[time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

Magnus Danielson magnus at rubidium.dyndns.org
Sun Dec 2 23:28:37 UTC 2012


On 12/02/2012 11:51 PM, Matt Davis wrote:
>> Date: Sun, 02 Dec 2012 22:16:52 +0100
>> From: Magnus Danielson<magnus at rubidium.dyndns.org>
>> 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!


More information about the time-nuts mailing list