MCSA/MCSE Self-Paced Training Kit (Exam 70-270): Installing ...

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Lesson 3 Configuring Wireless Connections
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■ Extended Service Set An extended service set (ESS) represents a network in
which multiple APs (and thus multiple BSSs) are used, as shown in Figure 15-18.
This allows for increased mobility because stations can move from one BSS to
another. APs can be interconnected with or without network cable (although most
of the time they are connected to one another with cables).
Basic Service Set
Station Station
Access Point
Extended Service Set
Figure 15-18 An ESS is a connection of multiple BSSs, the DS serving as the logical link
between BSSs.
■ Distribution System The distribution system (DS) is a logical component used
to interconnect BSSs in an ESS. The DS provides distribution services to allow for
the roaming of STAs between BSSs.
Exam Tip Although the architectural elements of 802.11 networking sound a bit intimidating,
it is important to understand the underlying components of the two modes in which you
can configure a wireless client to operate: ad-hoc mode, in which there is no AP, and infrastructure
mode, in which an AP is used. An ad-hoc network offers fewer configuration options
and is sometimes used in small workgroup environments. An infrastructure network provides
greater security and configurability and is the most common mode for wireless networking.
Introduction to Wireless Networking Security
DS
Basic Service Set
Station Station
Access Point
When a wireless network is used, security becomes of greater concern. On traditional
wired networks, there is a certain level of security to be had simply because you can
physically protect the networking cables. On a wireless network, you cannot physically
protect the radio frequencies used and so must rely on logical protection in the form
of authentication and encryption.