Re: FTP & SIP
There are NAT solutions for FTP and SIP.
Though certainly not elegant.
Probably IP6, or something like it is needed. But the so called "Internet of things" is actually irrelevant. My "things" want to be as simple as possible. The Gateway server (which can be an application on my existing Router or something like a Raspberry Pi) can provide a VPN and security.
If I'm using public WiFi I want a VPN. Does IP6 solve the security issues of Public WiFi? Tell me when the majority of WiFi and Gadgets are using IP6 for a year.
People that sell network gear keep claiming we are running out of IP4 (likely) and we should up grade to IP6(Well they would say that).
Of course many USA Universities, USA Organisations, USA Corporations and friends that need 6 to 600 public IP have as many public IPs assigned as a small country.