[Babel-users] Babel RTT settings for low and high latencies

[Juliusz Chroboczek]

> A year ago you said [1] that bird had not yet implemented "hysteresis on
> metrics" [...]  Has bird implemented this in the meantime?

I haven't checked the BIRD implementation recently (I know, I should be
doing more work on Babel, but I'm currently spending all my mana on
fighting the French administration), you'll need to wait until Toke comes
back from his Viking raid.

> And what is the difference between hysteresis and `rtt-decoy`?

decay/min/max are specific mechanisms, that completely avoid route flaps
in most (but not all) cases.  Hysteresis is a fully general mechanism,
that is effective at reducing the frequency of route flaps in all cases,
but cannot completely avoid them.

In practice, with well tuned min/max, route flaps don't happen, so
hysteresis is spurious.  When the decay/min/max algorithms fail,
hysteresis kicks in, and limits the frequency of route flaps to one every
few minuts.

-- Juliusz