When I joined DEC in 1985, they were the world leader in networking. Using their VMS operating system, I could type a simple copy command to a computer in California, specifying a file and machine name, to copy a file from a computer in Massachusetts. Even today, I can’t copy a file from Massachusetts to California nearly as easily with Unix or Windows. <\/p>\n
The people responsible for DEC’s network systems were the Network and Communications group (NAC). Around 1987, NAC asked for my help in designing a network time service. I decided that there were two somewhat conflicting requirements for a time service: delivering the correct time, and keeping the clocks on different computers closely synchronized. This paper describes the algorithms I devised for doing both. <\/p>\n
I withdrew the paper because Tim Mann observed that the properties I proved about the algorithms were weaker than the ones needed to make them interesting. The major problem is that the algorithms were designed to guarantee both a bound epsilon on the synchronization of each clock with a source of correct time and an independent bound delta on the synchronization between any two clocks that could be made much smaller than epsilon. Mann observed that the bound I proved on delta was not the strong one independent of epsilon that I had intended to prove. We believe that the algorithms do satisfy the necessary stronger properties, and Mann and I began rewriting the paper with the stronger results. But that paper is still only partly written and is unlikely ever to see the light of day. <\/p>\n","protected":false},"excerpt":{"rendered":"
When I joined DEC in 1985, they were the world leader in networking. Using their VMS operating system, I could type a simple copy command to a computer in California, specifying a file and machine name, to copy a file from a computer in Massachusetts. 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