Brian E Carpenter wrote: > There were very specific reasons why this was not done. And it doesn't > change the fact that an old-IP-only host cannot talk to a new-IP-only host > without a translator. It is that fact that causes our difficulties today. The fact is that an old-IP-only host can talk to a new-IP-only host without a translator, if the new IP uses port numbers for addressing/routing. Though NAT is doing similar thing with translation, the translation is not essential and can be reversed at end systems using NAT information obtained through UPnP/PCP. Masataka Ohta _______________________________________________ Ietf mailing list Ietf@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf