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List: beowulf
Subject: Re: [Beowulf] Broadcast - not for HPC - or is it?
From: "Lux, Jim (337C)" <james.p.lux () jpl ! nasa ! gov>
Date: 2010-10-08 21:07:37
Message-ID: C8D4D629.126AE%James.P.Lux () jpl ! nasa ! gov
[Download RAW message or body]
PTP (IEEE 1588) needs custom interface hardware, though. The Ethernet inte=
rface has added hardware to time stamp when the packet is sent/received, an=
d that's what the software uses to do the precision measurements.
I suppose one could (try to) use PTP over a wireless link. That would take=
an even more exotic wireless interface that had the PTP measurement hardwa=
re built into the interface. I don't know that anyone is actually making s=
uch hardware. There are some papers that turn up in a search, but that's a=
bout it.
I've tried to do something similar, using PC-ethernet-wireless AP :over the=
air: wireless AP-ethernet-PC, about 5 years ago, and it wasn't particularl=
y great. But there, I'm pretty sure the limiting issue was that there wasn=
't any deterministic timing between the ethernet wired interface and the 80=
2.11a wireless interface (that is, the boxes I was using were really wirele=
ss bridges and had internal storage)
On 10/8/10 1:23 PM, "David N. Lombard" <dnlombar@ichips.intel.com> wrote:
On Fri, Oct 08, 2010 at 05:40:28AM -0700, Matt Hurd wrote:
>
> Know some guys here in Australia that are doing extremely accurate
> timing with wireless, not for timing's sake but to measure movement in
> dam walls and other infrastructure. Kind of like a localised GPS.
> They have some very neat and accurate stuff.
>
> Had a play with some radio foo and managed to get about 880ns + air
> time on bit to bit from tx to rx but haven't quite figured out how to
> get super low latency yet. I think there may be a product in there
> for wireless PPS dissemination for accurate timing to a cluster like
> the guys do with the dam walls but I'm not sure if people really need
> much more than what ptp can already do.
Yes, PTP could enable fairly tight time sync across a cluster, if it
were used.
--
David N. Lombard, Intel, Irvine, CA
I do not speak for Intel Corporation; all comments are strictly my own.
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Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing
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<TITLE>Re: [Beowulf] Broadcast - not for HPC - or is it?</TITLE>
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<FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'>PTP \
(IEEE 1588) needs custom interface hardware, though. The Ethernet interface has \
added hardware to time stamp when the packet is sent/received, and that’s what \
the software uses to do the precision measurements.<BR> <BR>
I suppose one could (try to) use PTP over a wireless link. That would take an \
even more exotic wireless interface that had the PTP measurement hardware built into \
the interface. I don’t know that anyone is actually making such hardware. \
There are some papers that turn up in a search, but that’s about it.<BR> \
<BR> I’ve tried to do something similar, using PC-ethernet-wireless AP :over \
the air: wireless AP-ethernet-PC, about 5 years ago, and it wasn’t particularly \
great. But there, I’m pretty sure the limiting issue was that there \
wasn’t any deterministic timing between the ethernet wired interface and the \
802.11a wireless interface (that is, the boxes I was using were really wireless \
bridges and had internal storage)<BR> <BR>
<BR>
On 10/8/10 1:23 PM, "David N. Lombard" <<a \
href="dnlombar@ichips.intel.com">dnlombar@ichips.intel.com</a>> wrote:<BR> <BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN \
STYLE='font-size:11pt'>On Fri, Oct 08, 2010 at 05:40:28AM -0700, Matt Hurd wrote:<BR> \
><BR> > Know some guys here in Australia that are doing extremely accurate<BR>
> timing with wireless, not for timing's sake but to measure movement in<BR>
> dam walls and other infrastructure. Kind of like a localised GPS.<BR>
> They have some very neat and accurate stuff.<BR>
><BR>
> Had a play with some radio foo and managed to get about 880ns + air<BR>
> time on bit to bit from tx to rx but haven't quite figured out how to<BR>
> get super low latency yet. I think there may be a product in there<BR>
> for wireless PPS dissemination for accurate timing to a cluster like<BR>
> the guys do with the dam walls but I'm not sure if people really need<BR>
> much more than what ptp can already do.<BR>
<BR>
Yes, PTP could enable fairly tight time sync across a cluster, if it<BR>
were used.<BR>
<BR>
--<BR>
David N. Lombard, Intel, Irvine, CA<BR>
I do not speak for Intel Corporation; all comments are strictly my own.<BR>
_______________________________________________<BR>
Beowulf mailing list, <a href="Beowulf@beowulf.org">Beowulf@beowulf.org</a> sponsored \
by Penguin Computing<BR> To change your subscription (digest mode or unsubscribe) \
visit <a href="http://www.beowulf.org/mailman/listinfo/beowulf">http://www.beowulf.org/mailman/listinfo/beowulf</a><BR>
<BR>
</SPAN></FONT></BLOCKQUOTE>
</BODY>
</HTML>
_______________________________________________
Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing
To change your subscription (digest mode or unsubscribe) visit \
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