On 20 July 2013 15:34, Andrew Allen <aallen@xxxxxxxxxxxxxx> wrote: > There are obviously always alternative design choices but why would you want to include both a pre assigned device ID and a generated device ID in the same message? I think that reading this thread should provide you with ample reasons. The instance ID in outbound has certain stability requirements that do not strictly correspond to the lifetime of the hardware in use. The other use cases answer very different questions, which include: is this a stolen device, is this device authorized to use the networks, etc... I'm certain those questions can be answered without a device identifier traversing the network.