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Advantages of VPNs
VPNs promise two main advantages over competing approaches
-- cost savings, and scalability (that is really just a
different form of cost savings).
The
Low Cost of a VPN
One
way a VPN lowers costs is by eliminating the need for
expensive long-distance.
One
way a VPN lowers costs is by eliminating the need for
expensive long-distance leased lines.
With
VPNs, an organization needs only a relatively short
dedicated connection to the service provider. This
connection could be a local leased line (much less expensive
than a long-distance one), or it could be a local broadband
connection such as DSL service. Another way VPNs reduce
costs is by lessening the need for long-distance telephone
charges for remote access.
Recall
that to provide remote access service, VPN clients need only
call into the nearest service provider's access point. In
some cases this may require a long distance call, but in
many cases a local call will suffice.
A
third, more subtle way that VPNs may lower costs is through
offloading of the support burden. With VPNs, the service
provider rather than the organization must support dial-up
access, for example. Service providers can in theory charge
much less for their support than it costs a company
internally because the public provider's cost is shared
amongst potentially thousands of customers.
Scalability and VPNs
The
cost to an organization of traditional leased lines may be
reasonable at first but can increase exponentially as the
organization grows. A company with two branch offices, for
example, can deploy just one dedicated line to connect the
two locations. If a third branch office needs to come
online, just two additional lines will be required to
directly connect that location to the other two.
However, as an organization grows and more companies must be
added to the network, the number of leased lines required
increases dramatically. Four branch offices require six
lines for full connectivity, five offices require ten lines,
and so on. Mathematicians call this phenomenon a
"combinatorial explosion," and in a traditional WAN this
explosion limits the flexibility for growth. VPNs that
utilize the Internet avoid this problem by simply tapping
into the geographically-distributed access already
available.
Compared to leased lines, Internet-based VPNs offer greater
global reach, given that Internet access points are
accessible in many places where dedicated lines are not
available.
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