone,
and overnight express document carriers. To maintain security within extranets, almost
all organizations that created them did so by interconnecting private networks.
As the Web became more widely used, many organizations began using the Internet,
the public network on which the Web operates, as part of their extranets (and, in some
cases, intranets). The addition of VPN technologies allowed organizations to use the
Internet (a public network), yet have the same level of security over their data that had
been provided by their use of private networks in the past.
This evolution of technologies over time has led to some confusion today when people
use the terms public network, private network, VPN, intranet, and extranet. Remember
that “intranet” is used when the internet does not extend beyond the boundaries of a
particular organization; “extranet” is used when the internet extends beyond the
boundaries of an organization and includes networks of other organizations. The
technologies used (public networks, private networks, or VPNs) are independent of
organizational boundaries. For example, an intranet could use private networks, VPNs, or
even public networks (if security is not an issue).

INTERNET P ROTOCOLS
A protocol is a collection of rules for formatting, ordering, and error checking data sent
across a network. For example, protocols determine how the sending device indicates that
it has finished sending a message and how the receiving device indicates that it has received
(or not received) the message. A protocol also includes rules about what is allowed in a
transmission and how it is formatted. Computers that communicate with each other must
use the same protocol for data transmission. As you learned earlier in this chapter, the first
packet-switched network, the ARPANET, connected only a few universities and research
centers. Following its inception in 1969, this experimental network grew during the next
few years and began using the Network Control Protocol (NCP). In the early days of
computing, each computer manufacturer created its own protocol, so computers made by
different manufacturers could not be connected to each other. This practice was called
proprietary architecture or closed architecture. NCP was designed so it could be used by
any computer manufacturer and was made available to any company that wanted it. This
open architecture philosophy that was developed for the evolving ARPANET, which later
became the core of the Internet, included the use of a common protocol for all computers
connected to the Internet and four key rules for message handling:
• Independent networks should not require any internal changes to be con-
nected to the network.
• Packets that do not arrive at their destinations must be retransmitted from
their source network.

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