> This will work behind many NATs and firewalls, but not all.<p>While this is an interesting concept, the hard part in NAT traversal is getting it to work on all the possible NAT types. In particular, I believe that this method doesn't work for symmetric NAT devices[1], which are widespread in corporate environments. It's not a surprise that this idea from 2010 didn't take off, ICE/TURN are still kings.<p>[1] These devices assign a different port for each destination address, and this ICMP method doesn't help predict the port that will be assigned.