Re: Too aggressive TCP ACKs
- Reply: Zhenlei Huang : "Re: Too aggressive TCP ACKs"
- In reply to: Zhenlei Huang : "Too aggressive TCP ACKs"
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Date: Fri, 21 Oct 2022 14:34:04 UTC
> On 21. Oct 2022, at 16:19, Zhenlei Huang <zlei.huang@gmail.com> wrote: > > Hi, > > While I was repeating https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=258755, I observed a > strange behavior. The TCP ACKs from FreeBSD host are too aggressive. > > My setup is simple: > A B > [ MacOS ] <====> [ FreeBSD VM ] > 192.168.120.1 192.168.12.134 (disable tso and lro) > While A <--- B, i.e. A as server and B as client, the packets rate looks good. > > One session on B: > > root@:~ # iperf3 -c 192.168.120.1 -b 10m > Connecting to host 192.168.120.1, port 5201 > [ 5] local 192.168.120.134 port 54459 connected to 192.168.120.1 port 5201 > [ ID] Interval Transfer Bitrate Retr Cwnd > [ 5] 0.00-1.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes > [ 5] 1.00-2.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes > [ 5] 2.00-3.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 KBytes > [ 5] 3.00-4.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes > [ 5] 4.00-5.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 KBytes > [ 5] 5.00-6.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes > [ 5] 6.00-7.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 KBytes > [ 5] 7.00-8.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes > [ 5] 8.00-9.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 KBytes > [ 5] 9.00-10.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes > - - - - - - - - - - - - - - - - - - - - - - - - - > [ ID] Interval Transfer Bitrate Retr > [ 5] 0.00-10.00 sec 12.0 MBytes 10.1 Mbits/sec 0 sender > [ 5] 0.00-10.00 sec 12.0 MBytes 10.1 Mbits/sec receiver > > iperf Done. > > Another session on B: > > root@:~ # netstat -w 1 -I vmx0 > input vmx0 output > packets errs idrops bytes packets errs bytes colls > 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 > 342 0 0 22600 526 0 775724 0 > 150 0 0 9900 851 0 1281454 0 > 109 0 0 7194 901 0 1357850 0 > 126 0 0 8316 828 0 1246632 0 > 122 0 0 8052 910 0 1370780 0 > 109 0 0 7194 819 0 1233702 0 > 120 0 0 7920 910 0 1370780 0 > 110 0 0 7260 819 0 1233702 0 > 123 0 0 8118 910 0 1370780 0 > 109 0 0 7194 819 0 1233702 0 > 73 0 0 5088 465 0 686342 0 > 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 > > > > ================================================================ > > > While A ---> B, i.e. A as client and B as server, the ACKs sent from B looks strange. > > Session on A: > > % iperf3 -c 192.168.120.134 -b 10m > Connecting to host 192.168.120.134, port 5201 > [ 5] local 192.168.120.1 port 52370 connected to 192.168.120.134 port 5201 > [ ID] Interval Transfer Bitrate > [ 5] 0.00-1.00 sec 1.25 MBytes 10.5 Mbits/sec > [ 5] 1.00-2.00 sec 1.25 MBytes 10.5 Mbits/sec > [ 5] 2.00-3.00 sec 1.12 MBytes 9.44 Mbits/sec > [ 5] 3.00-4.00 sec 1.25 MBytes 10.5 Mbits/sec > [ 5] 4.00-5.00 sec 1.12 MBytes 9.44 Mbits/sec > [ 5] 5.00-6.00 sec 1.25 MBytes 10.5 Mbits/sec > [ 5] 6.00-7.00 sec 1.12 MBytes 9.44 Mbits/sec > [ 5] 7.00-8.00 sec 1.25 MBytes 10.5 Mbits/sec > [ 5] 8.00-9.00 sec 1.12 MBytes 9.44 Mbits/sec > [ 5] 9.00-10.00 sec 1.25 MBytes 10.5 Mbits/sec > - - - - - - - - - - - - - - - - - - - - - - - - - > [ ID] Interval Transfer Bitrate > [ 5] 0.00-10.00 sec 12.0 MBytes 10.1 Mbits/sec sender > [ 5] 0.00-10.00 sec 12.0 MBytes 10.1 Mbits/sec receiver > > iperf Done. > > Session on B: > > root@:~ # netstat -w 1 -I vmx0 > input vmx0 output > packets errs idrops bytes packets errs bytes colls > 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 > 649 0 0 960562 330 0 21800 0 > 819 0 0 1233702 415 0 27390 0 > 910 0 0 1370780 459 0 30294 0 > 819 0 0 1233702 415 0 27390 0 > 910 0 0 1370780 459 0 30294 0 > 910 0 0 1370780 460 0 30360 0 > 819 0 0 1233702 414 0 27324 0 > 910 0 0 1370780 460 0 30360 0 > 819 0 0 1233702 414 0 27324 0 > 910 0 0 1370780 460 0 30360 0 > 285 0 0 412287 147 0 9981 0 > 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 > 0 0 0 0 0 0 0 0 > > > The ACK packets replied from B (the FreeBSD VM) are too aggressive. They are > about one half of TCP packets received from A. > > I've tested with different bitrates, from 10m to 300m, all behave the same. > Tested with baremetal FreeBSD 13.1 Box as B (with intel em driver), the > bitrates is 1g, also behaves the same. > > Also tried different FreeBSD versions, 11.4, 12.3, stable/13 and current/14 all > behave the same. > > > My question is, is that the expected behavior of current default TCP stack? That is what I would expect. TCP (on FreeBSD) is acking every other packet. This is also what is specified. MacOS, at least newer versions, send less ACKs. Best regards Michael > > > > Best regards, > Zhenlei >