Josh Hoppes wrote:
While NAT breaks the end to end connectivity, it can be restored by end systems by reversing translations by NAT, if proper information on the translations are obtained through some protocol such as UPnP.
UPnP can scale to about the size of an average home use,
It depends on how you use UPnP and version of it. E.g. security to control UPnP gateway is not a problem if the gateway is configured statically.
but it's worth jack squat at the ISP level when NAT44 comes into play.
NAT44 or 444 means you only need small scale UPnP cascaded.
UPnP is not an ISP grade solution, it's a consumer one.
As I said "such as", PCP may be fine. But, recently, I found several fundamental defects in it, some if which are already corrected but the discussion is still continuing in its WG. Masataka Ohta