240/4 would be very useful if designated unicast. We should do that, in my opinion. But it's not immediately deployable. It can't be "fixed over time" in the sense that a prefix reserved from GUA might be; that is, it can't be deployed today and fixed over time. Rather, 240/4 is only useful after the fix is deployed. For what it's worth, to my knowledge none of the co-authors of draft-weil or draft-bdgks have ever expressed any love for the architectural impact of CGN. We all agree that IPv6 is the best choice from a forward-looking perspective. But we also know that the short-term needs of some service providers are driving them to deploy CGN as NAT444. This reservation may help make it less broken. But one concerned over IPv6 deployment may take solace in the fact that, even in the best case, CGN will be worse than native IPv6 in multiple dimensions. Just because I'm putting on a bandage today, doesn't mean that I consider it a good long-term solution. Cheers, -Benson |
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