802.11 Protocol Architecture
FIGURE 2.3
Wireless Distribution System
The DS medium may be a combination of wired and wireless segments,
all bridged together as one data-link broadcast domain, and configured
as one IP subnet. Marketing departments have given access points that
support special media combinations and feature sets peculiar names to
fit their applications such as, “wireless bridge”, “wireless repeater”, and
“wireless workgroup bridge.”
In summary, a DS brings indirect message delivery and portals to a set
of basic service sets and creates an extended service set. Without a DS,
all you have are Independent Basic Service Sets (IBSS) whose stations
have to communicate with each other directly, if at all.
Integration Service
If the distribution service, one part of the DS, determines that the
intended recipient of a message is a member of an integrated LAN, the
“output” point of the DS would be a portal instead of an access point.
Messages that are distributed to a portal cause the DS to invoke the
Integration function (conceptually after the distribution service). The
integration service is a DS service. Messages received from an
integrated LAN (via a portal) for an 802.11 station will invoke the
Integration function before the message is distributed by the
distribution service. The details of an integration function are
dependent on a specific DS implementation and are outside the scope
of the 802.11 standard. As illustrated in figure 2.4 below, the
distribution service comprises a thin layer above the MAC sublayer,
and the integration service is between the distribution service and the
integrated LAN.
