6to4 status (again)

Martin Millnert martin at millnert.se
Thu Feb 28 00:40:30 CET 2013


On 27 feb 2013, at 23:19, Dmitry Anipko <Dmitry.Anipko at microsoft.com> wrote:

>>> Yes, it's possible from Teredo side. But why 6to4 which can't be behind a NAT?
> I think BitTorrent folks, if they are on the alias, or anyone more closely familiar with their code would be able to comment better on the address selection logic they follow.

It's not so much about "prefer" as "not having a choice":
A call such as "connect($hostname)" , where $hostname is an IPv6 address, on a host which only has one interface providing public and global IPv6 connectivity, the 6to4 interface, must use that connectivity.

The NAT-traversal side is always happening on the Teredo-end of the connection, btw.

>>> Internet Explorer only?
> IE certainly, but not only IE. For example, all/most of the apps in Windows store would use the APIs relying on OS preferences, many W7 desktop apps would do so as well. I can't speak for other browsers, which may have their own way of selecting addresses.

Torrent clients use the same API:s AFAIK, but use IPv4 or IPv6 addresses rather than hostnames as I described above, which puts the AFI-selection part of the source address selection algorithm out of play.

Best regards,

> -----Original Message-----
> From: ipv6-ops-bounces+dmitry.anipko=microsoft.com at lists.cluenet.de [mailto:ipv6-ops-bounces+dmitry.anipko=microsoft.com at lists.cluenet.de] On Behalf Of Max Tulyev
> Sent: Wednesday, February 27, 2013 2:08 PM
> To: ipv6-ops at lists.cluenet.de
> Subject: Re: 6to4 status (again)
> On 27.02.13 23:57, Dmitry Anipko wrote:
>>>> I see a lot of BitTorrent traffic from Win7/WinXP preferring 6to4<->teredo.
>> My understanding is that some peer to peer apps are explicitly using Teredo, because it gives them some amount of NAT traversal "for free".
> Yes, it's possible from Teredo side. But why 6to4 which can't be behind a NAT?
>>>> What exactly Win7/Win8 software prefer v4<->v4?
>> Chris's statement about preference is correct for apps which do not explicitly specify, what interface/address they want to use - e.g. user doing web browsing and the browser using mainstream Windows networking APIs to make a connection.
>  - i.e. Internet Explorer only?

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