In article <[email protected]>, Hal Murray <[email protected]> wrote:
> In article <190320142025178186%[email protected]>, > Joe Gwinn <[email protected]> writes: > > >The original issue was to be able to drop IRIG support in honor of PTP > >via the ethernet infrastructure we always need. > > How stable is your local clock? These systems are tied to GPS with Rubidium local oscillators. The end nodes have crystal oscillators, some temperature compensated, and very few being oven stabilized. > What sort of accuracy to you need? Varies. In some systems, it's a hard limit -- absolute error cannot exceed one microsecond. In others, it's that we are trying to synchronize independent subsystems to a fraction of a microsecond with great reliability, which leads us to focus on the probability distribution of errors - the distribution tails matter. > How much traffic will be on the ethernet you want to use? Varies as well. The timing-related traffic is negligible. The application traffic is significant, is a mix of big (1.5 Kbyte) and small (64 byte) packets, but still a gigabit enet link is loafing. The big issue is as always timing-related packets being buffeted by the application traffic, because we care about outliers, not just means and medians. In many cases, this is solved by having a dedicated LAN for timing-related traffic, but this isn't always possible. Joe Gwinn _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
