[ntp:questions] .1 Microsecond Synchronization

Richard B. Gilbert rgilbert88 at comcast.net
Fri Jun 5 01:17:56 UTC 2009

ScottyG wrote:
> Thanks everyone for pointing out the, let call it silliness of this 
> requirement. Also thanks for all your quick responses.
> I went back to the traders who defined this requirement. They do 
> seem to think that they know what they want, it's just not what they 
> are asking for. From my talks with them, the main goal is to be able 
> to unravel what happened when a set of trades fail.
> To do this the order in which market data was received and trades 
> transmitted need to be maintained. I do know from their current log 
> files that 1 ms is not fine enough for this and that on occasion .1 
> ms is not good enough. They currently are using a feature of the 
> processors that seems to return clock tick on the microprocessor 
> (Some assembly language instruction). They have an algorithm for 
> controlling the skew that occurs using this method. This seems to 
> meet there needs in a single server scenario but when going across 
> machines this will obviously not work.
> What I would like to do is go back to them with reasonable 
> expectations. 
> What do you think you can achieve with let say 5,000-10,000 USD 
> budget for each data center? Could we get 1 micro, 10 micro, 100 
> micro, 1 milli?
> One catch is the not all the data centers have access to roof space 
> for us. One company claims that they can use CDMA as a source time. 
> Does anyone know the implications of this? It seems that the time 
> would be sourced from GPS and retransmitted via the cell towers. To 
> me this brings up more potential delays but I am not an expert.
> Scott

The reference signal from a CDMA cell phone base station contains 
extremely accurate timing information.  There are commercially available 
devices that can obtain the time from such a signal.  The base station 
obtains timing information from a GPS receiver.

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