But you missed the point I was trying to make. in those days, the inability
of the mail network (or at least parts of it) to support a single global
address space was correctly recognized as a deficiency in the network -
and people took action to solve the problem (notably deployng MX records).
Which broke DNS. We can no longer send an email to an IP number, mainly
due to this myopic choice. This choice also broke layer independency.
What the heck are you talking about? Sending email to an IP address never
was deprecated, and still works just fine... not that it is now or ever
was widely used. Sending mail to domains with only A records works just
fine also. Folks who have native IP connectivity and don't want to set
up MX records don't have to do so for their servers.
There was a switch from HOSTS.TXT to DNS, but this had nothing to do with
MX records. And not many people miss the days when everybody needed
to be in the HOSTS.TXT file in order to receive mail reliably.
Yes there are broken implementations that cannot send mail to IP addresses,
and cannot send mail to domains without an MX record. But they are quite
clearly broken, and this is clear from both RFC 974 and the recent revision
to RFC 821/974 that is now in the RFC Editor's queue. Don't confuse
broken implementations with bad design decisions.
It is time IMO for some at the IETF to stop pretending that the Internet
can made into a homogeneous network.
The Internet never has been homogeneous, and I don't know anyone who
has been around IETF very long who pretends that it is. It has always,
however, had some minimum standards for addressing and message format
which not only allowed consenting folks to choose whatever other
protocols and applications that they wanted to run, and allowed the
same host and application software to be reused from anywhere in the
network, and to reach well-known services from anywhere in the network.
But take away that little bit of uniformity - really the minimum necessary -
and all bets are off. People who use NATs - especially those using them
on a large scale - are discovering this the hard way.
Cooperation is not a bunch of people doing the same things at the same
time, but different people doing different things at different times and
places, for the same objective. Likewise, standardization is not
having the same rules for all at all places but having different rules that
interoperate for the same objective.
The whole point of the Internet has always been to allow folks to run
any of a wide variety of networked applications they wanted to run.
IP is fundamentally designed to give the maximum utility and flexibility
with a minimum of constraints on the networks and hosts supporting it.
By contrast, while folks can clearly do whatever they like with their
own networks, folks that put NATs on their networks are limiting the
set of applications that they can run. Now maybe you're right that
the existence of NATs is just another example of people doing what
they like with their networks - just as they always have. Maybe NATs
are the Internet's adolescence. But just like adolescents don't always
understand the consequences of their actions, neither do the folks who
install NATs on their networks.
IETF cannot compel people to stop using NATs, and it shouldn't try.
But it can and should develop solutions to the problems that NATs
purport to solve, which work better than NAT.