Lesson
12:Understanding Virtual Private Networks
VPNs are a common topic today. Just about
everyone is talking about implementing one. This module explains
what a VPN is and covers the basic VPN technology. We’ll
also go through some examples of VPNs including a return on
investment analysis.
The
Agenda
- What
Are VPNs?
- VPN
Technologies
- Access,
Intranet, and Extranet VPNs
- VPN
Examples
What Are VPNs?
Simply defined, a VPN is an enterprise network
deployed on a shared infrastructure employing the same security,
management, and throughput policies applied in a private network.

A VPN can be built on the Internet or on a service provider’s
IP, Frame Relay, or ATM infrastructure. Businesses that run
their intranets over a VPN service enjoy the same security,
QoS, reliability, and scalability as they do in their own
private networks.
VPNs based on IP can naturally extend the ubiquitous nature
of intranets over wide-area links, to remote offices, mobile
users, and telecommuters. Further, they can support extranets
linking business partners, customers, and suppliers to provide
better customer satisfaction and reduced manufacturing costs.
Alternatively, VPNs can connect communities of interest, providing
a secure forum for common topics of discussion.
Virtual Private Networks
Building a virtual private network means
you use the “public” Internet (or a service provider’s
network) as your “private” wide-area network.

Since it’s generally much less expensive to connect
to the Internet than to lease your own data circuits, a VPN
may allow to you connect remote offices or employees who wouldn’t
ordinarily justify the cost of a regular WAN connection.
VPNs may be useful for conducting secure transactions, or
transferring highly confidential data between offices that
have a WAN connection.
Some of the technologies that make VPNs possible are:
- Tunneling
- Encryption
- QoS
- Comprehensive security
Why Build a VPN?
Why should customers consider a VPN?
- Company information is secured
-VPNs allow vital company information to be secure against
unwanted intrusion
- Reduce costs
- Internet-based VPNs offer low-cost connectivity
from anywhere in the world, and can be considered a
viable replacement for leased-line or Frame Relay services
Using the Internet as a
replacement for expensive WAN services can cut costs by as
much as 60 percent,
according to Forrester Research
- Also lower remote costs by connecting a mobile user over the
Internet. (Often referred to as a virtual private dial-up
networking, or VPDN).
- Wider connectivity options for users
- A VPN can provide more connectivity options (for example,
over cable, DSL, telephone, or Ethernet)
- Increased speed of deployment
- Extranets can be created more easily (you don’t wait
for suppliers). This keeps the customer in control of their
own destiny.
However, for an Internet-based VPN to be considered as a viable
replacement for leased-line or Frame Relay service, it must
be able to offer a comparable level of security, quality of
service, and reliability.
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