Subject: Re: Last Call: draft-irtf-asrg-dnsbl (DNS Blacklists and Whitelists)

From: Joe St Sauver <[email-masked]>
Date: Tue, 11 Nov 2008 08:20:11 -0800

Theodore mentioned:

#Let me get this straight.  It's OK to block e-mail messages on the
#basis of unauthenticated rumors, 

Most DNS block lists are based on empirical factors, not rumors.

For example, in the case of manual anti-spam block lists, like the
Spamhaus SBL, typically listings include spam samples, although other 
block lists may use different empirical criteria (for example, the 
Day Old Bread list looks at the age of domain names in determining 
its coverage). Other lists may identify hosts from dynamic IP address
ranges, etc.

#but now you are complaining that it's somehow dirty pool to block 
#a standard based on the same thing?  

Block lists aren't going to go away if this standard isn't 
published; block lists have broad community acceptance in and of 
their own right.

On the other hand, without standards, block lists may be run in ways 
that will primarily disadvantage those who end up blocked by them.

Standards for block lists provide a basis for evaluating block
list operational practices, and a standard against which poorly
run block lists can (and should!) rightfully be pilloried.

As such, I think it is unfortunate that some have elected to oppose
this draft.

#Questions like, "so how does this work in the face of the expanded
#IPv6 address space", ideally should be addressed earlier during the
#standardization process, and not in last call (where, "oh well, we'll
#just block the whole /48 or /32" might have unfortunate side effects
#not forseen yet) --- but which don't make sense if the goal is to
#document existing practice.

I'm not aware of DNS block lists which cover IPv6 address spaces at
this time, probably in part because IPv6 traffic remains de minimis 
(see http://asert.arbornetworks.com/2008/8/the-end-is-near-but-is-ipv6/
showing IPv6 traffic as constituting only 0.002% of all Internet traffic).

#There's a big difference between "use" and "Use".  If a spamassassin
#configuration (by default) uses a DNSBL to add a point or a fraction
#of a point to a spam score, where it might take a spam score of 10-15
#before spam is dropped, that's a very different usage model than
#someone who, on the unsubstatiated word of SORBS or APEWS, drops the
#e-mail on the floor where it is never seen again.

Distinguish two types of spam filtering:

-- filtering at connect time, where a message that doesn't get accepted
   for delivery can signal that rejection to the system that's
   *still connected* to the rejecting MTA

-- filtering post connect time, as with SpamAssassin, where a message 
   that ends up scored as spam may (at best) end up filed in a spam 
   folder

DNS block lists can be used in either model, but they work best for
filtering at connect time because in that model, the delivering host
knows that a message has been accepted or rejected.

Post connect time filtering means that a message which has apparently
been accepted for delivery may never be seen (e.g., if it has been
spam foldered or deleted).

That critical difference is one reason why DNS blocks lists, used at
connect time, are vastly preferable to other non-deterministic
approaches, although things like SpamAssassin (particularly with 
SURBL rules) unquestionably play a crucial role in stopping some types 
of spam that can't be addressed by connect time DNS block lists. 

But let me just mention one other pragmatic reason why I believe DNS 
block lists used at connect time are preferable to some other 
alternatives, such as site-by-site local anti-spam rules. 

Consider a sending site that may have a temporary spam problem, perhaps 
due to a compromised user account, or an accidental system 
misconfiguration. Having emitted spam, that site ends up being blocked. 

If it is blocked by one (or two, or some small number <N>) DNS block 
lists, after that site has fixed its problem, there's one (or two, 
or some small <N>) places they need to go to get unblocked. Moreover,
DNS block list operators typically do a nice job of explaining how
to get in touch with them, and what sort of process is involved in
getting delisted. 

On the other hand, if thousands or tens of thousands of sites employ 
unannounced local blocks to deal with that temporary spam problem, you 
may be trying for months (if not years!) to get all those private 
site-by-site blocks removed.

#And for those who would argue that it's not their problem how the
#DNSBL is used, since after all that's the responsibility of the folks
#using the DNSBL, 

DNS block listings are the DNS block list operator's expression of an 
opinion about a site's email traffic. Just like a food critic's 
opinion about a restaurant, people can choose to pay attention to
that critic's opinions, or not.

