have emerged as the key technology for achieving security over the Internet. While
a VPN is an inherently simple concept, early VPN solutions were geared towards
large organizations and their implementation required extensive technical expertise.
As a consequence, small and medium-sized businesses were left out of the e-revolution.
Recently, VPN solutions have become available that focus specifically on the needs
of small and medium-sized businesses. Historically, the term VPN has also been
used in contexts other than the Internet, such as in the public telephone network
and in the Frame Relay network. In the early days of the Internet-based VPNs,
they were sometimes described as Internet-VPNs or IP-VPNs. However, that usage
is archaic and VPNs are now synonymous with Internet-VPNs.A firewall is an important
security feature for Internet users. A firewall prevents data from leaving and
entering an enterprise by unauthorized users. However, when packets pass through
the firewall to the Internet, sensitive data such as user names, passwords, account
numbers, financial and personal medical information, server addresses, etc. is
visible to hackers and to potential e-criminals. Firewalls do not protect from
threats within the Internet.
This is where a VPN comes into play.A VPN, at its
core, is a fairly simple concept-the ability to use the shared, public Internet
in a secure manner as if it were a private network. the flow of data between two
users over the Internet when not using a VPN. As shown by the dotted lines, packets
between a pair of users may go over networks run by many ISPs and may take different
paths. The structure of the Internet and the different paths taken by packets
are transparent to the two users. With a VPN, users encrypt their data and their
identities to prevent unauthorized people or computers from looking at the data
or from tampering with the data.A VPN can be
used for just about any intranet and e-business (extranet) application. Examples
on the following pages illustrate the use and benefits of VPN for mobile users
and for remote access to enterpriseresources, for communications between remote
offices and headquarters, and for extranet/e-business.