Round-trip time (RTT) is the time it takes for a client to send a request and the server to send
a response over the network, not including the time required for data transfer. Not sure if this
fits what you are trying to do, but have you tried Statistics -> IO Graphs Then set Units to Advanced.
Select "AVG(*)" as the Calc method. Enter tcp.analysis.ack_rtt You can apply a filter in the
appropriate location as well. Note that you will need "Analyze TCP sequence numbers" activated in
TCP protocol options in Wireshark preferences for this to work.

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