J'ai poursuivi un peu les investigations, avec des mesures iperf3, en UDP, depuis un serveur Lyonnais situé à moins de 3ms de chez moi (mais en dehors du réseau SFR quand même).
iperf3, UDP, mesure du sens descendant de la FTTH, pacing-timer par defaut (1ms):Débit émis | Débit reçu | % perte paquet |
5.00 Mbps | 4.99 Mbps | < 0.2% |
25.0 Mbps | 25.0 Mbps | < 0.2% |
50.0 Mbps | 50.0 Mbps | < 0.2% |
100 Mbps | 99.9 Mbps | < 0.2% |
200 Mbps | 200 Mbps | < 0.2% |
300 Mbps | 299 Mbps | < 0.2% |
400 Mbps | 399 Mbps | < 0.2% |
500 Mbps | 498 Mbps | 0.3% |
550 Mbps | 548 Mbps | 0.22% |
600 Mbps | 573 Mbps | 4.3% |
650 Mbps | 571 Mbps | 12% |
700 Mbps | 573 Mbps | 18% |
800 Mbps | 550 Mbps | 31% |
900 Mbps | 536 Mbps | 40% |
On vois qu'il y a systématiquement de la perte de paquet. Même sur des faibles débits, impossible d'être à 0% de perte.
On plafonne vers 550-570Mbps.
Maintenant, refaisons les tests, en ne changeant qu'un seul paramètre: --pacing-timer 10
iperf3, UDP, mesure du sens descendant de la FTTH, --pacing-timer 10 (10μs):Débit émis | Débit reçu | % perte paquet |
5.00 Mbps | 4.99 Mbps | 0.25% |
25.0 Mbps | 24.9 Mbps | 0.25% |
50.0 Mbps | 50.0 Mbps | < 0.2% |
100 Mbps | 99.9 Mbps | < 0.2% |
200 Mbps | 200 Mbps | < 0.2% |
300 Mbps | 299 Mbps | < 0.2% |
400 Mbps | 399 Mbps | < 0.2% |
500 Mbps | 499 Mbps | < 0.2% |
600 Mbps | 599 Mbps | < 0.2% |
700 Mbps | 698 Mbps | < 0.2% |
800 Mbps | 796 Mbps | 0.35% |
900 Mbps | 895 Mbps | 0.41% |
Il y a toujours de la perte par tout a fait négligeable, mais on arrive quasiment au 1 Gbps de l'offre commerciale.
Ce sont bien les pertes de paquet qui empêchent TCP de monter en débit, en particulier quand TCP Cubic est utilisé.
Après, où disparaissent ces paquets...
Les résultats bruts:
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-600.00 sec 358 MBytes 5.00 Mbits/sec 0.000 ms 0/258978 (0%) sender
[ 5] 0.00-600.05 sec 357 MBytes 4.99 Mbits/sec 0.103 ms 242/258978 (0.093%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-240.00 sec 715 MBytes 25.0 Mbits/sec 0.000 ms 0/517954 (0%) sender
[ 5] 0.00-240.04 sec 714 MBytes 25.0 Mbits/sec 0.051 ms 641/517954 (0.12%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-120.00 sec 715 MBytes 50.0 Mbits/sec 0.000 ms 0/517952 (0%) sender
[ 5] 0.00-120.04 sec 715 MBytes 50.0 Mbits/sec 0.019 ms 18/517952 (0.0035%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-60.00 sec 715 MBytes 100 Mbits/sec 0.000 ms 0/517949 (0%) sender
[ 5] 0.00-60.04 sec 715 MBytes 99.9 Mbits/sec 0.016 ms 12/517949 (0.0023%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 715 MBytes 200 Mbits/sec 0.000 ms 0/517942 (0%) sender
[ 5] 0.00-30.04 sec 715 MBytes 200 Mbits/sec 0.015 ms 141/517942 (0.027%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 1.05 GBytes 300 Mbits/sec 0.000 ms 0/776914 (0%) sender
[ 5] 0.00-30.04 sec 1.05 GBytes 299 Mbits/sec 0.014 ms 328/776914 (0.042%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 1.40 GBytes 400 Mbits/sec 0.000 ms 0/1035886 (0%) sender
[ 5] 0.00-30.04 sec 1.40 GBytes 399 Mbits/sec 0.013 ms 416/1035886 (0.04%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 1.75 GBytes 500 Mbits/sec 0.000 ms 0/1294859 (0%) sender
[ 5] 0.00-30.04 sec 1.74 GBytes 498 Mbits/sec 0.011 ms 3864/1294859 (0.3%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 1.92 GBytes 550 Mbits/sec 0.000 ms 0/1424345 (0%) sender
