I&#x27;m not saying we need NAT, just that without prior <i>need for NAT</i>, perpetuated by ISPs only giving us one IP, I doubt anybody would have <i>any</i> ingress filtering at the border. It&#x27;s a lot easier just to block ingress to the whole house than it is to ensure a dozen devices are secure against unwanted incoming connections... this problem will present itself with the IoT sooner or later.