ZyXEL Communications ZyWALL 2 Series User Manual

Page of 614
ZyWALL 2 Series User’s Guide 
Wireless LAN Screens 
7-1 
Chapter 7    
Wireless LAN Screens 
This chapter discusses how to configure Wireless LAN on the ZyWALL 2WE. 
7.1 Wireless 
LAN 
Overview 
This section introduces the wireless LAN (WLAN) and some basic scenarios. 
7.1.1 Additional Installation Requirements for Using 802.1x 
 A computer with an IEEE 802.11b wireless LAN card.  
 A computer equipped with a web browser (with JavaScript enabled) and/or Telnet. 
 A wireless client computer must be running IEEE 802.1x-compliant software. Currently, this is 
offered in Windows XP.  
 An optional network RADIUS server for remote user authentication and accounting. 
7.2 Wireless 
LAN 
Basics 
This section provides background information on WLAN. 
7.2.1 Channel 
A channel is the radio frequency(ies) used by IEEE 802.11b wireless devices. Choose the radio channel 
depending on your geographical area. Adjacent Access Points (APs) should use different channels to reduce 
crosstalk. Crosstalk occurs when radio signals from access points overlap and cause interference that 
degrades performance.   
7.2.2 ESS ID 
Extended Service Set (ESS) is defined as one or more APs acting as a bridge between a wired LAN and the 
associated wireless clients. The ESS ID is a unique ID given to the APs and the wireless clients that 
participate in the same wireless network. You can think of the ESS ID as being similar to a workgroup name 
in a Microsoft network.  
7.2.3 RTS/CTS  
A hidden node occurs when two stations are within range of the same access point, but are not within range 
of each other. The following figure illustrates a hidden node. Both stations (STA) are within range of the 
access point (AP) or wireless gateway, but out-of-range of each other, so they cannot “hear” each other, that