Date: Sat, 22 Oct 2022 10:51:32 +0800 From: Zhenlei Huang <zlei.huang@gmail.com> To: Michael Tuexen <michael.tuexen@lurchi.franken.de> Cc: freebsd-net@freebsd.org Subject: Re: Too aggressive TCP ACKs Message-ID: <330A9146-F7CC-4CAB-9003-2F90B872AC3E@gmail.com> In-Reply-To: <0FED34A9-D093-442A-83B7-08C06D11F8B5@lurchi.franken.de> References: <75D35F36-7759-4168-ADBA-C2414F5B53BC@gmail.com> <712641B3-5196-40CC-9B64-04637F16F649@lurchi.franken.de> <62A0DD30-B3ED-48BE-9C01-146487599092@gmail.com> <0FED34A9-D093-442A-83B7-08C06D11F8B5@lurchi.franken.de>
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--Apple-Mail=_0987CBA6-7ECA-4B84-BEC7-7256BD5AFCA9 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii > On Oct 22, 2022, at 2:16 AM, Michael Tuexen = <michael.tuexen@lurchi.franken.de = <mailto:michael.tuexen@lurchi.franken.de>> wrote: >=20 >> On 21. Oct 2022, at 17:00, Zhenlei Huang <zlei.huang@gmail.com = <mailto:zlei.huang@gmail.com>> wrote: >>=20 >>=20 >>> On Oct 21, 2022, at 10:34 PM, Michael Tuexen = <michael.tuexen@lurchi.franken.de = <mailto:michael.tuexen@lurchi.franken.de>> wrote: >>>=20 >>>> On 21. Oct 2022, at 16:19, Zhenlei Huang <zlei.huang@gmail.com = <mailto:zlei.huang@gmail.com>> wrote: >>>>=20 >>>> Hi, >>>>=20 >>>> While I was repeating = https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D258755 = <https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D258755>, I observed = a >>>> strange behavior. The TCP ACKs from FreeBSD host are too = aggressive. >>>>=20 >>>> My setup is simple: >>>> A B >>>> [ MacOS ] <=3D=3D=3D=3D> [ 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. >>>>=20 >>>> One session on B: >>>>=20 >>>> 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 =20 >>>> [ 5] 1.00-2.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 = KBytes =20 >>>> [ 5] 2.00-3.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 = KBytes =20 >>>> [ 5] 3.00-4.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 = KBytes =20 >>>> [ 5] 4.00-5.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 = KBytes =20 >>>> [ 5] 5.00-6.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 = KBytes =20 >>>> [ 5] 6.00-7.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 = KBytes =20 >>>> [ 5] 7.00-8.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 = KBytes =20 >>>> [ 5] 8.00-9.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 = KBytes =20 >>>> [ 5] 9.00-10.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 = KBytes =20 >>>> - - - - - - - - - - - - - - - - - - - - - - - - - >>>> [ 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 >>>>=20 >>>> iperf Done. >>>>=20 >>>> Another session on B: >>>>=20 >>>> 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 >>>>=20 >>>>=20 >>>>=20 >>>> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >>>>=20 >>>>=20 >>>> While A ---> B, i.e. A as client and B as server, the ACKs sent = from B looks strange. >>>>=20 >>>> Session on A: >>>>=20 >>>> % 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 = =20 >>>> [ 5] 1.00-2.00 sec 1.25 MBytes 10.5 Mbits/sec = =20 >>>> [ 5] 2.00-3.00 sec 1.12 MBytes 9.44 Mbits/sec = =20 >>>> [ 5] 3.00-4.00 sec 1.25 MBytes 10.5 Mbits/sec = =20 >>>> [ 5] 4.00-5.00 sec 1.12 MBytes 9.44 Mbits/sec = =20 >>>> [ 5] 5.00-6.00 sec 1.25 MBytes 10.5 Mbits/sec = =20 >>>> [ 5] 6.00-7.00 sec 1.12 MBytes 9.44 Mbits/sec = =20 >>>> [ 5] 7.00-8.00 sec 1.25 MBytes 10.5 Mbits/sec = =20 >>>> [ 5] 8.00-9.00 sec 