Re: list lag?

C Matthew Curtin (cmcurtin@research.megasoft.com)
Mon, 2 Jun 1997 22:06:33 -0400 (EDT)


>>>>> "Arvin" == Arvin Meyer <onsite@esinet.net> writes:

cmcurtin> Delays in your email are due to your ISP's DNS servers are
cmcurtin> functioning, uh, suboptimally.

Arvin> Not necessarily correct.

No, that is precisely the problem. Perhaps you didn't discern that
the text following my observation was a log entry noting that a DNS
timeout occurred during the hostname lookup.

Trust me, I know DNS.

Arvin> It takes approximately an hour or two
Arvin> for my messages to be posted.

Jun 2 19:46:00 gatekeeper sendmail[10629]: TAA10626: to=onsite@esinet.net, delay=00:42:31, xdelay=00:00:00, mailer=smtp, relay=mail.uu.net., stat=Deferred: Name server: mail.uu.net.: host name lookup failure

Gee, what do you know...

Arvin> Yet I can send myself mail
Arvin> through and internet forwarding account, and have it back in 4
Arvin> to 15 minutes depending on traffic and time of day.

Right. This is how it _usually_ works, but in some cases, when it's
time to refresh the DNS, gatekeeper tries to do the lookup and isn't
able. Then the mail is deferred, and it retries about 15 minutes
later.

Jun 2 20:23:24 gatekeeper sendmail[10821]: TAA10819: to=onsite@esinet.net, delay=00:54:54, xdelay=00:00:01, mailer=smtp, relay=esinet1.esinet.net. [208.197.151.2], stat=Sent (UAA12351 Message accepted for delivery)

Arvin> I don't
Arvin> know how Unix DNS servers work, but on NT a DNS file is cached
Arvin> after the first mail to that address.

I know precisely how DNS works. Whether it's on NT or Unix (or OS/2,
or MacOS) doesn't matter. (Except, perhaps, if you're considering
such things as stability...) Don't take this as a flame, but I just
want to make the point here... transient errors occur. Sometimes DNS
lookups fail, when things _look_ like they should be OK. Problems
with routing, overused network exchange points, high packet loss
between sites, etc., etc., etc., all contribute to this.

The Internet, generally speaking, isn't terribly healthy. Such is
life on a network that has experienced exponential growth in terms of
connected hosts, users, and traffic over a period of YEARS. Then
combine the efforts of self-serving fools like the morons that spam
the 'net with their "bulk email services" and similar such things, and
you can quickly see how timeouts in lookups and delays in email
delivery can occur.

I'll spare everyone a longwinded lecture on the relative fragility of
the Internet, its importance as a shared, finite resource, and the
responsibility of each netizen to ensure that it isn't abused. But,
just be aware that you're being spared one. :-)

-- 
Matt Curtin  Chief Scientist Megasoft Online  cmcurtin@research.megasoft.com
http://www.research.megasoft.com/people/cmcurtin/    I speak only for myself
Death to small keys.  Crack DES NOW!   http://www.frii.com/~rcv/deschall.htm