Matt,
On 12/02/2012 11:51 PM, Matt Davis wrote:
Date: Sun, 02 Dec 2012 22:16:52 +0100
From: Magnus Danielson<[email protected]>
On 12/02/2012 08:54 PM, Erich Heine wrote:
Examining the time "in switch" for various packets at the microsecond level
was needed to understand various delay curves for different network loads,
with an ultimate goal of proper statistical modeling reflecting reality as
close as possible.
This is a bold challenge, it's a difficult task (clear speak: there is a
reason for this to be a research field, industry never *really* got it
under control).
I agree with Magus, but measuring in-host (or in-switch) timing is
still possible.
Indeed. It is possible to measure, but difficult to fully model and
characterize. A friend of me did his PhD on the fractal behaviour of
network trafic. Then, even he didn't nailed it in a good way.
The research team I am with presented a paper at
ISPCS this year on the measuring of in-host latencies and looking at
where packet timestamps take place, such as SO_TIMESTAMP as Magnus
mentions below. I will point you to a link to our docs, email me off
the list if you do not have access to the IEEE online journals. The
paper is mainly focused on BSD systems; however, BSD is not unheard of
in the switch world so maybe it can give you a few tricks for what you
want to accomplish regarding your in-switch timing.
Paper: "Probing the Latencies of Software Timestamping"
http://www.synclab.org/docs/
People should dive into that link, there is a few goodies there it seems
from just pulling one paper.
Thanks for providing the pointer, Matt!
Cheers,
Magnus
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