Issue with UDP throughput and data loss in iperf3 tests

[adilnaveed]

Hello,

I am encountering an issue while conducting UDP throughput tests using iperf3 between a client and server setup. Here are the details of the problem:

Test Configuration:

Client: Amarisoft UE simulator acting as multiple clients, sending UDP data to the server.
Server: Receiving UDP traffic from multiple clients on different ports.
Test Parameters: Bitrate set to 1M and UDP buffer size (-w) configured as 2M.
Observations:

UDP Test (Client to Server):
Approximately half of the data sent from clients to the server is lost.
The server does not receive the expected 1M bitrate; instead, there is significant data loss.
UDP Test (Server to Client, using -R):
Data loss is not observed when testing in the reverse direction (server to clients).
TCP Tests:
No data loss is observed in either direction (client to server or server to client).
Question:

Issue Context: The problem appears to be specific to UDP tests from clients to the server with the chosen bitrate and buffer size configuration.
Hypothesis: What could be causing the data loss when using UDP in one direction while the reverse direction and TCP tests show no data loss?
Could you please provide insights or recommendations on how to mitigate this issue? Your assistance would be greatly appreciated.

[davidBar-On]

Hi, just to make sure, can you add some information:

1. Can you show the iperf3 commands you are using (no need to show the specific IP addresses)?
2. As the simulator is "acting as multiple clients", how many clients are active in parallel? What is the the bitrate (-b) set for each?
3. What cellular network is used (LTE/4G? 5G)?

From what I read, the Amarisoft UE simulator works over cellular network. In these networks, the downlink throughput (server to client) is much higher than the uplink (client to server) throughput. Can it be that uplink does not support the required 1Mbps, maybe because the uplink is busy because of other data sent over it?

If this is not the case, more analysis is required:

1. Does Amarisoft support logging that may help with such analysis?
2. What happens if you change the sent bitrate from the client to 256K bits (-b 256K)? 512Kbits?
3. What happens if you increase/decrease the packet length (using -l - the default is usually 1460 bytes)?
4. Can you use tools like Wireshark to analyze the traffic? It can help to see which packets are lost, are they lost in blocks or one arrive and one lost, etc.

[xia-s-xian]

Hi,

I have also encountered the same problem, when using UDP upstream test, the packet loss rate reached 50%, but the TCP upstream and downstream, UDP downstream are normal.

At present, I find that it is caused by the problem of the window environment. It is normal for me to switch to the ubuntu computer as the server test, but I do not know what causes the problem, and there is no effective way to confirm it at present.

Testing environment:
EVB Board(usb3.0)->USB to network adapter->window PC(ETH)
EVB Board(client),window PC(serve)

EVB Board(usb3.0)->USB to network adapter->Ubuntu PC(ETH)
EVB Board(client),Ubuntu PC(serve)

I tried to change the iperf version on the PC, but nothing worked. And the firewalls are down.

I'd like to know the root cause of this problem.

[davidBar-On]

Hi @xia-s-xian, several reasons can cause this issue, so more information is needed:

1. Run the clients and servers using -V option. What is block size used (the " byte blocks" size)? What is the iperf3 versions used?
2. Run TCP tests (in both environments) setting -l to the "bytes blocks" size used by the UDP tests and without limiting the throughput (i.e. without setting the -b option. What is the throughput (in both cases)? That throughput is the approximate maximum possible throughput.
3. The sending (client) side throughput for UDP is only limited by the sending computer resources (CPU, buffers, etc.). Therefore it is strange that the sending rate in your first test is different then the second test. Did you use the same EVB and USB adapter in both tests?
4. As you wrote, it may be that the problem is in the Windows PC. May be it is slower, ha limited resources, etc. It may also be because iperf3 under Windows is running over Cygwin. However, I assume that Ubuntu is using a much newer version of iperf3 and it is recommended to use a much newer iperf3 version before running the above tests.

