Технические ссылки для Cisco Cisco 4100 Series Wireless LAN Controller
5/26/05
config 802.11a dtim
OL-7427-02
config 802.11a dtim
config 802.11a dtim
In 802.11 networks, the Cisco 1000 Series lightweight access point WLANs broadcast a beacon at
regular intervals, which coincides with the DTIM (Delivery Traffic Indication Map). After the DTIM, if the
Cisco 1000 Series lightweight access point has any frames buffered for broadcast or multicast, it
transmits the buffered frames. This protocol allows power-saving clients to wake up at the appropriate
time if they are expecting broadcast or multicast data.
Normally, the DTIM value is set to 1 (transmit broadcast and multicast after every beacon) or 2
(transmit after every other beacon). For instance, if the beaconperiod is 100 ms, and the DTIM value is
set to 1, the Cisco 1000 Series lightweight access point transmits buffered broadcast and multicast
frames 10 times a second; if the beaconperiod is 100 ms, and the DTIM value is set to 2, the Cisco
1000 Series lightweight access point transmits buffered broadcast and multicast frames five times a
second; either of these settings may be suitable for applications, including VoIP, that expect frequent
broadcast and multicast frames.
However, the DTIM value can be set as high as 255 (transmit broadcast and multicast after every 255th
beacon), if all 802.11a clients have power save enabled. Because the clients only have to listen when
the DTIM time is reached, they can be set to listen for broadcasts and multicasts less frequently,
resulting in longer battery life. For instance, if the beaconperiod is 100 ms, and the DTIM value is set to
100, the Cisco 1000 Series lightweight access point transmits buffered broadcast and multicast frames
once every 10 seconds, allowing the power saving clients to sleep longer between periods when they
have to wake up and listen for broadcasts and multicasts, resulting in longer battery life.
Many applications cannot tolerate a long time between broadcast and multicast messages, resulting in
poor protocol and application performance. A low DTIM value is indicated for 802.11a networks that
support such clients.
To change the DTIM value for the whole 802.11a network, use the config 802.11a dtim command.
regular intervals, which coincides with the DTIM (Delivery Traffic Indication Map). After the DTIM, if the
Cisco 1000 Series lightweight access point has any frames buffered for broadcast or multicast, it
transmits the buffered frames. This protocol allows power-saving clients to wake up at the appropriate
time if they are expecting broadcast or multicast data.
Normally, the DTIM value is set to 1 (transmit broadcast and multicast after every beacon) or 2
(transmit after every other beacon). For instance, if the beaconperiod is 100 ms, and the DTIM value is
set to 1, the Cisco 1000 Series lightweight access point transmits buffered broadcast and multicast
frames 10 times a second; if the beaconperiod is 100 ms, and the DTIM value is set to 2, the Cisco
1000 Series lightweight access point transmits buffered broadcast and multicast frames five times a
second; either of these settings may be suitable for applications, including VoIP, that expect frequent
broadcast and multicast frames.
However, the DTIM value can be set as high as 255 (transmit broadcast and multicast after every 255th
beacon), if all 802.11a clients have power save enabled. Because the clients only have to listen when
the DTIM time is reached, they can be set to listen for broadcasts and multicasts less frequently,
resulting in longer battery life. For instance, if the beaconperiod is 100 ms, and the DTIM value is set to
100, the Cisco 1000 Series lightweight access point transmits buffered broadcast and multicast frames
once every 10 seconds, allowing the power saving clients to sleep longer between periods when they
have to wake up and listen for broadcasts and multicasts, resulting in longer battery life.
Many applications cannot tolerate a long time between broadcast and multicast messages, resulting in
poor protocol and application performance. A low DTIM value is indicated for 802.11a networks that
support such clients.
To change the DTIM value for the whole 802.11a network, use the config 802.11a dtim command.
>
config 802.11a dtim <period>
Syntax
config
Configure parameters.
802.11a
802.11a network parameters.
dtim
Delivery Traffic Indication Map.
<period>
DTIM value in number of beaconperiods.
Defaults
1 (every beaconperiod)
Examples
>config 802.11a dtim 2
to configure the 802.11a network to transmit multicast and broadcast
messages every other DTIM, or beaconperiod.
to configure the 802.11a network to transmit multicast and broadcast
messages every other DTIM, or beaconperiod.
Related Commands
show 802.11a, config 802.11a beaconperiod, config 802.11b dtim, config
802.11a disable, config 802.11a enable
802.11a disable, config 802.11a enable