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I was thinking of using the bytes_in_flgiht in order to estimate a TCP cwnd from passive traces but it is not clear for on how we can we derive its relation with the cwnd. I am joining the passive trace from the monitor to a TCP kernel state of the sender where we get the value of the cwnd that have the same sequence number in the trace file.

tcp_seq=1256867582, tcp_nxt_seq=1256869030, tcp_len=1448, tcp_window_size=29312, tcp_bytes_in_flight=11622, cwnd=16

Is there any way to derive (or estimate sort to say) the value of the congestion window (for example: cwnd=16) from the bytes_in_flight or the sequence number? I am so confused.

asked 25 Apr '17, 07:25

armodes's gravatar image

armodes
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edited 25 Apr '17, 07:44


cwnd is accounted in MSS. So, cwnd (in Bytes)=cwnd * MSS. BUT when you're estimating cwnd from bytes_in_flight, you have to consider in that case cwnd MUST be the limiting factor for the sender. In your case cwnd = 16 * MSS = 16 * 1448 Bytes = 23168 Bytes. This is much more than actual bytes_in_flight, and it just means the sender can continue sending packets without receiving ACKs.

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answered 26 Apr '17, 00:02

Packet_vlad's gravatar image

Packet_vlad
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accept rate: 20%

edited 26 Apr '17, 00:26

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question asked: 25 Apr '17, 07:25

question was seen: 1,477 times

last updated: 26 Apr '17, 00:26

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