Re: clock synchronization over IP

From	Chris <xxx.syseng.yyy@gfsys.co.uk>
Newsgroups	comp.arch.embedded
Subject	Re: clock synchronization over IP
Date	2018-09-21 22:35 +0100
Organization	Aioe.org NNTP Server
Message-ID	<po3o7a$1453$1@gioia.aioe.org> (permalink)
References	<d5b24da2-d75b-4557-b4c1-53d587fb87a6@googlegroups.com> <po2tii$1lgu$1@gioia.aioe.org> <fomaqd9uai7u7glmt9tvikd0evf6vch3qk@4ax.com>

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On 09/21/18 22:15, George Neuner wrote:

> Moreover, simply broadcasting the time from a master won't work[*] ...
> in order to synchronize the clocks youu need to know for each node (to
> a good approximation) the time it takes for the network to deliver the
> time packet.
>
> [*] except in a dedicated setup like a DGPS timing network.  The
> problem with such setups is that all the connections from the master
> to the slaves need to be exactly the same length (bit delay). That is
> very hard to achieve in most installations.
>
> George

There is cable delay, but that's in the order a few nS per foot at most,
where the requirement here is in mS, so that can probably be ignored.
As for the switch or hub delay, that could be modelled or even subject
to testing to find suitable products.

Ideally, I would use gps to sync, as it has all the outputs required to
within a few nS over a wide area, but you need a clear view of the sky
to make that work.

Still think it would be worth looking at broadcast methods, as it could
be made low cost at client and server ends, could be run on modest h/w
without use of an OS, even without a full tcp/ip stack and is probably
good enough for the application...

Chris

Thread

clock  synchronization over IP gp.kiwi@gmail.com - 2018-08-24 17:54 -0700
  Re: clock  synchronization over IP Paul Rubin <no.email@nospam.invalid> - 2018-08-24 18:28 -0700
  Re: clock  synchronization over IP wzab01@gmail.com - 2018-09-15 09:00 -0700
    Re: clock  synchronization over IP gp.kiwi@gmail.com - 2018-09-15 15:08 -0700
      Re: clock  synchronization over IP George Neuner <gneuner2@comcast.net> - 2018-09-16 08:49 -0400
        Re: clock  synchronization over IP gp.kiwi@gmail.com - 2018-09-17 01:45 -0700
          Re: clock  synchronization over IP George Neuner <gneuner2@comcast.net> - 2018-09-17 11:30 -0400
            Re: clock  synchronization over IP gp.kiwi@gmail.com - 2018-09-17 15:04 -0700
              Re: clock  synchronization over IP George Neuner <gneuner2@comcast.net> - 2018-09-17 22:10 -0400
                Re: clock  synchronization over IP graeme.prentice@gmail.com - 2018-09-18 04:23 -0700
                Re: clock  synchronization over IP Andrew Smallshaw <andrews@sdf.org> - 2018-09-18 13:19 +0000
                Re: clock  synchronization over IP Mikko OH2HVJ <mikko.syrjalahti@nospam.fi> - 2018-09-19 18:56 +0300
                Re: clock  synchronization over IP upsidedown@downunder.com - 2018-09-22 11:51 +0300
          Re: clock synchronization over IP Clifford Heath <no.spam@please.net> - 2018-09-18 21:10 +1000
  Re: clock  synchronization over IP Chris <xxx.syseng.yyy@gfsys.co.uk> - 2018-09-21 15:00 +0100
    Re: clock  synchronization over IP Dimiter_Popoff <dp@tgi-sci.com> - 2018-09-21 17:12 +0300
      Re: clock  synchronization over IP Robert Wessel <robertwessel2@yahoo.com> - 2018-09-21 09:58 -0500
        Re: clock  synchronization over IP Chris <xxx.syseng.yyy@gfsys.co.uk> - 2018-09-21 16:26 +0100
      Re: clock  synchronization over IP Chris <xxx.syseng.yyy@gfsys.co.uk> - 2018-09-21 16:02 +0100
    Re: clock  synchronization over IP George Neuner <gneuner2@comcast.net> - 2018-09-21 17:15 -0400
      Re: clock  synchronization over IP Chris <xxx.syseng.yyy@gfsys.co.uk> - 2018-09-21 22:35 +0100
        Re: clock  synchronization over IP "gp.kiwi@gmail.com" <graeme.prentice@gmail.com> - 2018-09-21 15:16 -0700
          Re: clock  synchronization over IP Chris <xxx.syseng.yyy@gfsys.co.uk> - 2018-09-22 00:11 +0100
            Re: clock  synchronization over IP "gp.kiwi" <graeme.prentice@gmail.com> - 2018-09-21 16:35 -0700
              Re: clock  synchronization over IP Chris <xxx.syseng.yyy@gfsys.co.uk> - 2018-09-22 14:19 +0100
              Re: clock  synchronization over IP gnuarm.deletethisbit@gmail.com - 2018-09-22 07:22 -0700
            Re: clock  synchronization over IP graeme.prentice@gmail.com - 2018-09-21 19:40 -0700
        Re: clock  synchronization over IP George Neuner <gneuner2@comcast.net> - 2018-09-21 22:17 -0400
          Re: clock  synchronization over IP Chris <xxx.syseng.yyy@gfsys.co.uk> - 2018-09-22 13:58 +0100
          Re: clock synchronization over IP Brett <ggtgp@yahoo.com> - 2018-09-22 18:50 +0000
    Re: clock  synchronization over IP upsidedown@downunder.com - 2018-09-22 11:56 +0300
      Re: clock  synchronization over IP gnuarm.deletethisbit@gmail.com - 2018-09-22 07:31 -0700
        Re: clock  synchronization over IP upsidedown@downunder.com - 2018-09-22 20:02 +0300
          Re: clock  synchronization over IP gnuarm.deletethisbit@gmail.com - 2018-09-22 14:40 -0700
    Re: clock  synchronization over IP gnuarm.deletethisbit@gmail.com - 2018-09-22 07:06 -0700
    Re: clock  synchronization over IP Mikko OH2HVJ <mikko.syrjalahti@nospam.fi> - 2018-09-22 20:16 +0300
      Re: clock  synchronization over IP Chris <xxx.syseng.yyy@gfsys.co.uk> - 2018-09-22 22:22 +0100

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