On Fri, Jan 04, 2008 at 07:57:29PM -0500, John C Klensin wrote:
>
>
>
> (3) As Keith Moore has pointed out repeatedly for the general
> case and as I and others have pointed out for more specific ones
> (including today's mail-and-DNS case), dual stack is a nice
> thing to do if one is developing operating systems and maybe if
> one is developing servers. But any form of "the application has
> a choice of multiple addresses or interfaces and must choose"
> puts the application into the routing business.
:) welcome to the end2end model and the rise of the
stupid network... :)
> Even the trivial example that Jeroen and Phillip used may be
> problematic, especially if there are multiple IPv4 and multiple
> IPv6 addresses. There are no MX rules at all about which
> address must be tried first and some handwaving in RFC 2821
> about how many addresses at a given preference level need to be
> tried at all. With most SMTP senders, such things can be
> configured, but the IETF has published approximately zero advice
> as to how to configure them (there actually is some reasonable
> advice in RFC 3974, but that isn't an IETF document and it bears
> one of the stronger forms of a "you really shouldn't pay any
> attention to this" disclaimer from the IESG.
well the failures fo the MX record for both DNS and
specific application use are well known and there was
a well designed "charge" to replace that capability
in the DNS with a more general purpose tool that does
help w/ the "which interface to use" problem.. which
is in fact, very old indeed.. I point you to the SRV RR.
--bill
> john
--
--bill
Opinions expressed may not even be mine by the time you read them, and
certainly don't reflect those of any other entity (legal or otherwise).
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