Re: [gpsd-dev] PPS over USB

[Dave Taht]

On Tue, May 8, 2012 at 12:38 AM, Ed W <address@hidden> wrote:
> On 08/05/2012 08:15, Eric S. Raymond wrote:
>>
>> Hal Murray<address@hidden>:
>>>>
>>>> One of the explicit goals of the Cosmic Backround Bufferbloat Detector
>>>> is to
>>>> sanity-check NTP.
>>>
>>> If you see anything that seems unreasonable, please let me know.  ntpd
>>> has a
>>> huge collection of heuristics (hacks?) that try to filter out all sorts
>>> of
>>> quirks/glitches.  I'm sure there are some cases that will get past the
>>> current filters.
>>
>> Oh trust me, if we find such phenomenae we are *not* going to be merely
>> whispering about them - you and every other Internet infrastructure geek
>> we know will get the A-OOGA A-OOGA red alert muy pronto. :-)
>
>
> I would have expected the kinds of problems you are describing above to be
> more easily studied/tested using models in a lab?  Just turn on the various

The internet escaped the lab a long time ago. Yes, lab work is needed.
But for a change, I'd like the reality to be tested, and the lab work
to line up with reality. And the tools used, to be trustable. And the
results, repeatable.

Useful research on real network problems has been lacking of late.

I don't trust the results from nearly any paper I've read written in the last
10 years. And I can back up that, as to why.

> traffic shaping options and you can make your connection appear to be
> dropping packets/arbitrarily slow/turn up congestion.  I have a script that
> we use to pretend to be on an Iridium satellite dialup, ie 2.4Kbits, ie 300
> bytes per second - for sure we test everything over a real connection, but
> it sure is helpful to be able to stress things in certain ways
>
> I don't really follow ntp development, but what I really like about chrony
> is every time you "have an idea" Miroslav agrees or disagrees with a whole
> bunch of investigative action and usually a graph or two.  He really loves
> to go to the field and show the results!  He is also the chap who published
> some interesting numbers comparing the accuracy and offsets of a large
> number of machines in pool.ntp.org

we'll chat with him.

>
> Good luck
>
> Ed W
>



-- 
Dave Täht
SKYPE: davetaht
US Tel: 1-239-829-5608
http://www.bufferbloat.net