Технические ссылки для Cisco Cisco 4100 Series Wireless LAN Controller
5/26/05
config 802.11b dtim
OL-7427-02
config 802.11b dtim
config 802.11b dtim
In 802.11 networks, the Cisco 1000 Series lightweight access point WLANs broadcast a beacon at
regular intervals, which coincide 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 802.11b/g 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 802.11b/g 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.
Note that 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 802.11b/g
networks that support such clients.
To change the DTIM value for the whole 802.11b/g network, use the config 802.11b dtim command.
Before you change the 802.11b/g DTIM value using the config 802.11b dtim command, make sure that
you have disabled the 802.11b/g network using the config 802.11b disable command. When you are
done changing the DTIM value, remember to enable the 802.11b/g network using the config 802.11b
enable command.
regular intervals, which coincide 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 802.11b/g 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 802.11b/g 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.
Note that 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 802.11b/g
networks that support such clients.
To change the DTIM value for the whole 802.11b/g network, use the config 802.11b dtim command.
Before you change the 802.11b/g DTIM value using the config 802.11b dtim command, make sure that
you have disabled the 802.11b/g network using the config 802.11b disable command. When you are
done changing the DTIM value, remember to enable the 802.11b/g network using the config 802.11b
enable command.
>
config 802.11b dtim <period>
Syntax
config
Configure parameters.
802.11b
802.11b/g network parameters.
dtim
Delivery Traffic Indication Map.
<period>
DTIM period in number of beaconperiods.
Defaults
1 (every beaconperiod)
Examples
>config 802.11b dtim 1
to configure the 802.11b/g network to transmit multicast and broadcast
messages every DTIM, or beaconperiod.
to configure the 802.11b/g network to transmit multicast and broadcast
messages every DTIM, or beaconperiod.
Related Commands
show 802.11b, config 802.11b beaconperiod, config 802.11a dtim, config
802.11b disable, config 802.11b enable
802.11b disable, config 802.11b enable