new ccna ine

new ccna ine.Beacon: one Non-ERP display: no Use protection: noFigure 6-6 Using Protected 802.11g Cells: Part 4This protection mechanism works well because 802.11b clients can listen to both RTS and CTS regardless of which client they are near. The other protection mechanism is clear send itself (CTStoself), but this is not the preferred method because clients farther away from the sender may not be able to listen to CTStoselfo5.2 Basic Topics 75Another side effect of 802.11b clients in 802Jlg cells is a domino effect. When an AP advertises as NON_ERP present:yes UseProtection:yesNearby APs that hear this beacon begin to announce NON__ERPpresent:no UseProtection:yesThe nearby cell announces NON_ERP present to indicate that it does not hear the NON_ERP device, however it also announces "Use Protection: yes" to ensure security. This effectively forces the cell to use protection even though it has no 802.11b clients, but this also reduces the performance of each f client in the cell. This is why the AP chooses to use only 802.11g.6.2.5 802.11aW 802.11a was approved in 1999 and operates in the 5GHz band. This makes it immune to interference from devices including microwaves, Bluetooth devices, and cordless phones, but also makes it incompatible with 802.11, 802.11b, and 802.11g. The market was late in embracing 802.11a, so it is not as widely used as the 802.11b and 802.11g protocols. Another difference between 802.11a and 802.11b/g is that 802.11a supports 12 non-overlapping channels, while 802.11b/g supports only 3 non-overlapping channels. Because OFDM modulation is used, the subchannels of 802.11a can overlap O802.11a is required to support data rates of 6, 12, and 24 Mbit/s, and it allows data rates of up to 54 Mbit/so Table 6-5 shows some details of the 802.11a standard./I-... Table 6-5 802.11a ProtocolDate of Approval 1999