graycrow 0 Nahlásit příspěvěk Odesláno October 31, 2003 The case of the 500-mile emailRead the FAQ about the story. The following is the 500-mile email story in the form it originally appeared, in a post to sage-members on Sun, 24 Nov 2002.: From trey@sage.org Fri Nov 29 18:00:49 2002Date: Sun, 24 Nov 2002 21:03:02 -0500 (EST)From: Trey Harris <trey@sage.org>To: sage-members@sage.orgSubject: The case of the 500-mile email (was RE: [sAGE] Favorite impossible task?) Here's a problem that *sounded* impossible... I almost regret posting thestory to a wide audience, because it makes a great tale over drinks at aconference. :-) The story is slightly altered in order to protect theguilty, elide over irrelevant and boring details, and generally make thewhole thing more entertaining. I was working in a job running the campus email system some years ago whenI 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. "Alittle bit more, actually. Call it 520 miles. But no farther." "Um... Email really doesn't work that way, generally," I said, trying tokeep panic out of my voice. One doesn't display panic when speaking to adepartment chairman, even of a relatively impoverished department likestatistics. "What makes you think you can't send mail more than 500miles?" "It's not what I *think*," the chairman replied testily. "You see, whenwe first noticed this happening, a few days ago--" "You waited a few DAYS?" I interrupted, a tremor tinging my voice. "Andyou 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 youcall earlier?" "Well, we hadn't collected enough data to be sure of what was going onuntil just now." Right. This is the chairman of *statistics*. "Anyway, Iasked one of the geostatisticians to look into it--" "Geostatisticians..." "--yes, and she's produced a map showing the radius within which we cansend email to be slightly more than 500 miles. There are a number ofdestinations within that radius that we can't reach, either, or reachsporadically, but we can never email farther than this radius." "I see," I said, and put my head in my hands. "When did this start? Afew days ago, you said, but did anything change in your systems at thattime?" "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, scarcelybelieving that I was playing along. It wasn't April Fool's Day. I triedto remember if someone owed me a practical joke. I logged into their department's server, and sent a few test mails. Thiswas in the Research Triangle of North Carolina, and a test mail to my ownaccount 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 startedtrying 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 afriend who lived in North Carolina, but whose ISP was in Seattle.Thankfully, it failed. If the problem had had to do with the geography ofthe human recipient and not his mail server, I think I would have brokendown 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 fairlynormal. In fact, it looked familiar. I diffed it against the sendmail.cf in my home directory. It hadn't beenaltered--it was a sendmail.cf I had written. And I was fairly certain Ihadn't enabled the "FAIL_MAIL_OVER_500_MILES" option. At a loss, Itelnetted into the SMTP port. The server happily responded with a SunOSsendmail banner. Wait a minute... a SunOS sendmail banner? At the time, Sun was stillshipping Sendmail 5 with its operating system, even though Sendmail 8 wasfairly mature. Being a good system administrator, I had standardized onSendmail 8. And also being a good system administrator, I had written asendmail.cf that used the nice long self-documenting option and variablenames available in Sendmail 8 rather than the cryptic punctuation-markcodes that had been used in Sendmail 5. The pieces fell into place, all at once, and I again choked on the dregsof my now-cold latte. When the consultant had "patched the server," hehad apparently upgraded the version of SunOS, and in so doing*downgraded* Sendmail. The upgrade helpfully left the sendmail.cfalone, 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 mostof the rules had at that point remained unaltered. But the new longconfiguration options--those it saw as junk, and skipped. And thesendmail binary had no defaults compiled in for most of these, so, findingno 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 theremote SMTP server. Some experimentation established that on thisparticular machine with its typical load, a zero timeout would abort aconnect 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 hittingthe POP and reaching a router on the far side. So time to connect to alightly-loaded remote host on a nearby network would actually largely begoverned by the speed of light distance to the destination rather than byincidental router delays. Feeling slightly giddy, I typed into my shell: $ units1311 units, 63 prefixes You have: 3 millilightsecondsYou want: miles * 558.84719 / 0.0017893979 "500 miles, or a little bit more." Trey Harris Quote Sdílet tento příspěvek Odkaz na příspěvek Sdílet na ostatní stránky
