On 02/01/13 02:57, Dennis Ferguson wrote:
On 27 Dec, 2012, at 15:13 , Magnus Danielson wrote:
On GE, a full-length packet is about 12 us, so a single packets head-of-line
blocking can be anything up to that amount, multiple packets... well, it keeps
adding. Knowing how switches works doesn't
Hi
The problem with your approach is that you can depart from "normal" for very
long periods of time. Consider my home network, running NTP to external
sources. Around 4 in the afternoon all the kids get home and start streaming
video. At 7 I get home and start doing the same thing. We each kee
On 27 Dec, 2012, at 15:13 , Magnus Danielson wrote:
> On GE, a full-length packet is about 12 us, so a single packets head-of-line
> blocking can be anything up to that amount, multiple packets... well, it
> keeps adding. Knowing how switches works doesn't really help as packets
> arrive in a
On Fri, 28 Dec 2012 19:18:06 -0800
Hal Murray wrote:
>
> att...@kinali.ch said:
> > From the data ntp gives me in the networks i manage. I hardly get any
> > jitter number below 1ms, even with unloaded network and unloaded hosts. The
> > 200us comes from the "usual" rtt time measurements on PCs.
att...@kinali.ch said:
> From the data ntp gives me in the networks i manage. I hardly get any
> jitter number below 1ms, even with unloaded network and unloaded hosts. The
> 200us comes from the "usual" rtt time measurements on PCs.
What sort of networks are you talking about? Are you synchron
ecise time and frequency measurement <
> time-nuts@febo.com>
> Sent: Fri, 28 Dec 2012 11:36 AM
> Subject: Re: [time-nuts] clock-block any need ?
>
> Hi
>
> It's still an encapsulated stack that just coughs up the information after
> it's done this and that to
On Fri, 28 Dec 2012 11:54:53 -0800
Dennis Ferguson wrote:
>
> > I'm not sure about this. Knowing about how switches work internally,
> > i'd guess they have "jitter" of something in the range of 1-10us, but
> > i've never done any measurements. Have you any hard numbers?
>
> I've measured it fo
, and it starts
at $15,000. I believe.
Didier
Sent from my Droid Razr 4G LTE wireless tracker.
-Original Message-
From: Bob Camp
To: Discussion of precise time and frequency measurement
Sent: Fri, 28 Dec 2012 11:36 AM
Subject: Re: [time-nuts] clock-block any need ?
Hi
It's sti
On 27 Dec, 2012, at 11:28 , Attila Kinali wrote:
> On Thu, 27 Dec 2012 10:55:12 -0800
> Dennis Ferguson wrote:
>
>> I don't think I buy this. It takes 70 milliseconds for a signal
>> transmitted from a GPS satellite to be received on the ground, but
>> we don't use this fact to argue that sub-
Hi
It's still an encapsulated stack that just coughs up the information after it's
done this and that to it. How long the this and that takes is dependent on how
busy the network is. It's going to watch packets on the net first and push data
to the Arduino second.
I'm beating on a similar par
On Fri, 28 Dec 2012 07:21:26 -0800
Jim Lux wrote:
> OK, so throw out the USB version..
>
> Just thinking out loud here: are these $20 wonders potentially a way to
> get "better" time transfer via Ethernet?
Depends on what your goal is.
> I can see that a PC interface version might not be ver
On 12/28/12 7:56 AM, Bob Camp wrote:
Hi
Everything I've seen on the Adruino are "single chip wonders". They encapsulate
the entire TCP/IP stack on the external chip. That will make getting at anything pretty
tough.
Well, they also do UDP..(at least the Wiznet 5100 does)..
I was wondering i
Hi
Everything I've seen on the Adruino are "single chip wonders". They encapsulate
the entire TCP/IP stack on the external chip. That will make getting at
anything pretty tough.
