Le TCP semble bien fonctionner, mais iperf en UDP semble se comporter de manière bizarre (c'est peut-être le serveur).
500Mbps => 19% de pertes :
~  ᐅ iperf3 -R -c ping6.online.net -p 5203 -u -b 500M --get-server-output
Connecting to host ping6.online.net, port 5203
Reverse mode, remote host ping6.online.net is sending
[  5] local 2a01:cb00:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx port 36023 connected to 2001:bc8:1::40 port 5203
[ ID] Interval           Transfer     Bitrate         Jitter    Lost/Total Datagrams
[  5]   0.00-1.00   sec  47.5 MBytes   398 Mbits/sec  0.016 ms  9512/44360 (21%)
[  5]   1.00-2.00   sec  48.2 MBytes   405 Mbits/sec  0.013 ms  8468/43882 (19%)
[  5]   2.00-3.00   sec  49.0 MBytes   411 Mbits/sec  0.011 ms  7742/43745 (18%)
[  5]   3.00-4.00   sec  49.0 MBytes   411 Mbits/sec  0.014 ms  7720/43692 (18%)
[  5]   4.00-5.00   sec  48.4 MBytes   406 Mbits/sec  0.017 ms  8539/44100 (19%)
[  5]   5.00-6.00   sec  48.2 MBytes   404 Mbits/sec  0.015 ms  8065/43465 (19%)
[  5]   6.00-7.00   sec  47.4 MBytes   398 Mbits/sec  0.016 ms  8667/43494 (20%)
[  5]   7.00-8.00   sec  48.2 MBytes   405 Mbits/sec  0.014 ms  8692/44101 (20%)
[  5]   8.00-9.00   sec  48.9 MBytes   410 Mbits/sec  0.015 ms  8305/44205 (19%)
[  5]   9.00-10.00  sec  47.9 MBytes   402 Mbits/sec  0.018 ms  8273/43456 (19%)
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Jitter    Lost/Total Datagrams
[  5]   0.00-10.00  sec   598 MBytes   501 Mbits/sec  0.000 ms  0/438500 (0%)  sender
[  5]   0.00-10.00  sec   483 MBytes   405 Mbits/sec  0.018 ms  83983/438500 (19%)  receiver
Server output:
Time: Wed, 22 Feb 2023 22:47:17 GMT
Accepted connection from 2a01:cb00:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx, port 37038
      Cookie: htbgkxk2ug3fo6jwfzyftf6o4vjnomlnlzox
[  5] local 2001:bc8:1::40 port 5203 connected to 2a01:cb00:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx port 36023
Starting Test: protocol: UDP, 1 streams, 1428 byte blocks, omitting 0 seconds, 10 second test
[ ID] Interval           Transfer     Bandwidth       Total Datagrams
[  5]   0.00-2.00   sec   115 MBytes   483 Mbits/sec  84526
[  5]   2.00-4.00   sec   119 MBytes   499 Mbits/sec  87443
[  5]   4.00-6.00   sec   119 MBytes   500 Mbits/sec  87579
[  5]   6.00-8.00   sec   120 MBytes   501 Mbits/sec  87770
[  5]   8.00-10.00  sec   119 MBytes   498 Mbits/sec  87255
[  5]  10.00-10.04  sec  5.97 MBytes  1.19 Gbits/sec  4387
- - - - - - - - - - - - - - - - - - - - - - - - -
Test Complete. Summary Results:
[ ID] Interval           Transfer     Bandwidth       Jitter    Lost/Total Datagrams
[  5]   0.00-10.04  sec   598 MBytes   499 Mbits/sec  0.000 ms  0/438960 (0%)
CPU Utilization: local/sender 3.0% (0.4%u/2.6%s), remote/receiver 2.9% (0.4%u/2.5%s)
500Mbps avec des paquets de 500 octets => 1,2% de pertes (bizarre que ça fonctionne mieux, en tout cas ça s'accompagne d'une forte charge CPU du serveur) :
~  ᐅ iperf3 -R -c ping6.online.net -p 5203 -u -b 500M --get-server-output -l 500