Lelik 0 Nahlásit příspěvěk Odesláno October 31, 2003 Ого, воистину анг.яз. - международный язык, вот так навскидку без перевода сбрасывают большой текст с уверенностью что будет понят,это о чём говорит, о том что можно вот так просто по английски, чему я и рад, а я давал с переводом, всё перстраиваюсь, у меня есть много что сказать на английском, моего то есть, а переводом заниматься не охото. Quote Sdílet tento příspěvek Odkaz na příspěvek Sdílet na ostatní stránky
graycrow 0 Nahlásit příspěvěk Odesláno October 31, 2003 По-началу у меня была мысль перевести этот текст, но потом я подумал что он большой да и аудитория, на которую он рассчитан, в принципе не самая эээ… “английсконепонимающая”. Что касается других веток форума, то я даже не знаю. В общем я — за, но что касается остальных… Может устроить голосование? или Хозяин выразит свою точку зрения? Quote Sdílet tento příspěvek Odkaz na příspěvek Sdílet na ostatní stránky
KOTRPA 0 Nahlásit příspěvěk Odesláno October 31, 2003 Я думаю такое пройдет только в этом разделе форума. Кстати об этой истории я как-то даже и не слыхал раньше. Очень похоже на слово-паразит даже несмотря на уверения рассказчика в том, что это правда. Quote Sdílet tento příspěvek Odkaz na příspěvek Sdílet na ostatní stránky
GDV 10008 Nahlásit příspěvěk Odesláno October 31, 2003 QUOTE (graycrow @ Oct 31 2003, 13:56) Хозяин выразит свою точку зрения? Выразит. Не стоит переводить, данный текст и без перевода будет понятен тем, кому адресован. А другим и перевод маловато скажет. Quote Sdílet tento příspěvek Odkaz na příspěvek Sdílet na ostatní stránky
Lelik 0 Nahlásit příspěvěk Odesláno October 31, 2003 QUOTE (KOTRPA @ Oct 31 2003, 10:56) Я думаю такое пройдет только в этом разделе форума. Но я хоть о чём, но только не о компьютерах. Quote Sdílet tento příspěvek Odkaz na příspěvek Sdílet na ostatní stránky
Lelik 0 Nahlásit příspěvěk Odesláno October 31, 2003 QUOTE (GDV @ Oct 31 2003, 11:05) А другим и перевод маловато скажет. Это точно. "Отгадал все буквы - слово прочитать не смог." (с) Quote Sdílet tento příspěvek Odkaz na příspěvek Sdílet na ostatní stránky
graycrow 0 Nahlásit příspěvěk Odesláno October 31, 2003 хе-хе я тут тесты провожу dove 4% uname -aUnixWare dove 5 7.1.1 i386 x86at SCO UNIX_SVR5dove 5% unitsyou have: 3 millilightsecondscannot recognize lightsecondyou have: $ uname -aFreeBSD gw.xxxxxxxxxx.org 4.9-PRERELEASE FreeBSD 4.9-PRERELEASE #2: Fri Sep 5 15:26:15 CEST 2003 dima@gw.xxxxxxxxxx.org:/usr/src/sys/compile/GRAYCROW i386$ units507 units, 54 prefixesYou have: 3 millilightsecondsunknown unit 'millilightseconds'You have: ^C$ У кого нибудь сантехника есть? Quote Sdílet tento příspěvek Odkaz na příspěvek Sdílet na ostatní stránky
KOTRPA 0 Nahlásit příspěvěk Odesláno October 31, 2003 QUOTE (graycrow @ Oct 31 2003, 13:19) У кого нибудь сантехника есть? $ uname -aLinux xxxxxxxxxxx 2.4.23 ....................blablabla....... GNU/Linux$ units1948 units, 71 prefixes, 28 functions You have: 3 millilightsecondsYou want: miles * 558.84719 / 0.0017893979 сан поищщем. Quote Sdílet tento příspěvek Odkaz na příspěvek Sdílet na ostatní stránky
GDV 10008 Nahlásit příspěvěk Odesláno October 31, 2003 "В моем доме папрашу не выражаться!" Quote Sdílet tento příspěvek Odkaz na příspěvek Sdílet na ostatní stránky
KOTRPA 0 Nahlásit příspěvěk Odesláno October 31, 2003 > uname -aSunOS xxxxxxxxx 5.8 Generic_108528-18 sun4u sparc SUNW,Ultra-80]> units you have: 3 millilightsecondscannot recognize lightsecond Quote Sdílet tento příspěvek Odkaz na příspěvek Sdílet na ostatní stránky
lovermann 8 Nahlásit příspěvěk Odesláno October 31, 2003 Ну, я всё понял, только вот я понятия не имею о принципах работы SunOS сендмейла, тем более, разных версий, поэтому ГДВ был прав, когда сказал, что текст можно и не переводить (я сначал имел другое мнение). Quote Sdílet tento příspěvek Odkaz na příspěvek Sdílet na ostatní stránky
Stm 0 Nahlásit příspěvěk Odesláno November 5, 2003 Я читал в переводе как раз. Но все равно долго смеялся. А понятно будет именно сисадминам и программистам, кто имел дело с юниксовыми операционками.(извините за страшные ругательства, впредь постараюсь воздерживаться) Quote Sdílet tento příspěvek Odkaz na příspěvek Sdílet na ostatní stránky