All, Happy to see this draft ! Have been struggling with explaining some of those issues and lack of such BCPs was sort of implicit prove that it is all fine to prepend at will.
Said this it seems clear that putting aside cases of unnecessary use or use by errors AS-PATH prepends we are still facing no Internet wide path de-prefernecing in BGP being commonly used other then mangling AS-PATH. The point is that multihoming is common and if someone needs at least to try to influence entrance to his domain AS-PATH prepend comes as low hanging fruit. Longer prefix will not work when on both ASBRs a /24 is injected. So let me ask a question here ... Have anyone tried to document that instead of doing AS-PATH prepend across set of upstreams (for whatever valid reason that may be) the preferred entrance should advertise the paths with IGP or EGP origin while the other ASBRs (which would otherwise prepend N times) with INCOMPLETE ? BGP best path should automatically across most implementations do the right path selection. Anyone see any issue with that ? If that works we could actually start to strongly discourage use of AS-PATH prepending. If not maybe we should think about a new attribute along the lines of cost community to be more widely used in a transitive manner and to have single meaning to allow to deprefer a prefix originated by given AS across number of ISP uplinks with a numeric value (just like MED or Local Pref are used locally). Another question the draft talks about AS-PATH prepends by actual sources .... well suffice to just take a look at Internet tables in few places to see that even some transit operators prepend themselves to the original paths (also already prepended). And yes I do have captures of those. Thx, R.
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