[ntp:questions] A proposal to use NIC launch time support to improve NTP

Brian Utterback brian.utterback at oracle.com
Thu Dec 13 02:52:52 UTC 2012

On 12/12/2012 8:57 PM, Rick Jones wrote:
> It would seem that at least one NIC has the ability to allow one to
> "schedule" the time at which a packet will be transmitted.  This is
> called "launch time support."  Someone in Linux-land has started
> asking about the prospect of enabling support of that in the stack,
> with his stated use case being to improve the jitter of NTP-based
> timekeeping.
> The initial posting can be found at:
> http://www.spinics.net/lists/netdev/msg219770.html
> rick jones

This is going to be very hard to get it to be useful. Looking at the 
specs for the card, the timestamp you give is relative to a clock that 
is internal to the controller, and is only accurate to the nearest 
second. That is, it is like the PPS in that it is assumed that the clock 
is in sync to within .5 seconds to avoid aliasing the timestamp.


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