[ 5] 0.00-30.04 sec 1.92 GBytes 548 Mbits/sec 0.013 ms 3111/1424345 (0.22%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 2.10 GBytes 600 Mbits/sec 0.000 ms 0/1553834 (0%) sender
[ 5] 0.00-30.04 sec 2.01 GBytes 573 Mbits/sec 0.012 ms 66974/1553828 (4.3%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 2.27 GBytes 650 Mbits/sec 0.000 ms 0/1683320 (0%) sender
[ 5] 0.00-30.04 sec 2.00 GBytes 571 Mbits/sec 0.013 ms 203634/1683314 (12%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 2.44 GBytes 700 Mbits/sec 0.000 ms 0/1812809 (0%) sender
[ 5] 0.00-30.04 sec 2.00 GBytes 573 Mbits/sec 0.011 ms 327106/1812796 (18%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 2.79 GBytes 800 Mbits/sec 0.000 ms 0/2071782 (0%) sender
[ 5] 0.00-30.04 sec 1.92 GBytes 550 Mbits/sec 0.013 ms 646605/2071757 (31%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 3.14 GBytes 900 Mbits/sec 0.000 ms 0/2330759 (0%) sender
[ 5] 0.00-30.04 sec 1.88 GBytes 536 Mbits/sec 0.012 ms 940111/2330728 (40%) receiver
PACING --pacing-timer 10
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-600.00 sec 358 MBytes 5.00 Mbits/sec 0.000 ms 0/258978 (0%) sender
[ 5] 0.00-600.04 sec 357 MBytes 4.99 Mbits/sec 0.070 ms 652/258978 (0.25%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-240.00 sec 715 MBytes 25.0 Mbits/sec 0.000 ms 0/517956 (0%) sender
[ 5] 0.00-240.04 sec 713 MBytes 24.9 Mbits/sec 0.032 ms 1279/517956 (0.25%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-120.00 sec 715 MBytes 50.0 Mbits/sec 0.000 ms 0/517956 (0%) sender
[ 5] 0.00-120.04 sec 715 MBytes 50.0 Mbits/sec 0.018 ms 232/517956 (0.045%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-60.00 sec 715 MBytes 100 Mbits/sec 0.000 ms 0/517956 (0%) sender
[ 5] 0.00-60.04 sec 715 MBytes 99.9 Mbits/sec 0.008 ms 214/517956 (0.041%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-60.00 sec 1.40 GBytes 200 Mbits/sec 0.000 ms 0/1035911 (0%) sender
[ 5] 0.00-60.04 sec 1.40 GBytes 200 Mbits/sec 0.027 ms 310/1035911 (0.03%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 1.05 GBytes 300 Mbits/sec 0.000 ms 0/776934 (0%) sender
[ 5] 0.00-30.04 sec 1.05 GBytes 299 Mbits/sec 0.019 ms 346/776932 (0.045%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 1.40 GBytes 400 Mbits/sec 0.000 ms 0/1035911 (0%) sender
[ 5] 0.00-30.04 sec 1.40 GBytes 399 Mbits/sec 0.018 ms 167/1035908 (0.016%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 1.75 GBytes 500 Mbits/sec 0.000 ms 0/1294890 (0%) sender
[ 5] 0.00-30.04 sec 1.75 GBytes 499 Mbits/sec 0.017 ms 600/1294886 (0.046%) receiver
[ 5] 0.00-30.00 sec 2.10 GBytes 600 Mbits/sec 0.000 ms 0/1553868 (0%) sender
[ 5] 0.00-30.05 sec 2.09 GBytes 599 Mbits/sec 0.034 ms 1181/1553868 (0.076%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 2.44 GBytes 700 Mbits/sec 0.000 ms 0/1812845 (0%) sender
[ 5] 0.00-30.04 sec 2.44 GBytes 698 Mbits/sec 0.018 ms 1537/1812842 (0.085%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 2.79 GBytes 800 Mbits/sec 0.000 ms 0/2071820 (0%) sender
[ 5] 0.00-30.05 sec 2.78 GBytes 796 Mbits/sec 0.016 ms 7322/2071820 (0.35%) receiver
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-30.00 sec 3.14 GBytes 900 Mbits/sec 0.000 ms 0/2330799 (0%) sender
[ 5] 0.00-30.05 sec 3.13 GBytes 895 Mbits/sec 0.015 ms 9472/2330799 (0.41%) receiver