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12 Jul 2007

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From: Fred Baker <fred@cisco.com>
Subject: Re: TCP congestion
Date: Thu, 12 Jul 2007 11:56:06 -0700
To: Brian Knoll ((TTNET)) <Brian.Knoll@tradingtechnologies.com>
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On Jul 12, 2007, at 11:42 AM, Brian Knoll ((TTNET)) wrote:
...
If the receiver is sending a DUP ACK, then the sender either never
received the first ACK or it didn't receive it within the timeframe it
expected.
or received it out of order.

Yes, a tcpdump trace is the first step.