On Thu, 25 Aug 2022, 16:31 Alistair Mackenzie, <magicsata@gmail.com> wrote:

There are some generally accepted and useful filters found at https://bgpfilterguide.nlnog.net/. There is one which covers excess prepends.

It's generally accepted to filter **very** long as paths.

As Alistair pointed to. The guide mentions 100x max path length as a (current!) value that won't filter out long current as paths. (And protect you from others missing filtering.)

https://bgpfilterguide.nlnog.net/guides/long_paths/

If you want to go for a lower than 100 value. RIB dumps from the ripe ris collectors / route-views may be the most accessible starting point for data to analyse.

If you want to read data about avg as path lengths over the years. APNIC publishes data about it. https://blog.apnic.net/2022/01/06/bgp-in-2021-the-bgp-table/