[ntp:questions] Re: NTP4 has 3 different time formats! Namly (32, 64, 128) bits wide

Richard B. Gilbert rgilbert88 at comcast.net
Thu Jul 13 13:41:50 UTC 2006

Danny Mayer wrote:

> Richard B. Gilbert wrote:
>>Danny Mayer wrote:
>>>Richard B. Gilbert wrote:
>>>>See RFC-1305 page 50.  In the description of the packet format the four
<big snip>
> Well VMS always used 64 bits for time. Windows has now added a 64 bit
> version of time_t and introduced 64-bit time functions. I don't think
> that the *BSD's will be far behind. Dunno about Linux or Solaris.

NTP could do worse than to adopt the VMS 64 bit time format.  IIRC it 
was a count of 100 nanosecond "ticks" since some date in (I think) 
November 1857.  The format will represent any date-time from the base 
date through the next thirty thousand years or so.  Of course VMS 
updates the clock by adding 10,000 "ticks" at a time.  There is no 
documented or supported interface that will allow you to set or read the 
clock to greater than centisecond precision.  I've often thought that 
VMS Engineering should support a little greater precision; Solaris can 
keep time to microsecond precision and even, with NTP, keep it 
accurately to that precision!

The current 64 bit NTP timestamp wastes some bits in picosecond 
precision.  I say "wastes" because even today's computers cannot 
exchange time without an uncertainty of two or three microseconds and 
those low order bits are meaningless noise.

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