North American Network Operators Group

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Re: Selection of Appropriate Local SMTP Relay

  • From: Joe Abley
  • Date: Mon Jan 10 19:17:18 2000

On Mon, Jan 10, 2000 at 09:01:49AM -0500, John R. Levine wrote:
> >Selection of Appropriate Local SMTP relAy (SALSA :)
> >  An alternative is to provide a method for a mail client to discover a
> >  suitable local smart relay in some dynamic fashion. This requires some
> >  ubiquitous, global, standard database which every operator uses...
> >  ... like the DNS.
> That's much too complicated.  What we need are some well-known IP
> addresses, analogous to well-known ports, that are not routable on the
> global Internet, but that are assigned to standard services within
> each network, e.g.:

I think that both approaches have some merit, and neither are without
complication. For example, the overloaded well-known-address approach
might lead to operational confusion in the event that a temporary
ISP doesn't provide the well-known service to a roaming user:

 + outbound packets from the user might spiral off into the default
   free zone, ultimately never connecting to anything

 + connection requests might follow the temporary ISP's default out to
   their transit provider who _does_ support the address, and that relay
   (correctly) refuses to relay for the user

 + the real identity of the well-known relay box that a given user
   connects to might change with time, making it harder to support the

This is going to provide operational confusion, I think. In this
respect, at least, the MX idea works more cleanly in the event that
there are _no_ MX records to be found.

Interesting idea, though; thanks for mentioning it.

It seems from some of the mail I have received that there is some
interest in this idea. Rather than cluttering up NANOG any further, I'll
take it to the roamops wg list at [email protected]