Bob
On Dec 28, 2012, at 10:21 AM, Jim Lux wrote:
> On 12/27/12 11:48 AM, Attila Kinali wrote:
>> On Thu, 27 Dec 2
On 12/27/12 11:48 AM, Attila Kinali wrote:
On Thu, 27 Dec 2012 11:30:37 -0800
Jim Lux wrote:
So, what about the USB-Ethernet dongles? (I use them a lot at work to
add a second interface for a laptop in test equipment setups, talking to
a Prologix, for instance)
A lot worse! One thing is tha
Björn,
On 12/28/2012 12:31 AM, b...@lysator.liu.se wrote:
Magnus,
Doing ~200 us for a non-trival network with real data on it sound about
right.
What kills many assumptions is that the noise-forms fail most of the
normal assumptions about "noise". It's not zero mean, it does not have a
static
Magnus,
> Doing ~200 us for a non-trival network with real data on it sound about
> right.
>
> What kills many assumptions is that the noise-forms fail most of the
> normal assumptions about "noise". It's not zero mean, it does not have a
> static mean, it does not have a static variance, it is no
On 12/27/2012 08:28 PM, Attila Kinali wrote:
On Thu, 27 Dec 2012 10:55:12 -0800
Dennis Ferguson wrote:
I don't think I buy this. It takes 70 milliseconds for a signal
transmitted from a GPS satellite to be received on the ground, but
we don't use this fact to argue that sub-70 ms timing from
att...@kinali.ch said:
> Here lies the big problem. While with GPS we pretty much know what the time
> is that the signal takes to reach earth, we have no clue with network
> packets in a loaded network.
I agree that if you are running on a busy network you are out of luck.
On the other hand, if
On Thu, 27 Dec 2012 11:30:37 -0800
Jim Lux wrote:
> So, what about the USB-Ethernet dongles? (I use them a lot at work to
> add a second interface for a laptop in test equipment setups, talking to
> a Prologix, for instance)
A lot worse! One thing is that USB has a polled protocol (ie the hos
Actually those "smart" interface and the low cost interface on dongles
use very dumb hardware and depend on software. So they are not as
deterministic as you'd like.The very best network hardware is
purpose built and expensive and does the timing in hardware.
I still think the lowest cos tmem
On 12/27/12 11:17 AM, Chris Albertson wrote:
On Thu, Dec 27, 2012 at 10:55 AM, Dennis Ferguson
wrote:
The reason you can't distribute ns level time over a network to normal
NTP clients is because of the random queing that happens inside the
client's ethernet interfaces. The normal installe
On Thu, 27 Dec 2012 10:55:12 -0800
Dennis Ferguson wrote:
> I don't think I buy this. It takes 70 milliseconds for a signal
> transmitted from a GPS satellite to be received on the ground, but
> we don't use this fact to argue that sub-70 ms timing from GPS is
> not possible. If you have a netw
On Thu, Dec 27, 2012 at 10:55 AM, Dennis Ferguson
wrote:
>
> I don't think I buy this. It takes 70 milliseconds for a signal
> transmitted from a GPS satellite to be received on the ground, but
> we don't use this fact to argue that sub-70 ms timing from GPS is
> not possible.
We don't care how
On 27 Dec, 2012, at 08:05 , Chris Albertson wrote:
>> You do not need to use something like the Clock-Block to build a very good
>> NTP server, but if you want to build the *ultimate* server it is part of the
>> mix.
>
> Yes this is true. The server can be "very good", meaning that if it
> we
> You do not need to use something like the Clock-Block to build a very good
> NTP server, but if you want to build the *ultimate* server it is part of the
> mix.
Yes this is true. The server can be "very good", meaning that if it
were better the clients that it servers could not "know" the
dif
The Clock-Block is a clock generator that is useful if you want to replace the
computer's onboard crystal clock with an external high-stability source. For
example, you can configure it to take a 10 MHz input from a GPSDO and create a
14.318182 MHz output to replace the crystal in a PC that use
hi,
I want to setup a time servere so I saw in many configuration that a clock-block
was used, do I need it too ? what are the benefits ?
thanks,
Dan
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