brant@manta.pha.pa.us (Brant Cheikes) (08/13/88)
This article is partly in response to mail CC'd to me from Gary
Trujillo, in which he asks the burning question "what will joining the
US domain do for me?" Lenny Tropiano recently posted a similar
inquiry, I suspect that others are wondering the same thing. So I
thought I'd try to discuss the potential benefits of joining the .US
domain. I'm pretty sure of most of the details here, but if anyone
has corrections, would you please post them? Note that I am writing
this from the point of view of sites all of whose links to the world
use UUCP (UUCP-only sites).
In a sentence, the primary effect of joining a domain such as .US is:
mail TO you from Internet sites will reach you reliably, and perhaps
more quickly.
Mail FROM you is unaffected, with the possible exception that bounced
mail will more likely bounce all the way back to you.
Mail BETWEEN your site and another UUCP-only site is unaffected,
except in certain obscure cases.
Now, some definitions.
A big-I Internet site is a site on the Defense Advanced Research
Projects Agency network (DARPAnet, aka ARPAnet, DoD Internet).
Internet sites communicate with each other over dedicated lines, using
the TCP/IP protocols. Users on Internet sites may be able to remote
login to other Internet sites, FTP service is supported between
Internet sites, etc. E-mail between Internet sites is generally very
fast, on the order of minutes.
The little-i internet is generally defined as the set of hosts
directly on the Internet as well as those "reachable" (by mail,
usually) from the Internet. Since numerous Internet/UUCP gateways
exist, UUCP sites are considered part of the internet.
When you join the .US domain (Ann Westine, westine@isi.edu, is the
domain administrator and handles new applications; requests for
applications should be addressed to her), you will be assigned a name
that is usually <your-host>.<city>.<state>.US. The <city> may be an
abbreviation, such as "pha" for Philadelphia, or a full city name,
such as "dallas". <state> is the usual two-letter abbreviation. What
you choose for <city> is between you and Ann Westine. Domain names
are case-insensitive.
Joining the .US domain requires that you make an explicit arrangement
with an Internet site that will serve as your Mail Exchanger (MX).
This means that said Internet site must agree to make sure that mail
addressed to user@you.city.state.us will reach you (the mechanism
behind this will be explained shortly). Ideally, the Internet site
should be a direct UUCP neighbor, but I hear that this is not
necessary.
Now, let's assume that site foo, in Philadelphia, has registered in
the .US domain and is now called foo.pha.pa.us. Say that Foo's MX is
linc.cis.upenn.edu, a direct uucp neighbor. What happens when someone
on another Internet site, like wharton.upenn.edu, tries to send mail
to bar@foo.pha.pa.us? The wharton user simply addresses mail to
"bar@foo.pha.pa.us" (no bang paths) and sends it off. The mail
transport agent at wharton.upenn.edu looks up in its tables the
Internet address of foo.pha.pa.us, but doesn't find one (foo isn't on
the Internet). So wharton next looks for a MX record, and finds that
linc.cis.upenn.edu forwards mail to foo.pha.pa.us. So wharton
establishes a network connection to linc and passes the mail on. Linc
then looks at the address, sees it really denotes a uucp neighbor, and
so queues it up for a uucp transfer to foo. Note that the admin on
Linc must have made special arrangements (in sendmail.cf for instance)
to translate user@foo.pha.pa.us into foo!user and dump it into the
uucp stream.
So what is the upshot? Mail from Internet sites to you goes directly
to your MX over the Internet (quite fast), then makes the rest of the
trip via uucp to you. If your MX forwards mail immediately upon
receipt (as mine does), then mail from any Internet site to you
arrives very fast and reliably.
A clear point to be made is that joining the .US domain will make
your Internet-based correspondents very happy. They don't have to
worry about bang paths or Internet/uucp gateways; they just address
the mail to you@youraddress and you get it.
But what about the other direction? What if you want to send mail to
user@random.Internet.site? Well, I'm afraid that unless you've made
some special and clever arrangements, you have to do whatever you
always did; being in .US doesn't help. Sometimes, Internet sites will
do a funny kind of rerouting (though I'm not sure it's condoned by the
Defense Communications Agency, which administers the Internet): if
they see foo!bar!bletch!random.inet.site!user, they will skip the
foo!bar!bletch and send directly (over Internet channels) to
user@random.inet.site. They may even short-circuit paths like
foo!bar!random.inet.site!bletch!user. So your Internet neighbor may
be able to help you out a bit here, but this has nothing to do with
your being part of the US domain.
As for uucp->uucp traffic, you will have to update your map entry to
list your alias:
foo= foo.pha.pa.us
Now uucp folks should be able to address mail to user@foo.pha.pa.us,
as well as user@foo, user@foo.uucp, and foo!user. But the basic
pathalias mechanism remains unchanged; mail still gets routed in the
usual way, though foo.pha.pa.us is now recognized as an alias for foo.
If a mail message passes through an Internet site that does the funny
rerouting as described above, it may get short-circuited to your MX
and then to you, but that's a rare case.
You will still route mail to uucp sites the same way you always did.
To summarize: mail TO you from Internet sites is vastly improved.
Mail from you is, by and large, unaffected, as is mail to you from
uucp sites. Bounced mail is more likely to reach you if it passes
back through a rerouting Internet site that recognizes your domain
name.
Once you join the .US domain, you will have to recompile smail (fixing
the #define of MYDOM) and news (or at least you should). If you don't
use smail (or sendmail), you should. But if you don't, it's silly to
join the US domain, since you're much too primitive for us :-)
My opinion: joining the US domain is unnecessary unless you or your
users exchange a significant amount of mail (you decide what that is)
with Internet sites.
Oh, joining the US domain is free, and they send you a Mr. Wizard
Magic Internet Packet Decoder Ring.
--
Brant Cheikes
University of Pennsylvania
Department of Computer and Information Science
Internet: brant@manta.pha.pa.us, UUCP: {bpa,drexel}!manta!brant