[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.
More information about the questions
mailing list