1.12 MBytes 9.44 Mbits/sec = =20 >>>> [ 5] 9.00-10.00 sec 1.25 MBytes 10.5 Mbits/sec = =20 >>>> - - - - - - - - - - - - - - - - - - - - - - - - - >>>> [ 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 >>>>=20 >>>> iperf Done. >>>>=20 >>>> Session on B: >>>>=20 >>>> 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 >>>>=20 >>>>=20 >>>> The ACK packets replied from B (the FreeBSD VM) are too aggressive. = They are >>>> about one half of TCP packets received from A. >>>>=20 >>>> 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=20 >>>> bitrates is 1g, also behaves the same. >>>>=20 >>>> Also tried different FreeBSD versions, 11.4, 12.3, stable/13 and = current/14 all=20 >>>> behave the same. >>>>=20 >>>>=20 >>>> 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. >> Thanks for fast response! >>=20 >> My have old memories about SACK which helps TCP performance. This = behavior >> seems odd from my mind. But those memories date back to 2008, that is = 14 years ago. > I don't think anything has changed since then from a specification = point of view Hacked some RFCs from 1122, and the transport protocol is stable, and = apparently it should be. >>=20 >> The current implementation of TCP stack in FreeBSD head is too = complexed for me. >> Can you please point me the RFCs specifying this? So I can start over = with a quick glue. > Send an ACK for every other frame if everything is OK, send it = immediately if there are some gaps: > https://datatracker.ietf.org/doc/html/rfc9293#section-3.8.6.3 = <https://datatracker.ietf.org/doc/html/rfc9293#section-3.8.6.3>; > This applies also to the case where you use SACK. I think I confused SACK with delayed ACK. Thanks! >=20 > Best regards > Michael >>=20 >> Thanks! >>>=20 >>> Best regards >>> Michael >>>>=20 >>>>=20 >>>>=20 >>>> Best regards, >>>> Zhenlei --Apple-Mail=_0987CBA6-7ECA-4B84-BEC7-7256BD5AFCA9 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii <html><head><meta http-equiv=3D"Content-Type" content=3D"text/html; = charset=3Dus-ascii"></head><body style=3D"word-wrap: break-word; = -webkit-nbsp-mode: space; line-break: after-white-space;" class=3D""><div = class=3D""><div><br class=3D""></div></div><div><blockquote type=3D"cite" = class=3D""><div class=3D"">On Oct 22, 2022, at 2:16 AM, Michael Tuexen = <<a href=3D"mailto:michael.tuexen@lurchi.franken.de" = class=3D"">michael.tuexen@lurchi.franken.de</a>> wrote:</div><br = class=3D"Apple-interchange-newline"><div class=3D""><blockquote = type=3D"cite" style=3D"font-family: Helvetica; font-size: 12px; = font-style: normal; font-variant-caps: normal; font-weight: normal; = letter-spacing: normal; orphans: auto; text-align: start; text-indent: = 0px; text-transform: none; white-space: normal; widows: auto; = word-spacing: 0px; -webkit-text-size-adjust: auto; = -webkit-text-stroke-width: 0px; text-decoration: none;" class=3D"">On = 21. Oct 2022, at 17:00, Zhenlei Huang <<a = href=3D"mailto:zlei.huang@gmail.com" = class=3D"">zlei.huang@gmail.com</a>> wrote:<br class=3D""><br = class=3D""><br class=3D""><blockquote type=3D"cite" class=3D"">On Oct = 21, 2022, at 10:34 PM, Michael Tuexen <<a = href=3D"mailto:michael.tuexen@lurchi.franken.de" = class=3D"">michael.tuexen@lurchi.franken.de</a>> wrote:<br = class=3D""><br class=3D""><blockquote type=3D"cite" class=3D"">On 21. = Oct 2022, at 16:19, Zhenlei Huang <<a = href=3D"mailto:zlei.huang@gmail.com" = class=3D"">zlei.huang@gmail.com</a>> wrote:<br class=3D""><br = class=3D"">Hi,<br class=3D""><br class=3D"">While I was repeating <a = href=3D"https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D258755" = class=3D"">https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D258755</a>,= I observed a<br class=3D"">strange behavior. The TCP ACKs from FreeBSD = host are too aggressive.