I’m setting up two Linux agents (based on Debian) to test TCP retransmission patterns using iperf3. The output looks like this:
# iperf3 -c 172.16.2.11 -p 5010 -t 5 -b 10M
Connecting to host 172.16.2.11, port 5010
[ 5] local 172.16.2.12 port 35440 connected to 172.16.2.11 port 5010
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 1.25 MBytes 10.5 Mbits/sec 2 87.4 KBytes
[ 5] 1.00-2.00 sec 1.25 MBytes 10.5 Mbits/sec 9 114 KBytes
[ 5] 2.00-3.00 sec 1.12 MBytes 9.44 Mbits/sec 21 96.1 KBytes
[ 5] 3.00-4.00 sec 1.25 MBytes 10.5 Mbits/sec 3 69.9 KBytes
[ 5] 4.00-5.00 sec 1.12 MBytes 9.44 Mbits/sec 8 78.6 KBytes
– – – – – – – – – – – – – – – – – – – – – – – – –
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-5.00 sec 6.00 MBytes 10.1 Mbits/sec 43 sender
[ 5] 0.00-5.00 sec 6.00 MBytes 10.1 Mbits/sec receiver
iperf Done.
As you can see, the ‘Retr’ value is 43. How can I calculate the retransmission percentage based on the total number of packets sent? Unfortunately, I don’t see any information about the total number of packets sent in the output.
Is there a different iperf3 option I should enable?