Overview of the services

4.5 Overview of the services4.5.1 General

There are many services specified by IEEE Std 802.11. Six of the services are used to support medium
access control (MAC) service data unit (MSDU) delivery between STAs. Three of the services are used to
control IEEE 802.11 LAN access and confidentiality. Two of the services are used to provide spectrum
management. One of the services provides support for LAN applications with QoS requirements. Another of
the services provides support for higher layer timer synchronization. One of the services is used for radio
measurement.
This subclause presents the services, an overview of how each service is used, and a description of how each
service relates to other services and the IEEE 802.11 architecture. The services are presented in an order
designed to help build an understanding of the operation of an IEEE 802.11 ESS network. As a result, the
services that comprise the SS and DSS are intermixed in order (rather than being grouped by category).
Each of the services is supported by one or more MAC frame types. Some of the services are supported by
MAC management messages and some by MAC data messages. All of the messages gain access to the WM
via the IEEE 802.11 MAC sublayer medium access method specified in Clause 9.
The IEEE 802.11 MAC sublayer uses three types of messages—data, management, and control (see
Clause 8). The data messages are handled via the MAC data service path.
MAC management messages are used to support the IEEE 802.11 services and are handled via the MAC
management service path.
MAC control messages are used to support the delivery of IEEE 802.11 data and management messages.

The examples here assume an ESS network environment. The differences between the ESS and the IBSS
network environments are discussed separately in 4.7.