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1、OntheChronometryandMetrologyofComputerNetworkTimescalesandtheirApplicationtotheNetworkTime1,2,3ProtocolDavidL.MillsElectricalEngineeringDepartmentUniversityofDelawareAbstractThispapersummarizesissuesincomputernetworktimekeepingwithrespecttotheNetworkTimeProtocol,whichisusedtosynchroniz
2、etimeinmanyofthehostsandgatewaysoftheInternet.ItdescribesthemethodsusedtocoordinateanddisseminateinternationaltimeservicesandhowtheyareincorporatedintoNTPtimeservers.ItdiscussesthehazardsonreckoningNTPdateswiththeconventionalcivilcalendarandastandardmethodfornumberingthedays.Finally,th
3、epaperdescribestheNTPtimescale,itsmappingtoconventionalciviltimeanddateanditsinterpretationofleapseconds.Keywords:networkclocksynchronization,standardminationofcomputertimeandfrequencyrelativetotimedistribution,timescalecoordination,leapseconds,internationalstandards,andoncalendarmetro
4、logy,NetworkTimeProtocol.whichisthedeterminationofconventionalciviltimeanddateaccordingtothemoderncalendar.Itdescribesthe1.IntroductionmethodsconventionallyusedtoestablishciviltimeandEachyearbringsexoticnewapplicationsforprecisiondateandthevarioustimescalesnowinuse.Inparticular,timekee
5、ping,suchasmeasuringthedensityoftheuni-itcharacterizestheNetworkTimeProtocol(NTP)times-verse[RAW87]andcalibratingglobalwarming[SCI91].calerelativetotheCoordinatedUniversalTime(UTC)Recentimprovementsintime-transfertechnologyhavetimescale,andestablishesthepreciseinterpretationofdoubledth
6、eprecisionsattainableabouteverysevenUTCleapsecondsinNTP.yearstothecurrentregimeofbetterthanafewnanosec-Inthefollowingdiscussionthetermstime,timescale,ondsovertheglobalrange.Whileinexpensive,ubiqui-oscillator,clock,epoch,timestamp,calendaranddatetoustimetransferusingaglobalcomputernetwo
7、rkareusedinatechnicalsense.Strictlyspeaking,thetimeordinarilycannotapproachsuchprecisions,accuraciesofaneventisanabstractionwhichdeterminestheorder-ofafewtensofmillisecondshavebeendemonstratedforingofeventsinsomegivenframeofreferenceortimes-mostpathsintheInternetoftoday[MIL90a].cale.