[ntp:questions] What level of timesynch error is typical on WinXP?
David J Taylor
david-taylor at blueyonder.co.uk.invalid
Sat Oct 23 08:09:40 UTC 2010
"Kevin Oberman" <oberman at es.net> wrote in message
news:20101022203504.B5BA51CC3E at ptavv.es.net...
>> From: "David J Taylor" <david-taylor at blueyonder.co.uk.invalid>
>> Date: Fri, 22 Oct 2010 20:43:01 +0100
>> Sender: questions-bounces+oberman=es.net at lists.ntp.org
>> "Evandro Menezes" <evandro at mailinator.com> wrote in message
>> news:f13f950a-3168-4a11-ba09-f4d225e7b6b1 at t13g2000yqm.googlegroups.com...
>> > On Oct 22, 10:23 am, "David J Taylor" <david-
>> > tay... at blueyonder.co.uk.invalid> wrote:
>> >> That could explain why I see higher NTP jitter on a Windows system
>> >> running
>> >> a USB network source (digital video data stream) than receiving a
>> >> similar
>> >> data stream on a PCI card under either Windows XP or Windows-7.
>> > Possibly, but USB, as a polled, token-ring like protocol, will always
>> > add jitters in this case.
>> Thanks. I don't understand enough about USB - do you have good
> For a good into, read the Wikipedia article:
> R. Kevin Oberman, Network Engineer
Thanks fir that pointer, Kevin. It's one I've used before.
I had mis-understood your comment to mean that data transfers on USB were
polled, and not interrupt driven, however I am not sure whether that was
what you meant to imply.
With the particular PC in question, the issue appears to be that with the
high-bandwidth (peaks of 20-25Mb/s, average 10Mb/s) USB device running and
it support software operating, the NTP software shows much higher offset
values than are typical for a LAN-synched Windows system. It may be that
the LAN packets are getting delayed by the DVB (digital video broadcast,
actually data) stream.
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