psamp vocabulary

[Rae McLellan <rae@research.bell-labs.com>]

> I agree with Nick about keeping PSAMP simple.
> At a minimum, PSAMP devices (via the MIB?) should advertise
> their capabilities in detail, so a collector application can
> decide if result comparisons between 2 samplers are meaningful.

KISS is the way to go...  I was attempting to do that by reducing
the number of things that needed to be specififed in psamp.
As the combination of 1 out of N sampling and deterministic
selectors on the IP header, appears to add complexity.

But since, as Nick pointed out, there are some things that true
random sampling can provide that hash functions can not,
it appears that the complexity of covering both types of
sampling is unavoidable.

> Beyond that, PSAMP can define specific packet selection mechanisms,
> that (hopefully) vendors will adopt and implement.  There needs
> to be some leeway here to allow for vendor differentiation,
> variation in platform capabilities and intended use, and future
> extensions.

The comparision of two sample streams I mentioned earlier was only
intended for verification of the sampling implementation and
conformance with psamp.  I did not envisage a network operator
comparing two sample streams in normal operation.

Ideally, psamp conformance would be binary information.  Either
an implementation conformed or it did not.  Levels of conformance
are a pain to test and operators are then reduced to using the
least common denominator for their sampling.  I'd much prefer
the vendor differentiation reside in the analysis aspect of psamp.
The information, how it is selected, and transported to the
collector should be interchangable amonst different vendors.
That's what interoperability is all about after all.
Leave the vendor differentiation to how the product analyzes
and uses the psamp information.

				Rae McLellan


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