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On 06/07/13 01:17, davidson@xxxxxxxxxxxxxxxxxxx wrote: > right. the IPv6 bestowed upon us does not extend IPv4, as it happens. > > and so i wonder, assuming there were practical considerations for this > decision, what were they? what made it so impractical to define a > correspondence between IPv4 and some subset of IPv6, given that such a > correspondence would have greatly facilitated the adoption of IPv6? > > pertinent references appreciated. > > -wes Hope I'm not muscling in here. If I may, I'd like to draw an analogy with the x86 instruction set: there is so much legacy cruft and completely wrong-headed rubbish still included in there for the undying zombie of backwards compatibility it's insane. For some reason, the IPv4 upgrade path didn't follow the same thought process - IPv6 could have just included as a subset all of the native IPv4 functionality and address spaces but chose to chuck the baby out with the bathwater instead. Why two different approaches to absolute critical technology? Who knows. Both approaches were stupid and are costing time, money and efficiency on a global scale right now. I'd like to think I would have done things differently, but you know how design by committee tends to work out - it's not like I would ever have been given (or even deserved) the right to unilaterally control this kind of stuff myself anyway. I'm way too lazy to bother digging up "pertinent references", but I recommend using your favourite search engine to look up "Vint Cerf IPv6 my mistake" for his regrets and reminiscences. Quote: ""One of the decisions his team needed to make was the size of the address space in the packets. Some researchers wanted a 128-bit space for the binary address, Cerf (recalled) ... But others said, "That's crazy," because it's far larger than necessary, and they suggested a much smaller space. Cerf finally settled on a 32-bit space that was incorporated into IPv4 and provided a respectable 4.3 billion separate addresses. "It's enough to do an experiment," he said. "The problem is the experiment never ended.""" Of course, that only explains why he regrets not bomb-proofing IPv4 in the first place, not why the people responsible for IPv6 didn't think this through a bit more thoroughly as you asked for, but hey, I'm not a fuc... oh wait, I better not say that. *cough* I am not a blooming magician, good sir! *cough* Judging by your email address, you're in a major American .edu: you've got IPv6 onsite there surely? You've also got internet2 hook ups I would have thought. Lucky fellow. Regards -- The Mailing List for the Devon & Cornwall LUG http://mailman.dclug.org.uk/listinfo/list FAQ: http://www.dcglug.org.uk/listfaq