Re: [ippm] Roman Danyliw's No Objection on draft-ietf-ippm-pam-08: (with COMMENT)

[Greg Mirsky <[e-mail]>]

Hi Roman,
we, Alex, I, and the authors and contributors, had a good discussion of the
question raised. As a result of that discussion, we've agreed to revert to
the text as in -08:
OLD TEXT:
   The monitoring of performance parameters to determine the quality of
   an interval is performed between the elements of the network that are
   referred to for the SLO corresponding to the performance parameter.
   Mechanisms of setting levels of a threshold of an SLO are outside the
   scope of this document.

To address your comment, we propose the following update -
s/pre-defined/configurable/, thus resulting in the following:
NEW TEXT:
   *  VI is a time interval during which at least one of the performance
      parameters degraded below its configurable optimal level
      threshold.

   *  SVI is a time interval during which at least one of the
      performance parameters degraded below its configurable critical
      threshold.

The attached working version includes all updates; the diff - highlights
them for your convenience.

Regards,
Greg

On Fri, Nov 17, 2023 at 10:58 AM Alexander L Clemm <[e-mail]> wrote:

> (Resending to complete list of recipients; apologies to ippm for the
> duplicate)
> On 11/17/2023 7:54 PM, Alexander L Clemm wrote:
>
> Hi,
>
> Roman, thank you for your questions and suggestions; Greg, thank you for
> for your responses.
>
> I actually disagree with one of the resolutions, as explained inline,
> <ALEX>.  Specifically, I believe that the original text in 3.1 should be
> reinstated as the new one is not only not quite correct but would introduce
> additional issues.
>
> Thanks
>
> --- Alex
> On 11/17/2023 12:56 AM, Greg Mirsky wrote:
>
> Hi Roman,
> thank you for your questions and suggestions. Please find my notes
> in-lined below tagged GIM>>. Attached, please find the new working version
> (Gmail believes that diff contains a virus ;(. )
>
> Regards,
> Greg
>
> On Thu, Nov 16, 2023 at 12:08 PM Roman Danyliw via Datatracker <
> [e-mail]> wrote:
>
>> Roman Danyliw has entered the following ballot position for
>> draft-ietf-ippm-pam-08: No Objection
>>
>> When responding, please keep the subject line intact and reply to all
>> email addresses included in the To and CC lines. (Feel free to cut this
>> introductory paragraph, however.)
>>
>>
>> Please refer to
>> https://www.ietf.org/about/groups/iesg/statements/handling-ballot-positions/
>> for more information about how to handle DISCUSS and COMMENT positions.
>>
>>
>> The document, along with other ballot positions, can be found here:
>> https://datatracker.ietf.org/doc/draft-ietf-ippm-pam/
>>
>>
>>
>> ----------------------------------------------------------------------
>> COMMENT:
>> ----------------------------------------------------------------------
>>
>> ** Section 3.1.  Consider defining or providing an explanation of “optimal
>> level threshold” and “critical threshold” in the definitions of VI and
>> SVI.
>> I’m assuming that these are two configured threshold levels.
>>
> GIM>> You are right. We planned that both thresholds are configured, i.e.,
> pre-defined, as noted in the document. Both reflect what can be described
> as "an acceptable deviation from an ideal performance metric". The optimal
> level may be used by a service provider to detect performance degradation,
> while the critical level reflects the requirements of the service customer.
> Would adding the following sentence make it clearer:
> OLD TEXT:
>    The monitoring of performance parameters to determine the quality of
>    an interval is performed between the elements of the network that are
>    referred to for the SLO corresponding to the performance parameter.
>    Mechanisms of setting levels of a threshold of an SLO are outside the
>    scope of this document.
> NEW TEXT:
>    The monitoring of performance parameters to determine the quality of
>    an interval is performed between the elements of the network that are
>    referred to for the SLO corresponding to the performance parameter.
>    The optimal level threshold may be used by a service provider to
>    detect performance degradation, while the critical level threshold
>    reflects the requirements of the service customer.  Mechanisms of
>    setting levels of a threshold of an SLO are outside the scope of this
>    document.
>
> <ALEX> Actually, I do not agree with this change.  In particular, I would
> take issue with the term "optimal level threshold".  What constitutes a
> Violated Interval is determined by the SLO.  It is the service level
> objective that, when breached, will cause a corresponding interval to be
> violated.
>
> Now, SVI has a notion of higher severity - and what constitutes that is
> again up to the network provider to define.  But there is no notion of
> optimality.  (Nor is there, in fact, a notion of criticality - it's SVI,
> not CVI.)
>
> I therefore find the new text to be misleading and believe the original
> text should be reinstated.  If we believe that additional clarification is
> needed, we could add another sentence that indicates that the configuration
> of a threshold which, when breached during an interval, will cause a
> violation to be registered for that interface, is determined per the
> definition of the SLO and configured accordingly.
>
> </ALEX>
>
>
>> ** Section 3.1.
>>    Beyond accounting for violated intervals, it is sometimes beneficial
>>    to maintain counts of packets for which a performance threshold is
>>    violated.
>>
>> No question of the utility of counting packets.  However, shouldn’t there
>> be a
>> count of flows too?  Section 1 said “This specification introduces a new
>> set of
>> metrics, Precision Availability Metrics (PAM), aimed at capturing
>> end-to-end
>> service levels for a flow, specifically the degree to which flows comply
>> with
>> the SLOs that are in effect.”
>>
> GIM>> Thank you for the question and highlighted text. PAM is intended to
> characterize a single flow, and it seems to me that the use of plural is
> confusing. I propose the update as follows:
> OLD TEXT:
>    This specification introduces a new set of metrics, Precision
>    Availability Metrics (PAM), aimed at capturing end-to-end service
>    levels for a flow, specifically the degree to which flows comply with
>    the SLOs that are in effect.
> NEW TEXT:
>    This specification introduces a new set of metrics, Precision
>    Availability Metrics (PAM), aimed at capturing end-to-end service
>    levels for a flow, specifically the degree to which the flow complies
>    with the SLOs that are in effect.
> I hope that this update clarifies the scope of PAM.
>
> _______________________________________________
> ippm mailing [e-mail]://www.ietf.org/mailman/listinfo/ippm
>
>