ZyXEL Communications ZyWall USG 50-H Series User Manual page 648

Appendix D Wireless LANs
Figure 481 Basic Service Set
ESS
An Extended Service Set (ESS) consists of a series of overlapping BSSs, each containing an
access point, with each access point connected together by a wired network. This wired
connection between APs is called a Distribution System (DS).
This type of wireless LAN topology is called an Infrastructure WLAN. The Access Points not
only provide communication with the wired network but also mediate wireless network traffic
in the immediate neighborhood.
An ESSID (ESS IDentification) uniquely identifies each ESS. All access points and their
associated wireless clients within the same ESS must have the same ESSID in order to
communicate.
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ZyWALL USG 50-H User's Guide