[xia-s-xian]

Hi,@davidBar-On:

The situation I tested updating to iperf3.17.1 is as follows（using -V option and tcp tests -l to the “bytes blocks”）:

---

EVB Board(usb3.0)->USB to network adapter->Window PC(ETH)
UDP TEST：

root@*:~#./iperf3 -V -c 169.254.146.6 -u -b 1000M -t 10
iperf 3.17.1
Linux * 5.10.59 #1 SMP Fri Jun 28 10:50:09 CST 2024 aarch64
Control connection MSS 1448
Setting UDP block size to 1448
Time: Sat, 13 Jul 2024 10:52:51 GMT
Connecting to host 169.254.146.6, port 5201
Cookie: cfumrj575hlnmh2ira4kmrks57pvu4n73a55
Target Bitrate: 1000000000
[ 5] local 169.254.10.10 port 41187 connected to 169.254.146.6 port 5201
Starting Test: protocol: UDP, 1 streams, 1448 byte blocks, omitting 0 seconds, 10 second test, tos 0
[ ID] Interval Transfer Bitrate Total Datagrams
[ 5] 0.00-1.00 sec 119 MBytes 999 Mbits/sec 86270
[ 5] 1.00-2.00 sec 107 MBytes 899 Mbits/sec 77646
[ 5] 2.00-3.00 sec 107 MBytes 900 Mbits/sec 77651
[ 5] 3.00-4.00 sec 124 MBytes 1.04 Gbits/sec 90002
[ 5] 4.00-5.00 sec 124 MBytes 1.04 Gbits/sec 89858
[ 5] 5.00-6.00 sec 83.0 MBytes 696 Mbits/sec 60081
[ 5] 6.00-7.00 sec 71.9 MBytes 603 Mbits/sec 52093
[ 5] 7.00-8.00 sec 106 MBytes 893 Mbits/sec 77121
[ 5] 8.00-9.00 sec 125 MBytes 1.05 Gbits/sec 90337
[ 5] 9.00-10.00 sec 123 MBytes 1.03 Gbits/sec 89173
Test Complete. Summary Results:
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-10.00 sec 1.07 GBytes 915 Mbits/sec 0.000 ms 0/790232 (0%) sender
[ 5] 0.00-10.00 sec 8.58 MBytes 7.20 Mbits/sec 0.008 ms 7077/13289 (53%) receiver
CPU Utilization: local/sender 79.1% (7.8%u/71.3%s), remote/receiver 11.2% (3.7%u/7.5%s)

iperf Done.

iperf 3.17.1
CYGWIN_NT-10.0-22631 test0018 3.5.3-1.x86_64 2024-04-03 17:25 UTC x86_64
Server listening on 5201 (test #5)
Time: Sat, 13 Jul 2024 10:52:21 GMT
Accepted connection from 169.254.10.10, port 50596
Cookie: cfumrj575hlnmh2ira4kmrks57pvu4n73a55
Target Bitrate: 1000000000
[ 5] local 169.254.146.6 port 5201 connected to 169.254.10.10 port 41187
Starting Test: protocol: UDP, 1 streams, 1448 byte blocks, omitting 0 seconds, 10 second test, tos 0
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-1.00 sec 8.58 MBytes 71.9 Mbits/sec 0.008 ms 7077/13289 (53%)
[ 5] 1.00-2.00 sec 0.00 Bytes 0.00 bits/sec 0.008 ms 0/0 (0%)
[ 5] 2.00-3.00 sec 0.00 Bytes 0.00 bits/sec 0.008 ms 0/0 (0%)
[ 5] 3.00-4.00 sec 0.00 Bytes 0.00 bits/sec 0.008 ms 0/0 (0%)
[ 5] 4.00-5.00 sec 0.00 Bytes 0.00 bits/sec 0.008 ms 0/0 (0%)
[ 5] 5.00-6.00 sec 0.00 Bytes 0.00 bits/sec 0.008 ms 0/0 (0%)
[ 5] 6.00-7.00 sec 0.00 Bytes 0.00 bits/sec 0.008 ms 0/0 (0%)
[ 5] 7.00-8.00 sec 0.00 Bytes 0.00 bits/sec 0.008 ms 0/0 (0%)
[ 5] 8.00-9.00 sec 0.00 Bytes 0.00 bits/sec 0.008 ms 0/0 (0%)
[ 5] 9.00-10.00 sec 0.00 Bytes 0.00 bits/sec 0.008 ms 0/0 (0%)
Test Complete. Summary Results:
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] (sender statistics not available)
[ 5] 0.00-10.00 sec 8.58 MBytes 7.20 Mbits/sec 0.008 ms 7077/13289 (53%) receiver
iperf 3.17.1

