ZyXEL Communications ZyWall USG 50-H Series, Руководство пользователя

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Appendix D Wireless LANs
ZyWALL USG 50-H User’s Guide
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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.
Preamble Type
Preamble is used to signal that data is coming to the receiver. Short and long refer to the length
of the synchronization field in a packet.
Short preamble increases performance as less time sending preamble means more time for
sending data. All IEEE 802.11 compliant wireless adapters support long preamble, but not all
support short preamble.
Use long preamble if you are unsure what preamble mode other wireless devices on the
network support, and to provide more reliable communications in busy wireless networks.
Use short preamble if you are sure all wireless devices on the network support it, and to
provide more efficient communications.
Use the dynamic setting to automatically use short preamble when all wireless devices on the
network support it, otherwise the ZyWALL uses long preamble.
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The wireless devices MUST use the same preamble mode in order to
communicate.
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:
Wireless Security Overview
Wireless security is vital to your network to protect wireless communication between wireless
clients, access points and the wired network.
Table 258 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)