Wednesday, May 6, 2020

How would I find out if I’m hitting an artificial limit?

We have supposedly 1Gbps circuits in Huntsville AL and the other in Seattle, Washington. They both supposedly have a 300Mbps provisioned with 1Gbps provisioned.

In iperf3 I can hit exactly 300Mbps on a single stream.

Server1: iperf3 -s server2: iperf3 -c server1 -R -t 60

This results in exactly 300Mbps for the 60s test. It will fluctuate to like 298, 301, 300, 300, 296, 300, 306, 302, 301, 299, 300, 300 etc.

Server1: iperf3 -s server2: iperf3 -c server1 -R -P 4

It will get a total of about 850-870Mbps or about 210-220 per stream. If I run 2 streams they will each be 300Mbps.

This seems too much of a coincidence that a single stream will hit 300Mbps and our supposed provisioned in 300Mbps.

Is there any way to validate that this isn’t a tcp window size and stream size issue with a tcpdump?



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