---

TCP TEST：

root@*:~#./iperf3 -V -c 169.254.146.6 -l 1448 -t 10
iperf 3.17.1
Linux * 5.10.59 #1 SMP Fri Jun 28 10:50:09 CST 2024 aarch64
Control connection MSS 1448
Time: Sat, 13 Jul 2024 11:03:21 GMT
Connecting to host 169.254.146.6, port 5201
Cookie: ke32iwcc7rkqjond2zfl76jmbwdaeauq4fyt
TCP MSS: 1448 (default)
[ 5] local 169.254.10.10 port 50610 connected to 169.254.146.6 port 5201
Starting Test: protocol: TCP, 1 streams, 1448 byte blocks, omitting 0 seconds, 10 second test, tos 0
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 59.5 MBytes 499 Mbits/sec 0 1.11 MBytes
[ 5] 1.00-2.00 sec 55.1 MBytes 462 Mbits/sec 0 1.11 MBytes
[ 5] 2.00-3.00 sec 49.5 MBytes 415 Mbits/sec 0 1.11 MBytes
[ 5] 3.00-4.00 sec 52.9 MBytes 444 Mbits/sec 0 1.11 MBytes
[ 5] 4.00-5.00 sec 49.5 MBytes 415 Mbits/sec 0 1.11 MBytes
[ 5] 5.00-6.00 sec 48.8 MBytes 410 Mbits/sec 0 1.11 MBytes
[ 5] 6.00-7.00 sec 50.2 MBytes 421 Mbits/sec 0 1.11 MBytes
[ 5] 7.00-8.00 sec 46.7 MBytes 392 Mbits/sec 0 1.11 MBytes
[ 5] 8.00-9.00 sec 45.2 MBytes 379 Mbits/sec 0 1.11 MBytes
[ 5] 9.00-10.00 sec 51.1 MBytes 429 Mbits/sec 0 1.11 MBytes

Test Complete. Summary Results:
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-10.00 sec 509 MBytes 427 Mbits/sec 0 sender
[ 5] 0.00-10.01 sec 504 MBytes 423 Mbits/sec receiver
CPU Utilization: local/sender 9.5% (1.9%u/7.6%s), remote/receiver 12.0% (3.0%u/9.0%s)
snd_tcp_congestion cubic

iperf Done.

