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How do I detect if I have TCP Congestion from looking at TCPDump data from a Linux box running a 2.6.x kernel ?

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It's not clear what it is you are trying to detect. What do you mean by "TCP congestion"? (Those two words are almost never used that way.) – David Schwartz Apr 18 '12 at 22:04

The congestion window is internal to the TCP stack and is not announced in packet headers or data in any way. You could consider the congestion avoidance algorithms employed with TCP and look for duplicate ACKs, SACKs and retransmits. TCP adapts transmission characteristics to the link's capability, so keep in mind that you would not see those continuously, they will just appear now and then.

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Could you see the TCP Congestion from using systemtap and if so, have any scripts been developed to do this ? – Rick. Apr 19 '12 at 21:32

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