At 16:34 +0000 10/31/06, Jeroen Massar wrote:
Like any IPv4 -> IPv6 transition mechanism: first try IPv6, then try IPv4.
There is the option to try both simultaneously. A query for the A RR can be sent in parallel to the AAAA RR. This is better from the point of view of the application user, there isn't a need to wait for a time out. On the other hand, this makes the application developer's job harder - having to juggle two potential answers and connections starting up (assuming TCP).
If you try IPv6 first, if IPv6 is available then the new technology will be used. However, there have been recommendations (I found a few just by googling for "disable ipv6") saying that to improve performance, disable IPv6. Then you will fall back to the more deployed and tested technology.
I can attest that there have been times in which disabling IPv6 at some conferences led to better networking performance. (Yes, I know I could reported this to the conference NOC, but my mission was to get some information, not play with a new technology.) Only because of that experience do I no longer agree that one should always try IPv6 (or any new technology) first.
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