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.
Station Services
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.
1 Comments
Helpful... Can u pls post solved questions related to this post
ReplyDelete