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Re: clock synchronization over IP

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On Fri, 21 Sep 2018 22:35:40 +0100, Chris <xxx.syseng.yyy@gfsys.co.uk>
wrote:

>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.

But the cable length can be up to 100m for twisted pair, 200m for thin
cable, and 500m for thick cable.  And up to 4 repeaters (5 cables) are
permitted between any pair of stations, provided the total CSMA/CD
collision sense time does not exceed the maximum allowed (which varies
by transmission speed).

Remember also that for twisted pair, switches establish new collision
domains for each switched port, but repeating hubs and L2 bridges do
not.  Even for twisted pair, you *still* can have up to 4 repeaters
between the central switch and any station.


And yes, there still are uses for non-switched repeater hubs.

George

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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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