Networking: A Beginner's Guide
any companies have multiple locations that need to share network
resources. For example, maybe the company's accounting system runs at the
headquarters building where the accounting and MIS staff are located, but
the warehouse across town still needs access to the accounting system for inventory
picking tickets, data entry, and other order fulfillment and inventory tasks. Or, perhaps
the company uses a groupware system such as Lotus Notes that requires regular
updates of information and messages from one site to another. In the real world, the
situation can become even more complex. Some companies have offices all around the
globe, and each office has different requirements both to access and update data in
All of these are situations in which a wide area network (WAN) can be useful. Certainly,
in a pinch, multiple offices can exchange data by using Federal Express and identical
tape machines, CD-R discs, external USB hard disks, or other media. Sure, it's possible
to simply send the data back and forth like this (assuming the application supports
exchanging data in this fashion), but such an arrangement has some drawbacks--the
biggest one being that it is pretty slow.
There are many ways to connect local area networks (LANs) in one location to
LANs in another location, and making such connections is the subject of this chapter.
But before looking into the different WAN technologies, you should assess your
networking requirements. Because of the cost and the time required to implement and
maintain a WAN, you usually do not want to install one unless it's the only way to
meet your needs.
Determining WAN Needs
WAN links are almost always fairly expensive to maintain. Bandwidth needs increase
over time; and these upgrades are costly. Also, WAN links are generally much more
prone to trouble than LANs, because many additional possible points of failure exist.
For these reasons, it's important to assess the need for a WAN carefully, and then study
the different options available, their costs, and the trade-offs involved.
Costs can vary wildly between different technologies, speeds, and other factors
(including your location), so you need to rely heavily on cost and availability data
from local providers for your own WAN analysis. Plus, prices and availability change
almost every week, so make sure to get current data from your local providers before
committing to a particular WAN technology.
Often, the need for a WAN can be satisfied using a technology called virtual private networks
(VPNs). A VPN is a private network created through a public network, typically the Internet. A VPN
is called "private" because all of the packets between two points are encrypted, so even though the
packets are transmitted over a public network, their information remains secure. And because VPNs use
the Internet, they're usually much cheaper than dedicated WAN links, and they often can make use of
existing Internet connections for two (or more) locations. VPNs are discussed in detail in Chapter 10.