Re: [Gen-art] Genart last call review of draft-ietf-rmcat-eval-test-08

[Zaheduzzaman Sarker <[e-mail]>]

Hi Stewart,

Thanks for a good review. 

For the security consideration section, we can use stronger words if that is required. This document merely specifies test cases when people are testing their algorithm in a controlled environment and does not specify protocol usage. I was wondering if using normative language is an overkill here. For those reasons we are actually thinking of taking out 2119 usage completely. I have a modified text proposal below. 

Please see inline below for more.

BR
Zahed
 

On 2019-02-04, 20:29, "Stewart Bryant" <[e-mail]> wrote:

    Reviewer: Stewart Bryant
    Review result: Almost Ready
    
    I am the assigned Gen-ART reviewer for this draft. The General Area
    Review Team (Gen-ART) reviews all IETF documents being processed
    by the IESG for the IETF Chair.  Please treat these comments just
    like any other last call comments.
    
    For more information, please see the FAQ at
    
    <https://trac.ietf.org/trac/gen/wiki/GenArtfaq>.
    
    Document: draft-ietf-rmcat-eval-test-08
    Reviewer: Stewart Bryant
    Review Date: 2019-02-04
    IETF LC End Date: 2019-02-11
    IESG Telechat date: Not scheduled for a telechat
    
    Summary:
    
    A well written documents an close to being ready for publication.
    
    I am concerned that the Security section is weak on use outside a
    controlled environment.
    
    There are a fair number of minor issues and nits that need attention,
    but most of them are simple to fix.
    
    One concern that I have that I doubt is readily fixable is that long
    multi-nested lists do not work well in paginated ASCII with line spaces
    and sometimes it is difficult to be sure of the context of a test element note.

[ZS] I share the concern here, but I don’t think I have a better alternative now.
    
    Major issues:
    
    8.  Security Considerations
    
       The security considerations in [I-D.ietf-rmcat-eval-criteria] and the
       relevant congestion control algorithms apply.  The principles for
       congestion control are described in [RFC2914], and in particular any
       new method MUST implement safeguards to avoid congestion collapse of
       the Internet.
    
       The evaluation of the test cases are intended to be run in a
       controlled lab environment.
    
    SB> I wonder if there shouldn't me a MUST in that sentence?
    SB> There have been issues on SP networks with users running unsuitable
    SB> performance benchmarks on live networks, including complaints to the
    SB> operators concerning the results achieved.
    
       Hence, the applications, simulators and
       network nodes ought to be well-behaved and should not impact the
       desired results.  It is important to take appropriate caution to
       avoid leaking non-responsive traffic from unproven congestion
       avoidance techniques onto the open Internet.
    
    SB> Again I am surprised this is not much stronger in prohibiting
    SB> use on the Internet.

[ZS] what about :

" The evaluation of the test cases are intended to be run in a
   controlled lab environment.  Hence, the applications, simulators and
   network nodes must be well-behaved and should not impact the
   desired results.  Moreover, proper measures must be taken to
   avoid leaking non-responsive traffic from unproven congestion
   avoidance techniques onto the open Internet. "
    
    ========
    
    Minor issues:
    
       This memo describes a set of test cases for evaluating congestion
       control algorithm proposals for real-time interactive media.
    
    SB> It would be useful to add here the statement in the abstract that
    SB> these tests should be done in a controlled environment.
[ZS] The abstract mentions the this "This document describes
   the test cases to be used in the performance evaluation of such
   congestion control algorithms in a controlled environment."

We can repeat that in the intro as well.
    
    ===========
    
       Expected behavior: depending on the convergence observed in test case
       5.1 and 5.2, the candidate algorithm may be able to avoid congestion
       collapse.  In the worst case, the media stream will fall to the
       minimum media bit rate.
    
    SB> Do you need to specify the variant of TCP? You do state it later, but some
    comment here would be useful. 

[ZS] Not sure what would be useful to describe here more, the expected behaviour is not really coupled to what TCP congestion control is used, the general demand is to avoid congestion collapse here.
 
SB> What behaviour do you expect the TCP to show.
    It would be bad if SB> an aggressive media application kill the TCP completely.

[ZS] I don’t think we should say anything about TCP behaviour here. The idea is to test the new congestion control behaviour with available TCP behaviours not vice versa. But TCP can certainly improve its performance from the test results (.
    
    ============
       the first flow
       (S1) MUST arrive at a steady-state rate approximately twice of that
       of the other two flows (S2 and S3).
    
    SB> I am not sure what you mean by priority I assume that you mean
    SB> QoS ranking in the routing system. In which case I don't see
    SB> how you can expect the result you specify.

[ZS] no this is not about routing priority on the network nodes, this is at the media sender. When a media sender has multiple flows that shares the same bottleneck then the media sender can use techniques to distribute the available bandwidth to the multiple flows that it is sending. The point here is the media flows should get their share of the available bandwidth as per the priority set by the application.
    
    ============
    
       Expected behavior: the candidate algorithm is expected to achieve
       full utilization at both bottleneck links without starving any of the
       three congestion controlled media flows.
    
    SB> I am not sure what you mean by this. Do you mean that the bottlenecks
    SB> will saturate, but make no comment about how much of the bottleneck
    SB> capacity each flow gets for itself?

[ZS] bottlenecks will saturate -- yes. The success criteria --- the existence of multiple bottleneck should not result in flow starvation to any flows that is sharing those bottlenecks. Yes, there is no comment on fairness here explicitly. Not sure we need one here, do we?
    
    ============
    
    Nits/editorial comments:
[ZS] thanks for those nits. will take care of them.
    
     Checking nits according to https://www.ietf.org/id-info/checklist :
      ----------------------------------------------------------------------------
    
      ** There are 9 instances of too long lines in the document, the longest one
         being 4 characters in excess of 72.
    
      == Outdated reference: A later version (-06) exists of
         draft-ietf-rmcat-wireless-tests-05
    
    ===========
    
    3.  Structure of Test cases
    
    SB> In the text below it was sometimes hard to get the context right in the
    SB> triple (or more) nested list. Please consider using subsections or some
    other SB> demarcation.
    
    ===========
    
             +  Bottleneck queue type: for example, Droptail, FQ-CoDel, or
                PIE.
    
    SB> There need references, and by convention expansion on first use.
    
    ==========
    
             +  Path loss ratio: characterizes the non-congested, additive,
                losses to be generated on the end-to-end path.  MUST
    SB> s/MUST/This MUST/ ?
    
    ==========
    
           B.  Variation in sending bit rate and goodput.  Mainly observing
               the frequency and magnitude of oscillations.
    
    SB> goodput needs a reference or a definition. I don't think it is a
    universally known term.
    
    ===========
    
       Expected behavior: the candidate algorithm is expected to detect the
       path capacity constraint, converges to the bottleneck link's capacity
    SB> s/converges/converge/
    
    ===========
    
    Due to asymmetric nature of the link
    
    SB> s/Due to/Due to the/
    
    ===========
    
    SB> Is there a diagram error in the figure above?
    
         Figure 6: Testbed Topology for TCP vs congestion controlled media
                                       Flows
    
    ===========
    
       have the same bandwidth share on the link.  It has to make it's way
    SB>s/it's/its/
    
    ===========
    
    The candidate algorithm MUST reflect the relative priorities
       assigned to each media flow.  In the previous example,
    SB> An explicit reference to the test would help the reader
    
    ==========