On Sat, 23 Aug 2025 at 23:32, Jakob Heitz via NANOG <nanog@lists.nanog.org> wrote:
Losses: Privacy. Telling your competitors what all your links and private peerings are may not be what you want. You might not advertise all your prefixes to some of your neighbors, but you still need the link for other prefixes.
This disjoint advertisement is a legitimate argument, but as explained elsewhere we could address it by registering more ASNs and moving the ASNs, not prefixes. Privacy appears to be the same argument for disjoint advertisements.
If you are only advertising the link, then any neighbor could send you traffic that you don't want to provide transit for. So you drop it. How does your neighbor know? You send him the routes for traffic you are willing to transit traffic for.
Your links that you advertise are the ASme-ASyou you provide traffic for. You don't advertise links you don't carry traffic for. So I would advertise ASme-ASme, ASme-AScustomer + ASprovider-ASme to my upstream, but I would not advertise ASme-ASupstream to my upstream. My upstream similarly would advertise to their peers and upstream ASupstream-ASme. This would allow anyone to validate those paths, because they expect ASme to have ASprovider-ASme adjancency, and they expect ASprovider to corroborate that with having ASprovider-ASme adjacency. Both link-states are signed and singatures verifiable by some out-of-band mechanism. I do think that in an alternate reality, where we would have anticipated that BGP abuse and +1M prefixes we would have landed somewhere entirely different than where we are today. And in that reality whatever limitations that feature has, we would have learned to live with them and started to think they are requirements, because they are requirements there, because we can only. build solutions on top of those that work with that stack. I have full confidence we could have made this link-state based reality work, and the Internet would work just the same for Internet users. I have no confidence that it would be worthwhile. It would be different and whatever it enables would seem like requirements to us now, while they were just solutions we ended up with the limitations we had. -- ++ytti