Tutorial:Internet
Understanding VPNs
And PPTP
A Virtual Private Network is an efficient and cost effective way to set up a WAN
by using the Internet for the long distance communications.
By Kevin Townsend
I
f you manage anything more than
It furthermore operates best only
sparently and as economically as pos
the smallest of LANs, the question
where the intranet technology (use of
sible.
is probably not so much Do I need
Web browsers, Internet email and so
Technically, this has long been pos
a VPN? as How soon should I imple
on) is strongly woven into the opera
sible but costly. You could dial into
ment one? .
tional organization of the company.
your office computers from almost
The business world is marching in
It is the third variant data carrying
anywhere in the world. But leased
exorably towards a paradigm that de
VPN with which this article is primar
lines are costly and fixed, and the cost
mands VPN (Virtual Private Network)
ily concerned. This is dial up connec
of long distance PSTN calls can rap
technology. Telecommuting and e
tion from a remote user to the
idly become excessive. And, of course,
commerce are growing and inevitable.
corporate LAN across the Internet. Its
the vast banks of necessary modems
And virtual private networks are the
primary advantage over other data
are both costly and potential bottle
ideal solution for such a world.
VPN variants is its flexibility. New us
necks (not to mention security risks).
ers can be added, and existing users are
The primary argument given for
Definition
not tied to any specific geographic lo
implementing a VPN is thus usually
cation.
cost. Vast savings (the usually quoted
So what exactly is a VPN? There are
So that's the basis for what follows:
figures are between 40% and 50%) can
several answers to this question. Pri
point to point VPNs using the Internet
be made by switching from PSTN dial
marily, there are two types: voice car
as the transmission medium. I shall be
up with its high costs to the usually
rying and data carrying.
considering the arguments in favour of
local charge for connecting to the In
Voice VPNs developed with the ad
implementing such a VPN, the re
ternet.
vent of increased telecommunications
quirements for a successful VPN, and
All you need are the right tools for
liberalization. They serve to simulate a
how the various elements work and
a VPN and an Internet Service
private network at a considerably
should be combined.
Provider (ISP) able to support VPNs
lower cost than the basic public
and offer global roaming (ie, with local
switched network. They started pri
Why Do It?
access numbers in the same parts of the
marily in the USA, but have become
world as your callers).
global over the last few years. Sprint,
There are many reasons for imple
Cost is not the only argument pro
AT&T,
Global
One
and
Uni
menting such a VPN. Fundamentally,
ductivity is another. It is generally con
world/World Partners are example
the nature of business is changing. The
sidered that users are more productive
providers.
notion of the office as a geographic and
when working from home, or at least
There are several variants of data
essential central location for all work
away from the main office. There are
carrying VPNs. One occurs when the
ers is shifting. More and more people
fewer social interruptions from work
entire network requirements are out
are using computers to work from
mates, and no loss of time spent com
sourced, probably to a carrier. A sec
home, from customer sites, from hotel
muting. But this requires turning the
ond variation occurs where two or
rooms, from the car or train or plane
user's local environment, whether it be
more LANs are linked together using
etc. It has been estimated by AT&T, for
the home, a customer site, a hotel room
the Internet as the connecting medium.
example, that home working can pro
or all three, into a virtual office. And
This would require the use of intranet
vide up to 45% productivity gains.
this can only realistically be done by
technology at the two LAN sites, to
But what hasn't changed is that the
connecting the PC to the corporate net
gether with firewalls between each site
central office remains the primary lo
work in as transparent a way as possi
and the Internet itself.
cation of corporate data. To work to
ble. That is, with a VPN. Without
While this approach has some ad
full capacity from remote locations we
access to the central data, the type of
vantages, it is static. If you are not con
consequently need to network our re
work that the remote user can perform
nected to one or other of the LANs,
mote PCs and the central server, and
is limited.
then you are not connected to the VPN.
this needs to be done as easily, as tran
There are other potential benefits
Issue 97 (July 1998) page 9
File: T1807.1
PC Network Advisor
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