D-Link Air DWL-900AP User Manual page 13

Network Topology (continued)
I
BSS would be a group of wireless-equipped laptop computers at a trade
show set up to share information. In this arrangement, one of the WLAN units
is elected to act as a controller or base station, similar to the function of a
wireless access point except there is no connection to a wired Ethernet LAN.
Ad-hoc networks are very easy to set up and require minimal involvement by
network administrators or MIS personnel.
ESS
An Extended Service Set is a series of two or more basic service sets
networked on an Ethernet or other type of LAN. Each access point provides
connection to the Ethernet LAN for their respective BSS.
Each BSS is identified by a unique number, the BSS-ID (the MAC address of
the Wireless Access Point). Wireless stations on an ESS automatically select
the access point or BSS that can best serve them. If no access point can be
found the device will scan for a usable access point.
An ESS can be set up so that wireless stations can roam anywhere within
the range of any available access point, that is, to any member BSS, and still
maintain links to both the WLAN and the Ethernet. In this case, each station
shares a common ESS. The ESS is identified by an ESS ID number used by
all stations in the ESS.
Wireless access points can also be used to segment a wireless network.
Under such circumstances, more than one ESS might be used. Two or more
separate Extended Service Sets can occupy the same physical space. Each
station on a wireless LAN can only use one ESS.