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Date:      Thu, 03 Jul 1997 09:27:09 -0400
From:      "Stephen F. Combs [Network Services]" <steve.combs@gemis.ge.com>
To:        Wes Peters <softweyr@xmission.com>
Cc:        "Andrew K. Adams" <akadams@wraith.psc.edu>, questions@FreeBSD.ORG
Subject:   Re: TrueTime GPS...
Message-ID:  <33BBA8AC.3F1B76CE@gemis.ge.com>
References:  <199707020030.UAA05757@wraith.psc.edu> <199707030716.BAA04660@obie.softweyr.ml.org>

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I've been evaluating a "TrueTime" Model NTS-100 for the last couple of
weeks (GPS Receiver with a network interface so you don't have to have
any specific S/W, just point your ntp S/W at it as a "server") and I
must say I haven't been tooooo terribly impressed.  It locks on to the
satellite(s) just fine (after I FINALLY found a good location for the
antenna!) but it's network response Sucks!  I've put it's AUI i/f on a
Cisco Catalyst switched-hub (it's own dedicated connection) wich is
directly attached to our FDDI campus ring.  10 pings of 100bytes result
in response times of 39ms to 256ms with AT LEAST 2 packets dropped!  I
attach a FBSD PC to the same port (using the SAME Twisted-Pair-to-AUI
tranceiver AND the same CAT-5 Cable) and get sub-2ms response times for
1000 packets of 100bytes with NO dropped packets!!  I have three
"stratum-5" ntp servers which sync to three machines in our corporate
FireWall office which work just fine.  The NTS-100 is currently driving
3 other NTP servers (it's a 'stratum-1' server, so the three machines I
have sync'ing to it are at 'stratum-2') which CONSTANTLY loose
syncronization with it!  For $4300 I'm NOT impressed!!!!
 I'm using a combination of FreeBSD and Sun Sparc systems as my NTP
servers for BOTH set-ups!  Running 'xntp3-5.90' on ALL systems.



Wes Peters wrote:

> Andrew K. Adams writes:
>  > I would like to attach a GPS to a FreeBSD box (for network
>  > synchronization) and would be very appreciative of any information
>  > anyone can offer.  I am currently looking at a model manufactured
> by
>  > TrueTime (XL-DC 600), since it (and my PC) is rack-mountable and it
>
>  > provides a serial port for communication -- I am unsure if the
> latter
>  > is useful with FreeBSD.
>
> Chances are pretty good it is a NMEA-0183 port, which uses RS-422
> signalling levels.  You should be able to plug it into a PC serial
> port,
> unless you have really bad hardware.
>
> You'll have to contact the manufacturer for information on the
> protocol
> they use.  There is *some* standardization in this area, but I
> wouldn't
> count on your software working with it.  Most manufacturers are pretty
>
> good about releasing protocol specs, though I've never heard of
> TrueTime.
>
> (I'm known as Barnacle Wes in another, *much* slower dimension.  ;^)
>
> --
>           "Where am I, and what am I doing in this handbasket?"
>
> Wes Peters
> Softweyr LLC
> http://www.xmission.com/~softweyr
> softweyr@xmission.com



--
----
Stephen F. Combs                 Internet:      CombsSF@Salem.GE.COM
GE Industrial Systems            Voice:         540.387.8828
Network Services                 Home:          CombsSF-Home@Salem.GE.COM
1501 Roanoke Blvd                FAX:           540.387.7106
Salem, VA  24153                 LapTop:        CombsSF-Mobile@Salem.GE.COM






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