Re: PROTO-11: Accuracy Report Interpretation

[Benoit Claise <bclaise@cisco.com>]

Andrew Johnson wrote:
> One comment inline:
>
> Benoit Claise wrote:
> > Dear all,
> >
> > We need a way of specifying the accuracy of our reported information, 
> > as PSAMP frameworks specifies: "the Report Stream must include 
> > information that enables the accuracy of measurements to be 
> > determined.". Here is some proposed text.
> >
> > _Section 7.4.4 Accuracy Report Interpretation_
> >
> > In order for the Collecting Process to determine the inherent 
> > accuracy of the reported quantities (for example timestamps), the 
> > PSAMP Device SHOULD send an Accuracy Report Interpretation.
> > The Accuracy Report Interpretation MUST be exported by an Option 
> > Template Record with a double scope that contains the TemplateId 
> > [PSAMP-INFO] and the Information Element for which the accuracy is 
> > required.
>
> If we make the templateId optional then you can have a mechanism for
> setting the accuracy for all uses of an element.  Is this useful /
> desirable?  It seems to me it is, since the measuring accuracy on
> a router (or measurement device) will generally be fixed.
Good point.

"The Accuracy Report Interpretation MUST be exported by an Option 
Template Record with a double scope that contains the TemplateId 
[PSAMP-INFO] and the Information Element for which the accuracy is 
required. "
becomes
"The Accuracy Report Interpretation MUST be exported by an Option 
Template Record with a scope that contains the Information Element for 
which the accuracy is required. In case the accuracy is specific to a 
template, a second scope containing the templateId value MUST be added 
to the Option Template Record."

Regards, Benoit.
> Andrew
>
>
> >  The accuracy SHOULD be reported either with the fixedAccuracy 
> > Information Element [PSAMP-INFO], or with the proportionalAccuracy 
> > Information Element [PSAMP-INFO].
> >
> > Accuracy Report Interpretation using the fixedAccuracy Information 
> > Element
> >  Scope:            TemplateId
> >                         InformationElementId
> >  Non-scope:     fixedAccuracy
> >
> > Accuracy Report Interpretation using the proportionalAccuracy 
> > Information Element
> >  Scope:            TemplateId
> >                         InformationElementId
> >  Non-scope:     proportionalAccuracy
> >
> > For example, the accuracy of an Information Element whose Abstract 
> > Data Type is dateTimeMilliSeconds [IPFIX-INFO], for which the unit is 
> > specified as milliseconds, can be specified with the fixedAccuracy 
> > Information Element with the milliseconds units. In this case, the 
> > accuracy is the Information Element value +/- the value reported in 
> > the fixedAccuracy.
> >
> > 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 proportionalAccuracy Information 
> > Element with the octet units. In this case, the accuracy is the 
> > Information Element value +/- the value reported in the 
> > proportionalAccuracy time Information Element value.
> >
> > Alternatively to reporting either the fixedAccuracy Information 
> > Element or the proportionalAccuracy 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.
> >
> > If the accuracy of a reported quantity changes on the Metering 
> > Process, a new Accuracy Report Interpretation MUST be generated. The 
> > Collecting Process MUST keep the accuracy of the latest Accuracy 
> > Report Interpretation.
> >
> > Example 1 (to be developed)
> > Records (using template 12):
> > 1. Scope: TemplateId = 5, InformationElementId = 152
> > Non-scope: fixedAccuracy = 2
> > => we have a accuracy of +/- 2ms)
> >
> > Example 2 (to be developed):
> > 1. Scope: TemplateId = 5, InformationElementId = 152
> > Non-scope: proportionalAccuracy = 0.005
> > => we had an accuracy of  +/- 0.5%
> >
> >
> > ---------------------
> > For the PSAMP information model:
> >
> > fixedAccuracy
> >
> >        Description:
> >           Describes the accuracy of an Information Element, as a 
> > negative
> >           and positive relative error in absolute value.
> >        Abstract Data Type: float64
> >        ElementId: 320
> >        Status: current
> >        Units: The units of the Information Element for which is 
> > accuracy is
> >           specified.
> >
> >
> > proportionalAccuracy
> >
> >     Description:
> >           Describes the accuracy of an Information Element as a negative
> >           and positive relative error, expressed as a value between 0 
> > and 1.
> >        Abstract Data Type: float64
> >        ElementId: 321
> >        Status: current
> >        Units: None
> >
> >  informationElementID
> >
> >      Description:
> >           Contains the ID of another Information Element.
> >        Abstract Data Type: unsigned16
> >        Data Type Semantics: identifier
> >        ElementId: 303
> >        Status: current
> >        Units: None
> >
> > Regards, Benoit.


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