<div dir="ltr">Thanks a lot Jonathan,Eddy and Richard.<div>With the help of you people i have cleared many concepts.</div><div>But still one point is not clear.</div><div>Richard Sir you said that Codel is better in notifying congestion to TCP senders.</div><div>But Sir how,i know codel does it at dequeue stage while RED does at enqueue stage.</div><div>The thing is congestion signal has to traverse the buffer.<br></div><div>Then how does it make difference that whether it is at enqueue or dequeue.i mean how it is quicker with codel?</div><div><br></div><div><br></div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Feb 24, 2015 at 8:33 AM, Richard Scheffenegger <span dir="ltr"><<a href="mailto:rscheff@gmx.at" target="_blank">rscheff@gmx.at</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><u></u>
<div bgcolor="#ffffff">
<div><font face="Arial">Sahil.,</font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">Codel tries to address the problems that RED
couldn't; First, the input signal into the algorithm (sojourn time vs. average
queue depth) is of a different quality; Second, Codel (in it's plain form)
does drop/mark on dequeue, while RED drops/marks on enqueue.
This means, that [TCP] congestion control loop is much quicker with Codel
over RED; thus the reaction by the sender will probably be timely and relevant
for that congestion epoch. With RED; the congestion signal (that lost
packet) has to traverse the filled-up buffer first, thus the control loop time
is much larger (includes the instantaneous queue length of the buffer) - and is
further delayed by the averaging going on.</font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">Codel, by design, doesn't need to be tuned
specifically for one particular drain rate (bandwidht) of the queue - unlike
RED; So it adjusts much better to variable bandwidth MACs (Wifi,
DOCSIS).</font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">I've been told, that RED is easier to implement in
HW due to that action being all done on enqueue. With PIE, there exists another
AQM that tries to re-use the hw engines that exist for RED, but the control
algorithms try to use a different input signal - making the best of
that.</font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">If you follow the AQM work in IETF, there is strong
consensus steer to these more modern AQMs.</font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">Best regards,</font></div>
<div><font face="Arial"> Richard</font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial"></font> </div>
<blockquote style="BORDER-LEFT:#000000 2px solid;PADDING-LEFT:5px;PADDING-RIGHT:0px;MARGIN-LEFT:5px;MARGIN-RIGHT:0px"><div><div class="h5">
<div style="FONT:10pt arial">----- Original Message ----- </div>
<div style="FONT:10pt arial;BACKGROUND:#e4e4e4"><b>From:</b>
<a title="sahilgrover013@gmail.com" href="mailto:sahilgrover013@gmail.com" target="_blank">sahil
grover</a> </div>
<div style="FONT:10pt arial"><b>To:</b> <a title="chromatix99@gmail.com" href="mailto:chromatix99@gmail.com" target="_blank">Jonathan Morton</a> </div>
<div style="FONT:10pt arial"><b>Cc:</b> <a title="codel@lists.bufferbloat.net" href="mailto:codel@lists.bufferbloat.net" target="_blank">codel@lists.bufferbloat.net</a>
</div>
<div style="FONT:10pt arial"><b>Sent:</b> Tuesday, February 24, 2015 5:20
PM</div>
<div style="FONT:10pt arial"><b>Subject:</b> Re: [Codel] why RED is not
considered as a solution to bufferbloat.</div>
<div><br></div>
<div dir="ltr">So we can say Codel is better than other AQM???</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Tue, Feb 24, 2015 at 9:24 PM, Jonathan Morton <span dir="ltr"><<a href="mailto:chromatix99@gmail.com" target="_blank">chromatix99@gmail.com</a>></span> wrote:<br>
<blockquote style="BORDER-LEFT:#ccc 1px solid;MARGIN:0px 0px 0px 0.8ex;PADDING-LEFT:1ex" class="gmail_quote">
<p dir="ltr">Simply put, RED is a very old algorithm, one of the first viable
AQM algorithms. However, it proved to be so difficult to configure properly
that almost nobody uses it, even though many carrier grade routers implement
it.</p>
<p dir="ltr">Codel not only performs better than an ideally configured RED,
but is far easier to configure. This makes it much more deployable.</p><span><font color="#888888">
<p dir="ltr">- Jonathan
Morton<br></p></font></span></blockquote></div><br></div>
</div></div><p>
</p><hr>
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