On 2/21/12 10:47 AM, Attila Kinali wrote:
On Tue, 21 Feb 2012 10:05:04 -0800
Chris Albertson<albertson.ch...@gmail.com> wrote:
Perhaps he has now given up on that approach and has
gone to using relative time and round trip timing which would work
even using a $2 TTL "can oscillator"
If you read carefully what the OP wrote, you'll see that he
wants to measure one way trips.
RTT is easy and well understood. You can use a standard PC and
get to ~100us resolution with no special components. If you take
a NIC with time stamping, you get well below that.
But the problem is, in order to understand how networks behave
exactly and how this behaviour is changing over time, you need
to know the one way delays (mostly due to asymetric routing
which leads to asymetric load etc pp). And to do this, you need
a global time scale for time stamping. There is no way around it.
What if one sends a message one way that triggers say, 10 response
messages 1 second apart. Then you get distribution statistics on the
return path. You still don't know what the absolute forward or reverse
path time was, of course.
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