[zeromq-dev] Precision Timestamping

Ilya Dmitrichenko errordeveloper at gmail.com
Wed Sep 7 13:46:55 CEST 2011


On 7 September 2011 04:13, Steven McCoy <steven.mccoy at miru.hk> wrote:
> All my research has shown packet timestamping to be completely worthless
> without hardware support, and even then it is a minefield.  You can see from
> the revision in the kernel support that there have been many problems to
> overcome.  Similarly documented quite well in MSDN for Windows is that there
> is no clock synchronisation between the NIC and the communicating CPU, you
> can get drift everywhere.
> Within OpenPGM I stamp with internal timer per incoming packet and make that
> timestamp available all the way through and so if the underlying API
> provided a stable solution it could be easily changed.  The accuracy is
> highly important to the PGM protocol as you need to use the CPU timer to
> calculate state timeouts from the packet timestamp.
> Reading the time can be quite expensive which is why it is nice to propagate
> the time up, but it is even better if you don't have to read it at all.
> --
> Steve-o

Seteve, what particular hardware/software (name and version) have you
used in your research ?



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