How does the LPN node initiate the iv update?

[Young]

Hi support team,

I have searched the forum , the infocenter and the specification, but didn't find the relevant info about how a LPN node initates the iv update if a LPN node exhausts its sequence number firstly in the mesh network. 

In the network_enable() in the LPN example, beacon isn't enabled.   So  if a LPN node exhausts its sequence number firstly in the mesh network, will the LPN nodes initiate the iv update procedure?  OR 

Do the friend nodes or other non-LPN nodes do something for the LPN nodes' initiating iv update?  I searched the relevant info in the source code, but cannot find the clue.  Could you give any clue?

nRF5 sdk for mesh 5.0, s132, SES

[Young]

We are just trying to figure out a solution for the scenario like below, I believe some other customers also meet this kind of scenario.  In the network, there are a few LPN nodes which only transmit packets  and other nodes except for the LPN nodes only recevice these packets (no ack), so the LPN nodes will exhaust the sequence number sometime. When this happens, how the LPN nodes update the iv index and let other nodes iv update?  could anybody  give any advice? 

[Hung Bui]

Hi Bo Yang, 

Usually LPN node will not be the node that send the most package and would run out of sequence number first.

But in your use case I agree that it may run out of sequence number before the friend nodes. 

The information I got from our Mesh team is that the code to to trigger IV update is there, however the network beacons are disabled. You may need to enable beacon advertiser manually. 

Another option is to set MESH_FEATURE_LPN_ACT_AS_REGULAR_NODE_OUT_OF_FRIENDSHIP. However that only works if the node is out of friendship (will happens when the sequence number exhausted I believe). 
But I think the approach to enable beacon advertiser is better. The main draw back is the power consumption. 

[Hung Bui]

Another tip: it would be more suitable that you let the friend node (s) /main powered node (s) to trigger the IV index update periodically instead of letting the LPN node initiate the IV index update. It may not be optimized because the IV index will be updated periodically , say every 192 hours, but it's would save the complexity and power consumption of the LPN node. 

[Young]

Hi Hung Bui,

Thanks for your tip.