In today's technologically advanced times, there are many, many different ways to communicate via host devices over large geographical distances. We call such a network a Wide Area Network or WAN. In the
CCENT certification examination, you need to be ready to respond to many potential questions about how Cisco Systems likes to categorize these many different WAN options.
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At the highest level, Cisco likes to categorize WAN options into three categories:
- Dedicated
- Switched
- Internet
The category of
Dedicated WAN connections include point-to-point link options often called
Leased Lines. An example is a
T1 or
E1 link.
The category of
Switched has two subcategories -
Circuit-Switched and
Packet-Switched. Classic examples of
Circuit-Switched technologies are the
Public Switched Telephone Network (PSTN) and
Integrated Services Digital Network (ISDN). These WAN circuits are identified by the fact that they create a connection when communications need to take place, and then the connections are torn down when no longer needed. The
Packet-Switched subcategory includes
Frame Relay and its predecessor
X.25. This category includes technologies that can create Permanent Virtual Circuits (PVCs). The circuits appear to be always available for the network to use. Some texts will distinguish yet another subcategory of
Packet-Switched WANs. This is called
Cell-Switched. The classic WAN technollogy example is
Asyunchrnonous Transfer Mode (ATM). You should be aware of this category for the CCENT exam. It is called
Cell-Switched because the technology sends information over the circuit in small, fixed-size cells.
The
Internet category features
Broadband and
VPN technologies. Examples include
Digital Subscriber Line (DSL),
Cable , and
Broadband Wireless. These options feature relative high-speed, low cost connections that are available in more and more regions of the world.
