Additional Wireless Terms; Table 42 Additional Wireless Terms - ZyXEL Communications P-660HN User Manual

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.

7.9.2 Additional Wireless Terms

The following table describes some wireless network terms and acronyms used in the ZyXEL
Device's Web Configurator.

Table 42 Additional Wireless Terms

TERM
RTS/CTS Threshold
Preamble
Authentication
Fragmentation
Threshold
IGMP
IGMP Snooping
P-660HN-Fx User's Guide
DESCRIPTION
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.
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.
The process of verifying whether a wireless device is allowed to use the
wireless network.
A small fragmentation threshold is recommended for busy networks, while a
larger threshold provides faster performance if the network is not very busy.
Traditionally, IP packets are transmitted in one of either two ways - Unicast (1
sender to 1 recipient) or Broadcast (1 sender to everybody on the network).
Multicast delivers IP packets to just a group of hosts on the network.
IGMP (Internet Group Management Protocol) is a network-layer protocol used
to establish membership in a multicast group - it is not used to carry user data.
The ZyXEL Device can passively snoop on IGMP packets transferred
between IP multicast routers/switches and IP multicast hosts to learn the IP
multicast group membership. It checks IGMP packets passing through it, picks
out the group registration information, and configures multicasting accordingly.
IGMP snooping allows the ZyXEL Device to learn multicast groups without
you having to manually configure them.
Chapter 7 Wireless LAN
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