On Mon, 4 Feb 2019 09:01:20 +0000 i3D.net - Martijn Schmidt <martijnschmidt@i3d.net> wrote:

Cogent does let you use RTBH, but on a separate BGP session to a blackhole server. So it's a bit more hassle to set it up policy-wise, because it deviates from the standard. Same story for "former GlobalCrossing", now CenturyLink's AS3549, which is still used for LATAM and Asia.

There are other providers that do this besides those you listed. I'm not sure one way or the other is truly "the standard" approach, but there may be an advantage and potentially good reason to have a separate session. If a no-multihop peering link/session is down, you might still be able to establish a RTBH peering session via another path. That may be what you need to get that direct neighbor back up. :-) John