Iperf3: Why there is no sender traffic at server site

Question

I tried to take the test between my two machines and the output is as below:

Server listening on 5201
-----------------------------------------------------------
Accepted connection from 192.168.100.113, port 41749
[  5] local 192.168.100.114 port 5201 connected to 192.168.100.113 port 41750
[ ID] Interval           Transfer     Bandwidth
[  5]   0.00-1.00   sec   479 MBytes  4.02 Gbits/sec                  
[  5]   1.00-2.00   sec   611 MBytes  5.13 Gbits/sec                  
[  5]   2.00-3.00   sec   615 MBytes  5.16 Gbits/sec                  
[  5]   3.00-4.00   sec   614 MBytes  5.15 Gbits/sec                  
[  5]   4.00-5.00   sec   616 MBytes  5.17 Gbits/sec                  
[  5]   5.00-6.00   sec   597 MBytes  5.01 Gbits/sec                  
[  5]   6.00-7.00   sec   519 MBytes  4.35 Gbits/sec                  
[  5]   7.00-8.00   sec   561 MBytes  4.70 Gbits/sec                  
[  5]   8.00-9.00   sec   590 MBytes  4.95 Gbits/sec                  
[  5]   9.00-10.00  sec   600 MBytes  5.03 Gbits/sec                  
[  5]  10.00-10.05  sec  27.5 MBytes  4.47 Gbits/sec                  
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth
[  5]   0.00-10.05  sec  0.00 Bytes  0.00 bits/sec                  sender
[  5]   0.00-10.05  sec  5.69 GBytes  4.87 Gbits/sec                  receiver

$ iperf3 -c 192.168.100.114 -w 300k
Connecting to host 192.168.100.114, port 5201
[  4] local 192.168.100.113 port 41750 connected to 192.168.100.114 port 5201
[ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
[  4]   0.00-1.00   sec   506 MBytes  4.24 Gbits/sec    0    216 KBytes       
[  4]   1.00-2.00   sec   613 MBytes  5.14 Gbits/sec    0    216 KBytes       
[  4]   2.00-3.00   sec   613 MBytes  5.14 Gbits/sec    0    216 KBytes       
[  4]   3.00-4.00   sec   615 MBytes  5.16 Gbits/sec    0    216 KBytes       
[  4]   4.00-5.00   sec   617 MBytes  5.18 Gbits/sec    0    216 KBytes       
[  4]   5.00-6.00   sec   595 MBytes  4.99 Gbits/sec    0    216 KBytes       
[  4]   6.00-7.00   sec   515 MBytes  4.32 Gbits/sec    0    216 KBytes       
[  4]   7.00-8.00   sec   565 MBytes  4.74 Gbits/sec    0    216 KBytes       
[  4]   8.00-9.00   sec   590 MBytes  4.95 Gbits/sec    0    216 KBytes       
[  4]   9.00-10.00  sec   601 MBytes  5.05 Gbits/sec    0    216 KBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.00  sec  5.69 GBytes  4.89 Gbits/sec    0             sender
[  4]   0.00-10.00  sec  5.69 GBytes  4.89 Gbits/sec                  receiver

From the output of client site, we could see there is sender and receiver traffic record but from the server site, there is only receiver traffic.

Than I run in a reverse mode, there is no receiver traffic at server site.

Server listening on 5201
-----------------------------------------------------------
Accepted connection from 192.168.100.113, port 41755
[  5] local 192.168.100.114 port 5201 connected to 192.168.100.113 port 41756
[ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
[  5]   0.00-1.00   sec   611 MBytes  5.13 Gbits/sec    0    212 KBytes       
[  5]   1.00-2.00   sec   629 MBytes  5.28 Gbits/sec    0    212 KBytes       
[  5]   2.00-3.00   sec   637 MBytes  5.35 Gbits/sec    0    212 KBytes       
[  5]   3.00-4.00   sec   642 MBytes  5.39 Gbits/sec    0    212 KBytes       
[  5]   4.00-5.00   sec   641 MBytes  5.38 Gbits/sec    0    212 KBytes       
[  5]   5.00-6.00   sec   643 MBytes  5.39 Gbits/sec    0    212 KBytes       
[  5]   6.00-7.00   sec   638 MBytes  5.35 Gbits/sec    0    212 KBytes       
[  5]   7.00-8.00   sec   641 MBytes  5.38 Gbits/sec    0    212 KBytes       
[  5]   8.00-9.00   sec   630 MBytes  5.29 Gbits/sec    0    212 KBytes       
[  5]   9.00-10.00  sec   637 MBytes  5.35 Gbits/sec    0    212 KBytes       
[  5]  10.00-10.04  sec  19.9 MBytes  4.15 Gbits/sec    0    212 KBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  5]   0.00-10.04  sec  6.22 GBytes  5.32 Gbits/sec    0             sender
[  5]   0.00-10.04  sec  0.00 Bytes  0.00 bits/sec                  receiver

$ iperf3 -c 192.168.100.114 -w 300k -R
Connecting to host 192.168.100.114, port 5201
Reverse mode, remote host 192.168.100.114 is sending
[  4] local 192.168.100.113 port 41756 connected to 192.168.100.114 port 5201
[ ID] Interval           Transfer     Bandwidth
[  4]   0.00-1.00   sec   631 MBytes  5.29 Gbits/sec                  
[  4]   1.00-2.00   sec   630 MBytes  5.29 Gbits/sec                  
[  4]   2.00-3.00   sec   638 MBytes  5.35 Gbits/sec                  
[  4]   3.00-4.00   sec   641 MBytes  5.38 Gbits/sec                  
[  4]   4.00-5.00   sec   640 MBytes  5.37 Gbits/sec                  
[  4]   5.00-6.00   sec   643 MBytes  5.39 Gbits/sec                  
[  4]   6.00-7.00   sec   641 MBytes  5.38 Gbits/sec                  
[  4]   7.00-8.00   sec   639 MBytes  5.36 Gbits/sec                  
[  4]   8.00-9.00   sec   631 MBytes  5.29 Gbits/sec                  
[  4]   9.00-10.00  sec   636 MBytes  5.34 Gbits/sec                  
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.00  sec  6.22 GBytes  5.34 Gbits/sec    0             sender
[  4]   0.00-10.00  sec  6.22 GBytes  5.34 Gbits/sec                  receiver

Can someone help to explain why? Thanks a lot.

score 1 · Accepted Answer · answered Aug 01 '17 at 20:39

For various reasons having to do with the ordering of messages on iperf3's control channel, the server cannot print summary statistics from the client side. This is a known issue (there are various issues in the iperf3 issue tracker around this problem such as #560 and #314). It's not particularly easy to fix because a solution to this problem would involve changing the ordering or semantics of iperf3's control messages which, unfortunately, aren't particularly well documented. We (ESnet) would be happy to entertain possible fixes.

Iperf3: Why there is no sender traffic at server site

1 Answers1