IPv6 isn't SMTP
dhc2 at dcrocker.net
Thu Mar 27 00:07:09 UTC 2014
On 3/25/2014 10:41 PM, Jimmy Hess wrote:
> (1) Architectural layers are a protocol design construction, only, which
> assist with standardization. They are not a separation of
Actually, they are specifically a separation of responsibilities.
That the separation doesn't work adequately and all the time means that
pragmatics requires wandering across layer boundaries. But pragmatics
also dictate being extremely careful when choosing to do that.
> A SMTP server has to take care to have an implementation of all layers.
There are two possible meanings to that sentence.
The first prompts a 'duh' reaction, since SMTP (usually) runs over
TCP/IP. So the server won't be very useful unless it 'has' an
implementation of all layers.
The other interpretation is that an SMTP package needs to have its own
version of TCP and IP. This, of course, is silliness. SMTP packages do
not typically implement TCP or IP. They might pay quite a lot of
attention to those lower layers, but they don't implement them.
> (2) The IP protocol layer is not actually independent. Moving to IPv6 does
> in fact have effective new requirements for SMTP servers.
Mostly, no. Not completely no, of course, but mostly.
Language like #2 is leading quite a few folk to try to treat email over
IPv6 as if it will be a separate service from the one currently running
over v4. It won't be a separate service. Or, at least, it has better
not be. The success of email has been through seamless, end-to-end
integration, not through disparate silos with different service models.
By way of example, please highlight which email packages require or
even allow an author to dictate which version of IP to send over.
For anything that someone thinks should be done for v6, pursue it
instead as a change for the entire global service. It's fine for
v6-related issues to /motivate/ global changes, but don't isolate the
work to v6 platforms.
> (4) When a major change will [by necessity] be made to any layer
> underlying the MTA application on the protocol stack,
> now is also a good time to look at the overall service as a whole.
Sure, but not 'also'. Rather 'only', except for relatively trivial layer
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