Subject: [rmcat] Comments on draft-singh-rmcat-cc-eval-02

From: Kevin Gross <[email-masked]>
Date: Thu, 18 Apr 2013 10:28:25 -0600

Based on a quick skim and discussion at IETF86 I did not support adopting
this draft for the working group. I've now reviewed it more carefully and
offer the following comments. Perhaps we can proceed with it. Perhaps
Michael's document is a better place to start.

Section 3

Proposed additional metrics
o Latency
o Delay variation
o Throughput variation

Point iv: media quality is at best indirect and at worst and unreliable
indicator of network performance. I would like to see it removed.

Section 4: duration of testing or simulation runs is also a critical
parameter in testing

Section 4.1: need more discussion of relationship between circuit breakers
and congestion collapse. Circuit breakers are intended to detect and
terminate unrecoverable congestive collapse. Congestion control should step
in when congestion is detected or perhaps when congestive collapse is
detected but before circuit breakers trip.

Section 4.2: "Changing the media encoding rate too often or by too much may
adversely affect the users' quality of experience." doesn't seem to belong
here.

Section 4.3: Should discuss the bursty nature of i-frames in video streams

Section 4.4: s/802.11x/802.11/

Section 4.4: I don't think it's true that it is always impossible to
distinguish congestion and transmission losses.

Section 4.5 presumes that congestion control will break down. We'd like
this not to be the case. Don't give up before we've started.

Section 4.6 needs to mention competing traffic as a source of changes in
capacity.

Section 4.8: We definitely do need to discuss cross traffic but the second
paragraph in this section needs to be deleted or rewritten. It is about
algorithms and should instead focus on evaluation.

Section 6, 2nd bullet: we want to measure, not specify end-to-end delay.

Section 6 topology: Needs diagrams.

Section 6.1: clarify that 2-5% is transmission loss, not congestion loss.

Section 6.1 last paragraph assumes that full capacity will be used in
the scenario. This is not necessarily the case.

Section 6.3 need to specify buffer capacity and behavior in this scenario
(and probably the others too).

Kevin Gross
+1-303-447-0517
Media Network Consultant
AVA Networks - www.AVAnw.com <http://www.avanw.com/>, www.X192.org