perfSONAR User Q&A and Other Discussion

[jim warner <>]

On 8/3/2011 6:27 PM, Alan Whinery wrote:
> Hi Jim,
>
> It took me a bit to digest your meaning. I apologize in advance, you
> just happened to ask a question about something I've been staring at. A
> lot. We should have talked about this in Alaska...
>
> The j-word is one of those things that induces confusion, especially
> around NTP, where there are at least two meanings of "jitter", and one
> is often cited as being the other.
>
> And you seem to be referring to neither one.
Sigh.  Clock jitter.  Packet jitter. Clock wander.  Thanks for the 
reply.  A lot of good information. It is not our plan to buy clocks to 
attach to perfsonar nodes.  I think what I was asking is 'how good is 
network time?'  The endrun technologies data sheet says 0.5 mS, and that 
says what I'm seeing is all I could expect.  It is even 2x better than that.

As you surmised, our NTP servers (endrun; one CDMA, one GPS) are on our 
network and not directly attached to perfsonar nodes.  I didn't know 
anyone  did that.

I don't know what kind of clock Stanford is using, or whether they 
edited the default list of time servers in the distribution.  I don't 
want to have to know that kind of info to use the tools.  I would, 
however, pay attention if the admin block at top of the Perfsonar web 
page included that sort of information -- but it doesn't.

-jim