iperf 3.17.1
CYGWIN_NT-10.0-22631 test0018 3.5.3-1.x86_64 2024-04-03 17:25 UTC x86_64
Server listening on 5201 (test #1)
Time: Sat, 13 Jul 2024 11:02:51 GMT
Accepted connection from 169.254.10.10, port 50608
Cookie: ke32iwcc7rkqjond2zfl76jmbwdaeauq4fyt
TCP MSS: 0 (default)
[ 5] local 169.254.146.6 port 5201 connected to 169.254.10.10 port 50610
Starting Test: protocol: TCP, 1 streams, 1448 byte blocks, omitting 0 seconds, 10 second test, tos 0
[ ID] Interval Transfer Bitrate
[ 5] 0.00-1.01 sec 54.6 MBytes 452 Mbits/sec
[ 5] 1.01-2.01 sec 54.7 MBytes 462 Mbits/sec
[ 5] 2.01-3.02 sec 50.4 MBytes 420 Mbits/sec
[ 5] 3.02-4.01 sec 52.5 MBytes 442 Mbits/sec
[ 5] 4.01-5.01 sec 49.8 MBytes 420 Mbits/sec
[ 5] 5.01-6.00 sec 47.6 MBytes 401 Mbits/sec
[ 5] 6.00-7.01 sec 49.9 MBytes 416 Mbits/sec
[ 5] 7.01-8.01 sec 47.8 MBytes 398 Mbits/sec
[ 5] 8.01-9.01 sec 44.6 MBytes 377 Mbits/sec
[ 5] 9.01-10.01 sec 52.6 MBytes 439 Mbits/sec
Test Complete. Summary Results:
[ ID] Interval Transfer Bitrate
[ 5] (sender statistics not available)
[ 5] 0.00-10.01 sec 504 MBytes 423 Mbits/sec receiver
iperf 3.17.1

---

EVB Board(usb3.0)->USB to network adapter->Ubuntu PC(ETH)
UDP TEST：

root@*:~#./iperf3 -V -c 169.254.146.3 -u -b 1000M -t 10
iperf 3.17.1
Linux * 5.10.59 #1 SMP Fri Jun 28 10:50:09 CST 2024 aarch64
Control connection MSS 1448
Setting UDP block size to 1448
Time: Sat, 13 Jul 2024 10:59:32 GMT
Connecting to host 169.254.146.3, port 5201
Cookie: ut74lzc77acxngkw4ox2eyquaivbsozkjynb
Target Bitrate: 1000000000
[ 5] local 169.254.10.10 port 45340 connected to 169.254.146.3 port 5201
Starting Test: protocol: UDP, 1 streams, 1448 byte blocks, omitting 0 seconds, 10 second test, tos 0
[ ID] Interval Transfer Bitrate Total Datagrams
[ 5] 0.00-1.00 sec 119 MBytes 1000 Mbits/sec 86314
[ 5] 1.00-2.00 sec 119 MBytes 1.00 Gbits/sec 86341
[ 5] 2.00-3.00 sec 119 MBytes 1000 Mbits/sec 86312
[ 5] 3.00-4.00 sec 119 MBytes 1.00 Gbits/sec 86342
[ 5] 4.00-5.00 sec 119 MBytes 999 Mbits/sec 86269
[ 5] 5.00-6.00 sec 119 MBytes 1000 Mbits/sec 86321
[ 5] 6.00-7.00 sec 119 MBytes 1.00 Gbits/sec 86374
[ 5] 7.00-8.00 sec 119 MBytes 1000 Mbits/sec 86310
[ 5] 8.00-9.00 sec 119 MBytes 1.00 Gbits/sec 86329
[ 5] 9.00-10.00 sec 119 MBytes 999 Mbits/sec 86288
Test Complete. Summary Results:
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-10.00 sec 1.16 GBytes 1000 Mbits/sec 0.000 ms 0/863200 (0%) sender
[ 5] 0.00-10.00 sec 1.16 GBytes 1000 Mbits/sec 0.014 ms 0/863200 (0%) receiver
CPU Utilization: local/sender 100.4% (15.2%u/85.2%s), remote/receiver 31.6% (4.3%u/27.2%s)

iperf Done.

