Reply to post: Re: Why NAT64?

FaceTime, WhatsApp UDP streams AWOL on iOS 9 beta with T-Mo US


Re: Why NAT64?

Can someone explain why NAT is even required with IPv6?

Technically NAT itself is not required with IPv6, however, I am running a IPv6 to IPv6 NAT (NAT66) without issues. Of course, I do not use facetime or whatapp, so I am not entirely sure how they work, but I can explain possibilities from a network standpoint. You can do anything you want if you throw enough computing power at the problem.

The issue is that ISPs need a way to enable their IPv6-only clients to get to the IPv4 internet. NAT64, is required with IPv6 for sites that do not use IPv6. They accomplish this by a complete header swap on each packet. NAT64 works with both TCP and UDP, but somehow in this case, something is not working. I am not sure if there is a tie on the client source port, or how that would work, but the NAT64 will pick a new source port at the point of NAT, with the intent of being able to map the packes back to the source. With IPv6 being larger, there is no need to swap the source ports, but on the IPv4 side, usually only one IPv4 address is tied to the NAT box. This single IPv4 address needs differentiators which usually means the NAT pick a unique port.

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