> > > Modern TCPs support and typically use window scaling (RFC 1323). You > may not notice it in packet dumps because the window scaling option is > negotiated once for the connection, not repeated in every packet. > > Absolutely. Most host OS should support this by now. Some test utilities however, like iperf (at least the versions I've used) default to a 16 bit window size though.
The goal of my response was to allude to the fact that TCP relies on windowing unlike UDP, thus explaining the discrepancies. This is a good article outlining these details: https://www.edge-cloud.net/2013/06/measuring-network-throughput/
