Nobody promised you a free lunch. In any case, the investment required to turn up IPv6 support is a lot less than the cost of carrier grade NAT. And the running costs of IPv6 are also lower,
Can you provide pointers to these analyses? Any evidence-backed data showing how CGN is more expensive would be very helpful.
It depends. If you plan to do IPv6 eventually, it's probably cheaper to do it now than to depend on NAT444. NAT444 breaks some things (fewer than you might expect, so it might not be as expensive as you think). Some of those things can be fixed by doing static port forwarding, but that means a support call explaining how to configure port forwarding on the LSN, and troubleshooting through the CPE. Cost analysis: more support calls, but might be even with IPv6 support calls. If your provisioning and OSS are centralized, you may need multiple instances inside each LSN (or tunnels, or some other way to cope with the fact that you now have multiple domains of 10/8 inside your network). Cost analysis: may be the same amount of development required to add IPv6 functionality, but additional hardware may be required. You need a pretty big logging infrastructure, so you have an answer when Smokey says, "Who had this address with this source port at time T six months ago?" and lawyers on hand to explain why you won't tell them all 500 customers who were using that address at the time. And a variety of things documented in draft-ford-shared-addressing-issues. Cost analysis: lots of disk, lawyers, for issues that don't exist in IPv6. All of your hardware already speaks IPv4, very little requires updates to support private addressing. Cost analysis: you probably have some hardware that doesn't support IPv6. If cost were the only criterion, it might be an even split between NAT444 and IPv6. Using NAT444 to delay replacing non-IPv6 hardware until the regular depreciation cycle means spending twice on development labor just to delay the capex. That math may or may not make sense for your network.. Lee