iperf 3.17.1
Linux xsx-Inspiron-5509 5.15.0-113-generic 123~20.04.1-Ubuntu SMP Wed Jun 12 17:33:13 UTC 2024 x86_64
Server listening on 5201 (test #1)
Time: Sat, 13 Jul 2024 10:59:32 GMT
Accepted connection from 169.254.10.10, port 50412
Cookie: ut74lzc77acxngkw4ox2eyquaivbsozkjynb
Target Bitrate: 1000000000
[ 5] local 169.254.146.3 port 5201 connected to 169.254.10.10 port 45340
Starting Test: protocol: UDP, 1 streams, 1448 byte blocks, omitting 0 seconds, 10 second test, tos 0
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-1.00 sec 119 MBytes 999 Mbits/sec 0.013 ms 0/86282 (0%)
[ 5] 1.00-2.00 sec 119 MBytes 1.00 Gbits/sec 0.014 ms 0/86340 (0%)
[ 5] 2.00-3.00 sec 119 MBytes 1000 Mbits/sec 0.015 ms 0/86312 (0%)
[ 5] 3.00-4.00 sec 119 MBytes 1.00 Gbits/sec 0.014 ms 0/86344 (0%)
[ 5] 4.00-5.00 sec 119 MBytes 999 Mbits/sec 0.014 ms 0/86270 (0%)
[ 5] 5.00-6.00 sec 119 MBytes 1000 Mbits/sec 0.014 ms 0/86324 (0%)
[ 5] 6.00-7.00 sec 119 MBytes 1.00 Gbits/sec 0.014 ms 0/86375 (0%)
[ 5] 7.00-8.00 sec 119 MBytes 1000 Mbits/sec 0.014 ms 0/86309 (0%)
[ 5] 8.00-9.00 sec 119 MBytes 1.00 Gbits/sec 0.014 ms 0/86331 (0%)
[ 5] 9.00-10.00 sec 119 MBytes 1000 Mbits/sec 0.013 ms 0/86291 (0%)
[ 5] 10.00-10.00 sec 29.7 KBytes 429 Mbits/sec 0.014 ms 0/22 (0%)
Test Complete. Summary Results:
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] (sender statistics not available)
[ 5] 0.00-10.00 sec 1.16 GBytes 1000 Mbits/sec 0.014 ms 0/863200 (0%) receiver
iperf 3.17.1

---

TCP TEST：

root@*:~#./iperf3 -V -c 169.254.146.3 -l 1448 -t 10
iperf 3.17.1
Linux * 5.10.59 #1 SMP Fri Jun 28 10:50:09 CST 2024 aarch64
Control connection MSS 1448
Time: Sat, 13 Jul 2024 11:00:49 GMT
Connecting to host 169.254.146.3, port 5201
Cookie: 7aleevzcq5lga2bf456clrppwuy6t2ra5kfa
TCP MSS: 1448 (default)
[ 5] local 169.254.10.10 port 50416 connected to 169.254.146.3 port 5201
Starting Test: protocol: TCP, 1 streams, 1448 byte blocks, omitting 0 seconds, 10 second test, tos 0
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 86.5 MBytes 725 Mbits/sec 0 33.9 KBytes
[ 5] 1.00-2.00 sec 89.5 MBytes 751 Mbits/sec 0 33.9 KBytes
[ 5] 2.00-3.00 sec 89.6 MBytes 751 Mbits/sec 0 33.9 KBytes
[ 5] 3.00-4.00 sec 89.5 MBytes 751 Mbits/sec 0 33.9 KBytes
[ 5] 4.00-5.00 sec 89.7 MBytes 752 Mbits/sec 0 33.9 KBytes
[ 5] 5.00-6.00 sec 90.3 MBytes 757 Mbits/sec 0 33.9 KBytes
[ 5] 6.00-7.00 sec 89.8 MBytes 754 Mbits/sec 0 45.2 KBytes
[ 5] 7.00-8.00 sec 90.0 MBytes 755 Mbits/sec 0 45.2 KBytes
[ 5] 8.00-9.00 sec 90.0 MBytes 755 Mbits/sec 0 45.2 KBytes
[ 5] 9.00-10.00 sec 90.0 MBytes 755 Mbits/sec 0 45.2 KBytes
Test Complete. Summary Results:
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-10.00 sec 895 MBytes 751 Mbits/sec 0 sender
[ 5] 0.00-10.00 sec 895 MBytes 750 Mbits/sec receiver
CPU Utilization: local/sender 99.5% (4.6%u/94.9%s), remote/receiver 39.7% (2.0%u/37.7%s)
snd_tcp_congestion cubic
rcv_tcp_congestion cubic

iperf Done.