<br class=3D""><br class=3D"">My setup is = simple:<br class=3D""> A = &n= bsp; &nbs= p; B<br class=3D""> [ = MacOS ] <=3D=3D=3D=3D> [ FreeBSD VM ]<br = class=3D"">192.168.120.1 = 192.168.= 12.134 (disable tso and lro)<br class=3D"">While A <--- B, i.e. A as = server and B as client, the packets rate looks good.<br class=3D""><br = class=3D"">One session on B:<br class=3D""><br class=3D"">root@:~ # = iperf3 -c 192.168.120.1 -b 10m<br class=3D"">Connecting to host = 192.168.120.1, port 5201<br class=3D"">[ 5] local 192.168.120.134 = port 54459 connected to 192.168.120.1 port 5201<br class=3D"">[ ID] = Interval = Transfer = Bitrate = Retr Cwnd<br = class=3D"">[ 5] 0.00-1.00 sec 1.25 = MBytes 10.5 Mbits/sec 0 257 = KBytes <br class=3D"">[ 5] = 1.00-2.00 sec 1.25 MBytes 10.5 = Mbits/sec 0 257 KBytes = <br class=3D"">[ 5] = 2.00-3.00 sec 1.12 MBytes 9.44 = Mbits/sec 0 257 KBytes = <br class=3D"">[ 5] = 3.00-4.00 sec 1.25 MBytes 10.5 = Mbits/sec 0 257 KBytes = <br class=3D"">[ 5] = 4.00-5.00 sec 1.12 MBytes 9.44 = Mbits/sec 0 257 KBytes = <br class=3D"">[ 5] = 5.00-6.00 sec 1.25 MBytes 10.5 = Mbits/sec 0 257 KBytes = <br class=3D"">[ 5] = 6.00-7.00 sec 1.12 MBytes 9.44 = Mbits/sec 0 257 KBytes = <br class=3D"">[ 5] = 7.00-8.00 sec 1.25 MBytes 10.5 = Mbits/sec 0 257 KBytes = <br class=3D"">[ 5] = 8.00-9.00 sec 1.12 MBytes 9.44 = Mbits/sec 0 257 KBytes = <br class=3D"">[ 5] = 9.00-10.00 sec 1.25 MBytes 10.5 Mbits/sec = 0 257 KBytes = <br class=3D"">- - - - - - - - - - - = - - - - - - - - - - - - - -<br class=3D"">[ ID] Interval = Transfer = Bitrate = Retr<br class=3D"">[ = 5] 0.00-10.00 sec 12.0 MBytes 10.1 = Mbits/sec 0 = se= nder<br class=3D"">[ 5] 0.00-10.00 sec = 12.0 MBytes 10.1 Mbits/sec = &n= bsp; receiver<br class=3D""><br class=3D"">iperf = Done.<br class=3D""><br class=3D"">Another session on B:<br class=3D""><br= class=3D"">root@:~ # netstat -w 1 -I vmx0<br = class=3D""> inp= ut vmx0 = output<br = class=3D""> packets errs idrops = bytes packets errs = bytes colls<br = class=3D""> 0 = 0 0 = 0 = 0 = 0 = 0 = 0<br = class=3D""> 0 = 0 0 = 0 = 0 = 0 = 0 = 0<br class=3D""> 342 = 0 0 = 22600 = 526 0 = 775724 0<br = class=3D""> 150 0 = 0 9900 = 851 0 = 1281454 0<br = class=3D""> 109 0 = 0 7194 = 901 0 = 1357850 0<br = class=3D""> 126 0 = 0 8316 = 828 0 = 1246632 0<br = class=3D""> 122 0 = 0 8052 = 910 0 = 1370780 0<br = class=3D""> 109 0 = 0 7194 = 819 0 = 1233702 0<br = class=3D""> 120 0 = 0 7920 = 910 0 = 1370780 0<br = class=3D""> 110 0 = 0 7260 = 819 0 = 1233702 0<br = class=3D""> 123 0 = 0 8118 = 910 0 = 1370780 0<br = class=3D""> 109 0 = 0 7194 = 819 0 = 1233702 0<br = class=3D""> 73 = 0 0 = 5088 = 465 0 = 686342 0<br = class=3D""> 0 = 0 0 = 0 = 0 = 0 = 0 = 0<br = class=3D""> 0 = 0 0 = 0 = 0 = 0 = 0 = 0<br class=3D""><br class=3D""><br class=3D""><br = class=3D"">=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D<br class=3D""><br = class=3D""><br class=3D"">While A ---> B, i.e. A as client and B as = server, the ACKs sent from B looks strange.