On Mon, Nov 3, 2008 at 1:21 PM, William Chops Westfield <westfw@mac.com> wrote:
> I don't think so.  It's like a "hard real time" operating system.
> "Determinism" means that you can guarantee packet delivery within a
> particular maximum time; latency and jitter UP TO that time are free
> to vary all over the place.
>
> Badly worded, I think.  Variation of latency is "jitter";  but it is
> the inability to guarantee a certain MAXIMUM latency, to put an upper
> bound on latency, that makes the network non-deterministic...

Thanks for the explanation.

Maybe I should not talk about determinism and hard-realtime. Both
are not necessary for many applications anyway.

An article about Real Time Ethernet.
http://www.datalinkcom.net/Real%20Time%20Ethernet2.pdf

It mentions something like the following.
"Ethernet/IP uses UDP/IP for RT communication,
adding jitter and non-determinism. If the jitter is quantifiable
and does not infect the system model, the system can still
be RT but will be unsuitable for fast and hard RT systems like
motion control."

I do not quite understand this. If the jitter is quantifiable,
it would have a maximum value. So it has determinism.
Right? Kind of confusing.


Regards,
Xiaofan
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