Configuring Advanced Wireless Settings

Use the advanced wireless settings to control low-level wireless networking settings, such as aging values and collision protection. When you first deploy the NetScreen-5GT Wireless device on your network, the network settings are already configured with default settings designed to work in most networking environments. However, you might want to edit these settings to meet your specific wireless networking needs.

You can edit the default values for the following wireless networking settings.

Configuring Aging

The aging interval is the amount of time (in seconds) that a wireless client or bridge remembers an access point after communication with the WAP is lost. To configure the aging setting:

  1. In the NSM navigation tree, select Device Manager > Devices. Double-click the device object to open the device configuration.
  2. In the device navigation tree, select Wireless Settings > Advanced, and then edit the default aging value.

The default is 300 seconds; acceptable range is 60 to 1,000,000 seconds. To disable aging, set the value to 0 (zero).

Configuring Beacons

A WAP broadcasts beacon packets to keep the wireless network synchronized and to inform wireless clients of waiting data. A beacon packet includes data such as the wireless LAN service area, the WAP address, and delivery traffic indicator maps (DTIMs).

To configure the beacon settings:

  1. In the NSM navigation tree, select Device Manager > Devices. Double-click the device object to open the device configuration.
  2. In the device navigation tree, select Wireless Settings > Advanced, and then edit the default values for the following settings:

Configuring Burst and Fragment Size

Use the burst and fragment setting to configure how the device transmits wireless packets over the network. To configure the burst and fragment settings:

  1. In the NSM navigation tree, select Device Manager > Devices. Double-click the device object to open the device configuration.
  2. In the device navigation tree, select Wireless Settings > Advanced, and then edit the default values for the following settings:

Configuring Control Frame Protection

Control frame protection is designed to help avoid collisions on the wireless network. Transmission collision usually occurs when two wireless devices are within range of the same WAP, but are not within range of each other (they are hidden nodes). If two wireless transmissions collide at the WAP, the data in each transmission is lost.

To avoid collisions, you can require wireless clients to first request permission to send data (clients must send a request-to-send (RTS) frame) and/or receive approval of that request (client must receive a clear-to-send (CTS) frame) before transmitting data.

Because 802.11b stations cannot hear 802.11g stations using orthogonal frequency-division multiplexing (OFDM), a method for wireless transmission that divides a signal and transmits the pieces at different frequencies simultaneously, traffic from these stations can collide on the network, reducing network efficiency. We recommend you enable protection to avoid collisions when supporting 802.11b and 802.11g operation modes.

Note: CTS protection is not supported when using 802.11b only.

To configure the control frame protection settings:

  1. In the NSM navigation tree, select Device Manager > Devices. Double-click the device object to open the device configuration.
  2. In the device navigation tree, select Wireless Settings > Advanced, and then edit the default values for the following settings:

Configuring Short Slots

Short slots, an 802.11g-only feature, can increase efficiency and throughput for wireless traffic. By default, the device supports 802.11g traffic that uses short slots. However, because 802.11b does not support short slots, you might want to disable short slots for all protocols when your wireless network is handling 802.11b traffic.

To disable short slot for 802.11g packets:

  1. In the NSM navigation tree, select Device Manager > Devices. Double-click the device object to open the device configuration.
  2. In the device navigation tree, select Wireless Settings > Advanced, and then select Long in the Set Slot Time option.

Configuring Preambles

A preamble is the sequence of bits within a transmission that, when recognized and received by a wireless client, enables the client to locate the remaining packets in the transmission. The preamble length is defined in the Synchronization field of a wireless packet, and can be long or short:

By default, the device does not support long preambles. To enable long preambles for 802.11b packets only:

  1. In the NSM navigation tree, select Device Manager > Devices. Double-click the device object to open the device configuration.
  2. In the device navigation tree, select Wireless Settings > Advanced, and, then select Long Transmit Preamble.

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