<br class=3D""><br = class=3D"">Session on A:<br class=3D""><br class=3D"">% iperf3 -c = 192.168.120.134 -b 10m<br class=3D"">Connecting to host 192.168.120.134, = port 5201<br class=3D"">[ 5] local 192.168.120.1 port 52370 = connected to 192.168.120.134 port 5201<br class=3D"">[ ID] Interval = Transfer = Bitrate<br class=3D"">[ 5] = 0.00-1.00 sec 1.25 MBytes 10.5 = Mbits/sec = &n= bsp; <br class=3D"">[ 5] = 1.00-2.00 sec 1.25 MBytes 10.5 = Mbits/sec = &n= bsp; <br class=3D"">[ 5] = 2.00-3.00 sec 1.12 MBytes 9.44 = Mbits/sec = &n= bsp; <br class=3D"">[ 5] = 3.00-4.00 sec 1.25 MBytes 10.5 = Mbits/sec = &n= bsp; <br class=3D"">[ 5] = 4.00-5.00 sec 1.12 MBytes 9.44 = Mbits/sec = &n= bsp; <br class=3D"">[ 5] = 5.00-6.00 sec 1.25 MBytes 10.5 = Mbits/sec = &n= bsp; <br class=3D"">[ 5] = 6.00-7.00 sec 1.12 MBytes 9.44 = Mbits/sec = &n= bsp; <br class=3D"">[ 5] = 7.00-8.00 sec 1.25 MBytes 10.5 = Mbits/sec = &n= bsp; <br class=3D"">[ 5] = 8.00-9.00 sec 1.12 MBytes 9.44 = Mbits/sec = &n= bsp; <br class=3D"">[ 5] = 9.00-10.00 sec 1.25 MBytes 10.5 Mbits/sec = &n= bsp; <br class=3D"">- - - - - - - - - - - - - - - = - - - - - - - - - -<br class=3D"">[ ID] Interval = Transfer = Bitrate<br class=3D"">[ 5] = 0.00-10.00 sec 12.0 MBytes 10.1 Mbits/sec = &n= bsp; sender<br class=3D"">[ 5] = 0.00-10.00 sec 12.0 MBytes 10.1 Mbits/sec = &n= bsp; receiver<br class=3D""><br class=3D"">iperf = Done.<br class=3D""><br class=3D"">Session on B:<br class=3D""><br = class=3D"">root@:~ # netstat -w 1 -I vmx0<br = class=3D""> inp= ut vmx0 = output<br = class=3D""> packets errs idrops = bytes packets errs = bytes colls<br = class=3D""> 0 = 0 0 = 0 = 0 = 0 = 0 = 0<br = class=3D""> 0 = 0 0 = 0 = 0 = 0 = 0 = 0<br class=3D""> 649 = 0 0 = 960562 = 330 0 = 21800 0<br = class=3D""> 819 0 = 0 1233702 = 415 0 = 27390 0<br = class=3D""> 910 0 = 0 1370780 = 459 0 = 30294 0<br = class=3D""> 819 0 = 0 1233702 = 415 0 = 27390 0<br = class=3D""> 910 0 = 0 1370780 = 459 0 = 30294 0<br = class=3D""> 910 0 = 0 1370780 = 460 0 = 30360 0<br = class=3D""> 819 0 = 0 1233702 = 414 0 = 27324 0<br = class=3D""> 910 0 = 0 1370780 = 460 0 = 30360 0<br = class=3D""> 819 0 = 0 1233702 = 414 0 = 27324 0<br = class=3D""> 910 0 = 0 1370780 = 460 0 = 30360 0<br = class=3D""> 285 0 = 0 412287 = 147 0 = 9981 0<br = class=3D""> 0 = 0 0 = 0 = 0 = 0 = 0 = 0<br = class=3D""> 0 = 0 0 = 0 = 0 = 0 = 0 = 0<br = class=3D""> 0 = 0 0 = 0 = 0 = 0 = 0 = 0<br class=3D""><br class=3D""><br class=3D"">The = ACK packets replied from B (the FreeBSD VM) are too aggressive. They = are<br class=3D"">about one half of TCP packets received from A.<br = class=3D""><br class=3D"">I've tested with different bitrates, from 10m = to 300m, all behave the same.<br class=3D"">Tested with baremetal = FreeBSD 13.1 Box as B (with intel em driver), the<span = class=3D"Apple-converted-space"> </span><br class=3D"">bitrates is = 1g, also behaves the same.<br class=3D""><br class=3D"">Also tried = different FreeBSD versions, 11.4, 12.3, stable/13 and current/14 = all<span class=3D"Apple-converted-space"> </span><br = class=3D"">behave the same.<br class=3D""><br class=3D""><br class=3D"">My= question is, is that the expected behavior of current default TCP = stack?<br class=3D""></blockquote>That is what I would expect. TCP (on = FreeBSD) is acking every other packet. This<br class=3D"">is also what = is specified. MacOS, at least newer versions, send less ACKs.<br = class=3D""></blockquote>Thanks for fast response!