[ntp:questions] Implementing NTP in a legacy system

Terje Mathisen "terje.mathisen at tmsw.no" at ntp.org
Thu Dec 13 11:24:58 UTC 2012

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
> synchronisation protocols.  Now I want to add a new subsystem which
> requires a NTP daemon to be available.  I have added a gateway device
> which will be used to run an NTP daemon to provide NTP based time
> synchronisation to the newly added subsystem.

Andreas, the most common method is to have one machine which has its 
system clock synchronized by the legacy system, then use ntp to 
distribute this (local clock) time to the other ntp-using systems.

You can do this with the local clock driver, which basically promises 
that "the local time is always correct, you can safely send it out to 
clients", but if you do so please keep the stratum level as high as you 
can, i.e. in the 12-14 range depending upon how many levels of clients 
you will have.

It should work quite well to keep the new systems synchronized with the 
legacy network!


> My questions are:
> 1. I want to use my legacy time synchronisation protocol/mechanism as the
> reference clock of the NTP daemon on the gateway device.  In my limited
> understanding this means that the NTP daemon on the gateway would become a
> stratum 1 server, right? Are there ways to "easily" add new reference
> clocks in popular implementations like ntpd preferably without setting the
> system time on the gateway?
> 2. Is it possible to prevent ntpd on the gateway from setting the system
> time on the gateway?
> Thanks in advance,
> aa
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- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"

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