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  1. #1
    Major Asshole! 2,500+ Posts
    Can't send email over 500 miles

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    Can't send email over 500 miles

    Just stumbled on this one, and I liked it so much I think I should share it with you guys. Of course, those not comfortable enough with the basic of linux, ip networks and how mail servers work will probably miss most of the nuances in this one.

    To: 0xdeadbeef@petting-zoo.net
    Subject: The case of the 500-mile email.
    Date: Tue, 26 Nov 2002 14:57:40 -0800

    Here's a problem that *sounded* impossible... I almost regret posting the story to a wide audience, because it makes a great tale over drinks at a conference. :-) The story is slightly altered in order to protect the guilty, elide over irrelevant and boring details, and generally make the whole thing more entertaining.

    I was working in a job running the campus email system some years ago when I got a call from the chairman of the statistics department.

    "We're having a problem sending email out of the department."

    "What's the problem?" I asked.

    "We can't send mail more than 500 miles," the chairman explained.

    I choked on my latte. "Come again?"

    "We can't send mail farther than 500 miles from here," he repeated. "A little bit more, actually. Call it 520 miles. But no farther."

    "Um... Email really doesn't work that way, generally," I said, trying to keep panic out of my voice. One doesn't display panic when speaking to a department chairman, even of a relatively impoverished department like statistics. "What makes you think you can't send mail more than 500 miles?"

    "It's not what I *think*," the chairman replied testily. "You see, when we first noticed this happening, a few days ago--"

    "You waited a few DAYS?" I interrupted, a tremor tinging my voice. "And you couldn't send email this whole time?"

    "We could send email. Just not more than--"

    "--500 miles, yes," I finished for him, "I got that. But why didn't you call earlier?"

    "Well, we hadn't collected enough data to be sure of what was going on until just now." Right. This is the chairman of *statistics*. "Anyway, I asked one of the geostatisticians to look into it--"

    "Geostatisticians..."

    "--yes, and she's produced a map showing the radius within which we can send email to be slightly more than 500 miles. There are a number of destinations within that radius that we can't reach, either, or reach sporadically, but we can never email farther than this radius."

    "I see," I said, and put my head in my hands. "When did this start? A few days ago, you said, but did anything change in your systems at that time?"

    "Well, the consultant came in and patched our server and rebooted it. But I called him, and he said he didn't touch the mail system."

    "Okay, let me take a look, and I'll call you back," I said, scarcely believing that I was playing along. It wasn't April Fool's Day. I tried to remember if someone owed me a practical joke.

    I logged into their department's server, and sent a few test mails. This was in the Research Triangle of North Carolina, and a test mail to my own account was delivered without a hitch. Ditto for one sent to Richmond, and Atlanta, and Washington. Another to Princeton (400 miles) worked.

    But then I tried to send an email to Memphis (600 miles). It failed. Boston, failed. Detroit, failed. I got out my address book and started trying to narrow this down. New York (420 miles) worked, but Providence (580 miles) failed.

    I was beginning to wonder if I had lost my sanity. I tried emailing a friend who lived in North Carolina, but whose ISP was in Seattle. Thankfully, it failed. If the problem had had to do with the geography of the human recipient and not his mail server, I think I would have broken down in tears.

    Having established that -- unbelievably -- the problem as reported was true, and repeatable, I took a look at the sendmail.cf file. It looked fairly normal. In fact, it looked familiar.

    I diffed it against the sendmail.cf in my home directory. It hadn't been altered -- it was a sendmail.cf I had written. And I was fairly certain I hadn't enabled the "FAIL_MAIL_OVER_500_MILES" option. At a loss, I telnetted into the SMTP port. The server happily responded with a SunOS sendmail banner.

    Wait a minute... a SunOS sendmail banner? At the time, Sun was still shipping Sendmail 5 with its operating system, even though Sendmail 8 was fairly mature. Being a good system administrator, I had standardized on Sendmail 8. And also being a good system administrator, I had written a sendmail.cf that used the nice long self-documenting option and variable names available in Sendmail 8 rather than the cryptic punctuation-mark codes that had been used in Sendmail 5.

    The pieces fell into place, all at once, and I again choked on the dregs of my now-cold latte. When the consultant had "patched the server," he had apparently upgraded the version of SunOS, and in so doing *downgraded* Sendmail. The upgrade helpfully left the sendmail.cf alone, even though it was now the wrong version.

    It so happens that Sendmail 5 -- at least, the version that Sun shipped, which had some tweaks -- could deal with the Sendmail 8 sendmail.cf, as most of the rules had at that point remained unaltered. But the new long configuration options -- those it saw as junk, and skipped. And the sendmail binary had no defaults compiled in for most of these, so, finding no suitable settings in the sendmail.cf file, they were set to zero.

