Subject: FW: Comments on draft-ietf-bmwg-mswitch-02

From: "Debby Stopp" <[email-masked]>
Date: Tue, 29 Feb 2000 16:05:23 -0800

I also found the ppm ref. confusing; I would prefer the metric to be
referred to as a percentage, rather than ppm.

You wrote:
   All ports MUST start transmitting their frames within 1% of the trial
   duration.  For a trial duration of 30 seconds, all ports SHOULD have
   started transmitting frames within 300 milliseconds of each other.

   All ports SHOULD stop transmitting frames after the specified trial
   duration, within 100 PPM.  The first test frame transmit time minus
   the last test frame transmit time SHOULD be within 100 PPM of the
   trial duration.  Each port's stop time MUST be in reference to its
   start time.  This trial duration error controls the accuracy of the
   Oload measurement and SHOULD be reported with the Oload measurement
   in the units of PPM.

To be consistant, perhaps a better wording of the second paragraph might be:

   All ports SHOULD stop transmitting frames after the specified trail
   duration withing 1% of the trial duration.  Each port's stop time MUST
   be reference to its start time.  This trial duration error controls the
   accuracy of the Oload measurement.

Debby Stopp

-----Original Message-----
From: [email-masked]
[mailto:[email-masked]]On Behalf Of Perser, Jerry
Sent: Tuesday, February 29, 2000 3:13 PM
To: BMWG (E-mail)
Subject: RE: Comments on draft-ietf-bmwg-mswitch-02

<snip>
> The fourth paragraph states that "all ports SHOULD stop
> transmitting frames
> after the specified trial duration, within 100 PPM." This is the first
> reference to a PPM metric. What is the unit of measurement here?
PPM stands for "Parts Per Million".  It is a unit-less measurement same as
percentage.  100 PPM is the same at 0.01%.  It is used in Electrical
Engineering on crystals and other tight tolerance devices.
Is PPM appropriate here?  Should I keep all the tolerances in percentage?  I
don't know if IETF uses EE terms or if I have to define them.