I've been adjusting tcp parameters for a week, capturing packets, and
laboriously looking through them. By increasing the tcp memory parameters
(which are by default quite low for a linux system) and changing from reno to
cubic for congestion control, I've gotten it to "only" take 26 to 51 seconds,
vs 4 to 10 minutes, to retransmit a lost segment. If this is not just because
I screwed something up (possible!), or a bizarre firewall issue, but a feature
of the kernel's tcp stack, it will play havoc with you trying to synchronize
data packets if you have any loss.
Jonathan
--- In "" <> wrote:
>
> On 11/15/2012 07:08 PM, ocean_research_jk wrote:
> >
> > I used chrony, which was small and easy to install.
> >
> Hi All,
>
> I have not reported back to the group because we are still doing a bunch
> of testing. I think we have the synchrony thing mostly solved but are
> still working on the tunnel. We are using vtun and now trying out
> openvpn. The 75XX has real troubles with the network, we have forced the
> 75xx to 10 (not 10/100) and still have real troubles with some of the cards.
>
> When we get thing working well I will report back.
>
> Angel
>
>
>
>
> >
> > --- In <ts-7000%40yahoogroups.com>,
> > Joseph Bouchard <jbouchard@> wrote:
> > >
> > > Debian's ntpdate package is simple and can probably do what you want. I
> > > haven't tried to use it to that degree of accuracy, but I suspect if
> > you
> > > set the sync time fairly tight (like maybe every 5 minutes) the drift
> > > over that period will be a few milliseconds. I would try it, if it
> > > doesn't work, then look for a more complex solution.
> > >
> > > On 10/24/2012 07:23 PM, Walter Marvin wrote:
> > > >
> > > >
> > > > Unfortunately, this is not a valid test, which is typical of
> > > > Technologic. First of all it is anedotal, and no real measurement is
> > > > made. Second it is probably not run long enough to make a statically
> > > > significant conclusion (although they don't say how long their "burn
> > > > in" runs) Third it is probably run with a simplistic program which
> > are
> > > > all the same, and presents no load or variation on the system.
> > > >
> > > > you have been warned
> > > >
> > > > Walter
> > > >
> > > >
> > > > ----------------------------------------------------------
> > > > *From:* Angel <angel@>
> > > > *To:* <ts-7000%40yahoogroups.com>
> > > > *Sent:* Wednesday, October 24, 2012 5:37 PM
> > > > *Subject:* Re: [ts-7000] syncing time on many TS-7550
> > > >
> > > > Hi All,
> > > >
> > > > Just as an update. I got this from Grant at TS.
> > > >
> > > > When TS-7550s are tested with the TS-752, we actually run a stress
> > test
> > > > that proves out the validity of a software solution. 20 or more units
> > > > are placed on a burn-in rack and they automatically run a burn-in/test
> > > > script. They synchronize their system time from our local NTP server,
> > > > and then they begin toggling relays and LEDs at 1Hz. The goal of this
> > > > is just to test the relays, but the ear and eye can tell that they are
> > > > reasonably synchronized and all the relays click as one. The
> > timing was
> > > > implemented with the attached C program and a shell wrapper that
> > uses it
> > > > to wait for the right time to toggle things using ts7500ctl.
> > > >
> > > > We are coding some stuff now and will have some results in a few days,
> > > > we need to butcher some harware. ntpd displines the TS clock to just a
> > > > few milliseconds and I suspect that it what I am going to do will
> > work.
> > > > If anyone is interested in the code snippet that Grant sent just ask.
> > > >
> > > > regards,
> > > >
> > > > Angel
> > > >
> > > > On 10/24/2012 04:30 PM, Ken Lu wrote:
> > > > >
> > > > > I did on TS-7400(connect to laptop by Ethernet), modified a telnet
> > > > > program, to synchronize PC's time, which comes from GPS connected to
> > > > > PC. But found that TS-Linux's date command can only set to the
> > > > > minute, so need to wait within a minute, depends on start
> > setting time.
> > > > >
> > > > > --- On *Wed, 10/24/12, Walter Marvin /<walter.marvin@
> > > > <walter.marvin%40ymail.com>>/* wrote:
> > > > >
> > > > >
> > > > > From: Walter Marvin <walter.marvin@
> > > > <walter.marvin%40ymail.com>>
> > > > > Subject: Re: [ts-7000] syncing time on many TS-7550
> > > > > To: " <ts-7000%40yahoogroups.com>
> > <ts-7000%40yahoogroups.com>"
> > > > < <ts-7000%40yahoogroups.com>
> > <ts-7000%40yahoogroups.com>>
> > > > > Received: Wednesday, October 24, 2012, 10:36 AM
> > > > >
> > > > > You could make a real time clock driver and use the hardware's
> > > > > alarm feature. this may mean using a different clock chip .
> > > > > Fortunately there are a number of IIC clock chips that can do this.
> > > > >
> > > > >
> > > > > ----------------------------------------------------------
> > > > > *From:* Angel <angel@ <angel%40tierrasaltas.net>>
> > > > > *To:* <ts-7000%40yahoogroups.com>
> > <ts-7000%40yahoogroups.com>
> > > > > *Sent:* Wednesday, October 24, 2012 9:30 AM
> > > > > *Subject:* [ts-7000] syncing time on many TS-7550
> > > > >
> > > > > Hi All,
> > > > >
> > > > > I have an application where I need to sync many TS-7550 in the
> > > > > field to
> > > > > within one tenth of a second of each other. I know I could do this
> > > > > with
> > > > > a GPS and a PPS on each one but the cost and trouble to place the
> > > > > antenna makes that a non-solution.
> > > > >
> > > > > We have a hardware one pulse per second on the daughter card that is
> > > > > deployed with system so we can generate one second data packages and
> > > > > send them over TCP/IP. All the 7550 have a RTC and all have ntpd
> > > > > running so I can discipline the hardware clocks to better than the
> > > > > 1/10th second requirement.
> > > > >
> > > > > What I am at a loss on how to do is to sync the one second data
> > > > > packets
> > > > > to the change of second of the RTC or any other stable time source.
> > > > >
> > > > > TS says that the FPGA can be asked to make a one pulse per
> > second but
> > > > > that syncing the PPS pulse to the RTC is not sure.
> > > > >
> > > > > If anyone has an idea on how to do this I would love to hear
> > from you.
> > > > >
> > > > > Regards,
> > > > >
> > > > > Angel
> > > > >
> > > > >
> > > > >
> > > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > >
> >
> >
>
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