nanog mailing list archives

Re: rfd


From: Job Snijders <job () instituut net>
Date: Tue, 18 Dec 2018 21:59:45 +0100

Hi Steve,

Lowering the LP would achieve the outcome you desire, provided there are
(stable) alternative paths.

What you advocate results in absolute outages in what may already be
precarious situations (natural disasters?) - what Saku Ytti suggests like a
less painful alternative with desirable properties.

Kind regards,

Job

On Tue, Dec 18, 2018 at 21:56 Naslund, Steve <SNaslund () medline com> wrote:

Mainly because propagating a flapping route across the entire Internet is
damaging to performance of things other your own equipment and that of your
customer.  It is just "bad manners" to propagate a flapping route to your
peers and it helps maintain a minimum level of stability that it required
to keep you "on the Internet".  Imagine a table where 1000s of providers
are each sending 100s of unstable routes and that those unstable routes
might be redistributing into various IGPs that may not respond very
gracefully to rapid table changes (like most distance vector IGPs).  Also
think of this scenario, your link to your customer might be flapping but
that same customer might have other carriers advertising the same address
space over a stable link.  In that case you would be doing a dis-service by
not withdrawing that route and having a local-pref does not help since you
don't necessarily have visibility to all of your customers other carrier
networks.

You do have the ability to clear the RFD timers for a route if you need to
manually intervene for example when you know for a fact that you fixed the
problem.  That means that if no one is watching or intervening the network
will "do the safe thing".

Steven Naslund
Chicago IL


I always wondered why does it have to be so binary.

I don't want to decide for my customers if partial visibility is better
than busy CPU, but I do appreciate stability. Why can't we have local-pref
penalty for flapping route. If it's only option, keep offering it, if there
are other, more >stable options, offer those.

--
 ++ytti


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