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A word of caution for Windows 7/8 users

MJN
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A word of caution for Windows 7/8 users

Following Jelv's experience of getting IPv6 up-and-running but seemingly some apps still preferring the use of IPv4 instead of IPv6 (the opposite of accepted general convention) it would appear that one potential cause of this is Microsoft's bespoke implementation of RFC 3484 - Default Address Selection for IPv6.
In particular, according to this MSDN blog post:
Quote
Windows 8 tests IPv6 connectivity when you connect to a new network that advertises IPv6 routabilty, and it will only use IPv6 if IPv6 connectivity is actually functioning. This approach is a modification of our implementation of RFC 3484. Instead of sorting addresses as a result of policy, we use the actual state of the network as input to our algorithm. On a misconfigured network, this approach improves the experience not only for browsers but also for apps that connect to dual-stack destinations using standard Windows APIs.
Windows 8 performs the network connectivity test when you first connect to a new network; it caches this information and repeats the test every 30 days. The actual test for connectivity is a simple HTTP GET to an IPv6-only server that is hosted by Microsoft. (For standards buffs, this is implemented between rules 5 and 6 of destination address sorting in our implementation of RFC 3484.)

Yes, it is referring to Windows 8 however many 'features' of Windows 8 are often released as updates to Windows 7 too and from digging around this looks to be one of them.
This is, in my view, a pretty poor thing for MS to do. The intent is understandable - afterall broken IPv6 stacks can cause mayhem - however their fix is using a sledgehammer to crack a nut. There are many ways in which the approach can fail and thus lead to a 'de-preferencing' of IPv6 even when it is actually available and working. Sure, Internet connectivity should continue but it doesn't help matters when you are trying to deploy and test IPv6 like we are here!
I haven't found whether or not there is a way to perform a retest (why does it wait 30 days?! 30 days!!) and it should be stressed that this won't always be the cause of IPv6 seemingly working but not being used.
If anyone sees similar, or knows/finds further information, I'd be interested to hear about it.
6 REPLIES 6
MJN
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Re: A word of caution for Windows 7/8 users

An update on this, the registry appears to allow this 'feature' to be tweaked:

Key edits to make would be the StaleThreshold (i.e. try retry interval, in days) to something a lot lower. Or, you might even prefer to disable the action altogether by setting EnableActiveProbing to 0. For the latter as I cannot reproduce the failure mode I don't know if this will retrospectively apply i.e. immediately remove the result of any previous decision about transport preference (one would hope it would otherwise you'd be trapped in IPv4 forever!).
chrcoluk
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Re: A word of caution for Windows 7/8 users

Personally I dont agree with the default prefer ipv6 all OS's are adopting.
when I was using a tunnel for ipv6 and the default prefer ipv6 I was having various issues on some sites.  Its clear a problematic ipv6 on a prefer ipv6 policy can regress user experience.  Sites that host using ipv6 may be in a experimental stage as well.  On a prefer ipv4 policy ipv6 will still be used if its the only choice.
However with all that said now I am on native ipv6 I am going to reconfigure my desktop again to prefer ipv6 and see how things go.  I am already using ipv6 to test various ipv6 sites I am managing and I am using it to connect to servers ftp/ssh etc.
Nibiru
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Re: A word of caution for Windows 7/8 users

Quote from: chrcoluk
Its clear a problematic ipv6 on a prefer ipv6 policy can regress user experience

Have you tried using the browser add-in "4or6" ?
Using that program, it not only indicates whether the current page came via IPv4 or IPv6, but by right mouse button clicking the indicator you can get to the advanced options where you can set on a site by site basis whether you want to disable IPv6 for that website.
Therefore if you did come across any dual-stacked website with problematic IPv6, then YOU have the ability to control whether you prefer to connect to that site using IPv4.
Plusnet FTTC 80/20 IPv4/30, Hurricane Electric 6in4 IPv6/48, Pulse8 landline & calls, SamKnows 600N
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chrcoluk
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Re: A word of caution for Windows 7/8 users

yep I installed it the day I started my trial, I think a guy on here made that plugin? its nice.
chrcoluk
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Re: A word of caution for Windows 7/8 users

now I have set ipv6 to preference again.
google loads much faster on ipv6 than ipv4.
MJN
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Re: A word of caution for Windows 7/8 users

I'm surprised you can see a difference, at least without there being a problem somewhere.
For curiosity, are you able to see how long a given page (including components) takes to load over each transport using a browser plug in?