When the modem isn't active (not used for client traffic)
An ICMP ping will be sent over the cellular connection every 60 seconds to ensure the modem remains available, should it be needed in the event of wired uplink failure. This keep-alive traffic should be less than 9MB total per month. Signal strength and status are determined locally by the modem with no traffic sent over the cellular network.
Note: Dependent on modem and carrier, other communication may occur between the modem and the tower/network. However, this traffic is not generated by the MX.
When the modem is active (used for client traffic)
Any client traffic and general communication with the Cloud Controller will be sent over the cellular link. Any Dashboard tools that require loading live data from the device, such as traffic graphs, will also produce increase cellular usage.