On Sun, 24 Aug 2025 at 05:52, Jeffrey Haas <jhaas@pfrc.org> wrote:
The easy way to picture some of the impacts of that is consider what it'd take to distribute "at the boundary of AS X->Y, don't distribute prefix P".
If we imagine that we would have day1 had concern of people abusing BGP and that we need to distribute >1M prefixes. We likely would have considered we need out-of-band for validation reasons alone. So we would have evolved a very different looking system. And what limitations that system would have and how to work with them would now look like requirements to us, when they were just the best solution we could come up, with the tools we had in front of us. I suspect all these disjoint advertisement problems that are legitimate would be addressed by registering more ASN and moving the ASNs between sites as needed. We do try to avoid disjoint today already, and many companies have a peering policy which forbids it or recommends against it. But it absolutely still happens, and in my experience it happens more today, because CDNs use disjoint advertisements to enforce their policies when customers override their policies with local-prefs. I'm very confident this system would just work, and Internet end users wouldn't be none the wiser. But I have no confidence that it would be worthwhile. -- ++ytti