[ntp:questions] How to keep Linux server in Chicago and Mumbai in sync to within 5 microseconds

Rick Jones rick.jones2 at hp.com
Wed Jan 12 23:26:43 UTC 2011


Hal Murray <hal-usenet at ip-64-139-1-69.sjc.megapath.net> wrote:
> In article <AANLkTinczE9ExUCs_6iOz3geoeXmZT3ETOj7BPL6BpWJ at mail.gmail.com>,
>  Chris Albertson <albertson.chris at gmail.com> writes:
> >On Wed, Jan 12, 2011 at 11:25 AM, unruh <unruh at wormhole.physics.ubc.ca> wrote:
> >
> >> ... There is nothing in CDMA that would require very accurate
> >> absolute time I presume. Thus there is no real reason why they
> >> should deliver absolute time with high precision. ...
> >
> >Tower triangulation based on time of flight delay is used to
> >determine location of a cell phone.  There is a requirement to
> >attach location to 911 calls and triangulation is a kind of last
> >resort method for non gps enabled phones.
>
> It's not a last-resort.  It's an ecnomoic decision.  Do you replace
> all the cell phones with new ones that have GPS chips or do you
> upgrade all your towers with gear to do the triangulation?

> Note that being able to do triangulation doesn't require that the
> time at the towers be accurate, just that they be in sync.
> Triangulation would all work if all the clocks were off by 1.37
> seconds.  (as long as they all used the same value of 1.37)

And since they will not be trying to triangulate between towers in
Mumbai and those in Chigago...

> -- 
> These are my opinions, not necessarily my employer's.  I hate spam.


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