Time for configuring node increases after deleting from mesh network

[JeffZ]

Hi guys,

I have the same issue as coca1989 had 2 years ago. Did anybody found a solution?

I am using health model and simple message model. Client and Provisioner are running on one device (demoboard). I can provision and configure upto 5 server nodes (dongles). I get health events from each connected server (all 10 seconds) and I can send and receive small messages on all server nodes.

Now, I would like to remove nodes from the mesh network and reconnect them (reprovisioning and reconfiguration). This are the steps that I am doing:

1. config_client_server_bind() and config_client_server_set() to the server node I would like to remove from network
2. config_client_node_reset()
3. the server gets the node reset event (CONFIG_SERVER_EVT_NODE_RESET) from client and performs node_reset() with:  mesh_stack_config_clear() and mesh_stack_device_reset()
4. the server responds to the client with CONFIG_CLIENT_EVENT_TYPE_CANCELLED and I do dsm_devkey_delete()

After removing the server node, I can reprovision and reconfigure the node successfully (getting health events and send/receive messages). But the configuration takes longer then the first time. Repeating this process (removing node and reconnecting) increases the configuration time each time.

Here is a time table:

First configuration: 2-3 seconds
Second configuration (after removing node from mesh): 10-11 seconds
Third configuration (after removing node from mesh):20-30 seconds
Fourth configuration (after removing node from mesh): 45 -50 seconds
Fifth configuration (after removing node from mesh): >80 seconds

This is reproduceable. Rebooting the client/provisioner device after removing a server node reduces the configuration time back to 2-3 seconds, but I do not get health events and no messages.

During reconfiguration (after removing the server from network) I am getting SAR mesh events on the server node. At the first configuration (fresh device) I dont have this SAR events.

I guess I have to delete more on client side? Maybe the simple message or health is still active on the last address handles?

[JeffZ]

Today I tried the following:

1. Provision fresh node 1 with address 500 and configuration models

2. Delete node 1 (500) from mesh (like I wrote above)

3. Reprovision node 1 with address 501. Provisioning and cofiguration time < 3 seconds (very good)

4. Delete node 1 (501) from mesh 

5. Reprovision node 1 again with address 500 Provisioning and configuration time > 10 seconds

4. Delete node 1 (500) from mesh

5. Reprovision node 1 again with address 501 Provisioning and configuration time > 20 seconds

and so on...

I can never reuse the address.

[Mttrinh]

Hi,

Like you already noticed, the method suggested would still have the problem of increasing configuration time.

From our developer:

Does he want to create a qualified Bluetooth Mesh product?

• If yes, according to Mesh Specification section 3.10.7 he cannot reuse addresses until IV index procedure completes in the network. The use case he is describing does not make sense from the perspective of the Mesh Profile Specification.
• If not, he can reuse the addresses by calling `replay_cache_clear()` API to clear the replay list on the provisioner without restarting. However, he may still have issues when re-provisioned node tries to communicate with other nodes around it (because replay protection on those nodes will start filtering packets with old sequence numbers). Clearing of the replay list creates a possibility of replay attacks.

[JeffZ]

Hi, thanks for response.

Maybe I see light at the end of the tunnel...

• replay_cache_clear() helps and works, but I have to wait about 20-30 seconds before re-provision the same node with the same address without increasing config time 
• re-starting the provisioner/client device helps too

What would you suggest as a better way - restart or replay_cache_clear()?
Will restart solve the problem of old sequence numbers with other nodes around?

Why does the use case makes no sense???
Connect, disconnect and reconnect (with same parameters) is basic in communications.

[Mttrinh]

Hi,

The problem of still having to wait for 20-30 seconds after use of replay_cache_clear():
This is probably due to the network cache filter. Try also calling `msg_cache_clear()` after `replay_cache_clear()`. This should help getting rid of extra wait time.

Why use case does not make sense?
As mentioned earlier, the scenario of using the same address for the node during the re-provisioning process is not allowed by the Mesh Specification unless the network goes through the IV update cycle. Resetting a replay list is a workaround to circumvent the issue. The Mesh specification mandates that the node should always filter out the packets that have sequence numbers lesser than or equal to the most recently seen sequence number from a that SRC address.