Using a "composite clock" time source? - NTP

This is a discussion on Using a "composite clock" time source? - NTP ; My NTP server is run at the local phone company. They already have a GPS fed stratum 2 (?) time source fed via GPS on the roof. The CO guy told me that they have lots of leads off their ...

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  1. Using a "composite clock" time source?

    My NTP server is run at the local phone company. They already have a
    GPS fed stratum 2 (?) time source fed via GPS on the roof. The CO guy
    told me that they have lots of leads off their "composite clock" and
    we could have one if we needed. Apparently this timing source feds all
    their telco gear (OC-X equipment, class 5 switch, etc).

    I asked him what I should google up and he said "composite clock." Is
    there some way to hook up a "composite clock" to the serial port on my
    server? It appears that a composite clock is three wires: tip, ring
    and ground? Any help on if it's possible to use this would be great.


  2. Re: Using a "composite clock" time source?


    >I asked him what I should google up and he said "composite clock." Is
    >there some way to hook up a "composite clock" to the serial port on my
    >server? It appears that a composite clock is three wires: tip, ring
    >and ground? Any help on if it's possible to use this would be great.


    I'm far from a real phone company wizard, but tip and ring are
    phone company terms. If you want to connect them to your system
    you need to go through a modem or equivalent for DS3/DS1/DS0.

    Basically, that level of the phone company is concerned about
    frequency rather than time. If I understand things correctly
    (which may be bogus), you get frequency without any way to connect
    it back to a time-stamp. (which is fine if you are a phone company)

    --
    These are my opinions, not necessarily my employer's. I hate spam.


  3. Re: Using a "composite clock" time source?

    > From: "scott.baker@gmail.com"
    > Date: Mon, 05 Nov 2007 16:34:02 -0800
    > Sender: questions-bounces+oberman=es.net@lists.ntp.org
    >
    >
    > My NTP server is run at the local phone company. They already have a
    > GPS fed stratum 2 (?) time source fed via GPS on the roof. The CO guy
    > told me that they have lots of leads off their "composite clock" and
    > we could have one if we needed. Apparently this timing source feds all
    > their telco gear (OC-X equipment, class 5 switch, etc).
    >
    > I asked him what I should google up and he said "composite clock." Is
    > there some way to hook up a "composite clock" to the serial port on my
    > server? It appears that a composite clock is three wires: tip, ring
    > and ground? Any help on if it's possible to use this would be great.


    This looks like it's probably a T1 connection to provide sync, not time,
    to telco equipment.

    Telcos think of "clock" as a highly synchronized T1 clocking signal to
    keep all of their equipment in sync. It provides very accurate clocking
    to ADMs, routers, switches and the like, but does not provide actual
    time. The GPS is used to assure that the clocking is consistent around
    the world.

    Make sure that they are providing time code, not just a clock signal. IF
    they are, it is most likely IRIG-B timecode and there are several ntpd
    supported reference clocks that support IRIG-B.

    We went through this last year when we moved our colos to a new provider
    and they told us that they could provide a a GPS based clock. They
    handed us a T1 and we had to explain that some of use actually want to
    know what time it is, not just how fast time is passing.
    --
    R. Kevin Oberman, Network Engineer
    Energy Sciences Network (ESnet)
    Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
    E-mail: oberman@es.net Phone: +1 510 486-8634
    Key fingerprint:059B 2DDF 031C 9BA3 14A4 EADA 927D EBB3 987B 3751

  4. Re: Using a "composite clock" time source?

    Kevin Oberman wrote:
    >> From: "scott.baker@gmail.com"

    > ...
    > Make sure that they are providing time code, not just a clock signal. IF
    > they are, it is most likely IRIG-B timecode and there are several ntpd
    > supported reference clocks that support IRIG-B.


    Spectracom makes a PCI board that reads a variety of timecodes, and they
    even have support for Linux:

    http://www.spectracomcorp.com/Home/P...6/Default.aspx

    Plus, of course, their 9200 and 9300 series "Network Time Servers" have
    an option to take IRIG input.

    All these inputs are normally fed on coax cable with BNC connectors.

    Hope this helps,

    /ji

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