ZyXEL Communications P-661H-61, Руководство пользователя

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Chapter 6 Wireless
P-661HNU-Fx User’s Guide
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6.7.1 Additional Wireless Terms
The following table describes some wireless network terms and acronyms used in
the ZyXEL Device’s web configurator.
6.7.2 Wireless Security Overview
By their nature, radio communications are simple to intercept. For wireless data
networks, this means that anyone within range of a wireless network without
security can not only read the data passing over the airwaves, but also join the
network. Once an unauthorized person has access to the network, he or she can
steal information or introduce malware (malicious software) intended to
compromise the network. For these reasons, a variety of security systems have
been developed to ensure that only authorized people can use a wireless data
network, or understand the data carried on it.
These security standards do two things. First, they authenticate. This means that
only people presenting the right credentials (often a username and password, or a
“key” phrase) can access the network. Second, they encrypt. This means that the
information sent over the air is encoded. Only people with the code key can
understand the information, and only people who have been authenticated are
given the code key.
Table 22 Additional Wireless Terms
TERM DESCRIPTION
RTS/CTS Threshold In a wireless network which covers a large area, wireless devices
are sometimes not aware of each other’s presence. This may cause
them to send information to the AP at the same time and result in
information colliding and not getting through.
By setting this value lower than the default value, the wireless
devices must sometimes get permission to send information to the
ZyXEL Device. The lower the value, the more often the devices must
get permission.
If this value is greater than the fragmentation threshold value (see
below), then wireless devices never have to get permission to send
information to the ZyXEL Device.
Preamble A preamble affects the timing in your wireless network. There are
two preamble modes: long and short.
If a device uses a different
preamble mode than the ZyXEL Device does, it cannot communicate
with the ZyXEL Device.
Authentication The process of verifying whether a wireless device is allowed to use
the wireless network.
Fragmentation
Threshold A small fragmentation threshold is recommended for busy networks,
while a larger threshold provides faster performance if the network
is not very busy.