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

Richard B. Gilbert rgilbert88 at comcast.net
Fri Jul 14 12:18:30 UTC 2006

Danny Mayer wrote:

> Richard B. Gilbert wrote:
>>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 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.
> That's for today. In 10 years that may very well not be true.

The limitation, I believe, is in the round trip delay.  My Sun Ultra 
10s, separated by a Cisco 1548M switch and a few feet of cable, show 
delays of the order of 4 microseconds at 100mb full duplex.  Gigabit 
Ethernet might shave a little off of that but not a whole lot.

If you are getting time over the internet you don't, and won't, have a 
clue what the nanoseconds should be.  Even over a fast LAN, the delay is 
a killer.

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