you might take a look at RFC 1888 Scott > On Aug 15, 2019, at 2:06 PM, tom petch <daedulus@xxxxxxxxxxxxx> wrote: > > ----- 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 >> >> >> >> >
