WLAN formation and WLAN infrastructure.

In WLAN formation I will show you little bit of WLAN theory.

WLAN networks consist of:

1) Distribution system - combination of bridging engine and backbone network.

2) Access Point (AP) - performs wireless to wired bridging function.

3) Wireless Medium - for exchanging frames among stations and backbone.

4) Station - PCs, laptops and other devices with wireless network card.

The basic block of 802.11 networks is BSS - Basic Service Set. This is group of the stations that communicate only among them.

There are two types of BSS – Independent and Infrastructure:

1) Independent BSS networks or ad hoc are only stations without Access Point. You can setup your WLAN home network, even without AP.

2) Infrastructure BSS networks - stations use Access Point for communication among them.
Why do we actually use Access Point, if it is not essential? There are few reasons for that:

- Access Point bridges wireless word to wired. So without Access Point you do not have a connection to the rest of the world.

- Longer range. Range of Infrastructure BSS is defined by the distance between station and access point. In Ad-Hoc network range is defined by distance between stations.

- With Access Point, stations save power. When station enters a power-saving mode, access point buffers frames for it.

Extended Service Set (ESS) - connects BSSs with backbone network. ESS connects stations with rest of the word - Internet.

From users' prospective, WLAN is Wireless Ethernet. Network administrators need to know that comparing to wired networks, the frame delivery is unreliable. Because that, 802.11 standard requires several additional services and more complex framing.