Subject: RE: FW: [bmwg] Some questions/comments on the multicast draft.

From: Jim McQuaid <[email-masked]>
Date: Thu, 18 Oct 2001 15:47:51 -0400

a semantic point, only.

If I sample at 10% compared to sampling at 1%, which is the "maximum
granularity?"  I would think sampling more = more granularity but this is
not a matter of science!  I know that if we say "coarse" and "fine" grained,
folks will not be confused.  

Limiting the maximum number of trials is good for completing a lot of tests
quickly, but it is the opposite of the goal of getting more detailed
results.  Any real world testing is a trade-off, of course.  But it seems
like our real goal in BMWG might be to limit the MINIMUM number of trials
that produce an acceptable result.

In other words, I think BMWG should encourage more fine-grained results, but
accept some minimum granularity (say 10%) rather than appear to be saying
that additional sampling is unnecessary.

So probably we agree but the tone of the language suggested no reason to
ever do more than 10%.

cheers,

Jim McQuaid

-----Original Message-----
From: Debby Stopp [mailto:[email-masked]]
Sent: Thursday, October 18, 2001 2:17 PM
To: 'Jim McQuaid'
Cc: Bmwg (E-mail)
Subject: RE: FW: [bmwg] Some questions/comments on the multicast draft.

Jim wrote:
> I think it might be clearer to the intent to say:
> 
> "The maximum granularity of the trials MUST be AT LEAST 10% 
> of the maximum
> offered load; a finer granularity is encouraged." (caps added 
> for emphasis
> here only)
> 
> On one hand, it is clear that a true throughput number must = 
> the maximum
> rate at which nothing is dropped.  However, a more coarse 
> granularity will
> yield a metric that is a known throughput rate but not necessarily the
> Maximum rate.  

I can see your point; however I think the intent of the original statement
was to limit the successive frame rate increases to not more than 10% at a
time, which would in turn limits the maximum number of trials to 10,
assuming frame loss occurred at every trial.  If what you're looking for is
a little more flexibility in the size of the frame rate change, I suggest an
alternate wording:

"The maximum granularity of the trials SHOULD be 10% of the maximum offered
load; a finer graularity is encourage."

This allows the tester to optionally use a coarser granularity (ie., greater
than 10%) but also stay w/in the confines of the methodology.

Debby Stopp 
Principal Software Engineer

IXIA
26601 W. Agoura Rd. 
Calabasas 
CA 91302 
Tel: 818 871 1800 (US) +1 818 871 1800 (international) 

[email-masked]
http://www.ixiacom.com 

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---

From: David Newman <[email-masked]>
Date: Thu, 18 Oct 2001 13:49:25 -0700 (PDT)

> folks will not be confused.

Strong agreement on this point. Less ambiguity is good.

Less wriggle room is also good. I would be more comfortable mandating 1
percent as the MUST rather than merely encouraging increments finer than
10 percent.

> So probably we agree but the tone of the language suggested no reason to

Right. Even 10 percent cuts way too much slack for marketeers of broken
implementations. Think about an ad for a box that drops 1 in 10 packets
in which the box maker claims the box is as good as drop-proof. It really
is that simple.

dn