Attached are some scripts that run two simple tests of ECN with veth devices, with and without ECN. The topology is:
client - middlebox (20Mbit htb+fq_codel egress both ways) - net (40ms netem delay both ways, i.e. 80ms RTT) - server
Here are some results from the APU2 with Debian 9 / kernel 4.9.0-8:
Test 1 (“One vs one”, two clients uploads competing, one flow each for 60 seconds, measure total data transferred):
No ECN, 63.2 + 63.5 transferred = 126.7MB
ECN, 63.2 + 61.5 transferred = 124.7MB
Test 2 (“One vs pulses”, client #1: upload for 60 seconds, client #2: 40x 1M uploads sequentially (iperf -n 1M), measure client #1 data transferred):
No ECN, 63.2 MB transferred
ECN, 65.0 MB transferred
Can anyone suggest changes to this test or a better test that would more clearly show the benefit of ECN? I guess we’d want more congestion and the cost of each lost packet to be higher, meaning higher RTTs and more clients?
Pete