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Hello,

I am trying to undestand TCP receive window. For example, on a iperf test, if I plot the TCP Time-Sequence Graph selecting any packet from client to server (remember iperf makes the test moving data from client to server), i see the above line looks like it is limiting the sender to send more data. But how that info can be found from a client to server packet? If I am not wrong, the "windows size" is the RWIN size, which means the amount of data that can be "received" by the client, which is not what we want to test. Am I correct?

thanks!

asked 26 Apr '15, 00:26

luicson's gravatar image

luicson
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converted to question 26 Apr '15, 05:21

grahamb's gravatar image

grahamb ♦
19.8k330206


RWIN is the amount of data that can be received by the receiver, meaning: the node that gets the data. It doesn't matter what you call a client or a server; both have window sizes. The window size of one is the amount the other can send without having to wait for an ACK, and vice versa. So if your "client" is sending data to the "server" it's the server's RWIN that matters.

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answered 27 Apr '15, 07:25

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Jasper ♦♦
23.8k551284
accept rate: 18%

If your question is about TCP Window size and Flow control, I think this section from the TCP/IP Guide should provide you the best answer:

http://www.tcpipguide.com/free/t_TCPWindowSizeAdjustmentandFlowControl-2.htm

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answered 27 Apr '15, 06:04

Amato_C's gravatar image

Amato_C
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accept rate: 14%

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question asked: 26 Apr '15, 00:26

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last updated: 27 Apr '15, 07:25

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