The Internet Encyclopedia (Volume 3)

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OVERVIEW OFPUBLICNETWORKCONCEPTS ANDSERVICES 167

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Figure 1: A private switched data network.

E-commerce purchases can be made automatically with

software.

A network that transfers data and information only

within a single business is called an intranet (Moody,

2001). Intranets use the same technologies as the Internet

but access is restricted to employees. They carry corporate

information that can range from being routine such as

e-mail, manuals, and directories or can be sensitive infor-

mation such as that of project management and internal

purchasing. An intranet can be built using a private or a

public network. A private network is naturally an intranet.

A business using a public network can ask that the data be

restricted to only go to other locations of the same busi-

ness. Of course, the bandwidth is still being shared with

other businesses that use the same public network.

An extranet is a hybrid between the public Internet and

the private intranet (Moody, 2001). A portion of the in-

tranet is extended to business partners in a controlled and

restricted way. The extranet can be used for project man-

agement of projects between partners. Another common

and practical use of the extranet is to allow partners access

to the stock levels and shipping status. Direct online pur-

chasing of supplies and other applications are made pos-

sible through the use of an extranet.

The global Internet can be used to provide an intranet

or an extranet by creating a virtual private network (VPN).

A VPN is a private network that is deployed over public

facilities, but provides the same levels of privacy, security,

quality of service, and manageability as private networks

(Cisco, 2001).

A VPN can be created when all sites are already con-

nected to the Internet. With a VPN, hosts at different

sites communicate across the Internet using either a tun-

nel mode between local networks, or by using a direct

transport communication. However, there are two serious

problems that can occur with VPNs since the company

no longer has control of the entire data network (Panko,

2001). One problem is the security of the data, because the

Internet was not designed to support secure transmission.

This problem can be solved through the use of encryption

and by using tunnel mode for communication. A second

problem is congestion on the Internet. Congestion can

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Figure 2: A public switched data network.