Incorrect TTL value setting in proxy device

RE: Incorrect TTL value setting in proxy device

Hieu — Wed, 24 May 2023 16:45:53 GMT

Hi Hitesh,

Could you please clarify what kind of performance issue you experienced with NCS v1.9.1?

There is an improvement on Mesh thanks to using extended advertiser. It "matured" from NCS v2.1.2. See CONFIG_BT_MESH_ADV_EXT. However, without knowing what the issue is, I can't confirm that will help.

Regards,

Hieu

RE: Incorrect TTL value setting in proxy device

hiteshk014 — Tue, 23 May 2023 10:26:48 GMT

Hi Hieu,

We modified TTL to 100 as per requirements and arrangements of devices assembeled in mesh, we observed some issues in performace in Mesh network post modifications, 1.9.1 Nordic Connect SDK we're using.

Until TTL count to 60 there's no issue in Mesh network, if we increase beyond 60 some issues in performance is observed.

We need to know can we have better synchronization and performance in Mesh network, if we update TTL to 100 in latest released nCS version 2.3.0

Thank you,

Regards,

Hitesh

RE: Incorrect TTL value setting in proxy device

Hieu — Mon, 20 Mar 2023 12:43:42 GMT

Hi Hitesh,

Unfortunately, with Bluetooth Mesh, there is no silver bullet when it comes to deciding mesh configuration parameters. Everything depends a lot on the physical setup of the nodes, and on the specific application.

Therefore, most of the time, you need to look at your physical setup, think about the traffic, and really understand all the mesh parameters to make the best configuration.

Thus, the following statement:

[quote user="hiteshk0104"]I've 100 devices in Mesh network and in Mobile app / provisioner, it is totally accceptable to have TTL count to 100 as number of devices in network are 100.[/quote]

is a statement that I would never dare to confirm. 😞

The consequences of having too high TTL is discussed in the DevZone thread I linked in my previous reply. Here is it again: RE: Mesh TTL clarification .

Here is another discussion on DevZone that can help you better understand the thought process in deciding the configuration and how things interact: Mesh Optimization / TTL, Relay Nodes, Difficult Floorplan.

Please give them a read, and if there are still anything unclear about the consequences of high TTL, please let me know.

Best regards,

Hieu

RE: Incorrect TTL value setting in proxy device

hiteshk014 — Mon, 20 Mar 2023 11:25:18 GMT

Hi Hieu,

Thank you very much for quick reply,

Final confirmation from what I understood please correct or add the following statement If I've missed,

I've 100 devices in Mesh network and in Mobile app / provisioner, it is totally accceptable to have TTL count to 100 as number of devices in network are 100.

Thank you,

Regards,

Hitesh

RE: Incorrect TTL value setting in proxy device

Hieu — Fri, 17 Mar 2023 19:40:39 GMT

Hi Hitesh,

Are you certain that TTL reaching 0 is the reason packets are lost? There are many reasons packets can be lost. A different example is where too many nodes being too close and interfere each other with retransmissions and relays.

Regarding using an overly high TTL value, my colleague Terje explains the mechanism in Bluetooth Mesh where each node only handle a message once, and the scenario of too high TTL in this DevZone thread: RE: Mesh TTL clarification .

I don't think there is any situation where TTL need to be higher than the number of nodes. As a thought experiment, let's imagine the worst physical layout, where N nodes are on a straight line, and two immediate neighbors are barely within range of each other. Even in this situation, a message can travel from one far end to the other with TTL = N.

Bluetooth Mesh does have a Hearbeat feature that can help you experiment and find out the ideal TTL value. I discussed about that in this DevZone thread: RE: Troubleshooting nRF Mesh Heartbeat Feature Configuration in Version 5.

Regards,

Hieu

RE: Incorrect TTL value setting in proxy device

hiteshk014 — Fri, 17 Mar 2023 09:39:02 GMT

Hi Hieu,

Thank you for response,

We need some inputs what is ideal TTL value to be set when have 100 devices in Mesh

we have a product requirement of having 100 max number of devices in Mesh network

Currently we have configured 40 devices in network and it is observed at times packet is not receiving in a arrangement where in the devices are in single lane with the current default configuration of TTL - 5,

If we modify the TTL value to the number of devices in network from provisioner / mobile app / nRF Mesh app, then what will be the consequence ? will that message create flooding effect which is having TTL-100 / TTL-50 ?

Thank you,

Regards,

Hitesh

RE: Incorrect TTL value setting in proxy device

Hieu — Fri, 10 Mar 2023 15:03:52 GMT

Hi Hitesh,

Does the proxy device do that with only the proxy messages or with its own messages as well?

Is TTL configured for the LE device/node or for the Proxy node? The Proxy probably simply send out the messages as configured for the LE device/node.

TTL can be set by the provisioner at any time. Please check if it is set by any provisioners beside the application's default.

Hieu