Re: Long-haul 100Mbps EPL circuit throughput issue

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/