802.11 Protocol Architecture
802.11 Services
The 802.11 standard defines an architecture that satisfies various
wireless requirements. A basic service set (BSS) involves one or more
wireless stations (hereafter referred to as, “mobile stations,” “client
stations,” or just, “stations”) that share a single coordination function.
An independent BSS (IBSS), which is often referred to as an Ad Hoc or
peer-to-peer network, enables connections between stations with
relatively little planning or provisioning. For example, two business
people in a meeting room can switch their wireless clients to Ad Hoc
mode and transfer documents to each other’s laptops. 802.11 data
frames in this form of network flow directly from one wireless client to
another.
The advantage of the IBSS is that you can form the network quickly
because such a network does not require an access point. An access
point is a station that has Distribution System (DS) services including
the distribution service responsible for delivering information between
access points. Access points relay information within 802.11 data
frames between stations on the same BSS and provide connections to
other BSSs through a DS (generally Ethernet). Access points may also,
and usually do, have an integration service to provide a portal function
so that the access point can bridge data frames in and out of the BSS.
The 802.11 extended service set (ESS) is made up of one or more BSSs
interconnected via access points. These types of networks are referred
to as infrastructure wireless LANs and are the most common
implementation of 802.11 networks in enterprises, homes, and public
hotspots.
Each access point in an ESS contains an 802.11 station, an 802.3 (or
similar) portal, and DS services. The access points enable stations to
send data frames to both wireless stations located within the ESS and
wired stations beyond the ESS. For example, a message being sent
from one station to another will traverse an access point. The access
point receives a data frame from User A and forwards its information to
User B in a different 802.11 data frame.