Connecting to host ping6.online.net, port 5203
Reverse mode, remote host ping6.online.net is sending
[  5] local 2a01:cb00:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx port 38276 connected to 2001:bc8:1::40 port 5203
[ ID] Interval           Transfer     Bitrate         Jitter    Lost/Total Datagrams
[  5]   0.00-1.00   sec  59.6 MBytes   500 Mbits/sec  0.005 ms  1082/126012 (0.86%)
[  5]   1.00-2.00   sec  59.4 MBytes   499 Mbits/sec  0.004 ms  866/125496 (0.69%)
[  5]   2.00-3.00   sec  60.0 MBytes   503 Mbits/sec  0.006 ms  733/126561 (0.58%)
[  5]   3.00-4.00   sec  55.1 MBytes   463 Mbits/sec  0.003 ms  1661/117306 (1.4%)
[  5]   4.00-5.00   sec  58.0 MBytes   487 Mbits/sec  0.004 ms  1857/123588 (1.5%)
[  5]   5.00-6.00   sec  63.5 MBytes   533 Mbits/sec  0.004 ms  976/134101 (0.73%)
[  5]   6.00-7.00   sec  59.0 MBytes   495 Mbits/sec  0.004 ms  1641/125305 (1.3%)
[  5]   7.00-8.00   sec  57.9 MBytes   486 Mbits/sec  0.006 ms  1492/122938 (1.2%)
[  5]   8.00-9.00   sec  57.7 MBytes   484 Mbits/sec  0.004 ms  2694/123764 (2.2%)
[  5]   9.00-10.00  sec  59.7 MBytes   500 Mbits/sec  0.006 ms  2598/127699 (2%)
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Jitter    Lost/Total Datagrams
[  5]   0.00-10.00  sec   598 MBytes   501 Mbits/sec  0.000 ms  0/1252770 (0%)  sender
[  5]   0.00-10.00  sec   590 MBytes   495 Mbits/sec  0.006 ms  15600/1252770 (1.2%)  receiver
Server output:
iperf 3.1.3
Linux ping 4.15.0-47-generic #50-Ubuntu SMP Wed Mar 13 10:44:52 UTC 2019 x86_64
-----------------------------------------------------------
Server listening on 5203
-----------------------------------------------------------
Time: Wed, 22 Feb 2023 22:48:38 GMT
Accepted connection from 2a01:cb00:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx, port 43396
      Cookie: k5rds5w6ooc7fn2yulzrza7bp362uv7iur5a
[  5] local 2001:bc8:1::40 port 5203 connected to 2a01:cb00:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx port 38276
Starting Test: protocol: UDP, 1 streams, 500 byte blocks, omitting 0 seconds, 10 second test
[ ID] Interval           Transfer     Bandwidth       Total Datagrams
[  5]   0.00-2.00   sec   119 MBytes   499 Mbits/sec  249374
[  5]   2.00-4.00   sec   114 MBytes   479 Mbits/sec  239621
[  5]   4.00-6.00   sec   123 MBytes   515 Mbits/sec  257693
[  5]   6.00-8.00   sec   118 MBytes   496 Mbits/sec  247921
[  5]   8.00-10.00  sec   120 MBytes   503 Mbits/sec  251258
[  5]  10.00-10.04  sec  3.57 MBytes   713 Mbits/sec  7484
- - - - - - - - - - - - - - - - - - - - - - - - -
Test Complete. Summary Results:
[ ID] Interval           Transfer     Bandwidth       Jitter    Lost/Total Datagrams
[  5]   0.00-10.04  sec   598 MBytes   499 Mbits/sec  0.000 ms  0/1253351 (0%)
CPU Utilization: local/sender 28.6% (3.6%u/24.9%s), remote/receiver 1.5% (0.1%u/1.4%s)
900Mbps en paquets de 500 octets => forte charge CPU côté serveur qui semble le limiter à 700Mbps, mais peu de pertes (parfois comme ici ça fait des out of order, et une forte charge CPU côté client) :