If the critic likes undercooked tainted and bland food poorly presented 
by surly wait staff, and that aligns well with your dining preferences, 
by all means follow that critic's reviews. Most diners, however, with 
more conventional preferences, will quickly learn to discount or
ignore that commentator's recommendations.

Better critics, critics with lasting followings, will do careful research
and objectively report their findings, and become trusted guides and
opinion leaders. And that's what the best of the blocklists, such as 
Spamhaus, represent for much of the email community today. 

Are their other bad block lists out there? Sure, in part because the 
community lacks professional standards that lay out the concrete steps 
required to run a block list well. *That's* what I'd like to see fixed. 

Regards,

Joe St Sauver ([email-masked])
http://www.uoregon.edu/~joe/
Disclaimer: speaking of opinions, all opinions expressed are strictly 
my own.
_______________________________________________
Ietf mailing list
[email-masked]
https://www.ietf.org/mailman/listinfo/ietf

---

From: David Kessens <[email-masked]>
Date: Tue, 11 Nov 2008 10:57:11 -0800

Joe,

> showing IPv6 traffic as constituting only 0.002% of all Internet traffic).

For the record: 

It seems that arbornetworks estimates are extremely low to the point
where one has to ask whether there were other issues that caused such
a low estimate.

There is no question that IPv6 traffic is quite low in the Internet.
However, many other reports that I have seen recently measure multiple
orders of magnitude more IPv6 traffic (for an easily accesible example
see: http://www.ams-ix.net/technical/stats/sflow/)

David Kessens
---

---

From: Harald Alvestrand <[email-masked]>
Date: Tue, 11 Nov 2008 21:38:07 +0100

> see: http://www.ams-ix.net/technical/stats/sflow/)
Google's measurements indicate that when faced with a dual-stack host 
(one with both an AAAA and an A record in the DNS), 0.5% of all hosts 
will access that host using IPv6.

(As presented at the RIPE meeting in Dubai last month.)

                    Harald

---

From: "Turchanyi Geza" <[email-masked]>
Date: Tue, 11 Nov 2008 21:49:18 +0100

Harald,

Your Half percent is great!

When Tim Berners-Lee presented the www at the JENC conference in
Insbruck in 1992, he said that according to the traffic mesurement
statistics, the www-related trafic is around half percent.

What was the ratio two years later? 40%

Half percent is a good "start" for a real revolution.

The question is: where is any similar movement to those pushed the web
development in the early nineties?

Best,
         Géza

On Tue, Nov 11, 2008 at 9:38 PM, Harald Alvestrand <[email-masked]> wrote:
>>> this time, probably in part because IPv6 traffic remains de minimis (see
>>> http://asert.arbornetworks.com/2008/8/the-end-is-near-but-is-ipv6/
> Google's measurements indicate that when faced with a dual-stack host (one
> with both an AAAA and an A record in the DNS), 0.5% of all hosts will access
> that host using IPv6.
>

---

From: Harald Alvestrand <[email-masked]>
Date: Tue, 11 Nov 2008 22:34:32 +0100

Sorry, I misremembered.

The correct number from the presentation is 0.238% - only Russia, 
Ukraine and France have more than 0.5% IPv6.

Presentation available from 
http://rosie.ripe.net/presentations-detail/Thursday/Plenary%2014:00/index.html.

                     Harald

---

From: Marc Manthey <[email-masked]>
Date: Tue, 11 Nov 2008 23:05:28 +0100

Am 11.11.2008 um 22:34 schrieb Harald Alvestrand:
> 8% - only Russia, Ukraine and France have more than 0.5% IPv6.
>
> Presentation available from http://rosie.ripe.net/presentations-detail/Thursday/Plenary%2014:00/index.html 
> .

wow , i am impressed  0.76% , so russia has more overall ipv6 traffic  
then the entire .u.s.a.

Guess this  realy need to be  changed !!!

Germany is not even on the list :(

regards

marc

--  
"Imagination  is more important than Knowledge".

web : http://www.let.de
-- YES WE CAN !!!! ---
http://isobamapresident.com
PGP/GnuPG: 0x1ac02f3296b12b4d  jabber :[email-masked]

---

From: Pekka Savola <[email-masked]>
Date: Wed, 12 Nov 2008 07:54:33 +0200 (EET)

On Tue, 11 Nov 2008, Harald Alvestrand wrote:
> The correct number from the presentation is 0.238% - only Russia, Ukraine and 
> France have more than 0.5% IPv6.
>

Depends on what you're looking for, but if you are interested in the 
amount of users that have any kind of IPv6 connectivity, this 
undercounts severely because address selection rules on recent OSs 
typically select IPv4 if their connectivity is 6to4 or Teredo.

