Insufficient Default Backoff Settings: rxdelay, txdelay, direct.txdelay

[KPrivitt]

The current default values are:
_prefs.rx_delay_base = 0.0f; // turn off by default, was 10.0;
_prefs.tx_delay_factor = 0.5f; // was 0.25f
_prefs.direct_tx_delay_factor = 0.3f; // was 0.2

These control the Random Backoff behavior of a repeater, which reduces the probability of a collision between neighbor repeaters.

Backoff is essential in avoiding collisions. Many repeater owners are not aware of this capability and do not change them, this leaves the mesh under configured in order to avoid collisions. The default values are too low and are not providing any significant backoff for the Mesh.

The default value for rx_delay = 0, which is off. So, this mechanism is not being utilized. A recommended minimum value for rxdelay is 3

The default value for direct.x_delay = 0.3, which is provides 2 backoff slots, which has a high probability of a collision. A recommended minimum value for direct.x_delay is 1 which will provide 5 backoff slots and reduces the probability of a collision.

The default value for tx_delay = 0.5, which is provides 2 backoff slots, additional backoff slots will reduce the probability of a collision. A recommended minimum value for txdelay is 1.6 which provides 8 backoff slots and reduces the probability of a collision.

These all are configurable using CLI commands so users are still free to select their own preferred values and can turn them off.

Enabling some level of backoff will improve the performance of the Mesh.

[beachmiles]

Wish these delay values were not evidently only relevant in 0.2 increments although I still dont see how this happens in the code.
Wish the defaults for flood adverts was 24 hours and local adverts set to 0 to reduce the advert network load on large meshes.

[KPrivitt]

The reason it's in .2 increments is because the txdelay and direct.txdelay values are multiplied by 5 (.2x5=1) then truncated (.19x5=0.95 which is still 0).

So it steps up only at the .2 boundary like stairs, your foot has to move up at least .2 ft to get to the next step, or .4 ft if you skip a step.

The other two defaults are for an "airtime" usage issue. PR's are single issue fixes, so these would need to be in a separate PR.

I agree regarding the 24Hr Flood Advert, but not for the 0-hop.

• 0-hop Adverts do not traverse the entire mesh and do not contribute to the entire mesh's airtime usage, only the region around the single repeater that transmitted it (it only lives for the one hop). This is useful because it updates the neighbor repeaters "neighbor list" and that would be used in the automatic algorithm I proposed. This PR is a "temporary" fix, if it is automated the default becomes obsolete since it is continuously updated. The algorithm removes "stale" neighbors (they are only removed by a reboot and are "permanent") so to keep it fresh they need to be periodically removed and are use to drive the automation.

Hope this helps...