Chapter 7 Wireless
VMG1312-B Series User’s Guide
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variet y of networks t o exist in the sam e place wit hout int erfering with one another. When you
creat e a net work, you m ust select a channel to use.
Since the available unlicensed spect rum varies from one country to anot her, t he num ber of
available channels also varies.
7.10.2 Additional Wireless Terms
The following t able describes som e wireless net work t erm s and acronym s used in t he Device’s Web
Configurator.
7.10.3 Wireless Security Overview
By their nature, radio com m unicat ions are sim ple to int ercept. For w ireless dat a networks, t his
m eans t hat anyone wit hin range of a wireless network w ithout security can not only read the dat a
passing over the airwaves, but also j oin t he network. Once an unauthorized person has access t o
the network, he or she can st eal inform at ion or introduce m alware ( m alicious soft ware) intended to
com prom ise the network. For t hese reasons, a variety of security system s have been developed t o
ensure that only aut horized people can use a wireless dat a netw or k, or underst and t he data carried
on it .
These securit y st andards do t wo things. First , they authent icat e. This m eans t hat only people
present ing the right credentials ( often a usernam e and password, or a “ key” phrase) can access t he
net work. Second, t hey encrypt . This m eans that the inform ation sent over the air is encoded. Only
people wit h t he code key can underst and the inform at ion, and only people who have been
aut hent icat ed are given the code key.
These security standards vary in effectiveness. Som e can be broken, such as t he old Wired
Equivalent Pr ot ocol ( WEP) . Using WEP is bet ter than using no securit y at all, but it will not keep a
det erm ined att acker out . Other security standards are secure in t hem selves but can be broken if a
user does not use them properly. For exam ple, the WPA- PSK secur ity standard is very secure if you
use a long key which is difficult for an att acker’s software t o guess - for exam ple, a t went y-let t er
long st ring of apparently random num ber s and lett ers - but it is not very secure if you use a short
key which is very easy to guess - for exam ple, a t hree- let t er word from t he dictionary.
Table 28 Addit ional Wireless Term s
TERM DESCRIPTION
RTS/ CTS Threshold I n a wireless network which covers a lar ge ar ea, wireless devices are som et im es not
aware of each other’s presence. This m ay cause them t o send inform at ion to the AP
at t he sam e t im e and result in inform ation colliding and not get t ing thr ough.
By set t ing this value lower than the default value, the w ireless devices m ust
som et im es get perm ission t o send inform at ion to t he Device. The lower the value, the
m ore oft en t he devices m ust get perm ission.
I f this value is greater than the fragm entation t hreshold value ( see below) , t hen
wireless devices never have t o get perm ission t o send inform at ion t o t he Device.
Pream ble A pream ble affect s t he tim ing in your wireless net work. There are two pream ble
m odes: long and short.
I f a device uses a different pream ble mode t han t he Device
does, it cannot com m unicat e with t he Device.
Authenticat ion The process of verifying whether a wireless device is allowed to use the w ireless
net work.
Fragm ent at ion
Threshold
A sm all fragm ent at ion thr eshold is recom m ended for busy networks, while a larger
thr eshold provides faster perform ance if the net work is not very busy.
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