On Fri, 17 Aug 2012, Michael Thomas wrote:
On 08/17/2012 01:51 PM, Daniel Feenberg wrote:
On Fri, 17 Aug 2012, John R. Levine wrote:
Hi. Remember the ASRG? I was hoping it might do a little research.
In talking to people about IPv6 mail, I'm still coming to the conclusion
that anyone who thinks they know how they're going to handle it, beyond
the current toy scale, doesn't understand the problem. Things we might
address include:
I would not expect to accept any IPv6 mail until users come forward to show
me that they wish to correspond with MTAs that have no IPv4 connection
ability. While this may happen in the fullness of time, I don't expect it
soon. Now and for the foreseeable future such a system would have very
little connectivity, far less than a blacklisted spam source.
Host operating systems -- all of them to my knowledge -- prefer v6 over
v4 if you have a public v6 address. So the mere existence of a AAAA
associated with the MX will cause the sender to pick the v6 destination.
I have a v6 mail system and got bitten because I had forgot to put up
the v6 reverse map. It will happen just as a natural consequence of
people enabling v6 on their infrastructure.
This sounds inconvenient. If I want to accept mail from one IPv6 host,
then all the IPv6 hosts will want to use IPv6, and unless I accept mail
from unknown IPv6 hosts, mail from hosts that would have been accepted
over IPv4 will be rejected? That is a problem, but I can't imagine IPv6
acceptance being so universal that there would be more desirable mail from
IPv6 only hosts than from IPv4 only hosts, at least not for some decades.
This is especially true since more important hosts are more likely to have
access to IPv4 addresses. I actually wonder if the transition could ever
occur as long as IPv4 is supported at all by ISPs.
daniel feenberg
NBER
Mike
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