In wireshark, I can easily get the round trip time graph in Statistics->TCP Flow Graph. But I have an intention to extract out the rtt data into a text or csv file, which stump me into some trouble. A blog of such kind[1] cannot give any hint on how to get things done, which is totally shit,fuck it.
Finally, this ppt help me to get things done.
Right-click on any column’s header → Column Preferences → Click the add button → Enter tcp.analysis.ack_rtt into Field Name → OK
The picture following clearly shows what I did.