U mode

U means UDP binding mode. The LWM2M Server expects that the LWM2M Client is reachable via the UDP binding at any time. The LWM2M Server must send requests to a LWM2M Client using the UDP binding. The LWM2M Client must send the response to such a request over the UDP binding.

The U binding mode is unlikely to be suitable for devices that only connect intermittently such as Cat-NB1, CatM1 or LORAWAN as most of the time the device is offline.

This is the default mode of operation.

Use of UE Reachability to wakeup a LWM2M device

For non-active, U-Mode Binding cellular devices, if the parameter monte.UE_REACHABILITY_ENABLED is enabled, then UE Reachability towards SCEF is setup. And when the device is reachable, then a CoAP message with Registration Update Trigger is sent to the device.

For more information on the parameter monte.UE_REACHABILITY_ENABLED, see section Sample values.yaml file for LWM2M deployment in IMPACT IoT Installation Guide.

Note: The LWM2M UDP Notification will be sent to the device IP address that was provided via the Authentication, Authorisation and Accounting Server(AAA). The network routing should be pre-established in order for this notification message to reach the device the IP address of the device must be addressable via IP from the LWM2M Server.