Re: [Int-dir] Intdir telechat review of draft-ietf-ippm-pam-08

[Greg Mirsky <[e-mail]>]

Hi Benson,
thank you for your kind words about our work on PAM; much appreciated. Your
thoughtful comments and suggestions are very helpful, please find my notes
below tagged GIM>>.

Regards,
Greg

On Wed, Nov 22, 2023 at 10:08 AM Benson Muite via Datatracker <
[e-mail]> wrote:

> Reviewer: Benson Muite
> Review result: Ready with Nits
>
> I am an assigned INT directorate reviewer for <draft-ietf-ippm-pam>. These
> comments were written primarily for the benefit of the Internet Area
> Directors.
> Document editors and shepherd(s) should treat these comments just like they
> would treat comments from any other IETF contributors and resolve them
> along
> with any other Last Call comments that have been received. For more
> details on
> the INT Directorate, see https://datatracker.ietf.org/group/intdir/about/
> <https://datatracker.ietf.org/group/intdir/about/>
>
> Based on my review, if I was on the IESG I would ballot this document as
> YES.
>
> The main aim of this informational draft is to introduce sampling of
> traffic
> flows to enable data reductions that make it feasible to check the quality
> of
> service, in particular by enabling checks on the number of packets
> delivered
> within a suitably defined time interval.  The notion that is introduced
> seems
> useful for a flow between two specified points.  It does not seem to
> impact any
> INT directorate related areas directly, though any resulting measurement
> techniques that are developed may be very useful, for example when
> comparing IPv4
> and IPv6.
>
>
> The following are minor issues (typos, misspelling, minor text
> improvements) with
> the document:
>
> a) The term precision availability metrics may be misleading, since counts
> are
> aggregated over a specified time interval. Maybe something like "Aggregated
> Availability Metrics" could be used instead?  There is a loss of precision
> since
> information about each packet is not recorded, but the resulting data
> reduction
> makes this concept useful.
>
GIM>> Aggregated is an interesting idea. Indeed, performance metrics for
each packet are not preserved. But the same can be said about any metric
derived based on a set of measurements, for example, mean, median, and
percentile. And, AFAICS, Service Level Indicators usually use a combination
of metrics that, in that sense, aggregate per packet measured metrics.

>
> b) At the beginning of section 3, it may be helpful to first introduce the
> notions of violated and severely violated, and then apply these to
> intervals and
> packet counts.  Alternatively, clear definitions could be given for the
> violated and severely violated packet counts.  One thing that is unclear
> is if
> the violated and severely violated packet counts apply to a single
> specified
> time interval, or are aggregated over multiple time intervals.
>
GIM>> The intention is to position the accounting of the violated/severely
violated packets as complementary to intervals that are aggregated over the
course of monitoring the flow. The scope of these metrics is explained in
the following:
   Maintaining such counts and comparing them with
   the overall amount of traffic also facilitates assessing compliance
   with statistical SLOs (see Section 4).

>
> c) Section 3.3 introduces a new topic, available and unavailable states.
> How
> this might be implemented is not fully specified.

GIM>> I think that that could be the subject of a set of specific documents
that demonstrate the applicability of the performance measurement protocols
with nodal functional requirements. We can discuss where that scope fits
better.

> It may be helpful to combine
> this with section 4, a section on possible extensions, as perhaps section
> 4.1,
> with material on possible statistical SLOs as 4.2. Both these sections
> could
> perhaps also be shortened and added as further bullet points in section 6.
>
GIM>> These are interesting ideas. The authors reviewed the scope of the
proposed updates, and we hope that you can agree with the current structure
of the document.