[Babel-users] Babel in Bird 1.6.0

[Juliusz Chroboczek]

>> The packet format encodes intervals in centiseconds, so it would make
>> sense to allow any fractional Hello interval down to 0.01 seconds.

> since the internal Bird timers run at a granularity of seconds only
> there's not much point in having the ability to configure smaller
> values.

That's uncool.

> I do seem to have forgotten to generate a new hello when reconfiguring
> (RFC section 3.4.1: "Equivalently, a node SHOULD send an unscheduled
> Hello immediately after increasing its Hello interval.").

It's not a big issue -- any well-implemented neighbour should recover
after the next Hello (see the bit about « undoing history »), but it's an
easy fix.

> I remember running into this. What happens here is that babeld sends an
> update without a preceding router_id TLV, with a wildcard address, but
> flag 0x40 set (meaning "infer the router ID from the address").
> While I'm not sure what the purpose of this is (a null update with a
> null router ID with infinity metric and interval?) it *is* technically
> in spec.

No, it isn't.

Earlier versions of babeld allowed a retraction (update with infinite
metric) without a router-id.  This is not allowed by RFC 6126.  Current
versions of babeld no longer send such retractions, but still honour them
when received.

The plan is to explicitly allow such retractions in RFC 6126-bis, but they
are clearly not allowed by RFC 6126.

-- Juliusz