Lotus Notes Traveler push framework typically uses TCP/IP for communication of new data (email, calendar updates, etc.) on the Domino server to a Lotus Notes Traveler client. Part of the framework is an algorithm that automatically determines the longest interval possible for the heartbeat for each specific device and network. The heartbeat is necessary since it is possible under some circumstances for the connection between the device and server to be lost without the device being notified of the outage. In this case, changes on the server that need to be synced to the client would not be pushed until some time later.
The heartbeat algorithm heuristically determines the smallest time-out in the device-to-server network path. These time-outs can be anything that causes the connection to terminate such as as VPN time-outs, NAT time-outs, etc. By automatically adjusting the heartbeat interval to slightly less than the smallest time-out, Lotus Notes Traveler is able to maintain the connection for immediate delivery of changed information from the Domino server. An often overlooked time-out is on Windows Mobile touch-screen devices when using a WiFi connection. These devices often turn off the WiFi connection when the device goes into Sleep Mode effectively timing-out the connection. The Lotus Notes Traveler algorithm will sense this as a network outage and adjust the heartbeat interval to slight less than this Sleep Mode interval, effectively preventing the device from going into sleep mode in this situation.
While the heartbeat interval for each connected client is automatically adjusted by Lotus Notes Traveler to be optimal, the configuration parameters can be tweaked to slightly improve operation. By default, the Heartbeat Algorithm Maximum Interval is set to 15 minutes in the Lotus Notes Traveler server's configuration document. This is a good default. However if you find that network conditions allow for larger heartbeat intervals, then this maximum value can be increased, thus reducing packets between the client and server, and thus increasing device battery life.
If you do modify the Heartbeat Algorithm Maximum Interval, set it to a number slightly less than the time-out of the underlying network connection for all users, if known. For example, if all Lotus Notes Traveler clients are connecting over a VPN that has an idle time-out of 30 minutes, then the maximum heartbeat interval should be set to 28 or 29 minutes.