<br class=3D""><br = class=3D"">My have old memories about SACK which helps TCP performance. = This behavior<br class=3D"">seems odd from my mind. But those memories = date back to 2008, that is 14 years ago.<br class=3D""></blockquote><span = style=3D"caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: = 12px; font-style: normal; font-variant-caps: normal; font-weight: = normal; letter-spacing: normal; text-align: start; text-indent: 0px; = text-transform: none; white-space: normal; word-spacing: 0px; = -webkit-text-stroke-width: 0px; text-decoration: none; float: none; = display: inline !important;" class=3D"">I don't think anything has = changed since then from a specification point of view</span><br = style=3D"caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: = 12px; font-style: normal; font-variant-caps: normal; font-weight: = normal; letter-spacing: normal; text-align: start; text-indent: 0px; = text-transform: none; white-space: normal; word-spacing: 0px; = -webkit-text-stroke-width: 0px; text-decoration: none;" = class=3D""></div></blockquote>Hacked some RFCs from 1122, and the = transport protocol is stable, and apparently</div><div>it should = be.</div><div><blockquote type=3D"cite" class=3D""><div = class=3D""><blockquote type=3D"cite" style=3D"font-family: Helvetica; = font-size: 12px; font-style: normal; font-variant-caps: normal; = font-weight: normal; letter-spacing: normal; orphans: auto; text-align: = start; text-indent: 0px; text-transform: none; white-space: normal; = widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; = -webkit-text-stroke-width: 0px; text-decoration: none;" class=3D""><br = class=3D"">The current implementation of TCP stack in FreeBSD head is = too complexed for me.<br class=3D"">Can you please point me the RFCs = specifying this? So I can start over with a quick glue.<br = class=3D""></blockquote><span style=3D"caret-color: rgb(0, 0, 0); = font-family: Helvetica; font-size: 12px; font-style: normal; = font-variant-caps: normal; font-weight: normal; letter-spacing: normal; = text-align: start; text-indent: 0px; text-transform: none; white-space: = normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none; float: none; display: inline !important;" = class=3D"">Send an ACK for every other frame if everything is OK, send = it immediately if there are some gaps:</span><br style=3D"caret-color: = rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: = normal; font-variant-caps: normal; font-weight: normal; letter-spacing: = normal; text-align: start; text-indent: 0px; text-transform: none; = white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none;" class=3D""><a = href=3D"https://datatracker.ietf.org/doc/html/rfc9293#section-3.8.6.3" = style=3D"font-family: Helvetica; font-size: 12px; font-style: normal; = font-variant-caps: normal; font-weight: normal; letter-spacing: normal; = orphans: auto; text-align: start; text-indent: 0px; text-transform: = none; white-space: normal; widows: auto; word-spacing: 0px; = -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" = class=3D"">https://datatracker.ietf.org/doc/html/rfc9293#section-3.8.6.3</= a><br style=3D"caret-color: rgb(0, 0, 0); font-family: Helvetica; = font-size: 12px; font-style: normal; font-variant-caps: normal; = font-weight: normal; letter-spacing: normal; text-align: start; = text-indent: 0px; text-transform: none; white-space: normal; = word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: = none;" class=3D""><span style=3D"caret-color: rgb(0, 0, 0); font-family: = Helvetica; font-size: 12px; font-style: normal; font-variant-caps: = normal; font-weight: normal; letter-spacing: normal; text-align: start; = text-indent: 0px; text-transform: none; white-space: normal; = word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: = none; float: none; display: inline !important;" class=3D"">This applies = also to the case where you use SACK.