[Babel-users] Babel instability in WLAN-SI

[Juliusz Chroboczek]

> BTW, how should VPN links be handled in this case? They are currently
> marked as wired, but they can also experience packet loss. Does this
> mean that bad VPN links can also cause huge amounts of control traffic?

It depends.  How likely are they to lose two Hellos in a row?

Babeld marks a wired link as down whenever it loses two out of three
successive Hellos.  If this only happens occasionally (loss probability is
below 2% or so), then it's fine.  If this happens often, then you should
enable link quality estimation on them.

In case of doubt, I suggest enabling link quality -- the really bad case
is not having link quality estimation on lossy links, the opposite case
(lq on lossless links) is inefficient but not too bad.  If you want
a quick fix, just change your firmware to run link quality everywhere (-w).

If very lossy tunnels are a common occurrence in your network, I'll
implement a metric specifically for them.  But let's get your network
running stably first.  (Nexedi are using babeld over a lot of tunnels, but
their tunnels are lossless, which is why we implemented RTT-based routing
for them.)

-- Juliusz