[Feature Request]: Routers behave as clients when they see another router, so clients will not see both and retransmit.

[quimnut]

Platform

other

Description

My understanding is that a client will not flood route if it sees a retransmit.

In the scenario that an actor operates 2 routers, a client that hears both will not flood route.

This means a router will break any client mutes behind a client and as such breaks a mesh, it would require router mode for any intermediate hop like a roof top.

I feel an option would be a router should act as a client if it sees another router in hop 0.

Happy to be wrong, thanks for all the love. Meshtastic is a great community.

[GUVWAF]

Unfortunately this is an edge case, which indeed may happen, but it doesn't matter that there are two routers, it can happen with one router and even with clients only. Take this scenario for example (taken from #2856):

Here node 1 is rebroadcasting the packet from 0, because it has the worst SNR. Then 2 won't rebroadcast, because it hears 1 doing so already. However, in this case it would have been better if 2 rebroadcasted it, such that it reaches 3.
In this case if 2 was a ROUTER, it would be solved.

In your case it's like your CLIENT_MUTE is node 3, your CLIENT node is 2 and node 1 is a ROUTER. Node 1 will always rebroadcast first, causing the CLIENT not to. It doesn't matter if the original transmitter is a ROUTER or not.

[quimnut]

Thank you @GUVWAF that's a very clear summary.

[quimnut]

Can we expand on why this is an edge case?

[GUVWAF]

Maybe not really an edge case, but something that can happen in a specific scenario like this. In a slightly different scenario, where there would be another node that can hear 0 but not 1, it would also rebroadcast and 3 could receive that.

There's a trade-off between reliability and redundancy here. If every node would rebroadcast, this scenario would still work, as long as it doesn't create collisions.

[quimnut]

How specific is a case of 2 routers in earshot?

[GUVWAF]

But how would that create this issue in scenarios where it would otherwise still work?
Anyone rebroadcasting earlier than you causes you to not rebroadcast. So, it might get worse if someone is setting its node as router, but I don't see how 2 routers would make it happen in more scenarios than 1 router.

[fifieldt]

Seems related: https://en.m.wikipedia.org/wiki/Hidden_node_problem

[GUVWAF]

The hidden node problem is indeed what causes collisions. This is more similar to the "Exposed node problem", where you prevent from sending when someone else did, while your neighbor didn't receive the other's transmission.