It's unfair to say it's a "feature". It was an oversight back in 1989 based on nobody expecting we'd end up where we are today. Filtering is easy if your just

It's unfair to say it's a "feature". It was an oversight back in 1989 based on nobody expecting we'd end up where we are today. Filtering is easy if your just doing it for downstream customers. But how do Tier 1's filter from each other? Once you go up the tree a few times it gets really hard to build any sort of valid filter list of what you should be getting from provider X or provider Y. BGPSEC and RPKI are unfortunately not really workable yet, in terms of full-path validation. And obviously the source data to do it is a long way off.