Tony – I understand what Chris wrote. And if customers could do what he suggested then they would not have an issue.
But there are deployments where what he suggested is not possible – largely I think because the set of “prefixes of interest” is in itself large. So while not all customers have an issue, some customers do and we are trying to find a way to address those deployments. As far as the alternative proposals, I will comment on them if/when there is something visible – but I think they will all suffer from scale issues. Les From: Tony Li <[email protected]> On Behalf Of Tony Li Sent: Monday, January 10, 2022 1:41 PM To: Les Ginsberg (ginsberg) <[email protected]> Cc: Christian Hopps <[email protected]>; Peter Psenak (ppsenak) <[email protected]>; Robert Raszuk <[email protected]>; Shraddha Hegde <[email protected]>; Aijun Wang <[email protected]>; Hannes Gredler <[email protected]>; lsr <[email protected]> Subject: Re: [Lsr] BGP vs PUA/PULSE Les, We have received requests from real customers who both need to summarize AND would like better response time to loss of reachability to individual nodes. If they could operate at the necessary scale without summarizing they would have already – so telling customers to simply make sure they don’t use summaries isn’t helpful. To be clear: I think the suggestion was to not summarize the endpoints that you want detailed information about. Summarizing the rest of the area is certainly sensible. This should not be hard to accomplish: simply advertise the loopbacks for the relevant systems out of another prefix and then leak them. This should give you both scalability and specific information. It also has the advantage that the scale pressure is present in the steady state, not in failure scenarios. Failing into the worst case situation is always a serious concern. Having to add heuristic mechanisms to prevent scalability failures is pretty indicative that this is not a very robust approach. If response time really is the key concern, then why are we relying on flooding? We know that that’s not rapid as it will be hop-by-hop with arbitrary delay. If response time really is the priority, then the other alternatives we’ve discussed (BGP, BFD, a pub-sub mechanism) would all seem to be preferable. Bottom line: this doesn’t seem like it should be in the IGP. Regards, Tony
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