Re: [IPFIX] IPFIX observationPointId uniqueness

Paul,

At first glance, it looks reasonable.
But what would be the consequence on the Selection Sequence Report 
Interpretation(see http://tools.ietf.org/html/rfc5476#section-6.5.1). If 
we use the observationPointId and it's not unique, then we need to 
include the observationPointType?
Note that the sentence "It is RECOMMENDED that this identifier is also 
unique per IPFIX Device." was inserted specifically for this.

Regards, Benot
> Dear IPFIX experts,
>
> IPFIX observationPointId (#138) is defined as:
>
>          An identifier of an Observation Point that is unique per
>          Observation Domain.  It is RECOMMENDED that this identifier is
>          also unique per IPFIX Device.  Typically, this Information
>          Element is used for limiting the scope of other Information
>          Elements.
>
> We now also have observationPointType (#277), defined as:
>
>           Type of observation point. Values assigned to date are:
>
>           1. Physical port
>           2. Port channel
>           3. Vlan.
>
>
> Could we relax the uniqueness requirements of observationPointId when 
> an observationPointType is also exported, such that the { 
> observationPointType, observationPointId } pair must be unique, though 
> not the observationPointId itself.
>
> The reason being that observation points of different types already 
> have IDs, though these are not unique. eg, we have interface 1, 2, 3, 
> ...; vlan 1, 2, 3, ...; port 1, 2, 3, ...
>
> So an extra mediation layer is required to convert values from each of 
> these number spaces into unique IDs in the observationPointId number 
> space - which becomes harder as we add more places that observations 
> can be made, ie more observationPointTypes.
>
> Whereas prefixing with the observationPointType achieves the required 
> uniqueness in a faster, simpler, and more reliable way.
>
> To achieve this, I'd propose the following definition change:
>
>          An identifier of an Observation Point that is unique per
>          Observation Domain and per observationPointType, if specified.
>          It is RECOMMENDED that this identifier is
>          also unique per IPFIX Device.  Typically, this Information
>          Element is used for limiting the scope of other Information
>          Elements.
>
> For backwards compatibility, we could define observationPointType = 0 
> to be "unspecified".
>
> Thanks,
> P.
>
>
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