When RRG was launched the driving force was the so-called scalability problem. Currently the biggest issue is the expiration of available IPv4 addresses. That however would be a non-issue if the FQDN were mapped to {IPv4 addr of destination user; locator of ETR} in a single strike based on DNS while taking care that IPv4 addresses of the same locator were mutually unique. LISP-DDT neither does so now, nor would be able to do so ever. Hence IPv4's lifetime is up to NAT as long as solutions like LISPv2.0 or my TARA are discarded/ignored. There are much more knowledgable folks around who know the disadvantages of the NAT sinfall better than myself. I can only add one disadvantage: With a network layer based on TCP (NAT) you can never enable Multicast with a roaming sender.
I think this IPv4-depletion issue is the most urgent problem at all. Heiner
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