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TCP DUP ACK and TCP Windows Update

Posted on 2010-08-30
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Last Modified: 2012-05-10
I know there have been several questions asked on this topic and I have reviewed them.  

Here is my question.  i am doint a Wireshark capture over two 100/full connections that appear to be clean except for these two flags.  There are no re-transmits or fast re-transmits.  All of the DUP ACK and TCP Window Updates are gernated from my source server out to the server that sends me the data stream.  
Here is how my data flow works.  I connect out from my server to a remote server to start a data stream over a 100/FULL local connection.  Once the stream starts it is only a one way street.  My side is only consuiming the stream.  When I look at the wireshark logs filtered with tcp.analysis.flags it show tons of TCP DUP ACK errors from my side to the feed side.  I have changed my buffers on my NIC and various other items.  Is there anything that I am missing?  I have verified my switch logs and everything is clean there also.
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Question by:ericluoma
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mikebernhardt earned 500 total points
ID: 33568308
Depending on your mirroring topology and where exactly you are capturing from, you could simply be seeing the same ACKs twice. For example if you were capturing on links both in and out of a switch. Usually this would mean seeing all packets twice but again, it's possible to see one side once and the other side twice. Think it through and make changes as required.
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