Re: I-D Action: draft-ietf-idr-deprecate-as-set-confed-set-02.txt

Hi folks!

we have a standing PR in FRRouting regarding this change too:
https://github.com/FRRouting/frr/pull/5305

On Sun, Nov 10, 2019 at 7:01 AM Sriram, Kotikalapudi (Fed)
<[email protected]> wrote:
>
> Alejandro,
> Sander,
>
> [Alejandro]
> >>As a comment, we did a small research and
> >>these are our findings (hope the table shows ok):
> >>.....snip.....
>
> [Sander]
> >Those numbers are very manageable. If we gather a couple
> >of volunteers we could personally contact each AS.
>
> Thanks for the measurement numbers and your comments.
>
> We had earlier reported similar numbers (totals across all RIR regions)
> with many more details:
> https://mailarchive.ietf.org/arch/msg/idr/tE8o0HZeLLUEulMkszVBlxqILeU
>
> The link to our detailed data is here:
> https://www.nist.gov/sites/default/files/documents/2019/10/23/detailed-as_set-analysis.txt
>
> Our numbers and yours are consistent, except that we also showed that
> globally there only 21 unique routes (prefixes) with AS_SET that seem meaningful!
> The rest of the routes with AS_SET (about 450) seem meaningless; details at the link above.
>
> Even the 21 will likely do fine if they did not use AS_SET. They can deaggregate and
> provide the full AS path or they can aggregate and put in AGGREGATOR and
> ATOMIC_AGGREGATE.  If you look at this part of our data:
>
> *** When there is AGGREGATOR without AS_SET ***
>         # Unique prefixes (with or without AS_SET) : 826535
>         # Unique prefixes without AS_SET but with AGGREGATOR: 75698
>         % Unique prefixes without AS_SET but with AGGREGATOR: 9.158%
>         # Unique prefixes with ATOMIC_AGGREGATE: 47258
>         # Unique prefixes with AGGREGATOR and ATOMIC_AGGREGATE: 44971
>         # Unique prefixes with AGGREGATOR and without ATOMIC_AGGREGATE: 31769
>            (the last three lines added newly)
>
> it seems clear that a very large number of routes/ASes aggregate without AS_SET
> and very likely many of them face similar scenario as those with AS_SET
> and yet they do not seem to encounter problems (despite not using AS_SET).
> I think the main reason is that even if the aggregate is received
> via another upstream provider and gets installed in as AS that contributed to the aggregate,
> the AS really never uses that aggregate to route data because it has received
> the other components (more specifics) of the aggregate from the provider who aggregated.
> As Jeff has pointed out, if a more specific gets cut off (due to outage), then looping
> in the data plane can occur.
> This would typically last only for a short period until recovery happens.
> Now a days, the recovery times are fast. And possibly looping of data for a brief period
> is not much worse than the data not reaching its destination for that period.
>
> Sriram
>
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-- 
Donatas

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