Subject: Re: implications of 6to4 for v6coex

From: Nathan Ward <[email-masked]>
Date: Fri, 3 Oct 2008 12:43:47 +1300

On 3/10/2008, at 2:26 AM, Erik Kline wrote:
> On Sun, Sep 21, 2008 at 7:12 PM, Brian E Carpenter
> <[email-masked]> wrote:
>> On 2008-09-20 12:54, Nathan Ward wrote:
>>> On 20/09/2008, at 12:15 PM, james woodyatt wrote:
>>>> There is clearly something broken about 6to4, and I'm not sure  
>>>> how to
>>>> fix it.  Can it be saved as a standard?
>>
>> Just to be clear, the issue is not with basic 6to4, which was  
>> intended
>> to be implemented only in routers. It's with the "obvious" extension
>> to allow host-based 6to4, which led fairly quickly to the notion
>> of anycast relays and the resulting lack of both configuration and of
>> a discovery protocol.
>
> Well it seems to be working well enough (or popular enough, anyway).
> What if I said that 69.8% of IPv6-enabled users who visit google.com
> have 6to4?

So, Brian disagrees with the host based 6to4 thing, ie. the way  
Windows Vista and XPSP2 do it.

I don't think that the anycast relays has anything to do with the host  
based stuff. It might have been related thought trains in peoples'  
minds in 2001, but the anycast relays are just as relevant to router- 
based 6to4 as they are to host-based 6to4.

For example, Airport Extreme, Linksys RVS4000, Cisco 8XX+config, etc.
So, it's not just Windows.

I'm not so hot on 6to4 stacks in hosts either, but my problem is wider  
- it is more with automatically configured 6to4, which is not specific  
to hosts.

My feeling is still that this whole relay stealing thing is a non- 
issue in current implementations, I'll write up in a draft with some  
recommendations to remove that paragraph and bring it in line with  
most existing deployments.

Also, these stats are interesting, and are roughly the same as what  
I'd expect.
So, my understanding is that this test is to a hostname with A and  
AAAA records, right? That would make sense, as Teredo will only be  
used by XP SP2 and Linux boxes who have Teredo enabled (Vista prefers  
A over AAAA if it only has Teredo IPv6 connectivity).

I don't think that you can accurately say that that you tested all  
IPv6 enabled users, because you aren't testing whether they are Vista  
and have Teredo enabled. Point em at a hostname with only AAAA and my  
expectation is that you'll significantly see different results - close  
to what I see, which are like:
- ~90% Teredo
- ~7-8% 6to4
- rest Native

--
Nathan Ward

---

From: Brian E Carpenter <[email-masked]>
Date: Fri, 03 Oct 2008 14:32:33 +1300

On 2008-10-03 12:43, Nathan Ward wrote:
>>>>> There is clearly something broken about 6to4, and I'm not sure how to
>>> Just to be clear, the issue is not with basic 6to4, which was intended

That's the least I'd expect, as an author of 6to4 ;-)

Any stats for Teredo?

> 
> 
> So, Brian disagrees with the host based 6to4 thing, ie. the way Windows
> Vista and XPSP2 do it.

No, I don't disagree with it, I just want to remind people that most
of the thinking about how 6to4 routes should be announced was based
on the router model, without considering either automatic discovery
or anycast.

> based stuff. It might have been related thought trains in peoples' minds
> in 2001, but the anycast relays are just as relevant to router-based
> 6to4 as they are to host-based 6to4.

Except that the idea was that router relationships for 6to4 would be
configured by mutually consenting operators; whereas the anycast model
implies zero-conf. There's a gap in the middle where a discovery
protocol could live.

> I'm not so hot on 6to4 stacks in hosts either, but my problem is wider -
> it is more with automatically configured 6to4, which is not specific to
> hosts.

OK, but it's dominated by hosts, especially because of Vista.

