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4
The RADIUS server distributes the PMK to the AP. The AP then sets up a key
hierarchy and management system, using the PMK to dynamically generate
unique data encryption keys. The keys are used to encrypt every data packet that
is wirelessly communicated between the AP and the wireless clients.
Figure 182
WPA(2) with RADIUS Application Example
WPA(2)-PSK Application Example
A WPA(2)-PSK application looks as follows.
1
First enter identical passwords into the AP and all wireless clients. The Pre-Shared
Key (PSK) must consist of between 8 and 63 ASCII characters or 64 hexadecimal
characters (including spaces and symbols).
2
The AP checks each wireless client's password and allows it to join the network
only if the password matches.
3
The AP and wireless clients generate a common PMK (Pairwise Master Key). The
key itself is not sent over the network, but is derived from the PSK and the SSID.
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4
The AP and wireless clients use the TKIP or AES encryption process, the PMK and
information exchanged in a handshake to create temporal encryption keys. They
use these keys to encrypt data exchanged between them.
Figure 183
WPA(2)-PSK Authentication
Security Parameters Summary
Refer to this table to see what other security parameters you should configure for
each authentication method or key management protocol type. MAC address
filters are not dependent on how you configure these security features.
Table 93
Wireless Security Relational Matrix
AUTHENTICATION
METHOD/ KEY
MANAGEMENT
PROTOCOL
ENCRYPTIO
N METHOD
ENTER
MANUAL KEY
IEEE 802.1X
Open
None
No
Disable
Enable without Dynamic WEP
Key
Open
WEP
No
Enable with Dynamic WEP Key
Yes
Enable without Dynamic WEP
Key
Yes
Disable
Shared
WEP
No
Enable with Dynamic WEP Key
Yes
Enable without Dynamic WEP
Key
Yes
Disable
WPA
TKIP/AES
No
Enable
WPA-PSK
TKIP/AES
Yes
Disable
WPA2
TKIP/AES
No
Enable
WPA2-PSK
TKIP/AES
Yes
Disable
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Antenna Overview
An antenna couples RF signals onto air. A transmitter within a wireless device
sends an RF signal to the antenna, which propagates the signal through the air.
The antenna also operates in reverse by capturing RF signals from the air.
Positioning the antennas properly increases the range and coverage area of a
wireless LAN.
Antenna Characteristics
Frequency
An antenna in the frequency of 2.4GHz (IEEE 802.11b and IEEE 802.11g) or 5GHz
(IEEE 802.11a) is needed to communicate efficiently in a wireless LAN
Radiation Pattern
A radiation pattern is a diagram that allows you to visualize the shape of the
antenna’s coverage area.
Antenna Gain
Antenna gain, measured in dB (decibel), is the increase in coverage within the RF
beam width. Higher antenna gain improves the range of the signal for better
communications.
For an indoor site, each 1 dB increase in antenna gain results in a range increase
of approximately 2.5%. For an unobstructed outdoor site, each 1dB increase in
gain results in a range increase of approximately 5%. Actual results may vary
depending on the network environment.
Antenna gain is sometimes specified in dBi, which is how much the antenna
increases the signal power compared to using an isotropic antenna. An isotropic
antenna is a theoretical perfect antenna that sends out radio signals equally well
in all directions. dBi represents the true gain that the antenna provides.
Types of Antennas for WLAN
There are two types of antennas used for wireless LAN applications.
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Omni-directional antennas send the RF signal out in all directions on a horizontal
plane. The coverage area is torus-shaped (like a donut) which makes these
antennas ideal for a room environment. With a wide coverage area, it is possible
to make circular overlapping coverage areas with multiple access points.
Directional antennas concentrate the RF signal in a beam, like a flashlight does
with the light from its bulb. The angle of the beam determines the width of the
coverage pattern. Angles typically range from 20 degrees (very directional) to
120 degrees (less directional). Directional antennas are ideal for hallways and
outdoor point-to-point applications.
Positioning Antennas
In general, antennas should be mounted as high as practically possible and free of
obstructions. In point-to–point application, position both antennas at the same
height and in a direct line of sight to each other to attain the best performance.
For omni-directional antennas mounted on a table, desk, and so on, point the
antenna up. For omni-directional antennas mounted on a wall or ceiling, point the
antenna down. For a single AP application, place omni-directional antennas as
close to the center of the coverage area as possible.
For directional antennas, point the antenna in the direction of the desired
coverage area.
WiFi Protected Setup
Your ZyXEL Device supports WiFi Protected Setup (WPS), which is an easy way to
set up a secure wireless network. WPS is an industry standard specification,
defined by the WiFi Alliance.
WPS allows you to quickly set up a wireless network with strong security, without
having to configure security settings manually. Each WPS connection works
between two devices. Both devices must support WPS (check each device’s
documentation to make sure).
Depending on the devices you have, you can either press a button (on the device
itself, or in its configuration utility) or enter a PIN (a unique Personal Identification
Number that allows one device to authenticate the other) in each of the two
devices. When WPS is activated on a device, it has two minutes to find another
device that also has WPS activated. Then, the two devices connect and set up a
secure network by themselves.
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Push Button Configuration
WPS Push Button Configuration (PBC) is initiated by pressing a button on each
WPS-enabled device, and allowing them to connect automatically. You do not need
to enter any information.
Not every WPS-enabled device has a physical WPS button. Some may have a WPS
PBC button in their configuration utilities instead of or in addition to the physical
button.
Take the following steps to set up WPS using the button.
1
Ensure that the two devices you want to set up are within wireless range of one
another.
2
Look for a WPS button on each device. If the device does not have one, log into its
configuration utility and locate the button (see the device’s User’s Guide for how to
do this - for the ZyXEL Device, see
Section 6.4 on page 93
).
3
Press the button on one of the devices (it doesn’t matter which).
4
Within two minutes, press the button on the other device. The registrar sends the
network name (SSID) and security key through an secure connection to the
enrollee.
If you need to make sure that WPS worked, check the list of associated wireless
clients in the AP’s configuration utility. If you see the wireless client in the list,
WPS was successful.
PIN Configuration
Each WPS-enabled device has its own PIN (Personal Identification Number). This
may either be static (it cannot be changed) or dynamic (you can change it to a
new random number by clicking on a button in the configuration interface).
When you use the PIN method, you must enter the enrollee’s PIN into the
registrar. Then, when WPS is activated on the enrollee, it presents its PIN to the
registrar. If the PIN matches, the registrar sends the network and security
information to the enrollee, allowing it to join the network.
The advantage of using the PIN method rather than the PBC method is that you
can ensure that the connection is established between the devices you specify, not
just the first two devices to activate WPS in the area. However, you need to log
into the configuration interfaces of both devices.
Take the following steps to set up WPS using the PIN method.

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