Re: [PSAMP] PSAMP-INFO IE realtiveError

["Zseby, Tanja" <[e-mail]>]

Hi Benoit,

I think we need no new section in PSAMP-PROTO and can only introduce the
CI limits in PSAMP-INFO. We can stick with the example in PSAMP-PROTO
but need to clarify that the example is only for the accuracy of
measured values. That means mainly to remove the 2 sentences that refer
to estimation error. It depends how much we can still change in
PSAMP-PROTO. Is removing 2 sentences o.k.?

Kind regards
Tanja

> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]] On Behalf
> Of Benoit Claise
> Sent: Friday, August 01, 2008 12:46 AM
> To: Zseby, Tanja
> Cc: psamp; Juergen Quittek
> Subject: Re: [PSAMP] PSAMP-INFO IE realtiveError
> 
> Hi Tanja,
> 
> 
> 	Hi Benoit and Paul,
> 
> 
> 
> 	here my suggestions for clarification of the error IEs in PSAMP-
> INFO.
> 
> 	-    I suggest to rename the fixedError to absoluteError
> 
> No problem with that, but [PSAMP-PROTO] must follow otherwise we have
a
> problem Can we still change that in AUTH48 maybe?
> 
> 
> 
> 
> 	-    I suggest to introduce CI limits and level to also report
> estimation errors
> 
> I'm wondering whether this is a good idea to add upperCILimit,
> lowerCILimit, and confidenceLevel at this stage.
> Because it implies that we need a complete new section in
[PSAMP-PROTO]
> (as opposed to just editorial change) similar to "Accuracy Report
> Interpretation" but for the accuracy statement for estimated value.
> Now, the simple solution is to add the information elements in PSAMP-
> INFO and don't discuss the accuracy statement for estimated value in
> [PSAMP-PROTO].
> 
> 
> 
> 
> 	-    If it is still possible I would suggest to make a few small
> changes in PSAMP-PROTO for consistency.
> 
> 	-    Upper and lower CI limits can be also specified as provided
> absolute or relative limits. So we could also add 2 more IEs (for the
> relative CI limits)
> 
> 
> 
> 	New description of IEs:
> 
> 
> 
> 	absoluteError
> 
> 	This Information Element specifies the maximum possible
> measurement error of the reported value for a given Information
> Element. The absoluteError has the same unit as the information
element
> it is associated to. The real value of the metric can differ by
> absoluteError (positive or negative) from the measured value. This
> information element provides only the error for measured values. If an
> information element contains an estimated values (from sampling) the
> confidence boundaries and confidence level have to be provided
instead.
> 
> 
> 
> 	relativeError
> 
> 	This Information Element specifies the maximum possible
> measurement error of the reported value for a given Information
Element
> as percentage of the measured value. The real value of the metric can
> differ by relativeError percent (positive or negative) from the
> measured value. This information element provides only the error for
> measured values. If an information element contains an estimated
values
> (from sampling) the confidence boundaries and confidence level have to
> be provided instead.
> 
> I like your suggestions for absoluteError and relativeError because
> something that was not clear (neither from PSAMP-PROTO or PSAMP-INFO)
> is that we wanted to quantify the accuracy of the measurement
> estimation, as opposed to the accuracy of the estimated value
> 
> 
> 
> 
> 
> 
> 	upperCILimit
> 
> 	This Information Element specifies the upper limit of a
> confidence interval. It is used to provide an accuracy statement for
an
> estimated value. The confidence limits define the range in which the
> real value is assumed to be with a certain probability p. Confidence
> limits always need to be associated with a confidence level that
> defines this probability p. Please note that a confidence interval
only
> provides a probability that the real values lies within the limits.
> That means the real value can lie outside the confidence limits.
> 
> 
> 
> 	lowerCILimit
> 
> 	This Information Element specifies the lower limit of a
> confidence interval. For further information see the description of
> upperCILimit.
> 
> 
> 
> 	confidenceLevel
> 
> 	This Information Element specifies the confidence level. It is
> used to provide an accuracy statement for estimated values. The
> confidence level provides the probability p with which the real value
> lies within a given range. A confidence level always needs to be
> associated with confidence limits that define the range in which the
> real value is assumed to be.
> 
> 
> 
> 
> 
> 	Changes to PSAMP-PROTO if still possible:
> 
> 
> 
> 	-    Rename fixedError to absoluteError
> 
> 	-    Slightly modify paragraph 2
> 
> 	OLD:
> 
> 	...  The accuracy SHOULD be reported either with the fixedError
> Information Element [PSAMP-INFO
<http://tools.ietf.org/html/draft-ietf-
> psamp-protocol-09#ref-PSAMP-INFO> ], or with the relativeError
> Information Element [PSAMP-INFO
<http://tools.ietf.org/html/draft-ietf-
> psamp-protocol-09#ref-PSAMP-INFO> ].
> 
> 	NEW:
> 
> 	... The accuracy for a measured information elelment SHOULD be
> reported either with the fixedError Information Element [PSAMP-INFO
> <http://tools.ietf.org/html/draft-ietf-psamp-protocol-09#ref-PSAMP-
> INFO> ], or with the relativeError Information Element [PSAMP-INFO
> <http://tools.ietf.org/html/draft-ietf-psamp-protocol-09#ref-PSAMP-
> INFO> ]. T
> 
> To be consistent with my statement above, I would not add the
following
> sentence.
> 
> 
> 	he accuracy for an estimated information element (from sampling)
> SHOULD be reported with confidence limits and confidence level.[PSAMP-
> INFO]
> 
> 
> 
> 	-    Remove the following paragraph (very important! Otherwise
it
> would lead to confusion):
> 
> 	For example, the accuracy of an Information Element to estimate
> the accuracy of a sampled flow, for which the unit would be specified
> in octets, can be specified with the relativeError Information Element
> with the octet units.  In this case, the error interval is the
> Information Element value +/- the value reported in the relativeError
> times the reported Information Element value.
> 
> 
> 
> 	-    Avoid the term error interval
> 
> 	OLD:
> 
> 	In this case, the error interval is the Information Element
value
> +/- the value reported in the fixedError.
> 
> 	NEW:
> 
> 	In this case, the real values lies within the range of the
> Information Element value +/- the value reported in the absoluteError.
> 
> 
> 
> 
> 
> 	-    Remove the following paragraph (since absolute or relative
> error are just different representations I would not gain something if
> I report both)
> 
> 	Alternatively to reporting either the fixedError Information
> Element or the relativeError Information Element in the Accuracy
Report
> Interpretation, both Information Elements MAY be present.  This
> scenario could help in more complex situations where the system clock
> drifts, on the top of having its own accuracy, during the duration of
a
> measurement.
> 
> I would also change "Accuracy Report Interpretation" into "Measurement
> Accuracy Report Interpretation" in  [PSAMP-PROTO]
> 
> Regards, Benoit.
> 
> 
> 
> 
> 
> 
> 	Sorry for the late comments, I was quite busy with PSAMP-TECH
> before...
> 
> 
> 
> 	Kind regards,
> 
> 	Tanja
> 
> 
> 
> 
> 

_______________________________________________
PSAMP mailing list
[e-mail]
https://www.ietf.org/mailman/listinfo/psamp