Proposal: Accurate-ish time/date/clock/NTP sync across mesh

[skylarmt]

With 2.7's new UI, almost every node will soon be more useful standalone and will have a very large and noticeable clock "app", so setting an accurate time is more important than ever.

Nodes with NTP configured should broadcast a time/date signal every few minutes for the benefit of other nodes on the mesh that don't have their own local clock source. The signal includes the current timestamp and the NTP stratum the mesh node is at (ranging from 2-16, basically one higher than the NTP server the node set its time from).

If a node receives conflicting time signals, it can use info like distance/hop count and the stratum sent in the time signal to determine which node likely has the most accurate time: the closest and lowest-strata node is probably the most accurate. Time signals could use a weighted average where farther or higher-strata nodes are given less weight.

I have a fixed router node at my house on a hill. It has WiFi enabled. I also have a Stratum 1 NTP server in my basement. That is basically the most accurate and reliable clock signal you can easily obtain. It would be great if my node could use that high-quality signal to make the local mesh better.

NTP stands for Network Time Protocol, so we could call this protocol MTP: Meshtastic Time Protocol.

[fifieldt]

Hi, indeed, time is important.

Generally, we have those fallbacks in place. A node with a GPS (i.e. Stratum 1 level) is considered more reliable than NTP, NTP is considered more reliable than Mesh time, and Mesh time is considered a source for an unconfigured device.

You can see the priority list at:
https://github.com/meshtastic/firmware/blob/master/src/gps/RTC.h

There are also a few little tweaks for devices that have dedicated RTC modules.

So, you are helping to make mesh time better :)

[skylarmt]

That's great! How often does that info get sent, or does it use the timestamp on each message? If it only goes every half hour or something I'd like to broadcast it more often since my area's mesh is pretty quiet and I have a dedicated time server.

There's basically no mention of how time works in the documentation or anything, so I assumed it only synced with NTP or GPS or Bluetooth and if your node doesn't have internet or a GPS or a phone it was just out of luck as far as having accurate time.

I flashed a node and it didn't get the time until I ran a command on the Meshtastic Python CLI, then it instantly got the right one. However, it was about 10 seconds off from another node (with a GPS antenna but no sats), and both of them were a few seconds away from the actual time. Meanwhile, this all happened about 20 feet from my router node that has NTP configured.

[fifieldt]

I believe it's on message/nodeinfo, but would have to read the code. You're right that it would be great to have this documented!