    One of the settings that was set to zero was the timeout to connect to the remote SMTP server. Some experimentation established that on this particular machine with its typical load, a zero timeout would abort a connect call in slightly over three milliseconds.

    An odd feature of our campus network at the time was that it was 100% switched. An outgoing packet wouldn't incur a router delay until hitting the POP and reaching a router on the far side. So time to connect to a lightly-loaded remote host on a nearby network would actually largely be governed by the speed of light distance to the destination rather than by incidental router delays.

    Feeling slightly giddy, I typed into my shell:

    $ units
    1311 units, 63 prefixes

    You have: 3 millilightseconds
    You want: miles
    * 558.84719
    / 0.0017893979

    "500 miles, or a little bit more."

    Trey Harris

    Pasted from http://www.csua.berkeley.edu/~ranga/humor/500_mile_email.txt
    ' "But the salesman said . . ." The salesman's an asshole!'
    Mascan42

    'You will always find some Eskimo ready to instruct the Congolese on how to cope with heat waves.'

    Ibid

    I'm just an ex-tech lurking around and spreading disinformation!

  2. #2
    Major Asshole! 2,500+ Posts
    Can't send email over 500 miles

    mrwho's Avatar
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    Another one like that - a car allergic do Vanilla icecream. It should teach us techs that, as the punchline says, no matter how silly the customer's description sound, it can sometimes be the real thing, and we shouldn't treat the customers as crazy at least until we examine the problem.

    "For the engineers among us who understand that the obvious is not always the solution, and that the facts, no matter how implausible, are still the facts ...
    A complaint was received by the Pontiac Division of General Motors:
    "This is the second time I have written you, and I don't blame youfor not answering me, because I kind of sounded crazy, but it is a fact that we have a tradition in our family of ice cream for dessert after dinner each night. But the kind of ice cream varies so, every night, after we've eaten, the whole family votes on which kind of ice cream we should have and I drive down to the store to get it. It's also a fact that I recently purchased a new Pontiac and since then my trips to the store have created a problem. You see, every time I buy vanilla ice cream, when I start back from the store my car won't start. If I get any other kind of ice cream, the car starts just fine. I want you to know I'm serious about this question, no matter how silly it sounds: 'What is there about a Pontiac that makes it not start when I get vanilla ice cream, and easy to start whenever I get any other kind?'"
    The Pontiac President was understandably sceptical about the letter, but sent an engineer to check it out anyway. The latter was surprised to be greeted by a successful, obviously well-educated man in a fine neighbourhood. He had arranged to meet the man just after dinner time, so the two hopped into the car and drove to the ice cream store. It was vanilla ice cream that night and, sure enough, after they came back to the car, it wouldn't start.
    The engineer returned for three more nights. The first night, the man got chocolate. The car started. The second night, he got strawberry. The car started. The third night he ordered vanilla. The car failed to start.
    Now the engineer, being a logical man, refused to believe that this man's car was allergic to vanilla ice cream. He arranged, therefore, to continue his visits for as long as it took to solve the problem. And toward this end he began to take notes: he jotted down all sorts of data, time of day, type of gas used, time to drive back and forth, etc.
    In a short time, he had a clue: the man took less time to buy vanilla than any other flavour. Why? The answer was in the layout of the store.
    Vanilla, being the most popular flavour, was in a separate case at the front of the store for quick pickup. All the other flavours were kept in the back of the store at a different counter where it took considerably longer to find the flavour and get checked out.
    Now the question for the engineer was why the car wouldn't start when it took less time. Once time became the problem -- not the vanilla ice cream -- the engineer quickly came up with the answer: vapour lock. It was happening every night, but the extra time taken to get the other flavours allowed the engine to cool down sufficiently to start. When the man got vanilla, the engine was still too hot for the vapour lock to dissipate.
    Moral of the story: even insane-looking problems are sometimes real."

    at The Pontiac that was Allergic to Vanilla Ice Cream
    ' "But the salesman said . . ." The salesman's an asshole!'
    Mascan42

    'You will always find some Eskimo ready to instruct the Congolese on how to cope with heat waves.'

    Ibid

    I'm just an ex-tech lurking around and spreading disinformation!

  3. #3
    Service Manager 250+ Posts
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    Had some panasonics that did crazy things several years ago (lot of years) the machines were the FP 3030 and the FP 4650. we had a 4650 in office that would like some people and would not work for others. it would set there ready to copy and when someone it didn't like walked toward it , the light would turn red and not let them copy. as soon as they got so far away the thing would go back to ready. also had one in a lawyers office and it would not let him copy but all the girls and the other lawyer could use it all day with out a hitch. had one in a realty office and it liked all the girls but a guy that worked there could ever get it to work for him. they got rid of the guy. even the duplex worked for them in that office. FP 3030 was just as bad. some customer ran the hell out of them and others were calling all the time. never knew what caused as it was easier to switch machines. haven't worked on any of the panasonics since about 95

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