ZyXEL Communications Corporation B220 Manuel D’Utilisation
ZyAIR Wireless LAN Utility
Wireless LAN Security
5-1
Chapter 5
Advanced Configuration
This chapter shows you how to configure advanced features of the ZyAIR.
5.1 Overview
The following sections introduce the advanced features you can configure.
5.1.1 Threshold Control
RTS/CTS Threshold
The RTS (Request To Send) Threshold prevents collision when there is a hidden node problem. Hidden
node problem occurs when two stations are within the range of the same access point, but are not within the
range of each other. The following figure illustrates the hidden node problem. Both stations (STA) are
within the range of the AP, however, they cannot hear each other. Therefore, they are considered as hidden
nodes from each other. When a station starts data transmission with the access point, it might not know that
the other station is already using the wireless medium. When these two stations send data at the same time,
they might collide when arriving simultaneously at the AP. The collision will most certainly result in a loss
of messages for both stations.
The RTS (Request To Send) Threshold prevents collision when there is a hidden node problem. Hidden
node problem occurs when two stations are within the range of the same access point, but are not within the
range of each other. The following figure illustrates the hidden node problem. Both stations (STA) are
within the range of the AP, however, they cannot hear each other. Therefore, they are considered as hidden
nodes from each other. When a station starts data transmission with the access point, it might not know that
the other station is already using the wireless medium. When these two stations send data at the same time,
they might collide when arriving simultaneously at the AP. The collision will most certainly result in a loss
of messages for both stations.
Figure 5-1 RTS Threshold
Thus, RTS Threshold mechanism provides a solution to prevent data collisions. When you enable RTS
Threshold on a possible hidden station, this station and its AP will use a Request to Send/Clear to Send
protocol (RTS/CTS). The station will send an RTS message to the AP, informing that it is going to transmit
the data. Upon receipt, the Access Point will respond with a CTS message to all stations within its range to
Threshold on a possible hidden station, this station and its AP will use a Request to Send/Clear to Send
protocol (RTS/CTS). The station will send an RTS message to the AP, informing that it is going to transmit
the data. Upon receipt, the Access Point will respond with a CTS message to all stations within its range to