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I have been doing some reading into TCP Receive Window (RWIN), Maximum Segment Size (MSS) and Maximum Transmission Unit (MTU). Right off the bat I have some questions and I need a power user's help!

The following questions are based on my using of Wireshark with a Win7 client to view the frames in a TCP stream:

  1. Where do you look (in the TCP stream) to find the RWIN in use? Is it the SYN, SYN-ACK, or ACK? I am under the impression it is in the SYN packet of the 3-way handshake.
  2. What is the remote machine saying by a "Window Size Value" of 16425, and a "Calculated window size" of 65700 (Wireshark states a scaling factor of 4, i.e. 16425 * 4 = 65700) in the ACK packet?
  3. Which machine dictates the RWIN value used during transmission - the client or remote machine?
  4. As per TCP connection termination there is a FIN-ACK which indicates the remote machine wants to terminate the connection followed by an ACK from the client and then an RST-ACK again by the client thus closing the connection. Does the RWIN value in the FIN-ACK and ACK packets during this termination process have any significance because they are very different from the RWIN values stated in the 3-way handshake?

I have some more questions but answer here may have a bearing on them so I shall wait for some answers first :)

Thanks. QF

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closed as off topic by kce, Dave M, Ward, mdpc, voretaq7 May 6 '13 at 22:04

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What is your goal? – ewwhite May 5 '13 at 23:08
@ewwhite To understand: TCP throughput, bandwidth (rated i.e. as in a 100mbps link), Round Trip Time (RTT)/latency, sliding window, the effects of changing RWIN, jumbo frames, and why for an MSS of 1460 a 64240 Byte RWIN value gives better throughput than an RWIN value of 65700 Byte. Thanks. – unkle_junky May 6 '13 at 0:44
Please don't cross-post. I'm voting to close this question because it doesn't address a practical, answerable question based on actual problems that you face (see FAQ). – kce May 6 '13 at 18:00

I answered this question over on SuperUser. Adding here just for completeness.

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