The IEEE 802.11 defines a set of services that provides the functionality needed to let the LLC layer send and receive MSDUs (MAC Service Data Units). These services include two categories:
(1) Station Services: These include Authentication, Deauthentication, Privacy, and MSDU delivery.
(2) Distribution System Services: These include Association, Disassociation, Distribution, Integration, and Reassociation.
The 802.11 standard defines services for providing functions among stations. A station may be within any wireless element on the network, such as a handheld PC or handheld scanner. All access points implement station services.
Authentication: Used to prove identity of one station to another. Station must be authenticated in order to access WLAN for data delivery.
Deauthentication: Used to remove previously authenticated station. Deauthenticated station cannot access WLAN for data delivery.
Privacy: Prevents message contents from being read by unintended recipient. Wired equivalency protocol (WEP) – designed to provide same level of protection as found on wired networks. Only protects data over wireless links, not end-to-end.
Data delivery: Provides reliable delivery of data from MAC of one station to MAC of other stations.
Distribution System Services
Distribution system services provide functionality across a distribution system. Access points provide distribution system services.
Association service: Each station must initially invoke the association service with an access point before it can send information through a distribution system. Each station can associate with only a single access point, but each access point can associate with multiple stations.
Reassociation service: Used when station moves to new BSS (new Access Point). Allows new AP to contact old AP to get packets that may be buffered there for the station.
Disassociation service: Station can use this service to inform AP that it no longer requires service from WLAN. For example, an access point may disassociate all its stations if being removed for maintenance. Station must associate again to access WLAN after disassociation.
Distribution service: Determines where to send packets( Back to own BSS, to another AP, to wired network).
Integration service: The integration function performs all required media or address space translations. The integration service connects the IEEE 802.11 WLAN to other LANs. The integration service translates IEEE 802.11 frames to frames that may traverse another network, and vice versa.