Speaking as WG member:

From: Lsr <lsr-boun...@ietf.org> on behalf of Robert Raszuk <rob...@raszuk.net>
Date: Tuesday, June 14, 2022 at 9:27 AM
To: Christian Hopps <cho...@chopps.org>
Cc: Gunter Van de Velde <gunter.van_de_ve...@nokia.com>, lsr <lsr@ietf.org>, 
"draft-ppsenak-lsr-igp-ureach-prefix-annou...@ietf.org" 
<draft-ppsenak-lsr-igp-ureach-prefix-annou...@ietf.org>, 
draft-wang-lsr-prefix-unreachable-annoucement 
<draft-wang-lsr-prefix-unreachable-annoucem...@ietf.org>
Subject: Re: [Lsr] Thoughts about PUAs - are we not over-engineering?

All,

> What is wrong with simply not doing summaries

What's wrong is that you are reaching the scaling issue much sooner than when 
you inject summaries.

Note that any good implementation will allow one to punch holes in their area 
ranges so that critical prefixes are advertised or included in the range 
existence criteria.

Thanks,
Acee


Note that the number of those host routes is flooded irrespective of the actual 
need everywhere based on the sick assumption that perhaps they may be needed 
there. There is no today to the best of my knowledge controlled leaking to only 
subset to what is needed.

But this is not the main worry. Main worry is that in redundant networks you 
are seeing many copies of the very same route being flooded all over the place. 
So in a not so big 1000 node network the number of host routes may exceed 8000 
easily. cri

Sure when things are stable all is cool. But we should prepare for the worst, 
not the best. In fact, the ability to encapsulate to an aggregate switch IP 
(GRE or UDP) or nowadays SRv6 has been one of the strongest advantages.

So as started before the problem does exist. Neither PULSE nor PUE solve it 
which are both limited to PE failures detection which is not enough (maybe even 
not worth). But PE-CE failures need to be signalled in the case of injecting 
summaries. Maybe as I said in previous msg just BGP withdrawal is fine. If not 
we should seek a solution which addresses the real problem, not an infrequent 
one.

Best,
R.



On Tue, Jun 14, 2022 at 2:51 PM Christian Hopps 
<cho...@chopps.org<mailto:cho...@chopps.org>> wrote:


> On Jun 14, 2022, at 04:59, Van De Velde, Gunter (Nokia - BE/Antwerp) 
> <gunter.van_de_ve...@nokia.com<mailto:gunter.van_de_ve...@nokia.com>> wrote:
>
> What is wrong with simply not doing summaries and forget about these PUAs to 
> pinch holes in the summary prefixes? this worked very well during last two 
> decennia. Are we not over-engineering with PUAs?

100% yes, IMO.

Thanks,
Chris.
[as wg-member]
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