ZyXEL Communications P8701T, Руководство пользователя

Страница: 186 / 240

Chapter 14 Wireless
Basic Home Station VDSL2 P8701T User’s Guide
186
• Every device in the same wireless network must use security compatible with the AP.
Security stops unauthorized devices from using the wireless network. It can also protect the
information that is sent in the wireless network.
Radio Channels
In the radio spectrum, there are certain frequency bands allocated for unlicensed, civilian use. For
the purposes of wireless networking, these bands are divided into numerous channels. This allows a
variety of networks to exist in the same place without interfering with one another. When you
create a network, you must select a channel to use.
Since the available unlicensed spectrum varies from one country to another, the number of
available channels also varies.
14.7.2 Additional Wireless Terms
The following table describes some wireless network terms and acronyms used in the VDSL Router’s
Web Configurator.
14.7.3 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
Table 71
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 VDSL Router. 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 VDSL
Router.
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 VDSL
Router does, it cannot communicate with the VDSL Router.
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.