ChirpStack Network Server supports the handling and configuration of rejoin-requests for LoRaWAN® 1.1.x devices. Using a rejoin-request, a device is able to request the network-server to re-activate, without being ‘disconnected’ until receiving the activation. In other words, when it doesn't receive a new activation, the device will continue to use the old security context.
With the rejoin-request, it is possible to reset the device context including all radio parameters (device address, frame counters, session-keys, radio parameters, …) restore a lost session context or rekey a device (device address, session-keys and frame-counters).
ChirpStack Network Server supports configuring devices so that they will send a rejoin-request based on a time and / or frame-counter based interval.
For more details on rejoin-requests, please refer to the LoRaWAN specification.