Mesh Key refresh approach questions

Question

Hi, 
 As per mesh SDK 2.1.1, if I removing the provisioned node through key refresh approach from provisioner then... 
 1. First should I required to update the all node's(except one, which is removing) network key b y " config_client_netkey_update() ", with the help of binding config client to each config server one by one and use this API? Is there any method so that all the provisioned node's network key can be updated in single cycle? 
 2. Then after in provisioner should I start the key refresh procedure for changing the network key? so that by receiving secured network beacons in NRF_MESH_BEACON_SECURE_NET_BCAST_INTERVAL_SECONDS interval all nodes start key refresh procedure by itself. 
 what if in this approach some of the nodes are powered off or out of network at that time? Is there any solution or workaround for such type of scenario?

Bjørn Kvaale · Answer

Hi, 
 Sorry for the delayed response. I would recommend reading the key refresh procedure in Chapter 3.10.4 of the Bluetooth Mesh profile spec if you have not already (it seems you have read this section already though). 
 1) You are correct that you can use the config_client_netkey_update() function to update the netkey via the config client on the provisioner & the config servers on the mesh nodes. 
 By single cycle, are you referring to the different phases in the mesh profile spec in Figure 3.48 Key Refresh Diagram. 
 2) Yes, as soon as the first phase is complete (i.e. new keys (network and/or application keys) are distributed to each node), the provisioner will transmit a secure network beacon to tell the other nodes that each node has received new keys. 
 If one of the nodes is powered off before it has received the new keys or right after it has received the new keys, the provisioner will know this & either wait for the node to be powered back on or update the powered off device's network key once it is back up & running. Either way, the mesh sdk takes care of this. If I were you, I would test this out yourself. 
 Kind Regards, 
 Bjørn

Mesh Key refresh approach questions

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