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WLAN Extended Service Set - WLAN ESS
| | WLAN Extended Service Set (ESS) links BSSes together with the backbone area. Backbone is usually Ethernet. |
WLAN networks offer these stations in different BSSes can communicate among. When a backbone area is one broadcast domain - one VLAN, 802.11 networks can offer link-layer mobility.
The distribution system is the key of ESS. It provides mobility by connecting access points. DS is responsible for tracking location of stations.A router on the picture just sends a frame to destination by MAC address. The distribution system delivers frames to the right access point, and access point delivers frame to a specific station.
Inter-access point communication - method to manage associations among access points. Station first associate to the AP1 and then AP1 sends packet - I “have” that station, to other access points (AP2, AP3 and AP4).
IAPP (Inter-Access Point Protocol) is recommendation described by IEEE 802.11F. IIt provides the communication of the access points of different vendors.
The wireless medium also can be a distribution system. Wireless Distribution or Wireless Bridge allows you to connect two distinct locations. You could connect to your neighbor network with two Wireless Bridges.
802.11 networks have overlapping Network boundaries. This fuzziness is even desirable. If we make closer AP1 to AP3 (or increase their powers), BSS1 and BSS3 overlaps. So, when station moves from BSS1 to BSS3, it will not lose network even if AP2 fails.
Looking above, 802.11 networks look like Wireless Ethernet. If you are familiar with Ethernet, you will have no problems with WLAN.
From the user’s prospective, WLAN is the same as Ethernet. Network administrators have to know that frame delivery is unreliable, compared to wired networks. Because that, 802.11 standard requires the numbers of additional services and more complex framing.
If you want to know more about services, click WLAN Network Services
Return from Extended Service Set to What is WiFi
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