* Mark Tinka > I understand your points - to your comment, my question is around > whether it is cheaper (for you) to just run IPv6 in lieu of IPv6 and > IPv4.
We've found that it is. IPv6-only greatly reduces complexity compared to dual stack. This means higher reliability, lower OpEx, shorter recovery time when something does go wrong anyway, fewer SLA violations, happier customers, and so on - the list goes on and on. Single stack is essentially the KISS option. It also means that we'll essentially never have to perform IPv4 renumbering exercises in order to accomodate for growth. Those tend to be very costly due to the man-hours required for planning and implementation. Besides, it means we don't need IPv4 to number customer infrastructure. As you probably know, IPv4 numbers have a real cost these days. My point of view is ASP/MSP/data centre stuff. I know I'm not alone in going down the IPv6 road here, though. Facebook is another prominent example. Other operators in different market segments are also doing IPv6-only. Kabel Deutschland and T-Mobile US, for example. I'm guessing they have similar motivations. Tore