Configuring Short Slots; Configuring Preambles - Juniper NETWORK AND SECURITY MANAGER 2010.4 - CONFIGURING SCREENOS DEVICES GUIDE REV 01 Manual

Configuring ScreenOS Devices Guide

Configuring Short Slots

Configuring Preambles

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On—When selected, wireless clients must first receive a CTS frame from the device
before sending data.
Off—When selected, wireless clients do not send CTS control frames.
Auto—When selected, the device automatically detects the CTS mode used by the
wireless client. This is the default setting.
CTS Protection Type—The protection type defines the level of control frame protection
enforced by the device. Select one of the following protection types:
CTS Only—When selected, wireless clients must first receive a single, self-directed
CTS frame from the device before sending data. This is the default setting.
CTS-RTS—When selected, wireless clients must first send an RTS frame and receive
a CTS frame from the device before sending data (a two-frame exchange occurs
prior to the actual network transmission).
CTS Rate—The CTS rate defines the data rate (in Mbps) at which CTS frames are sent.
The default rate is 11 Mbps; acceptable values are 1, 2, 5.5, and 11.
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:
In the NSM navigation tree, select Device Manager > Devices. Double-click the device
1.
object to open the device configuration.
In the device navigation tree, select Wireless Settings > Advanced, and then select
2.
Long in the Set Slot Time option.
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:
A long preamble (128 bits) provides the wireless client more time to process the
preamble, which can provide greater interoperability with older wireless protocols and
non-short-preamble equipment. All 802.11 devices support a long preamble.
A short preamble (56 bits) can improve efficiency because the client does not spend
time processing the preamble. However, older wireless protocols do not support short
preambles.
By default, the device does not support long preambles. To enable long preambles for
802.11b packets only:
Copyright © 2010, Juniper Networks, Inc.