The case of the 500-mile email

http://www.ibiblio.org/harris/500milemail.html

by mqt • 18 years ago

80 28 18 years ago

ibiblio.org

sidsavara• 18 years ago

An old story but one of my favorites =)

_hgt1• 18 years ago

The case of the 500-year anecdote.

light3• 18 years ago

I thought it was a made up story till i got to the end O.o

petercooper• 18 years ago

Oldie but a goodie. Highly recommend reading this but if you don't want to..

SPOILER - though you should be reading the article first anyway if you care!

An accidental downgrade of Sendmail made Sendmail have a zero second timeout on sending mail that ultimately worked out at 3 milliseconds, just enough to hit servers within a certain radius..

I bet there are several pieces of software that could have a zero timeout triggered in a similar way. The difficulty of figuring it out? About the same as with this guy ;-)

13ren4• 18 years ago

my shell doesn't have "units": http://www.google.com/search?q=.003+lightseconds+in+miles

mqt2• 18 years ago

units isn't a shell function; it's a program that's a standard part of Unix. You can install GNU Units on Linux.

It even lets you define your own units in units.dat. Pretty cool.

http://en.wikipedia.org/wiki/Units_(Unix)

13ren4• 18 years ago

I've really got to learn to stop posting anything to HackerNews that in any way can be construed as an admission of weakness or vulnerability. I sensed that was the case here when I was writing, but didn't think it was necessary to hide it. I will be more careful in future to not reveal more than is absolutely necessary, and so avoid this typical, casually condescending reply. It's annoying because it's the "mistake" that gets seized on, instead of what I'm saying... as if there's more interest in correction than communication.

Maybe I am alone here in disliking unsolicited advice, but ironically, when I ask a question here, I usually don't get any help...

...so perhaps the secret is not to ask, but state something that incidentally reveals the lack of knowledge, so the scent of inexcusable ignorance rouses the instinctive hacker display of superior knowledge. I will try this.

Or maybe, I am just not a hacker. Although I love coding (especially to help other people) and I'm not a corporate type, I am coming to think this more and more; because behaviour like giving unsolicited advice seems to be totally acceptable and approved of on sites like this, but by my values is a form of trolling, and has never sat well with me.

EDIT I just checked the site mqt lists in his profile (http://mark.nirv.net/), and judging by his May 26, 2007 entries, he does troll at times ("What a f______ p___"; "Use a spell checker next time, a______." - to me, that's really abusive). Trolls have sometimes gotten under my radar by combining genuine knowledge and apparent helpfulness with their trolling. Oh well, you live and you learn; without risking mistakes and uncongeniality, one cannot learn.

mqt2• 18 years ago

"Have you run tcpdump or strace?"

If you're curious about where to start debugging, this blog post gives a good rundown:

http://sysadvent.blogspot.com/2008/12/sysadmin-advent-day-1....

kajecounterhack• 18 years ago

Yeah it's old but I never did figure out how his geostatisticians knew how to see if the email went further than 500 miles...I mean, that'd mean they know to measure where the mail servers are rather than the actual user, right? oh well.

IsaacSchlueter2• 18 years ago

Back then, most of the users were probably within a local telephone call of their mail server.

diN0bot• 18 years ago

back then in the good old days of 2002...

(not sure if i'm joking or serious. depends on one's perception of chance)

jcl• 18 years ago

Also, most of the people they were trying to write to were probably at academic institutions, which function as their own ISP.

jmtame• 18 years ago

And I was fairly certain I hadn't enabled the "FAIL_MAIL_OVER_500_MILES" option.

That would be a great feature to have as part of a "new admin initialization" program or something :D

nazgulnarsil• 18 years ago

why did he freakout? surely the idea of distance = ping time and there being some sort of timeout going on is one of the simplest explanations?

donw• 18 years ago

You're obviously not a sysadmin, living on the front line between the non-technical, and mountains of computer hardware. I've worked at more than a few places where "I can't send an email more than 500 miles." translates to "One person 500 miles away has had their automatic spam filter nab my message."

I'm much more inclined to believe user error first. That said, the words "consultant" and "upgrade" give me cold chills...

blurry• 18 years ago

I am not a sysadmin either but I had exact same reaction as nazgulnarsil. I would think a sysadmin's thought process would follow the path of distance->latency->timeout pretty quickly. In other words, I understand what you are saying about sysadmins having to deal with non-technical users, but in this case I actually think the "customer was right". From what I've gathered from this story, the end user was highly analytical in figuring out the exact issue and made an intelligent and acccurate analysis. The sysdamin's emotional filter was the problem, if anything.

SlowOnTheUptake• 18 years ago

I'm a little unclear on one point: knowing that 3ms * 186000 miles/sec is roughly 550 miles, wouldn't the radius be ~275 miles? (Round trip travel time before timeout)

That is assuming that packets could actually travel that fast through a wire.

The case of the 500-mile email

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