Chapter 7 Wireless LAN

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

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

A small fragmentation threshold is recommended for busy networks, while a

Threshold

larger threshold provides faster performance if the network is not very busy.

 

 

IGMP

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.

 

 

IGMP Snooping

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.

 

 

 

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P-660HN-F1 User’s Guide