    Brian

> 
> My feeling is still that this whole relay stealing thing is a non-issue
> in current implementations, I'll write up in a draft with some
> recommendations to remove that paragraph and bring it in line with most
> existing deployments.
> 
> 
> 
> Also, these stats are interesting, and are roughly the same as what I'd
> expect.
> So, my understanding is that this test is to a hostname with A and AAAA
> records, right? That would make sense, as Teredo will only be used by XP
> SP2 and Linux boxes who have Teredo enabled (Vista prefers A over AAAA
> if it only has Teredo IPv6 connectivity).
> 
> I don't think that you can accurately say that that you tested all IPv6
> enabled users, because you aren't testing whether they are Vista and
> have Teredo enabled. Point em at a hostname with only AAAA and my

---

From: Nathan Ward <[email-masked]>
Date: Fri, 3 Oct 2008 16:06:23 +1300

> on the router model, without considering either automatic discovery

That's interesting eh, as so many people think of 6to4 the other way  
around.

>> minds

Yes.

I have some thoughts around this I wouldn't mind whiteboarding with  
you - I'll get in touch next week.

> OK, but it's dominated by hosts, especially because of Vista.

Yes.

This is easy to see that, at least for Vista and XP, because the  
address is of the form:
2002:AABB:CCDD::AABB:CCDD (Where AA.BB.CC.DD is the IPv4 address)

Note that AABB:CCDD is repeated in the last 32 bits as well as in bits  
33-48.

--
Nathan Ward

---

From: "Erik Kline" <[email-masked]>
Date: Fri, 3 Oct 2008 00:01:04 -0400

> That's the least I'd expect, as an author of 6to4 ;-)

This test was against a dual-stacked hostname.  Teredo comes in around
1.2%.  The same or less than ISATAP.

A full presentation by the engineer who did the work will be at
RIPE57.  (I tried to find a reference to Steinar Gunderson's talk on
http://www.ripe.net/ripe/meetings/ripe-57/meeting-plan.html and
related but I seem to be having connectivity problems.)  Hopefully I
haven't stolen any thunder.

>> to what I see, which are like:

Yeah, but this doesn't represent reality for me as a content provider.
 We spoke about this at APNIC26, IIRC, but to put it on-record on the
list:

I (with my Google hat on) am not interested in "how much Teredo is
_deployed_", e.g. in the sense of "how much Teredo _might_ I see".
I'm interested purely in "how much Teredo am I _actually_ seeing", to
help answer the question "should I bother to deploy my own Teredo
relay and/or actually have Teredo VIPs for services?".  Right now that
answer appears to be "don't bother yet".

And, to state the obvious, google.com is never going turn off IPv4 and
still leave IPv6 up for any service until there's so few IPv4 users
that it's operationally not a financial win (i.e. we save more money
operationally by turning it off than revenue sacrificed by doing so).

Not that Teredo isn't amazing and can leap tall buildings and make my
espresso for me; I understand.  :-)
-Erik

---

From: Rémi Denis-Courmont <[email-masked]>
Date: Fri, 03 Oct 2008 09:33:09 +0200

> 1.2%.  The same or less than ISATAP.

I expect that Teredo should be _forever_ close to 0% against *dual-stacked*

hostnames, thanks to source address selection. I have been proposing to fix

the address scoping rules of RFC3484 to get that number even lower: RFC1918

IPv4 addresses should global scope (which they are because of NATs), w.r.t.

to source address selection. It appears that Windows already does this; if

it did not it would prefer Teredo over native NAT'ed IPv4 in face of a

dual-stacked hostnames.

Teredo should be statically meaningful only with IPv6-only hostnames.

(...)

> Yeah, but this doesn't represent reality for me as a content provider.

I tend to agree that content provider should not have to care much about

Teredo. To me, it seems more useful for peer-to-peer use cases. I would

say, that's a concern for "consumer ISPs", not for Google.

-- 

Rémi Denis-Courmont

---

From: David Malone <[email-masked]>
Date: Sat, 4 Oct 2008 10:06:28 +0100

> 1.2%.  The same or less than ISATAP.