Mikael Abrahamsson made a test on a p2p-related web-site, and the 
result was that 6% of users had IPv6 connectivity:

http://www.ops.ietf.org/lists/v6ops/v6ops.2008/msg01582.html

As shown in later messages, the figure is actually even higher. Teredo 
users running Windows Vista are not included in that 6% because Vista 
doesn't do do AAAA lookups at all if all you have is Teredo 
connectivity.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
_______________________________________________
Ietf mailing list
[email-masked]
https://www.ietf.org/mailman/listinfo/ietf

---

From: Harald Alvestrand <[email-masked]>
Date: Wed, 12 Nov 2008 11:06:35 +0100

> typically select IPv4 if their connectivity is 6to4 or Teredo.
Pekka,

can you identify the OSes that prefer IPv4 when on 6to4, and pointers to 
docs?

Steinar (the guy who did the Google experiment) has tried to dig through 
the documentation on both Vista and Linux, and has drawn a blank (Vista 
with Teredo doesn't even look up the AAAA record if it has IPv4 
connectivity, according to the documentation, so it seems that it will 
not use IPv6 to IPv6-only hosts; it will never find the address.)

                Harald

---

From: "Hallam-Baker, Phillip" <[email-masked]>
Date: Wed, 12 Nov 2008 08:25:08 -0800

It looks to me as if these are developer and interoperability issues that are not going to be addressed of their own accord through regular IETF meetings.
 
I think that the only way we could expect progress here would be to have a series of interop events that involve representatives from all the interested parties - ISPs, O/S, network infrastructure providers, core DNS.
 
And they are going to find a large number of such missing pieces that need to be fed into the standards process. 
 
In this type of situation I think that we have got to expect the standards process to be descriptive rather than normative. Rather than having a group of folk get together to propose what should work we have to have the interop folk tell us what did work.
 
Some parts of this can take part in the regular IETF process but it really is not the type of project that I think is going to be effectively completed unless there is some fairly radical change in the approach. 

Transition from IPv4 to IPv6 has to be effortless for the end user. We can adopt a HDTV type approach where users are expected to deploy some sort of $50 'converter' box. What we cannot do is to propose an architecture that requires end-users to think about the change.
 
My home network is IPv4. I have many devices that are not IPv6 aware and have zero intention of changing them. The network is behind a NAT because I don't see a business case to pay $10 per network device per month for unique IP addresses. That would be $120 a month for me - if Comcast actually supported it as an option which they do not, they allow up to 4 IPv4 addresses per residential connection.

The core problem here is that the current Internet 'architecture' requires applications to know rather too much about the internal workings of the network that they are connected to. Everyone now accepts that IPv4 address space is going to be quickly exhausted. What fewer people currently understand is that 16 bit port numbers are no longer a scalable means of protocol description. And 16 bit DNS RRs are no better in that respect either.

________________________________

From: [email-masked] on behalf of Harald Alvestrand
Sent: Wed 11/12/2008 5:06 AM
To: Pekka Savola
Cc: [email-masked]; [email-masked]
Subject: Re: IPv6 traffic stats

Pekka,

                Harald

---

From: Geoff Huston <[email-masked]>
Date: Thu, 13 Nov 2008 06:08:16 +1100

I've been looking at this as well and reported on the relative amount  
of IPv6 traffic over the past 4 years at the most recent NANOG (http://www.potaroo.net/presentations/2008-10-13-ipv6-deployment.pdf 
)

in recent times I am also seeing 0.5% of hosts preferring to use IPv6  
to access a dual-stacked site - the good news it that this number has  
risen sharply in the past 18 months. The not-so-good news it thats its  
still a bloody small number!

The AS count might also be of interest - 15% of the non-stub IPv4  
addresses (AS's that offer transit to other ASes) also originate IPv6  
prefixes.

    Geoff

---

From: Peter Sherbin <[email-masked]>
Date: Wed, 12 Nov 2008 11:55:52 -0800 (PST)

> The AS count might also be of interest - 15% of the
> non-stub IPv4 addresses (AS's that offer transit to
> other ASes) also originate IPv6 prefixes.

