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Two points,
<div class=""><br class="">
</div>
<div class="">below...</div>
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<div>
<blockquote type="cite" class="">
<div class="">On 25 Feb 2015, at 09:42, Alex Elsayed <<a href="mailto:eternaleye@gmail.com" class="">eternaleye@gmail.com</a>> wrote:</div>
<br class="Apple-interchange-newline">
<div class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">Bob
Briscoe wrote:</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<blockquote type="cite" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
Sahil,<br class="">
<br class="">
At 06:46 25/02/2015, Mikael Abrahamsson wrote:<br class="">
<blockquote type="cite" class="">On Tue, 24 Feb 2015, sahil grover wrote:<br class="">
<br class="">
<blockquote type="cite" class="">(i) First of all,i want to know whether RED was implemented or not?<br class="">
if not then what were the reasons(major) ?<br class="">
</blockquote>
<br class="">
RED has been available on most platforms, but it was generally not<br class="">
turned on. It also needs configuration from an operator, and it's<br class="">
hard to know how to configure.<br class="">
</blockquote>
<br class="">
About a decade ago my company (BT) widely deployed RED in the<br class="">
upstream 'head-end' of our global MPLS network, i.e. the likely<br class="">
bottleneck in the customer edge router where the customer's LAN<br class="">
traffic enters their access link. We deployed it as WRED, i.e.<br class="">
different configurations of RED across the various diffserv classes,<br class="">
in order to minimise queuing latency in all the classes, including<br class="">
the lowest priority class. A configuration calculator was developed<br class="">
to help the engineers during set up. We still use this setup<br class="">
successfuly today, including for all our particularly latency<br class="">
sensitive customers in the finance sector.<br class="">
<br class="">
We did not deploy RED on our broadband platform (ie public Internet),<br class="">
altho in retrospect we should have done, because any AQM is much<br class="">
better than none. We're fixing that now.<br class="">
<br class="">
<blockquote type="cite" class="">
<blockquote type="cite" class="">(ii)Second, as we all know RED controls the average queue size from<br class="">
growing.<br class="">
So it also controls delay in a way or we can say is a solution to<br class="">
bufferbloat problem. Then why it was not considered.<br class="">
</blockquote>
<br class="">
It was designed to fix "bufferbloat" long before the bufferbloat<br class="">
word was even invented. It's just that in practice, it doesn't work<br class="">
very well. RED is configured with a drop probability slope at<br class="">
certain buffer depths, and that's it. It doesn't react or change<br class="">
depending on conditions. You have to guess at configure-time.<br class="">
<br class="">
What we need are mechanisms that work better in real life and that<br class="">
are adaptive.<br class="">
</blockquote>
<br class="">
If you were prepared to read a paper, I would have suggested:<br class="">
"The New AQM Kids on the Block: An Experimental Evaluation of CoDel and<br class="">
PIE" <<a href="http://infocom2014.ieee-infocom.org/GI14-slides/GI14-s2-3.pdf" class="">http://infocom2014.ieee-infocom.org/GI14-slides/GI14-s2-3.pdf</a>><br class="">
<br class="">
This compares CoDel and PIE against Adaptive RED, which was a variant<br class="">
of RED proposed by Sally Floyd & co-authors in 2001 and available<br class="">
since Linux kernel version 3.3. ARED addressed the configuration<br class="">
sensitivity problem of RED by adapting the parameters to link rate<br class="">
and load conditions.<br class="">
<br class="">
The paper convinced me that ARED is good enough (in the paper's<br class="">
simulations it was often better than PIE or CoDel), at least for<br class="">
links with fixed rate (or only occasionally varying rate like DSL).*<br class="">
This is important for us because it means we can consider deploying<br class="">
AQM by adding soft controls on top of the RED implementations we<br class="">
already have in existing equipment. This could reduce deployment<br class="">
completion time from decades to a few months.<br class="">
<br class="">
* I'm not sure ARED would be able to cope with the rapidly changing<br class="">
rate of a wireless link tho.<br class="">
</blockquote>
<br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">One
thing that was brought up on the CoDel list (which Sahil's original<span class="Apple-converted-space"> </span></span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">question
was cross-posted to) by Dave Taht is that much of this testing<span class="Apple-converted-space"> </span></span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">utterly
fails to account for two crucial factors:</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">1.)
