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

[Juliusz Chroboczek]

>> Some of the VM's are in the same data center (latency < 1ms) and some
>> are very far away (Germany <-> Hong Kong 300ms-400ms). Which rtt-min,
>> rtt-max and rtt-cost/max-rtt-penalty would be suitable for such
>> a network?

rtt-min should be chosen so that all links below rtt-min are local -- the
idea is that below rtt-min, it's not worth optimising the path.  The
default value (10ms) should be fine in most networks.

rtt-max should be larger than all good links in your network -- the idea
is that above rtt-max, it's no longer worth optimising the path.  In your
case, you might want to increase the value to 350ms or so.

> we are running re6st a mesh network based on babel. We have almost the
> same setup as you: around 400 machines connected worldwide. Our default
> options for babel are:

> max-rtt-penalty 5000
> rtt-max 500
> rtt-decay 125

That's a little bit extreme, but since Nexedi's network is uncongested,
Babel should be fairly stable even with such extreme parameters.

-- Juliusz