iperf 3.17.1
Linux xsx-Inspiron-5509 5.15.0-113-generic #123~20.04.1-Ubuntu SMP Wed Jun 12 17:33:13 UTC 2024 x86_64
Server listening on 5201 (test #2)
Time: Sat, 13 Jul 2024 11:00:49 GMT
Accepted connection from 169.254.10.10, port 50414
Cookie: 7aleevzcq5lga2bf456clrppwuy6t2ra5kfa
TCP MSS: 0 (default)
[ 5] local 169.254.146.3 port 5201 connected to 169.254.10.10 port 50416
Starting Test: protocol: TCP, 1 streams, 1448 byte blocks, omitting 0 seconds, 10 second test, tos 0
[ ID] Interval Transfer Bitrate
[ 5] 0.00-1.00 sec 86.4 MBytes 724 Mbits/sec
[ 5] 1.00-2.00 sec 89.5 MBytes 751 Mbits/sec
[ 5] 2.00-3.00 sec 89.6 MBytes 752 Mbits/sec
[ 5] 3.00-4.00 sec 89.5 MBytes 751 Mbits/sec
[ 5] 4.00-5.00 sec 89.7 MBytes 752 Mbits/sec
[ 5] 5.00-6.00 sec 90.3 MBytes 757 Mbits/sec
[ 5] 6.00-7.00 sec 89.8 MBytes 754 Mbits/sec
[ 5] 7.00-8.00 sec 90.0 MBytes 755 Mbits/sec
[ 5] 8.00-9.00 sec 90.0 MBytes 755 Mbits/sec
[ 5] 9.00-10.00 sec 90.0 MBytes 755 Mbits/sec
[ 5] 10.00-10.00 sec 38.2 KBytes 106 Mbits/sec
Test Complete. Summary Results:
[ ID] Interval Transfer Bitrate
[ 5] (sender statistics not available)
[ 5] 0.00-10.00 sec 895 MBytes 750 Mbits/sec receiver
rcv_tcp_congestion cubic

Did you use the same EVB and USB adapter in both tests?
->Yes.

[davidBar-On]

Hi, from the TCP tests it seems that the throughput limitation is in the Windows PC - either the in Windows or in iperf3. Are you able to try the TCP tests using iperf (iperf2)? iperf is not using Cygwin, so that may show whether the problem is in iperf3 or Windows (or the Windows PC).

Regarding the UDP test using Windows. It seems that the server is stuck. This is either iperf3 or Cygwin problem (note that iperf3 is not supported formally under Windows). Can you try running few UDP tests using Windows with limiting the client bit rate to 300M, 500M, 700M? This may show whether this is an iperf3 problem in all bit rates.

[xia-s-xian]

Hi, David:

1.It is normal to test udp using iperf2 version. It should be a problem with iperf3 version.

