
Roaming in 802.11 WLANs: General Principles
STA
STA
STA
Figure 3.5: Basic Service Set.
address of the AP is used to identify that BSS and is called the Basic Service Set Identification
(BSSID). A sample BSS is shown in Figure 3.5. The figure shows three STAs communicating
via one AP. Note that it is common practice to drop the “B” in BSS and refer to the “Basic
Service Set” as the “Service Set.” The Service Set ID (SSID), which we saw earlier in an
802.11 frame, is the name given to a group of access points that jointly provide wireless access
to a given IP subnet.
3.2.5 Active and Passive Scanning
In passive scanning, an STA will iteratively listen on