Hi,
In my honest opinion we are mixing two different issues:
- current hop penalty value not really significant
- OGM link quality measurements do not reflect the metric we'd like it to
be
problem 2 is not going to be solved by hacking the hop penalty. It needs further investigation/research and NDP is probably a good starting point towards a possible solution (I think we all agree on this).
you are right - these are 2 different issues.
For what concern the hop penalty, as far as I understood, it is in charge of making batman prefer a shorter route in case of equal TQs over the traversed links. Instead of hacking the value...what about redesigning the way the hop penalty affects the TQ value of forwarded OGMs? Maybe using a different function (poly of deg>1 or exp) instead of a simple linear decreasing? May this help all the scenarios we mentioned?
The hop penalty is not as linear as you think. The formula is: tq * (TQ_MAX_VALUE - hop_penalty)) / (TQ_MAX_VALUE
With a hop penalty of 10 you get the following results: tq = 255, penalty = 10, resulting tq = 245 tq = 200, penalty = 8, resulting tq = 192 tq = 150, penalty = 6, resulting tq = 144 tq = 100, penalty = 4, resulting tq = 96 tq = 50, penalty = 2, resulting tq = 48
As you can see the more the tq goes down the less influence the hop penalty has.
Regards, Marek