Re: PROTO-11: Accuracy Report Interpretation

[Andrew Johnson <andrjohn@cisco.com>]

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.

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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