A few more key benefits of the ICMP approach :- Capport detection is made easier for the client, even when RFC 7710 (or any API) is NOT implemented (as long as the NAS is Capport compliant).- "Signaling" can be done by different components (NAS, iptables, rate-limiter, PCEF, etc), without (necessarily) needing to coordinate with a central service.- In defining the RFC in how a NAS should handle blocking traffic for Capport compliant devices, we are also defining how the NAS should handle Legacy devices - which is, there is no difference - they both get ICMP Dest Unreach w/Capport extension) - which is helpful.