How did this 15% change over the past 4 years and/or past 18 months? What percentage would that be of the total AS count? 

Thanks,

Peter

--- On Wed, 11/12/08, Geoff Huston <[email-masked]> wrote:

> From: Geoff Huston <[email-masked]>
> To: "Harald Alvestrand" <[email-masked]>
> Cc: [email-masked], "Pekka Savola" <[email-masked]>, [email-masked]
> Date: Wednesday, November 12, 2008, 2:08 PM
> I've been looking at this as well and reported on the
> relative amount of IPv6 traffic over the past 4 years at the
> most recent NANOG
> (http://www.potaroo.net/presentations/2008-10-13-ipv6-deployment.pdf)
> 
> in recent times I am also seeing 0.5% of hosts preferring
> to use IPv6 to access a dual-stacked site - the good news it
> that this number has risen sharply in the past 18 months.
> The not-so-good news it thats its still a bloody small
> number!
> 
> The AS count might also be of interest - 15% of the
> non-stub IPv4 addresses (AS's that offer transit to
> other ASes) also originate IPv6 prefixes.
> 
> 
>    Geoff
>

---

From: Pekka Savola <[email-masked]>
Date: Wed, 12 Nov 2008 22:09:04 +0200 (EET)

On Wed, 12 Nov 2008, Harald Alvestrand wrote:
>>  amount of users that have any kind of IPv6 connectivity, this undercounts
>>  severely because address selection rules on recent OSs typically select
>>  IPv4 if their connectivity is 6to4 or Teredo.
>

If an implementation implements RFC3484 and the user is not using 
custom address selection policy, all compliant RFC3484 implementations 
should prefer v4 when connecting to native from 6to4 (rule 5 of 
destination address selection AFAIR).

FWIW, in Linux this was changed as the default maybe about 2-3 years 
ago.  I suppose may other operating systems, especially recent ones, 
also operate in this manner. For Linux, some info is here: 
http://people.redhat.com/drepper/linux-rfc3484.html

This has been discussed on v6ops and ipv6 lists but unfortunately I 
can't find the threads despite search attempts.

Maybe someone else with better memory could provide better references.

This is why observing ipv6 traffic on a dual-stack hostname will 
mostly just in observing those that use native v6 (with Mikael, this 
was 0.5% of users).  If you're interested in wider picture of IPv6 
penetration, you'll put the content on v6-only hostname (with Mikael, 
this was reachable by 6% of users). If you want to also cover for 
Vista users with Teredo, you'd put the content on a site and refer to 
it using a numeric address instead of a hostname (this would result in 
even a higher percentage).

So, if you're interested in any kind of IPv6 connectivity at all (even 
6to4, teredo, ...), at least in some user communities (p2p users), I'm 
pretty sure IPv6 penetration is already over 10%.  At least 6% is 
already proven by measurements :-)

---

From: Danny McPherson <[email-masked]>
Date: Wed, 12 Nov 2008 13:15:07 -0700

> where one has to ask whether there were other issues that caused such

No, the methodology is outlined in the referenced report.
Given what we were measures and what data was supplied, those
were the results.

> see: http://www.ams-ix.net/technical/stats/sflow/)

Indeed, and multiple orders (less than two) of magnitude is still,
from this, only .1% on average.  I believe the point remains very
much the same.

-danny

---

From: Danny McPherson <[email-masked]>
Date: Wed, 12 Nov 2008 13:17:31 -0700

> Presentation available from http://rosie.ripe.net/presentations-detail/Thursday/Plenary%2014:00/index.html 

Indeed, and according to the same stats,

• 0.238% of users have useful IPv6 connectivity (and prefer IPv6)
• 0.09% of users have broken IPv6 connectivity

Nearly 38% of that .238% is broken...

-danny

---

From: Iljitsch van Beijnum <[email-masked]>
Date: Wed, 12 Nov 2008 21:22:22 +0100

On 12 nov 2008, at 21:09, Pekka Savola wrote:

> custom address selection policy, all compliant RFC3484  
> implementations should prefer v4 when connecting to native from 6to4  
> (rule 5 of destination address selection AFAIR).

