[tt-tf] TTM Task Force/TSC clock.

Dear All,

The third thing I promised for this week...

Some years ago, Darryl Veitch at U.Melbourne suggested to use the TSC
register found in modern Pentium chips as a reference clock reference.
The TSC register is related to the internal clock of the chip and very
stable even when the chip is mounted inside a regular PC.  Darryl and
colleagues published a paper on the principle at IMC.

If this works as expected, it will allow for a TTM setup without the need
for a local GPS antenna.  This will obviously make deployment a lot
easier.  The setup will require a stratum 1 NTP server a few hops away
and there will be some loss of accuracy.  All this will have to be
quantified and calibrated.

Over the last years, we have been trying to us this idea in TTM.  Mark
Santcroos worked on this while still at the NCC.  When he left last year,
the system worked but it had to be calibrated.  This was to be done by
the U.Melbourne.  For various reasons, they only started on this in June
this year.

We now have a setup where the user can switch between standard GPS-based
timestamping and TSC-based timestamping.  We still have to add a switch
and some code to the TTM software to do this for TTM.  The idea is to do
measurements with this setup in various circumstances, switching back and
forth between timekeeping models, and compare the results.

First results look good, but a lot of work still has to be done.  The
goal is to have this ready by RIPE53.

Henk

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Henk Uijterwaal                           Email: henk.uijterwaal(at)ripe.net
RIPE Network Coordination Centre          http://www.amsterdamned.org/~henk
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