~  ᐅ iperf3 -R -c ping6.online.net -p 5203 -u -b 900M --get-server-output -l 500
Connecting to host ping6.online.net, port 5203
Reverse mode, remote host ping6.online.net is sending
[  5] local 2a01:cb00:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx port 52261 connected to 2001:bc8:1::40 port 5203
[ ID] Interval           Transfer     Bitrate         Jitter    Lost/Total Datagrams
[  5]   0.00-1.00   sec  79.9 MBytes   670 Mbits/sec  0.009 ms  163469/331001 (49%)
[  5]   1.00-2.00   sec  79.4 MBytes   666 Mbits/sec  0.005 ms  -157057/9445 (-1.7e+03%)
[  5]   2.00-3.00   sec  83.0 MBytes   697 Mbits/sec  0.005 ms  5319/179449 (3%)
[  5]   3.00-4.00   sec  84.5 MBytes   708 Mbits/sec  0.004 ms  7405/184522 (4%)
[  5]   4.00-5.00   sec  78.6 MBytes   659 Mbits/sec  0.009 ms  6942/171695 (4%)
[  5]   5.00-6.00   sec  78.1 MBytes   655 Mbits/sec  0.005 ms  536/164360 (0.33%)
[  5]   6.00-7.00   sec  82.0 MBytes   688 Mbits/sec  0.006 ms  3985/175998 (2.3%)
[  5]   7.00-8.00   sec  81.9 MBytes   687 Mbits/sec  0.004 ms  2285/174053 (1.3%)
[  5]   8.00-9.00   sec  80.0 MBytes   671 Mbits/sec  0.004 ms  2761/170578 (1.6%)
[  5]   9.00-10.00  sec  82.3 MBytes   690 Mbits/sec  0.004 ms  3589/176111 (2%)
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Jitter    Lost/Total Datagrams
[  5]   0.00-10.00  sec   829 MBytes   695 Mbits/sec  0.000 ms  0/1737212 (0%)  sender
[SUM]  0.0-10.0 sec  324587 datagrams received out-of-order
[  5]   0.00-10.00  sec   810 MBytes   679 Mbits/sec  0.004 ms  39234/1737212 (2.3%)  receiver
Server output:
iperf 3.1.3
Linux ping 4.15.0-47-generic #50-Ubuntu SMP Wed Mar 13 10:44:52 UTC 2019 x86_64
-----------------------------------------------------------
Server listening on 5203
-----------------------------------------------------------
Time: Wed, 22 Feb 2023 22:49:06 GMT
Accepted connection from 2a01:cb00:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx, port 41514
      Cookie: mlngbjsmbgyhmrh3fljex54a2p2pu4vh7wxw
[  5] local 2001:bc8:1::40 port 5203 connected to 2a01:cb00:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx port 52261
Starting Test: protocol: UDP, 1 streams, 500 byte blocks, omitting 0 seconds, 10 second test
[ ID] Interval           Transfer     Bandwidth       Total Datagrams
[  5]   0.00-2.00   sec   159 MBytes   667 Mbits/sec  333670
[  5]   2.00-4.00   sec   173 MBytes   727 Mbits/sec  363571
[  5]   4.00-6.00   sec   161 MBytes   673 Mbits/sec  336642
[  5]   6.00-8.00   sec   167 MBytes   700 Mbits/sec  349830
[  5]   8.00-10.00  sec   165 MBytes   693 Mbits/sec  346544
[  5]  10.00-10.04  sec  3.58 MBytes   703 Mbits/sec  7515
- - - - - - - - - - - - - - - - - - - - - - - - -
Test Complete. Summary Results:
[ ID] Interval           Transfer     Bandwidth       Jitter    Lost/Total Datagrams
[  5]   0.00-10.04  sec   829 MBytes   692 Mbits/sec  0.000 ms  0/1737772 (0%)
CPU Utilization: local/sender 35.7% (4.3%u/31.4%s), remote/receiver 40.1% (4.9%u/35.2%s)