[ipv6hackers] Windows 7/2008 R2 Improved Resilliency to IPv6 Floods

Doug Barton dougb at dougbarton.us
Mon Apr 15 04:52:24 CEST 2013

On 04/02/2013 06:43 PM, Jim Small wrote:
> Thanks Doug - excellent thread.
> So to summarize for Microsoft KB 2750841 which retrofits Windows 8/2012 IPv6 NCSI behavior to 7/2008R2:
> Q1)  If you have some sort of temporary interruption in your IPv6 connectivity at boot time will you lose IPv6 for the lifetime of the session?
> A1)  No, from the Microsoft product manager:
> Only a combination of no proxies, AAAA resolution success, a default route, and a failure to connect to the beacon - enables this functionality to activate. And its activation is limited to depreferencing the default route. Any scoped routes that have been configured are untouched.

... which is irrelevant to the majority of users.

> Q2) Are the NCSI results cached?
> A2) Per the Microsoft product manager, only positive results are cached.  Negative results are re-tried at each network attach (or disable/re-enable interface).

... which is also irrelevant to the majority of users (unless DHCP lease 
renewals count here).

I read and understood the feedback about what this does, and how it does 
it. My point is that for the overwhelming majority of users if there is 
a temporary interruption of IPv6 at the time they boot their systems 
they will lose IPv6 connectivity until they reboot. Of course, the 
converse is also true.

In my mind, that's a poor tradeoff. I would much rather have seen MS 
implement happy eyeballs. It would have much greater overall benefit, 
and none of the drawbacks.


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