:~$ iperf -c 169.254.254.188 -i 1 -u -b 1000M
Client connecting to 169.254.254.188, UDP port 5001
Sending 1470 byte datagrams, IPG target: 11.22 us (kalman adjust)
UDP buffer size: 208 KByte (default)
[ 3] local 169.254.254.180 port 57597 connected with 169.254.254.188 port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0- 1.0 sec 113 MBytes 944 Mbits/sec
[ 3] 1.0- 2.0 sec 112 MBytes 942 Mbits/sec
[ 3] 2.0- 3.0 sec 113 MBytes 946 Mbits/sec
[ 3] 3.0- 4.0 sec 113 MBytes 950 Mbits/sec
[ 3] 4.0- 5.0 sec 113 MBytes 949 Mbits/sec
[ 3] 5.0- 6.0 sec 112 MBytes 941 Mbits/sec
[ 3] 6.0- 7.0 sec 113 MBytes 949 Mbits/sec
[ 3] 7.0- 8.0 sec 112 MBytes 938 Mbits/sec
[ 3] 8.0- 9.0 sec 112 MBytes 941 Mbits/sec
[ 3] 9.0-10.0 sec 113 MBytes 951 Mbits/sec
[ 3] 0.0-10.0 sec 1.10 GBytes 945 Mbits/sec
[ 3] Sent 803639 datagrams
[ 3] Server Report:
[ 3] 0.0-10.0 sec 1.10 GBytes 945 Mbits/sec 0.021 ms 280/803639 (0.035%)

.\iperf-2.2.n-win64.exe -s -u -i 1
Server listening on UDP port 5001
UDP buffer size: 64.0 KByte (default)
[ 1] local 169.254.254.188 port 5001 connected with 169.254.254.180 port 57597
[ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams
[ 1] 0.00-1.00 sec 112 MBytes 942 Mbits/sec 0.017 ms 146/80287 (0.18%)
[ 1] 1.00-2.00 sec 112 MBytes 942 Mbits/sec 0.011 ms 0/80094 (0%)
[ 1] 2.00-3.00 sec 113 MBytes 946 Mbits/sec 0.011 ms 0/80427 (0%)
[ 1] 3.00-4.00 sec 113 MBytes 950 Mbits/sec 0.008 ms 0/80795 (0%)
[ 1] 4.00-5.00 sec 113 MBytes 950 Mbits/sec 0.020 ms 0/80749 (0%)
[ 1] 5.00-6.00 sec 112 MBytes 941 Mbits/sec 0.012 ms 4/80039 (0.005%)
[ 1] 6.00-7.00 sec 113 MBytes 949 Mbits/sec 0.014 ms 8/80708 (0.0099%)
[ 1] 7.00-8.00 sec 112 MBytes 937 Mbits/sec 0.030 ms 122/79762 (0.15%)
[ 1] 8.00-9.00 sec 112 MBytes 940 Mbits/sec 0.013 ms 0/79965 (0%)
[ 1] 9.00-10.00 sec 113 MBytes 951 Mbits/sec 0.018 ms 0/80813 (0%)
[ 1] 0.00-10.00 sec 1.10 GBytes 945 Mbits/sec 0.022 ms 280/803639 (0.035%)

2.Try running few UDP tests using Windows with limiting the client bit rate to 300M, 500M, 700M.

ubuntu:~$ iperf3 -c 169.254.254.188 -u -b 300M -t 10
Connecting to host 169.254.254.188, port 5201
[ 5] local 169.254.254.180 port 39559 connected to 169.254.254.188 port 5201
[ ID] Interval Transfer Bitrate Total Datagrams
[ 5] 0.00-1.00 sec 35.7 MBytes 300 Mbits/sec 25884
[ 5] 1.00-2.00 sec 35.8 MBytes 300 Mbits/sec 25898
[ 5] 2.00-3.00 sec 35.8 MBytes 300 Mbits/sec 25898
[ 5] 3.00-4.00 sec 35.8 MBytes 300 Mbits/sec 25896
[ 5] 4.00-5.00 sec 35.8 MBytes 300 Mbits/sec 25900
[ 5] 5.00-6.00 sec 35.8 MBytes 300 Mbits/sec 25897
[ 5] 6.00-7.00 sec 35.8 MBytes 300 Mbits/sec 25896
[ 5] 7.00-8.00 sec 35.8 MBytes 300 Mbits/sec 25900
[ 5] 8.00-9.00 sec 35.8 MBytes 300 Mbits/sec 25898
[ 5] 9.00-10.00 sec 35.8 MBytes 300 Mbits/sec 25892
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-10.00 sec 358 MBytes 300 Mbits/sec 0.000 ms 0/258959 (0%) sender
[ 5] 0.00-10.04 sec 346 MBytes 289 Mbits/sec 0.022 ms 8585/258959 (3.3%) receiver
iperf Done.

