Over the air activation (OTAA) of devices

  • 13 June 2018
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When OTAA is used for the activation of devices, the DevEUI, AppEUI and AppKey are needed to register the device on the KPN LoRa network.
The NwkSKey and AppSKey are derived when joining the network.

OTAA Join procedure

During the OTAA Join the network forwards the join request message to the Application Server identified by the AppEUI. This Application Server is supposed to have been provisioned with the end-device's AppKey. Based on the AppKey and the content of the Join request message sent by the end-device, the Network:
  • Generates a NwkSKey and AppSKey and sends the NwkSKey information to the KPN Core Network.
  • Forms a Join response payload that will allow the end-device to compute a NwkSKey and AppSKey.

OTAA re-join

The advice for the frequency of periodically rejoining (and thus renewing the NwkSKey and the AppSKey) depends on the number of messages sent by the end-device and the level of security required.
A device should re-join:
  • Every time it has lost the session context information.
  • Every x days
  • Every y messages
The x and y values may differ depending on the level of security required, appropriate values could be once a month or maybe once every 2-3 months. The security risk depends on the application: metering applications sending a low amount of values typically don't need very frequent re-keying while critical applications (e.g. alarms) would require more frequent re-keying. Currently KPN has no precise defined time or number of messages when a rejoin will be forced, customers should make sure their device and application can still work and build a connection when a rejoin is required.

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