[ntp:questions] Implementing NTP in a legacy system

andreas.ames at de.transport.bombardier.com andreas.ames at de.transport.bombardier.com
Wed Dec 12 18:12:41 UTC 2012


Hi unruh,

unruh <unruh at invalid.ca> schrieb am 12.12.2012 18:37:33:

> On 2012-12-12, andreas.ames at de.transport.bombardier.com <andreas.
> ames at de.transport.bombardier.com> wrote:
> > Dear all,
> >
> > I'm rather new to NTP so please forgive me, if my question is trivial.
> >
> > I'm maintaining a legacy system with its own proprietary time 
> 
> Why be coy. Why not tell us what that legacy system is. And why you
> would want to keep its own proprietary time sync protocol.

Well I guess I'm shy by nature :-).

I cannot change the synchronisation protocol in the legacy part
because that would mean a lot of changed components including
3rd-party.  That's simply not practical.

> > synchronisation protocols.  Now I want to add a new subsystem which 
> > requires a NTP daemon to be available.  I have added a gateway device 
> 
> Subsystem as in new hardware or as in a program? If the latter then one
> thing to remember is that there is (usually) only one system clock on a
> system, and having two systems try to control that one clock is a
> recipie for total and complete disaster. If that is what you want to do,
> you cannot. ntp is not a way for programs to figure out what the time
> is, it is a way for the system to control the system clock.

Ok, point taken, thanks.  I'll drop the requirement not to touch the
system time of the gateway device.

The new subsystem is a complete Ethernet LAN with numerous devices
attached which use the NTP daemon on the gateway as their time base.
The legacy part is a distributed control system with three different
bus systems (two fieldbusses and one Ethernet LAN) all of which have
subscribers that want to synchronise their time.

> If you would be more forthcoming, people could probably give better
> advice. 

What I'm looking for is an API/other interface in NTPD to attach to a
currently non-supported reference clock (most probably by writing the
needed adapter code).  And this (adapted) NTPD shall run on the
gateway device to feed the ntp clients in the new subsystem. 


TIA,

aa

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