[Babel-users] Adding a monetary factor to routing cost

[Juliusz Chroboczek]

> I've got a working commit that adds price as an unsigned integer in
> between the metric and prefix fields in route updates.

You're modifying the base protocol rather than doing an extension, so
please change the header so that unmodified Babel routers don't try to
associate with your routers.  (Just change the "Magic" value in the packet
header to some other arbitrary value.)

> I think the best way to really handle this is just to add a price TLV,

Or a sub-TLV of the Update TLV.  No need for the mandatory bit, I believe,
but I'm not sure.

> which is somewhat more complicated to implement but more clean from a
> network perspective as price may not change as often as routes update
> for other metric reasons.

Another possible optimisation is to put the sub-TLV in the Router-ID TLV,
which will allow you to carry a single price for multiple routes
advertised by the same router.

> The easiest way I found to do it was to use a wireguard tunnel as
> a neighbor and then have an external program monitor the rtt,

Babeld can monitor RTT out of the box.  Please check the manual page, and also

  https://arxiv.org/abs/1403.3488

-- Juliusz