David Farmer wrote on 15/04/2026 20:45:
Given the prevalence of seemingly excessive numbers of AS prepends on the Internet, this guidance seems appropriate.
This is the point: how would the WG define "excessive"? A baseline of having no prepends won't stop hijacking from happening, and also won't stop the hijacking from having an impact on traffic destined to the network in question. Even adding a single prepend will have an additional impact, and there's an argument to be made that even a single prepend is in excess of what you would want to aim for, if it causes additional service impact.
Fundamentally, wide-area distance vector routing algorithms work on the basis that external networks trust the total distance, so anything that adds to an already low single-digit metric should be considered harmful. But I don't see this as being useful advice to give in an RFC.
That said, all this takes the focus away from the reality that it's not the prepending that causes the problems: it's the hijacking, and whether you prepend or not, hijacking is going to have an impact on service.
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