This document enhances the Babel routing protocol by allowing gathering of RTT measurements from neighbours (and then using that for routing decisions). From reading the Security Considerations of RFC 8966 (last para), it seems that geolocation privacy was a concern with the original Babel spec. Allowing extremely-fine-grained (1 microsecond) RTT measurements makes that infinitely worse, especially for users on mobile or behind VPNs, who typically have special privacy needs. 

The IETF has thought a lot about privacy concerns with RTT measurement and how to balance them with operational needs, but before delving into that I wanted to check if this was a concern that was identified or discussed.