There are hundreds of millions of IPv4 computers and perhaps millions of individual IPv4 transport networks, large and small. Here are some useful points along the way from pure IPv4 to pure IPv6. A. Every new computer is able to talk IPv6 B. Every transport is able to talk IPv6, i.e. every network from tier 1 ISPs down through wifi hot spots and every internal corporate network C. Every major service, e.g. Google, CNN, Amazon, is reachable via IPv6 D. Every new computer is not able to talk IPv4 E. A substantial number of transports are unable to talk IPv4 F. A substantial number of major services are not directly accessible via IPv4 (but, of course, will be accessible via gateways) I haven't included supporting details like DNS and gateways between IPv4 and IPv6. We're basically at A. Give some thought to the dates you'd assign to B through F. Feel free to disagree that these are significant steps along the path, but if you do disagree, please propose other reasonable and measurable mark points. I didn't include the bitter end of this process, i.e. the complete disappearances of IPv4. If we get through steps A through F, the rest won't matter much. I have trouble believing this will all happen in less than 20 years. I do not have trouble imagining it might take much longer. I don't have any stake in the outcome. It's fine with me if it happens faster. However, the mechanisms for interoperability between IPv4 and IPv6 are still being worked out and the products to do the work, i.e. application gateways, are not yet plentiful. Moreover, even when the first products appear, there's a long maturation cycle. As one example, two years ago the ICANN Security and Stability Advisory Committee (SSAC) looked at the products in the security area -- firewalls, etc. -- to see whether the feature sets for IPv6 were the same as for IPv4. The good news was the products did actually support IPv6. The bad news was the feature sets were noticeably poorer. Our report, SAC 021, http://www.icann.org/committees/security/sac021.pdf , concluded with:
The situation is probably better now, but I would guess there's still some distance to go. Imagine the decision process for the CIO or network architect of a medium or large company. A security policy exists and it's implemented with a collection of commercial products -- firewalls, routers, intrusion detection systems, etc. -- all configured and managed to support the company's security policy. Further imagine the both the transport and the individual devices are all capable of supporting and using IPv6. How quickly will the CIO or network architect decide that it's time to switch everyone over to IPv6? Among other things, he will likely want to make sure he can continue to implement the company's security policy. As of two years ago, he couldn't buy products that would function at the same level. IPv6 is definitely necessary and we should all do everything we can to move in that direction. I'm just noting that even when IPv6 is widely available and in broad use, there will be a long tail before IPv4 fades from the scene. Steve On Sep 17, 2009, at 2:36 AM, Olivier MJ Crepin-Leblond wrote:
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