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<p style="margin: 0 0 1em 0; color: black;">One question about TCP small
queues (which I don't think is a good solution to the problem). For 802.11
to be able to perform well it needs to form maximum size aggregates. This
means that it needs to maintain a minimum queue size of at least 64
packets, and sometimes more. Will TCP small queues prevent this? </p>
<p style="margin: 0 0 1em 0; color: black;">Simon </p>
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<p
style="color: black; font-size: 10pt; font-family: Arial, sans-serif; margin: 10pt 0;">On
May 15, 2015 6:44:21 AM Jim Gettys <jg@freedesktop.org> wrote:</p>
<blockquote type="cite" class="gmail_quote"
style="margin: 0 0 0 0.75ex; border-left: 1px solid #808080; padding-left: 0.75ex;"><div
dir="ltr"><div class="gmail_default" style="font-size:small"><br></div><div
class="gmail_extra"><br><div class="gmail_quote">On Fri, May 15, 2015 at
9:09 AM, Bill Ver Steeg (versteb) <span dir="ltr"><<a
href="mailto:versteb@cisco.com"
target="_blank">versteb@cisco.com</a>></span> wrote:<br><blockquote
class="gmail_quote"
style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Lars-<br>
<br>
You make some good points. It boils down to the fact that there are several
things that you can measure, and they mean different things.<br>
<span class="HOEnZb"><font color="#888888"><br>
Bvs<br>
</font></span><div class="HOEnZb"><div class="h5"><br>
<br>
-----Original Message-----<br>
From: Eggert, Lars [mailto:<a
href="mailto:lars@netapp.com">lars@netapp.com</a>]<br>
Sent: Friday, May 15, 2015 8:44 AM<br>
To: Bill Ver Steeg (versteb)<br>
Cc: Aaron Wood; <a
href="mailto:cake@lists.bufferbloat.net">cake@lists.bufferbloat.net</a>;
Klatsky, Carl; <a
href="mailto:cerowrt-devel@lists.bufferbloat.net">cerowrt-devel@lists.bufferbloat.net</a>;
bloat<br>
Subject: Re: [Bloat] [Cerowrt-devel] heisenbug: dslreports 16 flow test vs
cablemodems<br>
<br><br>
I disagree. You can use them to establish a lower bound on the delay an
application over TCP will see, but not get an accurate estimate of that
(because socket buffers are not included in the measurement.) And you rely
on the network to not prioritize ICMP/UDP but otherwise leave it in the
same queues.<br></div></div></blockquote><div><br></div><div><div
class="gmail_default" style="font-size:small;display:inline">On recent
versions of Linux and Mac, you can get most of the socket buffers to
"go away". I forget the socket option
offhand.</div> </div><div><div class="gmail_default"
style="font-size:small">And TCP small queues in Linux means that Linux no
longer gratuitously generates packets just to dump them into the queue
discipline system where they will rot.</div><div class="gmail_default"
style="font-size:small"><br></div><div class="gmail_default"
style="font-size:small">How accurate this now can be is still an
interesting question: but has clearly improved the situation a lot over 3-4
years ago.</div><br></div><blockquote class="gmail_quote"
style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div
class="HOEnZb"><div class="h5">
<br>
> If you can instrument TCP in the kernel to make instantaneous RTT
available to the application, that might work. I am not sure how you would
roll that out in a timely manner,
though.<br><br></div></div></blockquote><div class="gmail_default"
style="font-size:small">Well, the sooner one starts, the sooner it gets
deployed.</div><div class="gmail_default"
style="font-size:small"><br></div><div class="gmail_default"
style="font-size:small">Jim</div><div class="gmail_default"
style="font-size:small"><br></div></div></div></div>
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</blockquote>
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