11GFIGURE 6-1 11G CELL WITH NO 11B CLIENTSASSUME THAT INIT...

802.11g

Figure 6-1 802.11g Cell with No 802.11b Clients

Assume that initially 802.11b clients do not exist. The default behavior of an AP is to send

beacons that include information about the AP and the wireless cell. Without 802.11b

clients, the AP sends the following information in a beacon:

NON_ERP present: no

Use Protection: no

ERP is Extended Rate Physical. These are devices that have extended data rates. In other

words, NON_ERP is talking about 802.11b clients. If they were ERP, that would support

the higher data rates, making them 802.11g clients.

Now, going back to Figure 6-1 with no 802.11b clients, the AP tells everyone that 802.11b

clients are unavailable and that they do not need to use protection mechanisms.

After an 802.11b client associates with the AP, things change. In Figure 6-2, the AP alerts

the rest of the network about the NON_ERP client. This is done in the beacon that the

AP sends.

Beacon:

Non-ERP Present: Yes

Use Protection: Yes

Client A

Client B