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Article #237Re: Synchonizing watches
From: pds
Date: Tue, 08 Sep 1992 13:37
Date: Tue, 08 Sep 1992 13:37
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1631 bytes
In article <1992Sep4.174143.13747@hubcap.clemson.edu>, mln@sunkj.larc.nasa.gov (Michael L Nelson) writes: > I must be missing something here, because this looks quite simple. > > -A & B already know this procedure. > > A: says "Bing" to B > B responds with "Bing" to A > > this is ABBA time - the total delay Yup. > A: > 1. says "Bong" at time T say, message arrives at B at T+AB > 2. waits, say N minutes (N > ABBA) > 3. says "Bong" again at time T+N say, message arrives at B at T+N+AB > B already knows what N is, and can then determine > What AB is (Bong2 - Bong1 - N) No - he just receives two messages N minutes apart: (Bong2-Bong1-N) = T+N+AB-(T+AB)-N = 0, not AB > (un)synchronized ;-) Patrick --------------------------------------------------------------------------- Engineers think that theory approximates reality | Mathematicians never Physicists think that reality approximates theory | make the connection --------------------------------------------------------------------------- Patrick Surry, JCMB 2254, Edinburgh, Scotland e||) Edinburgh Parallel EMail: pds@epcc.ed.ac.uk Tel: (031) 650-5960 c||c Computing Centre ---------------------------------------------------------------------------
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Path: arc1-ca.pugleaf.net!sparky!uunet!sun-barr!sh.wide!wnoc-tyo-news!etl.go.jp!gama!lab!nttlab!daemon From: pds@epcc.edinburgh.ac.uk Newsgroups: fj.mail-lists.parallel Subject: Re: Synchonizing watches Message-ID: <315151@nttlab.ntt.JP> Date: 8 Sep 92 13:37:34 GMT Sender: daemon@nttlab.ntt.JP Distribution: fj Lines: 39 Approved: news@nttlab.ntt