[ntp:questions] frequency adjusting only

Bill Unruh unruh at physics.ubc.ca
Wed Apr 30 17:19:33 UTC 2008

m.louvel at gmail.com (maxime louvel) writes:

>On Tue, Apr 29, 2008 at 6:27 PM, Unruh <unruh-spam at physics.ubc.ca> wrote:

>> m.louvel at gmail.com (maxime louvel) writes:
>> >Hi,
>> >I have know run a lot of tests.
>> >Just to let you know what I've got so far.
>> >I have tried NTP, and NTP + PTP (Precision Time Protocol).
>> >I haven't tried Chrony nor TSClock.
>> >I have used the software only implementation of PTP (ptpd).
>> >With NTP only I have got an accuracy around 1ms,

Actually, I have no idea what the difference is between the "software
implimentation" of PTP and standard NTP is. The advantage of PTP is the
HARDWARE timestamping of the packets as they come into the ethernet card
(special purpose ethernet cards with clocks on board) and possibly PTP
aware switches which race through the PTP packets without delay.
 Software only means
that PTP uses exactly the same kernel routines, etc. to read the computer
clock as does ntp I assume. I cannot see how it can be better unless there are some
severe bugs in NTP. 
What version of NTP are you running?

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