PSINet/Cogent Latency

Wed Jul 24 14:55:43 UTC 2002

Actually RRDTool interpolates any late replys to the nearest specified
collection timepoint (e.g., every 5th minute.) It doesn't really resample.

Joe

                    Matt                                                                                           
                    Zimmerman            To:     nanog at merit.edu                                                   
                    <mdz                 cc:                                                                       
                    @csh.rit.edu>        Subject:     Re: PSINet/Cogent Latency                                    
                    Sent by:                                                                                       
                    owner-nanog                                                                                    

                    07/23/2002                                                                                     
                    09:46 AM                                                                                       

On Mon, Jul 22, 2002 at 10:50:03PM -0700, Doug Clements wrote:

> I think the problem with using rrdtool for billing purposes as described
> is that data can (and does) get lost. If your poller is a few cycles
late,
> the burstable bandwidth measured goes up when the poller catches up to
the
> interface counters. More bursting is bad for %ile (or good if you're
> selling it), and the customer won't like the fact that they're getting
> charged for artifically high measurements.

RRDtool takes into account the time at which the sample was collected, and
if it does not exactly match the expected sampling period, it is resampled
on the fly.  See:

http://people.ee.ethz.ch/~oetiker/webtools/rrdtool/tutorial/rrdtutorial.html

under "Data Resampling" for more information.

RRDtool has some quirks when used for billing purposes, but it is not
guilty
of the error that you describe.

--
 - mdz