--On Friday, 04 January, 2008 12:01 -0800 Bill Manning
<bmanning@xxxxxxx> wrote:
>> Again, there is no specific root server issue in any of this,
>> but it concerns me that none of the relevant committees or
>> studies appear to have considered the possible applications
>> implications of the change.
>...
> actually, there was on at least two occasions the explicit
> scoping of the consideration to the DNS-specific issues.
> interactions with other applications was ruled out of scope
> regarding the issues of adding what is effectively a new
> address family to the DNS. The general answer when needing
> to communicate between similar applications that run on
> different address families has traditionally been the
> application layer gateway (ALG) ...
Then, IMO, whoever ruled it out of scope should look for a job
describing large animals by touch and while blindfolded. If
said large animal responds to inappropriate poking by stomping
on the individual we can make a nomination for the Darwin Awards.
Seriously, a competent SMTP server running in a competent
dual-stack environment should be nearly agnostic about whether
connections are occurring via IPv4 or IPv6. There are several
server-environment pairs that are that competent. Most major
contemporary SMTP servers have their origins in multiple
transport environments (not just different address families) and
RFC 821 was explicitly written to recognize and accommodate
multiple transport environments. If we are now making
decisions about IPv6 deployment that effectively force the use
of an ALG, rather than servers that can handle both
environments, we have taken the fine art of shooting ourselves
in the foot to new heights.
I also note that, even if one ignores "other applications", the
DNS has already recognized email as a special case, with its
own, applications-protocol-specific RR type and rules --both
rules within the application protocol and rules about additional
information that is returned with MX queries. If the MX
resolution doesn't work smoothly for IPv6, then the DNS isn't
IPv6-ready no matter how many AAAA records are defined and
spread around. Even if one thinks an ALG is needed, one has to
find the ALG host. I hope the additional information rules have
been adjusted if needed to encourage return of relevant AAAA
records if they exist: it hadn't even occurred to me to check
until now, but your comment about ALGs forces me to wonder
whether DNS changes for IPv6 have ignored the fact that there is
an Internet out there on which people run applications.
Mumble.
john
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