CNET News.com: Will Vista stall Net traffic
Vista will also support the current IPv4. The side effect, according to Mockapetris, is that a Vista PC will make two DNS requests, one for each IP version, instead of just one.
“It is going to try a DNS lookup for the IPv6 address and then a DNS lookup for the IPv4 address,” Mockapetris said. “It just uses more DNS, and until we increase the supply, things are going to go slower.”
The article is a bit too sensational for my tastes. The clear and simple answer to the question “Will Vista stall net traffic?” is no.
I do not see how a computer on a network with a router that is only passing IPv4 traffic is going to cause problems. The router will not allow any IPv6 requests out. It is also seriously unlikely that Vista would send a DNS query for an IPv6 address if the computer has not been configured with its own IPv6 address.
Traffic on the root DNS servers may increase as networks transition over to IPv6. Vista’s behavior at this point may begin to cause problems. Micosoft will likely change this behavior before Vista ships, or release a security update to change the behavior.
It seems that a machine that has an IPv6 address and routing for IPv6 should first query DNS for an IPv6 address. If none is found, then it should send a query for the IPv4 address. How do open source operating systems handle this?