[ntp:questions] LAN synch question

Richard B. Gilbert rgilbert88 at comcast.net
Fri Sep 12 00:03:28 UTC 2008

rochertov at gmail.com wrote:
> Hello,
>    I am conducting research with TDMA on a wired emulated network.  I
> want all of the machines in the experiment to have the same time.
> Ideally, the maximum offset would be on the order of 100 micro-
> seconds.  The machines are connected by a 1 Gbps LAN so delay is not a
> problem. Additionally, I don't care about the correctness of the clock
> compared to global time.  I am curious what is he best way to set this
> up.  I was thinking to have on dedicated ntp server that operated in
> broadcast mode, and also configure the clients to poll it every 16
> seconds.  Additionally, there are two planes: experimental and
> control.  Since the experimental traffic is separated from the control
> traffic, there should be little variance in delay for ntp packets.
> Thanks,
> Roman

I don't think you want to both broadcast AND have the clients poll.  One 
or the other but not both!   When a client is using broadcast mode, it 
initializes by exchanging packets with the broadcast server to determine 
the typical value of delay.  It then uses this figure to correct 
subequent broadcast packets.

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