What Are 802.11 Topologies? We’re Going Back to Basics
For all its simplicity to end users, Wi-Fi is really an incredibly complex technology. In this series, we “get back to basics” of the technology.
In the last installment of of my “Back to the Basics” blog series I discussed 2.4 GHz Channel Planning. This week we will take a look at 802.11 topologies.
Before getting straight into 802.11 topologies, it is important to note that there are four major wireless topologies–
WWAN: wireless wide area network
WMAN: wireless metropolitan area network
WPAN: wireless personal area network
WLAN: wireless local area network
The 802.11 wireless medium is a perfect fit for local area networking (WLAN), which is the fourth topology listed above. This is what I will focus on for the remainder of this blog. The main component of an 802.11 wireless network is the radio. The radio can be inside a wireless access point or can be used as a client station.
Looking a little more closely, there are four 802.11 service sets that describe how these radios may be used to communicate with each other. The first is a basic service set (BSS) which is the foundation of an 802.11 network. A BSS consists of one AP radio with one or more client stations. These client stations connect to the AP and communicate through the AP. The physical area of coverage provided by an access point in a BSS is known as the basic service area (BSA).
Next is the extended service set (ESS). An extended service set is two or more basic service sets connected by a distribution system medium. The distribution system medium (DSM) is a physical medium that is used to connect access points. The most common DSM is a wired medium.
Third is the independent basic service set (IBSS). An IBSS is made up solely of client stations and no access points. The client stations transmit frames to each other directly, which is called peer to peer communication.
And lastly we have the mesh basic service set (MBSS). When access points support mesh functions, they may be deployed where wired network access is not available or possible. By using mesh functions, the access points provide wireless distribution for network traffic and form a mesh basic service set. One or more mesh APs will usually be connected to the wired infrastructure and the other mesh APs that are not connected to the wired network will form wireless backhaul connections to that specific AP.
In summary, there are four main service sets as defined by the 802.11 standard, and each has a specific purpose. Network administrators typically work with extended service sets but each of the four sets can be used in a multitude of situations.
In my next installment, I will discuss Radio Frequency and Antenna Concepts.
All Posts In The Back To Basics Series: