Introduction to WAN

When an enterprise grows to include branch offices, e-commerce services, or global operations,
a single local-area network (LAN) is no longer sufficient to meet its business requirements.
Wide-area network (WAN) access has become essential for larger businesses today.
A variety of WAN technologies meet the different needs of businesses, and there are many
ways to scale the network. Adding WAN access introduces other considerations, such as
network security and address management. Consequently, designing a WAN and choosing
the correct carrier network services is not a simple matter.
In this chapter, you will begin exploring some of the options available for designing enterprise
WANs, the technologies available to implement them, and the terminology used to
discuss them. You will learn about selecting the appropriate WAN technologies, services,
and devices to meet the changing business requirements of an evolving enterprise. The
activities and labs confirm and reinforce your learning.
After completing this chapter, you will be able to identify and describe the appropriate WAN
technologies to enable integrated WAN services over a multilocation enterprise network.
Introducing Wide-Area Networks (WANs)
One way to categorize networks is to divide them into local-area networks (LAN) and
wide-area networks (WAN). LANs typically are connected workstations, printers, and other
devices within a limited geographic area such as a building. All the devices in the LAN are
under the common administration of the owner of that LAN, such as a company or an educational
institution. Most LANs today are Ethernet LANs.
WANs are networks that span a larger geographic area and usually require the services of a
common carrier. Examples of WAN technologies and protocols include Frame Relay, ATM,
and DSL.
What Is a WAN?
A WAN is a data communications network that operates beyond the geographic scope of a
LAN. Figure 1-1 shows the relative location of a LAN and WAN.