42 devices, 16 routers.
Zigbee will do up to 4 retries over up to 30 seconds - https://community.silabs.com/s/article/how-does-the-emberznet-stack-retry-work-x?language=en_US
What are they?
In 85 node mesh, all the routers are zigbee 3.0; the one's that do the bulk of the work are TuYa USB zigbee repeaters and Sonoff USB dongles flashed to be routers.
It is interesting. As you stated I had no issues with these when they were on ST. They worked flawlessly and none of my other devices had any issues with them connected.
Is it possible there's something quirky about the Sonoff outlets where they might need their own driver instead of using the generic one?
It’s probably just that they don’t have a high enough output. Mine work fine (receive the message), but don’t seem to be good enough to be chosen as one of the 16 strongest routers for the hub even though one of them is less than 15 feet away.
Sure, but if a SmarterThings hub isn't having problems where a Hubitat hub is, that implies the hub could be taking steps to accommodate a weak router.
The HE hub is smaller than the SmartThings hub and possibly has a smaller antenna. A few years ago when I switched from SmartThings I had to make changes in Hub placement to better accommodate the new hub. It was a bit of a learning process for the first six or so months, but once I accepted that there were going to be things I had to do differently, I was able to build a much more reliable system than what I had before.
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It's more persistent than that (not sure about the 30 seconds, though.. retries happen over much shorter interval). Gives you an appreciation why they (well, at least the Alliance) say Zigbee transmissions get through (eventually) in spite heavy interference.
Transmission retries are happening at three protocol layers (application, network, and media access); so it goes like this:
a: APS > NWK (send message)
b: NWK > MAC (check for channel clear to transmit-- nothing else transmitting, do it... if channel busy, repeat up to 5X wait period up to 7 backoff periods of 320uS each)
c: MAC transmits packet, waits for ACK, if received within 864uS, DONE (no wait if broadcast)
If NO ACK--> repeat (c:) up to 3 times, if still NO ACK, MAC reports failure to NWK layer (so 4 transmits so far)
NWK layer waits up to 48ms, then retries (b:); still no ACK, repeat (b:) until 250mS elapsed, then report failure to APS layer. (at this point, have done at least 8 retries)
APS layer waits specified interval, then tells NWK layer to retry at (a:)
If still no ACK (after at least 16 retries, so far) APS layer retries all of the above starting at (a:) TWO MORE TIMES. Resulting in up to 48 transmission retries for a single unacknowledged packet....
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I'm using WebCoRE and Action Tiles and these both can put a significant load on the hub. Whenever I've looked, hub utilization is 3% but maybe there are spikes or other intermittent resource issues that cause the hub to lose track of things very occasionally. Either that or there are bugs and this is happening to everyone with some probability under some circumstances with some device. That's why I'm posting here to see if these weirdnesses others are reporting are similar to the ones I'm experiencing. Things are working great for the most part and I've been able to work around some other weirdnesses and none of it has been radio related so far.
Since I switched to channel 25, it seems to have become much more reliable.
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Good to hear and know. I may try that and see if I still have issues.
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