In my opinion, this is a bug. This is the default policy table from a  
FreeBSD system, which is the RFC 3484 table IIRC:

 > ip6addrctl
Prefix                          Prec Label      Use
::1/128                           50     0        0
::/0                              40     1   646064
2002::/16                         30     2        0
::/96                             20     3        0
::ffff:0.0.0.0/96                 10     4        0

The last line catches IPv4. It's two steps below the 6to4 prefix.  
However, the fact that the label for the 6to4 prefix doesn't match  
the ::/0 label means that IPv4 will be used.

This happens on FreeBSD and XP, and I assume also on Vista. But not on  
MacOS, because it doesn't implement the policy table. I don't know  
about Linux. (If you want to test, try to connect to  
6to4test.runningipv6.net and see what happens. Both addresses are  
unreachable, though.)
_______________________________________________
Ietf mailing list
[email-masked]
https://www.ietf.org/mailman/listinfo/ietf

---

From: Iljitsch van Beijnum <[email-masked]>
Date: Wed, 12 Nov 2008 21:26:02 +0100

> Nearly 38% of that .238% is broken...

No, 0.238% is the working IPv6 users, so the total is 0.328% of which  
27% is broken. I would be interested to see the OS breakdown for that  
0.09%. I'm betting it's mostly Vista 6to4 users who have a public IPv4  
address but are behind a firewall that blocks protocol 41.
_______________________________________________
Ietf mailing list
[email-masked]
https://www.ietf.org/mailman/listinfo/ietf

---

From: David Kessens <[email-masked]>
Date: Wed, 12 Nov 2008 12:58:47 -0800

Danny,

> Given what we were measures and what data was supplied, those

The report as presented at the RIPE meeting indeed mentions the
possibility of undercounting. However, it appears that there is an
undercount of several orders of magnitude. At that point you really
cannot claim that the report provides a perspective on Internet IPv6
traffic as it does. It is quite reasonable to conclude that something
went wrong with the methodology, measurements or analysis.

> from this, only .1% on average.  I believe the point remains very

The difference between something that is barely measurable and
something small but measurable like 0.1% is huge. Basically, 0.1% on
the scale of the Internet means that a very large group of people is
using IPv6 today. There is no question that that group pales to the
total number of Internet users but it sure is more than a few people
in IETF experimenting with IPv6.

David Kessens
---

---

From: "TJ" <[email-masked]>
Date: Wed, 12 Nov 2008 16:02:35 -0500

>-----Original Message-----
>From: [email-masked] [mailto:[email-masked]] On Behalf Of
>Iljitsch van Beijnum
>> . 0.238% of users have useful IPv6 connectivity (and prefer IPv6) .
>> 0.09% of users have broken IPv6 connectivity
>No, 0.238% is the working IPv6 users, so the total is 0.328% of which 27%
is
>broken. I would be interested to see the OS breakdown for that 0.09%. I'm
>betting it's mostly Vista 6to4 users who have a public IPv4 address but are
>behind a firewall that blocks protocol 41.

Or that, sadly, have an apparently-public IP that gets NATed to another
public IP.

/TJ

---

From: Danny McPherson <[email-masked]>
Date: Wed, 12 Nov 2008 18:11:11 -0700

On Nov 12,

> went wrong with the methodology, measurements or analysis.

Nothing is wrong in the methodology and the places where
undercounting likely occurred (namely: flow types supported
by exporting routers, Teredo data channels, etc..) have been
identified.  Caveat-aware, I believe the report to be both
very quantitive and qualitative.  Furthermore, what we measured
is what the ISPs involve have visibility to, which is a critical
consideration - if you can't see it, and can't measure it, then
you certainly can't qualify it.

If you have any more *quantitative* and qualitative studies
that you can point to I and many others would be quite
interested.

> in IETF experimenting with IPv6.

That's great news, and I look forwarding to seeing more
data from this large group of people...

To be clear, our attempt with this study was to measure
observable IPv6 traffic in production networks across a
large number of production ISP networks.  It was not to
discredit IPv6 in any way, quite the contrary.

I look forward to any credible data that you can provide
to support wider adoption, or being made aware of any
unacknowledged issues with our methodology.

-danny

---

From: David Kessens <[email-masked]>
Date: Wed, 12 Nov 2008 21:37:37 -0800

Danny,

> unacknowledged issues with our methodology.

As I mentioned in another mail to the ietf list today:

 various presentations on this topic from the last RIPE
 meeting are available on rosie.ripe.net, look for ipv6 working group
 or plenary

David Kessens
---

---

From: "Olivier MJ Crepin-Leblond" <[email-masked]>
Date: Thu, 13 Nov 2008 08:41:46 +0100

> discredit IPv6 in any way, quite the contrary.

