----- Original Message ----- From: "Keith Moore" <moore@xxxxxxxxxxxxxxxxxxxx> To: <ietf@xxxxxxxx> Sent: Thursday, August 15, 2019 4:29 PM > On 8/15/19 3:33 AM, shyam bandyopadhyay wrote: > > > To: > > The Entire IETF community > > > > Sub: Why do we need to go with 128 bits address space if > > whatever is been trying to achieve with the existing > > approach of IPv6, can be achieved by 64 bits address > > space as well? > > > > Dear Folks, > > > > I raised this issue couple of times earlier. My intention was to collect > > all the points in support of 128 bits address space and try to figure out > > whether they can be solved with 64 bits address space as well. > > The answer is no, they cannot, particularly not if either address > assignment or routing are hierarchical. > > It remains to be seen whether 128 bits is sufficient. I'd place even > odds on an extension to IPv6 to permit addresses longer than 128 bits, > gaining favor while I'm still alive. > > (Though it's also possible that global climate change will eventually > make even 32 bits more than enough.. But it doesn't seem prudent to > presume that.) > > More generally, any decision made long in the past can always be > second-guessed. But the people who insist that a different decision > should have been made, have little reason to have confidence in their > belief. After all, they didn't have the burden of making their > preferred choices work in the real world. > > It's also hard to believe that with nearly 25 years of painful > investment in IPv6, dual-stack transition, /and/ NAT, with plenty of > accumulated evidence that IPv6 actually does (mostly) work better than > the alternatives, that people are going to somehow abandon all of that > investment for a completely new packet format that has the worst > features of both IPv4 and IPv6 - insufficient address space AND > transition burden. To put it differently, IPv6 is going to have to > fail a lot worse than it has, before there's sufficient interest to face > another transition. And while anything is possible, IPv6 really was > designed to last for several decades (and with the assumption that human > population AND internet appliances will continue to grow > exponentially). 64bit addresses were considered for IPng, and that > would have likely been the choice had they appeared to be sufficient. Keith When I started teaching IPng in the late 1990s, ATM was the up-and-coming link protocol and what immediately struck me was that the link identifier of ATM was (potentially) more than 64 bits and so could never fit into the bottom half of a 128-bit address. So yes, I always expected the address structure of IPng to be too small. Tom Petch > Keith > > > >
