From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 107f24,582dff0b3f065a52 X-Google-Attributes: gid107f24,public X-Google-Thread: 103376,bc1361a952ec75ca X-Google-Attributes: gid103376,public X-Google-Thread: 109fba,582dff0b3f065a52 X-Google-Attributes: gid109fba,public X-Google-Thread: 1014db,582dff0b3f065a52 X-Google-Attributes: gid1014db,public X-Google-ArrivalTime: 2001-08-23 10:01:08 PST Path: archiver1.google.com!newsfeed.google.com!sn-xit-02!supernews.com!news.tele.dk!small.news.tele.dk!195.64.68.27!newsgate.cistron.nl!newscore.univie.ac.at!193.154.160.102.MISMATCH!newsfeed.Austria.EU.net!newsfeed.kpnqwest.at!newsfeed.wu-wien.ac.at!not-for-mail From: Markus Mottl Newsgroups: comp.lang.ada,comp.lang.c,comp.lang.c++,comp.lang.functional Subject: Re: How Ada could have prevented the Red Code distributed denial of Date: Thu, 23 Aug 2001 16:52:01 +0000 (UTC) Organization: University of Economics and Business Administration, Vienna, Austria Message-ID: <9m3cbh$dvu$3@bird.wu-wien.ac.at> References: <3B834E5D.B0D26AB1@adaworks.com> <9lvsic$bet9s$1@ID-9852.news.dfncis.de> <0sDnZRVkz5qL@eisner.encompasserve.org> <3b83847d.1117251944@news.worldonline.nl> <3B83F498.E0F6C582@timesys.com> <7aTg7.10919$2u.78544@www.newsranger.com> <3B842DEA.E01CA1BE@timesys.com> <5M7h7.11864$2u.82854@www.newsranger.com> <3B85294F.BB780B7F@timesys.com> NNTP-Posting-Host: miss.wu-wien.ac.at X-Trace: bird.wu-wien.ac.at 998585521 14334 137.208.107.17 (23 Aug 2001 16:52:01 GMT) X-Complaints-To: news-admin@wu-wien.ac.at NNTP-Posting-Date: Thu, 23 Aug 2001 16:52:01 +0000 (UTC) User-Agent: tin/pre-1.4-981225 ("Volcane") (UNIX) (OSF1/V4.0 (alpha)) Xref: archiver1.google.com comp.lang.ada:12340 comp.lang.c:76471 comp.lang.c++:85192 comp.lang.functional:7656 Date: 2001-08-23T16:52:01+00:00 List-Id: In comp.lang.functional Adam Fineman wrote: > Sounds like a horribly bad idea to me. I don't have any particular > complaints about HP/UX as a general-purpose operating system, but it > is _not_ a real time OS and should not be used to run the engines of > a warship. A real time OS makes guarantees about the maximum time it requires to handle certain operations. This does not mean that a general-purpose (non-real-time) OS is useless for real time tasks: it's all a matter of latencies, probabilities and costs. Given the probability distribution of the time the OS requires to handle some critical request, you can very well compute how probable it is that it will not be able to do so in time: just integrate the area below the probability density function to the right of the maximum allowed latency. Then multiply this probability with the costs of e.g. having some warship dead in the water. Add these costs to the price of buying an off-the-shelve general-purpose OS and compare the result to the price of a real time OS for this specific purpose. Voila, your decision criterion for when to buy what kind of OS. Of course, the probability density function and the costs of losing a warship may be difficult to estimate, but I hope the Navy employs competent managers + technical staff for that purpose. Anyway, I don't know anything about the requirements of warship engines so maybe our current general-purpose OSes are not good enough... Regards, Markus Mottl -- Markus Mottl, mottl@miss.wu-wien.ac.at, http://miss.wu-wien.ac.at/~mottl