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Hi Barry,<br>
<br>
Welcome to the TCP testing mess :)<br>
From my experience:<br>
- do consider buffering policies. It's much more critical than
anything else<br>
- to this extent, do not trust delay generators: they have to buffer
packets, and sometimes the buffer they have is simply too small so
that they end up adding a huge loss probability.<br>
- same for shapers buffering and algorithms. How big is the buffer?<br>
- similarly, do not trust iperf too much. Especially the window
parameter is very fuzzy in my experience.<br>
<br>
Another hint: avoid connecting gbps links to arrive to a bottleneck
which is 2 order of magnitude slower. that means that 100 packets
arrive at the congested buffer while only 1 packet can exit. As you
can imagine, the burstiness makes everything worse...<br>
<br>
FYI, we have done similar tests, and got similar results. I can
forward then to you if you like.<br>
<br>
Hope this helps,<br>
Marco<br>
<br>
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<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">I did some
testing to compare various TCP stack behaviors in the midst
of traffic policing.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">It is common
practice for a network provider to police traffic to a
subscriber level agreement (SLA).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">In the iperf
testing I conducted, the following set-up was used:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Client ->
Delay (50ms RTT) -> Cisco (with 10M Policing) ->
Server<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">The delay was
induced using hardware base commercial gear.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">50 msec RTT and
bottleneck bandwidth = 10 Mbps, so BDP was 62,000 bytes.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Ran Linux,
Windows XP, and Windows 7 clients at 32k, 64k, 128k window
(knowing that policing would <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">kick in at 64K)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">
Throughput for Window (Mbps)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="DE">Platform
32K 64K 128K<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="DE">--------------------------------------------<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="DE">Linux
4.9 7.5 3.8<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">XP
5.8 6.6 5.2<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Win7
5.3 3.4 0.44<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Do anyone have
experience with the intricacies of the various OSes in the
midst of <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Traffic
policing? I was surprised to see such a variation in
performance, especially since Windows 7 is supposed to more
advanced than XP,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">I am going to
comb through the packet captures, but wondered if anyone had
insight.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Thank you,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Barry<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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