That's great and it will be even better when this study is repeated in
a few months using the same data set and methodology. This way, you
can start tracking growth.
Comparing this set of results with other sets obtained using different
methodologies & data sets would be like comparing apples and oranges.

Warm regards,

Olivier

-- 
Olivier MJ Crepin-Leblond, Ph.D
Global Information Highway Ltd
http://www.gih.com/ocl.html

---

From: Pekka Savola <[email-masked]>
Date: Thu, 13 Nov 2008 14:17:53 +0200 (EET)

On Thu, 13 Nov 2008, Rémi Després wrote:
>>  If an implementation implements RFC3484 and the user is not using custom
>>  address selection policy, all compliant RFC3484 implementations should
>>  prefer v4 when connecting to native from 6to4 (rule 5 of destination
>>  address selection AFAIR).

Actually, my above statement is incomplete.  Thanks for your eagle 
eyes :-)

In case the user has a RFC1918 IPv4 address and the destination is 
global v4 address, you'd use 6to4.  In case IPv4 address is global and 
destination is global, or both are RFC1918, you would use IPv4.

As such:

> Can we derive from this that Google's IPv6 address is necessarily 
> 6to4 (most of its US customers using it are 6to4), and that Google 
> has therefore a guaranteed path toward other 6to4 hosts?

I believe Google is using native addresses.  The 6to4 hits are 
probably caused by the users with private v4 addresses or users whose 
implementation does not support rfc3484.

> Besides, isn't this a strong reason in favor of native IPv6 (albeit like Free 
> did it with 6rd on its IPv4 infrastructure) vs 6to4?

Native is in many cases better than 6to4 or Teredo (but in some cases 
6to4 <-> 6to4 is better than native).  But this is something I 
specifically didn't comment on in my mail.

---

From: Pekka Savola <[email-masked]>
Date: Thu, 13 Nov 2008 14:24:17 +0200 (EET)

On Wed, 12 Nov 2008, Iljitsch van Beijnum wrote:
> In my opinion, this is a bug. This is the default policy table from a FreeBSD 
> system, which is the RFC 3484 table IIRC:

You should probably bring this up on 6MAN WG list then.

>>  ip6addrctl
> Prefix                          Prec Label      Use
> : : 1/128                           50     0        0
> : :/0                              40     1   646064
> 2002::/16                         30     2        0
> : :/96                             20     3        0
> : : ffff:0.0.0.0/96                 10     4        0
>
> The last line catches IPv4. It's two steps below the 6to4 prefix. However, 
> the fact that the label for the 6to4 prefix doesn't match the ::/0 label 
> means that IPv4 will be used.
>
> This happens on FreeBSD and XP, and I assume also on Vista. But not on MacOS, 
> because it doesn't implement the policy table. I don't know about Linux. (If 
> you want to test, try to connect to 6to4test.runningipv6.net and see what 
> happens. Both addresses are unreachable, though.)

I'm not sure whether you're agreeing with me or something else; I 
don't see where you're saying the bug is.  But if we start talking 
about issues in RFC3484, it should happen on 6MAN list.

Your test is inconclusive due to the fact that the A record is a 
private address.  Depending on whether the connecting host has a 
global or private address, the results are different (see my mail to 
Remi for more).

---

From: Rémi Després <[email-masked]>
Date: Thu, 13 Nov 2008 10:01:57 +0100

> destination address selection AFAIR).
Can we derive from this that Google's IPv6 address is necessarily 6to4 
(most of its US customers using it are 6to4), and that Google has 
therefore a guaranteed path toward other 6to4 hosts?

Besides, isn't this a strong reason in favor of native IPv6 (albeit like 
Free did it with 6rd on its IPv4 infrastructure) vs 6to4?

RD
> was 0.5% of users).
Except if the dual stack server, like that of Google, uses different 
URLs for IPv6and IPv4, right?
> If you're interested in wider picture of IPv6 penetration, you'll put 
> the content on v6-only hostname (with Mikael, this was reachable by 6% 
> of users). If you want to also cover for Vista users with Teredo, 
> you'd put the content on a site and refer to it using a numeric 
> address instead of a hostname (this would result in even a higher 
> percentage).
>