ZyXEL Communications G-570U, User Manual

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ZyXEL G-570U User’s Guide
Appendix C Wireless LANs 135
A large Fragmentation Threshold is recommended for networks not prone to interference
while you should set a smaller threshold for busy networks or networks that are prone to
interference.
If the Fragmentation Threshold value is smaller than the RTS/CTS value (see previously)
you set then the RTS (Request To Send)/CTS (Clear to Send) handshake will never occur as
data frames will be fragmented before they reach
RTS/CTS size.
IEEE 802.11g Wireless LAN
IEEE 802.11g is fully compatible with the IEEE 802.11b standard. This means an IEEE
802.11b adapter can interface directly with an IEEE 802.11g access point (and vice versa) at
11 Mbps or lower depending on range. IEEE 802.11g has several intermediate rate steps
between the maximum and minimum data rates. The IEEE 802.11g data rate and modulation
are as follows:
IEEE 802.1x
In June 2001, the IEEE 802.1x standard was designed to extend the features of IEEE 802.11 to
support extended authentication as well as providing additional accounting and control
features. It is supported by Windows XP and a number of network devices. Some advantages
of IEEE 802.1x are:
• User based identification that allows for roaming.
• Support for RADIUS (Remote Authentication Dial In User Service, RFC 2138, 2139) for
centralized user profile and accounting management on a network RADIUS server.
• Support for EAP (Extensible Authentication Protocol, RFC 2486) that allows additional
authentication methods to be deployed with no changes to the access point or the wireless
stations.
RADIUS
RADIUS is based on a client-server model that supports authentication, authorization and
accounting. The access point is the client and the server is the RADIUS server. The RADIUS
server handles the following tasks:
Table 37 IEEE 802.11g
DATA RATE (MBPS) MODULATION
1 DBPSK (Differential Binary Phase Shift Keyed)
2 DQPSK (Differential Quadrature Phase Shift Keying)
5.5 / 11 CCK (Complementary Code Keying)
6/9/12/18/24/36/48/54 OFDM (Orthogonal Frequency Division Multiplexing)