On 02/12/15 21:00, Joachim Fabini wrote:
> NTP algorithms rely on symmetric connection delay but DSL delay is
> commonly highly asymmetrical. In measurements for my setup (VDSL;
> 8Mbit/s DL, 768kbit/s UL), the VDSL one-way delay at low packet payload
> averages 12ms for DL and 6ms for UL. Very
Thanks for all the info folks. I've been tracking the offsets to several
GPS-based stratum-1 servers at different places around the US and they
all show the same offset. This seems like the most likely explanation of
what's going on.
I see that others have considered mods to allow offsets for
I could use some advice about verifying the performance of a home-built
stratum-1 NTP server.
The server is based on an HP55300A reference clock. The PPS signal and
time-of-day serial port are connected to an Arduino Mega with an
Ethernet shield and some miscellaneous interface circuitry.
NTP algorithms rely on symmetric connection delay but DSL delay is
commonly highly asymmetrical. In measurements for my setup (VDSL;
8Mbit/s DL, 768kbit/s UL), the VDSL one-way delay at low packet payload
averages 12ms for DL and 6ms for UL. Very surprising if you consider the
DL/UL capacity ratio
Whoops, sent the first reply just to Joachim...here it is for the list:
Joachim,
Thanks very much. Your paper "M2M Communication Delay Challenges" is a good
read. I'm afraid I don't have the resources available to make some of those
one-way delay measurements.
One idea did occur to me however