Asymmetric paths. When the uplink is considerably smaller than the<span class="Apple-converted-space"> </span></span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">downlink,
he's seen significant behavioral differences - and that's<span class="Apple-converted-space"> </span></span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">_exactly_
the case of DSL.</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">2.)
Elephants, mice and ants - response of mixed (and latency-sensitive)<span class="Apple-converted-space"> </span></span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">traffic
under load. The RRUL (Realtime Response Under Load) toolkit he<span class="Apple-converted-space"> </span></span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">created
is explicitly designed to test this case... which is a close match<span class="Apple-converted-space"> </span></span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">to
common use cases like watching a Youtube video, but still needing things<span class="Apple-converted-space"> </span></span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">like
DNS to be responsive. Or the bursty traffic of web browsing while a<span class="Apple-converted-space"> </span></span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">VoIP
call is occurring.</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">The
former is completely ignored by the presentation you linked to,</span></div>
</blockquote>
<div><br class="">
</div>
<div>Why exactly did you think we should have looked at asymmetric paths? To study what?</div>
<div>( I'm not debating that asymmetric paths play out different in behavior. I'm just saying that one needs to be clear about what exactly is being investigated, and why.)</div>
<div><br class="">
</div>
<br class="">
<blockquote type="cite" class="">
<div class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">and
the<span class="Apple-converted-space"> </span></span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">latter
is a one-line mention under "future work":</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">"More
realistic traffic types (here, only bulk TCP traffic) including</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">bursty
traffic"</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
<span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">Considering
those, that slide deck convinces me of very, very little indeed.</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
</div>
</blockquote>
<div><br class="">
</div>
<div>- it's not just a slide deck, it's a paper, in case you're interested. The longer version is freely available:</div>
<div><a href="https://www.duo.uio.no/bitstream/handle/10852/37381/khademi-AQM_Kids_TR434.pdf?sequence=5" class="">https://www.duo.uio.no/bitstream/handle/10852/37381/khademi-AQM_Kids_TR434.pdf?sequence=5</a></div>
<div><br class="">
</div>
<div>Why no other traffic types? Because we felt that looking at just bulk TCP is enough to make the key point that we wanted to get across: maybe it's worth taking a look at the vast amount of work that exists on AQMs, as even a stone old mechanism like ARED
does not seem to generally be significantly worse than CoDel and PIE.</div>
<div><br class="">
</div>
<div>We didn't really want to sell ARED as it is as a much better solution under all conditions and say that it should now be used instead of CoDel and PIE (though we do conclude that it creating an ARED++ type mechanism seems worth considering). To make that
point, I'd agree that one would have to see other traffic types too. A paper saying "We propose ARED++ as a replacement for CoDel or PIE" should have that.</div>
<div><br class="">
</div>
<div>My point is: when developing something new, compare against the state of the art. RED is *not* the state of the art, it's very old. I have seen arguments like needing parameterless operation because that was the failure of RED. Well, Sally Floyd addressed
that with ARED ages ago. Most papers cited in this survey:</div>
<div><a href="http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6329367" class="">http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6329367</a></div>
<div>begin with "RED didn't work because parameters had to be tuned. We propose a mechanism that doesn't require such tuning..."</div>
<div><br class="">
</div>
<div>What I've seen so far:</div>
<div>- CoDel compared with RED and BLUE</div>
<div>- PIE compared with CoDel</div>
<div>- ARED compared with CoDel and PIE</div>
<div><br class="">
</div>
<div>... it would seem reasonable to take one of the many, many mechanisms that exist - one that was already shown to be better than RED and many others - , make it use delay as input, and test CoDel and PIE against that. Then I'd say we have a comparison against
the state of the art. Now we don't really have that, there's a gap here.</div>
<div><br class="">
</div>
<div>Cheers,</div>
<div>Michael</div>
<div><br class="">
</div>
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