Babel in Bird

[Ondrej Zajicek]

On Wed, May 11, 2016 at 03:48:19PM +0200, Juliusz Chroboczek wrote:
> > BTW, why Babel accepts unfeasible updates of non-selected routes? It will
> > not cause problems as such route cannot be selected later (due to its
> > unfeasibility) but it seems strange.
> 
> Yeah, very good question.  It's counterintuitive for me too, but it turns
> out to work better that way:
> 
> 1. Having an unfeasible route available makes it possible to use it for
>    fallback after a single seqno increase.  If the route were not in your
>    routing table at all, you'd need to acquire it after your selected
>    route disappears, which may take some time, and will require even more
>    time for things like link quality and hysteresis to converge.
> ...

Thanks, that makes sense.

But now i wonder why not to accept unfeasible updates of selected routes?
(At least in a case where router ids differ and the the update is handled
as retraction.) Obviously, that would case the route to be de-selected.

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
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"To err is human -- to blame it on a computer is even more so."