Subject: some more comments on draft-ietf-psamp-sample-tech-05.txt

From: Benoit Claise <[email-masked]>
Date: Sun, 13 Feb 2005 21:28:36 +0100

Dear all,

In order to produce the next version of the PSAMP MIB, I've reviewed the 
"sampling and filtering techniques for IP packet selection" draft... 
this time with a PSAMP MIB hat. I still have a few comments on the draft.

1. section 2 "PSAMP Documents Overview"
  [PSAMP-MIB]  "Definitions of Managed Objects for Packet Sampling" 
describes the PSAMP management Information Base.
I see that the current MIB description use the same definition. However, 
the MIB specifications go well beyond sampling... there is also 
filtering and hashing!
What about "definitions of managed objects for sampling and filtering 
techniques for IP packet selection"?
Note
    - the draft "A Framework for Packet Selection and Reporting" should 
be changed accordingly
    - the MIB definition should be changed accordingly

2. "Packet Content" definition
[IPFIX-REQUIRE] -> [IPFIX-REQ]

3. If I recall correctly, the following terms have been changed in the 
latest "A Framework for Packet Selection and Reporting" (at least I 
recall some discussions on the mailing list): population size, sample 
size, configured selection fraction, attained selection fraction

4. Table in section 4
Change "Filter" to "Filtering" in the category column
Same section, change "cascade of a filter and a Sampling scheme" to 
"cascade of Filtering and Sampling schemes"

5. Section 5.2.2.3
Still non-ascii characters with "sample and hold" and "local export"

6. Section 6.2.1.1
"In the former case determines pseudorandom variates rather than 
selection probabilities" ??

7. Section 6.3 "Router State Filtering"
Remove the OR.

8. Section 7
"In order to be compliant with PSAMP, it is sufficient to implement one 
of the proposed schemes".
As far as I recall, this will be a standard track document, so it should 
be written in a more formal way.
"In order to be compliant with PSAMP, one least of the proposed scheme 
MUST be implemented"

9. section 7.1
SELECTOR_ID: ... the ID can be calculated under consideration of the 
ASSOCIATIONS and a local ID.
What does the "under consideration" mean?

10. section 7.1
case non-uniform probabilistic and case flow state both refer to section 
5.2.2.4.
However, both the method descriptions and the 5.2.2.4 section don't 
clearly explain which SELECTOR_PARAMETERS we need

11. section 7.1
"The ASSOCIATIONS field describes the Observation Point and (possibly) 
the IPFIX processes"
Possibly -> optionally without parentheses.
Note: the MIB should take care that these parameters are optional. 
Proposal: a value of 0 means unspecified?

12. section 7.1
Case Matching -> this is not too clear that these are pairs of (field, 
value). And that in case of multiple match criteria, we have several 
"case matching" bound by a logical AND.
BTW, IPFIX speaks of information element and not field, so I guess it 
should be a (information element, value) pair.

13. section 7.1
case hashing -> this is not too clear how the parameters in there match 
the definitions of hash domain, hash range, hash selection range, 
hash-based selection, etc... BTW I have the same problem with the MIB 
definitions (which obviously match these definitions)

14. section 7.1
"all router state entries can be linked by AND, OR, NOT operators" ->to 
be limited by AND

15. there are still a lot of capitalized terms before definition. The 
list is too long is to described in an email.
  Either use the find function, either call me as I marked them down on 
the paper draft I reviewed.

Regards, Benoit.

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---

From: Tanja Zseby <[email-masked]>
Date: Wed, 16 Feb 2005 18:32:45 +0100

Hi Benoit,

see comments inline

Benoit Claise wrote:

> Dear all,
>
> In order to produce the next version of the PSAMP MIB, I've reviewed 
> the "sampling and filtering techniques for IP packet selection" 
> draft... this time with a PSAMP MIB hat. I still have a few comments 
> on the draft.
>
> I see that the current MIB description use the same definition. 
> However, the MIB specifications go well beyond sampling... there is 
> also filtering and hashing!
According to out definition sampling and filtering are both packet 
selection techniques So in my opiniton the MIB title should change to 
"Definitions of Managed Objects for Packet Selection",  the FW document 
title can remain.

> [IPFIX-REQUIRE] -> [IPFIX-REQ]
done (changed for new version)

> size, configured selection fraction, attained selection fraction

Nick and I had a teleconferecne some time ago and agreed on those terms. 
So they are consistent in both drafts.

> "cascade of Filtering and Sampling schemes"
done

> Still non-ascii characters with "sample and hold" and "local export"

done

> selection probabilities" ??
changed

> 7. Section 6.3 "Router State Filtering"
done (now only AND is possible)
Since it seems no problem for the MIB or implementation to also have a 
NOT we could also allow a NOT for the matching filter combination
Thomas, Benoit do you agree ?

> 8. Section 7
> "In order to be compliant with PSAMP, it is sufficient to implement 
> one of the proposed schemes".
> As far as I recall, this will be a standard track document, so it 
> should be written in a more formal way.

done

> What does the "under consideration" mean?

To get a unique ID both need to be conisdered (local ID and associations 
) ==> changed the text to "calculated as combination of..."

> 10. section 7.1
> case non-uniform probabilistic and case flow state both refer to 
> section 5.2.2.4.

Yes, because we decided that those techniques are not mature enough 
nowadays to define generic parameters for the scheme and this is stated 
in 5.2.2.4

> Proposal: a value of 0 means unspecified?

changed. 0 (unspecified) than means it should apply to all IPFIX 
processes at this observation point ?

> should be a (information element, value) pair.

changed and sentence added

> 13. section 7.1
> case hashing -> this is not too clear how the parameters in there 
> match the definitions of hash domain, hash range, hash selection 
> range, hash-based selection, etc... BTW I have the same problem with 
> the MIB definitions (which obviously match these definitions)
>
done

> 14. section 7.1
> "all router state entries can be linked by AND, OR, NOT operators" 
> ->to be limited by AND
>
done. Maybe possible to allow NOT operators ?

> the paper draft I reviewed.
TODO

Regards
Tanja

-- 
Dipl.-Ing. Tanja Zseby			    	      	
Fraunhofer Institute FOKUS			Email: [email-masked]	
Kaiserin-Augusta-Allee 31			Phone: +49-30-3463-7153
D-10589 Berlin, Germany				Fax:   +49-30-3463-8153
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