In the stats I did on ftp.heanet.ie's log files, I saw a big rise
in teredo mid 2006, to the level of being a few percent of the IPv6
addresses connecting (see Figure 4 in this):

	http://www.maths.tcd.ie/~dwmalone/p/addr-pam08.pdf

Strangely, the increase didn't seem to be due to Vista, based on
the user agent srings. ISATAP use seemed to grow between 2004 and
2005, but Teredo seemed to overtake it in 2006.  I haven't rechecked
the stats for 2008, but I could do if someone was interested.

	David.

---

From: Rémi Després <[email-masked]>
Date: Mon, 06 Oct 2008 16:08:01 +0200

>> What if I said that 69.8% of IPv6-enabled users who visit google.com

As we discussed in Montreal, this proves that there is, for v6 packets 
that have the prefix of 6to4 (2002::/16), a path from ipv6.google.com 
servers to the IPv4 Internet.

But it doesn't prove that clients of IPv6.Google, if they try to reach 
another IPv6 server, will always have a 6to4 return path for their 
packets. similarly, they may not be reachable, as servers, from any 
client having native IPv6 connectivity.

This is the reason why I introduced 6rd (draft-despres-6rd-00).

A 6rd ISP simply replaces, in IPv6 prefixes its provides to its 
customers, the standard 6to4 prefix  by an IPv6 prefix that has been 
assigned to it. Thus any customer site of this ISP as guaranteed IPv6 
connectivity, provided 6rd is supported in its home-gateway. A return 
path is available from any server or client remote host that has IPv6 
connectivity (a 2002::/16 route form this host toward to 6to4 relay is 
no longer needed).

So far, Free, the second ISP in France with several million customers, 
is AFAIK the only one that has deployed IPv6 using 6rd.

I am about to revise draft-despres-6rd-00, essentially to no longer 
include a proposal for a 6rd DHCP option. ((1) It isn't necessary for 
ISPs that, like Free, deploy IPv6 in sites where they provide 
home-gateways. (2) Without the DHCP option, the proposed RFC stays 
purely informational. Having no IANA or protocol implication, it can 
follow a much much shorter path to be published.)

Regards,

RD

PS: If not too complex, it would be really nice to have additional 
statistics giving, in the 30% users that are not 6to4, which proportion 
is Teredo (2001:0000::/32), and which proportion is neither.

Even more ideally, at least for me, on would have the percentage of Free 
customers  (2a01:0e30::/28)

Thanks if you can do anything on this.

---

From: Rémi Denis-Courmont <[email-masked]>
Date: Mon, 6 Oct 2008 18:55:34 +0300

Hello,

> client having native IPv6 connectivity.

Last time I checked, Google used HTTP, HTTP ran on TCP, and TCP checked 
return-routability in the three-way handshake.

I don't disagree that the lack of built-in return-routability in 6to4 _is_ a 
problem in certain circumstances. Namely, when there is an IPv4 firewall on 
the proto-41 path. But lets not pretend it is worse than it really is.

-- 
Rémi Denis-Courmont
http://www.remlab.net/

---

From: Rémi Després <[email-masked]>
Date: Mon, 06 Oct 2008 19:01:16 +0200

Rémi Denis-Courmont   (m/j/a) 10/6/08 5:55 PM:
> 	Hello,
> 
> Le lundi 6 octobre 2008 17:08:01 RÃ©mi DesprÃ©s, vous avez Ã©critÂ :

Did I suggest the contrary in any way?

> the proto-41 path. But lets not pretend it is worse than it really is.

1.
In my understanding, the problem is not only with firewalls.

If you have seen a proof that all ISPs that offer IPv6 have a guaranteed
route for the 2002::/16 prefix toward the IPv4 Internet, with a quality
they can control, that's good news :-), but it's not the state of the
art I know.

2.
I don't "pretend" anything. I just tell what I believe is true, when
IMHO it helps IETF to make progress.

Please remember that thanks to this kind of analysis, I now have native
IPv6 at home. My ISP, Free, which didn't consider offering IPv6 across
6to4 relays, deployed IPv6 at no charge for customers after I had
explained 6rd's potential.

Regards,

RD