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12 Jul 2007

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To: Philip Lavine <source_route@yahoo.com>
Cc: nanog <nanog@merit.edu>, owner-nanog@merit.edu
Subject: Re: TCP congestion
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From: Joe Loiacono <jloiacon@csc.com>
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owner-nanog@merit.edu wrote on 07/12/2007 02:07:00 PM:
...
Typical Problem Scenario: Data transmission is humming along
consistently at 2 Mbps, all of a sudden transmission rates drop to
nothing then pickup again after 15-20 seconds. Prior to the drop off
(based on packet capture) there is usually a DUP ACK/SACK coming
from the receiver followed by the Retransmits and congestion
avoidence. What is strange is there is nothing prior to the drop off
that would be an impetus for congestion (no high BW utilization or
packet loss).
Perhaps you're filling buffers by flowing from a 1Gbps link into a 9Mbps
circuit. Dropped packets induces slow-start/congestion avoidance.

Joe
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<br><font size=2><tt>owner-nanog@merit.edu wrote on 07/12/2007 02:07:00
PM:<br>
<br>
> Typical Problem Scenario: Data transmission is humming along <br>
> consistently at 2 Mbps, all of a sudden transmission rates drop to
<br>
> nothing then pickup again after 15-20 seconds. Prior to the drop off<br>
> (based on packet capture) there is usually a DUP ACK/SACK coming <br>
> from the receiver followed by the Retransmits and congestion <br>
> avoidence. What is strange is there is nothing prior to the drop off<br>
> that would be an impetus for congestion (no high BW utilization or
<br>
> packet loss).<br>
</tt></font>
<br><font size=2><tt>Perhaps you're filling buffers by flowing from a 1Gbps
link into a 9Mbps circuit. Dropped packets induces slow-start/congestion
avoidance.</tt></font>
<br>
<br><font size=2><tt>Joe</tt></font>
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