ubuntu:~$ iperf3 -c 169.254.254.188 -u -b 500M -t 10
Connecting to host 169.254.254.188, port 5201
[ 5] local 169.254.254.180 port 42525 connected to 169.254.254.188 port 5201
[ ID] Interval Transfer Bitrate Total Datagrams
[ 5] 0.00-1.00 sec 59.6 MBytes 500 Mbits/sec 43160
[ 5] 1.00-2.00 sec 59.6 MBytes 500 Mbits/sec 43166
[ 5] 2.00-3.00 sec 59.6 MBytes 500 Mbits/sec 43150
[ 5] 3.00-4.00 sec 59.6 MBytes 500 Mbits/sec 43174
[ 5] 4.00-5.00 sec 59.6 MBytes 500 Mbits/sec 43152
[ 5] 5.00-6.00 sec 59.6 MBytes 500 Mbits/sec 43155
[ 5] 6.00-7.00 sec 59.6 MBytes 500 Mbits/sec 43169
[ 5] 7.00-8.00 sec 59.6 MBytes 500 Mbits/sec 43177
[ 5] 8.00-9.00 sec 59.6 MBytes 500 Mbits/sec 43156
[ 5] 9.00-10.00 sec 59.6 MBytes 500 Mbits/sec 43152
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-10.00 sec 596 MBytes 500 Mbits/sec 0.000 ms 0/431611 (0%) sender
[ 5] 0.00-10.04 sec 558 MBytes 466 Mbits/sec 0.007 ms 27766/431591 (6.4%) receiver

iperf Done.
@ubuntu:~$ iperf3 -c 169.254.254.188 -u -b 700M -t 10
Connecting to host 169.254.254.188, port 5201
[ 5] local 169.254.254.180 port 54562 connected to 169.254.254.188 port 5201
[ ID] Interval Transfer Bitrate Total Datagrams
[ 5] 0.00-1.00 sec 83.4 MBytes 700 Mbits/sec 60417
[ 5] 1.00-2.00 sec 83.4 MBytes 700 Mbits/sec 60427
[ 5] 2.00-3.00 sec 83.4 MBytes 700 Mbits/sec 60415
[ 5] 3.00-4.00 sec 83.4 MBytes 700 Mbits/sec 60427
[ 5] 4.00-5.00 sec 83.4 MBytes 700 Mbits/sec 60420
[ 5] 5.00-6.00 sec 83.5 MBytes 700 Mbits/sec 60458
[ 5] 6.00-7.00 sec 83.5 MBytes 700 Mbits/sec 60432
[ 5] 7.00-8.00 sec 83.4 MBytes 700 Mbits/sec 60420
[ 5] 8.00-9.00 sec 83.4 MBytes 700 Mbits/sec 60389
[ 5] 9.00-10.00 sec 83.5 MBytes 700 Mbits/sec 60458
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-10.00 sec 834 MBytes 700 Mbits/sec 0.000 ms 0/604263 (0%) sender
[ 5] 0.00-10.04 sec 569 MBytes 476 Mbits/sec 0.017 ms 191826/604219 (32%) receiver

iperf Done.

[davidBar-On]

Hi,
Thanks for the input from the tests you run it is quite clear that iperf3 performance on Windows is limited and that at least for high bandwidth tests iperf2 is preferred in such environments.

Since formally iperf3 is not supported on Windows, I am not sure if this issue will be handled, especially if the problem is because of using Cygwin.

[xia-s-xian]

Hi:

Got it. Recently, I browsed the discussion board and saw that many people have encountered the same problem. If possible, I hope someone can fix this problem.

Thank you.