Slow WiFi with Android Marshmallow & IPv6?

[Lorenzo Colitti]

Android does not behave well when configured with IPv6 DNS servers that do
not work. This is because it prefers IPv6, does not (yet) ignore
unresponsive DNS servers, and has quite high resolver timeouts.

One infamous example is a German ISP whose CPE announces an IPv6 address in
RDNSS but never responds to queries to that address. Perhaps because no
other operating system has a problem in this situation, the ISP has not
fixed this, and users have been blaming Android. This is by no means the
only case, though. Some of you know who you are :)

Future Android releases will likely ignore broken DNS servers. This is
unfortunate; we'd hoped that ISPs that provision devices with IPv6
connectivity would be able to ensure that the DNS servers are responsive
and that as IPv6 matured this problem would go away. Unfortunately it has
not.

As Erik said, the way to debug this problem would be to have someone
running 6.0.1 on voo to run "adb shell dumpsys connectivity --diag" and
open a bug as described at
https://source.android.com/source/report-bugs.html .

On Sun, Apr 24, 2016 at 11:21 PM, Brzozowski, John Jason <jjmb at jjmb.com>
wrote:

> Android is properly trying to query DNS over IPv6 unlike other
> devices/OSes.  Most other mobile platforms still prefer the querying of DNS
> over IPv4 for A/AAAA RR query types.
>
> On Sun, Apr 24, 2016 at 10:17 AM, Eric Vyncke (evyncke) <evyncke at cisco.com
> > wrote:
>
>> Jeroen, Erik and John,
>>
>> Thanks for the hint. I will advise the ISP to investigate any DNS issue
>> (such as not returning an error message when requesting a non-existing
>> AAAA) but I wonder why it is linked to that specific Android Marshmallow
>> version.
>>
>> -éric
>>
>> From: <ipv6-ops-bounces+evyncke=cisco.com at lists.cluenet.de> on behalf of
>> "Brzozowski, John Jason" <jjmb at jjmb.com>
>> Date: Sunday 24 April 2016 at 16:01
>> To: Erik Kline <ek at google.com>
>> Cc: Jeroen Massar <jeroen at massar.ch>, IPv6 Ops list <
>> ipv6-ops at lists.cluenet.de>
>> Subject: Re: Slow WiFi with Android Marshmallow & IPv6?
>>
>> My customers saw this issue at one point.  We had issues with DNS over
>> IPv6.  Bad DNS and/or network configurations.  Once these were fixed, the
>> problems cleared up.
>>
>> On Sunday, April 24, 2016, Erik Kline <ek at google.com> wrote:
>>
>>> On 24 April 2016 at 19:53, Jeroen Massar <jeroen at massar.ch> wrote:
>>> > On 2016-04-24 11:51, Eric Vyncke (evyncke) wrote:
>>> >> One of the first Belgian ISP to deploy IPv6 (VOO) is now recommending
>>> to
>>> >> its Android Marshmallow (6.0.1) users to deactivate IPv6 on their
>>> >> residential WiFi CPE... :-(
>>> >>
>>> >> It appears that the issue is about IPv6 web sites/apps being really
>>> >> slower when using IPv6.
>>> >
>>> > Is it a DNS issue maybe?
>>> >
>>> > https://www.sixxs.net/faq/dns/?faq=ipv6slowconnect
>>> >
>>> > As that has been the general cause of "Disable IPv6!!!!!" around the
>>> > world for many years already.
>>> >
>>> > Of course, without more details, little one really can say. Bug number
>>> > maybe?
>>> >
>>> > Greets,
>>> >  Jeroen
>>> >
>>>
>>> Yeah, a link to something that eventually leads to a bug report would be
>>> good.
>>>
>>> Also if anybody has adb installed they can just try "adb shell dumpsys
>>> connectivity --diag" and see what the over-simplified diagnostic
>>> output shows.
>>>
>>
>
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