> And for users, it does not really matter if they have to visit router admin page to set up NAT port forwarding or open up the port in firewall. It matters wh

> And for users, it does not really matter if they have to visit router admin page to set up NAT port forwarding or open up the port in firewall. It matters when port forwarding is impossible because the user lacks a unique IPv4 address. Earth has 7 billion people and 4 billion IPv4 addresses, so carrier grade NAT is inevitable.