The Delivery Traffic Indication Message interval helps routers to broadcast wireless traffic to multiple hosts with greater efficiency. DTIM intervals are sent as part of a regular wireless broadcast known as a wireless beacon. They effectively serve as a warning to wireless clients that a multicast transmission is incoming, helping to ensure that all necessary hosts are online and waiting for the transmission when it arrives.

Multicast Transmission

Multicast transmission is a form of network transmission whereby one device sends the same data to several recipients at once. It differs from one-to-one transmission in that network hosts do not respond to multicast senders to say that they have received the data. If the hosts were to respond, the sender would likely be flooded with traffic. As a result, the sender has no way of knowing whether or not its data was received. If one of the receivers was offline at the moment of transmission, the data would almost certainly be lost unbeknownst to the sender or receiver.

DTIM Intervals

DTIM intervals are used to maximize the chances of a multicast message reaching its intended recipients. When a DTIM-enabled router receives traffic to be sent over multicast, it sends a DTIM interval to all the message's intended hosts. The interval tells the hosts that a multicast message is waiting, and notifies them when it will be sent. This causes any network hosts that are in power-saving mode to come back online and await the incoming multicast.

Beacon Interval

DTIM intervals are sent as part of a wireless beacon. Wireless beacons are sent by routers to the clients on a network at regular intervals. These beacons help to ensure that all the network's clients stay synchronized. When a router sends a DTIM interval, it indicates to the clients on the network how many beacons will be broadcast before the multicast traffic is sent. As the clients know how often beacons are broadcast, they can use this information to work out when the multicast will arrive.

Configuring DTIM Interval

Many routers allow you to configure a DTIM interval through a configuration menu. The necessary settings will usually be located in the device's wireless setup page, sometimes under an Advanced Settings tab. Before configuring a DTIM interval, you must first set a beacon interval. This is the time in milliseconds between each beacon transmission from the router. Next, specify the number of beacons that you want to pass in between the interval and the transmission using the router's DTIM Interval menu option.