</span><br style=3D"caret-color: = rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: = normal; font-variant-caps: normal; font-weight: normal; letter-spacing: = normal; text-align: start; text-indent: 0px; text-transform: none; = white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; = text-decoration: none;" class=3D""></div></blockquote>I think I confused = SACK with delayed ACK.</div><div><br class=3D""></div><div>Thanks!<br = class=3D""><blockquote type=3D"cite" class=3D""><div class=3D""><br = style=3D"caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: = 12px; font-style: normal; font-variant-caps: normal; font-weight: = normal; letter-spacing: normal; text-align: start; text-indent: 0px; = text-transform: none; white-space: normal; word-spacing: 0px; = -webkit-text-stroke-width: 0px; text-decoration: none;" class=3D""><span = style=3D"caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: = 12px; font-style: normal; font-variant-caps: normal; font-weight: = normal; letter-spacing: normal; text-align: start; text-indent: 0px; = text-transform: none; white-space: normal; word-spacing: 0px; = -webkit-text-stroke-width: 0px; text-decoration: none; float: none; = display: inline !important;" class=3D"">Best regards</span><br = style=3D"caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: = 12px; font-style: normal; font-variant-caps: normal; font-weight: = normal; letter-spacing: normal; text-align: start; text-indent: 0px; = text-transform: none; white-space: normal; word-spacing: 0px; = -webkit-text-stroke-width: 0px; text-decoration: none;" class=3D""><span = style=3D"caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: = 12px; font-style: normal; font-variant-caps: normal; font-weight: = normal; letter-spacing: normal; text-align: start; text-indent: 0px; = text-transform: none; white-space: normal; word-spacing: 0px; = -webkit-text-stroke-width: 0px; text-decoration: none; float: none; = display: inline !important;" class=3D"">Michael</span><br = style=3D"caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: = 12px; font-style: normal; font-variant-caps: normal; font-weight: = normal; letter-spacing: normal; text-align: start; text-indent: 0px; = text-transform: none; white-space: normal; word-spacing: 0px; = -webkit-text-stroke-width: 0px; text-decoration: none;" = class=3D""><blockquote type=3D"cite" style=3D"font-family: Helvetica; = font-size: 12px; font-style: normal; font-variant-caps: normal; = font-weight: normal; letter-spacing: normal; orphans: auto; text-align: = start; text-indent: 0px; text-transform: none; white-space: normal; = widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; = -webkit-text-stroke-width: 0px; text-decoration: none;" class=3D""><br = class=3D"">Thanks!<br class=3D""><blockquote type=3D"cite" class=3D""><br = class=3D"">Best regards<br class=3D"">Michael<br class=3D""><blockquote = type=3D"cite" class=3D""><br class=3D""><br class=3D""><br class=3D"">Best= regards,<br = class=3D"">Zhenlei</blockquote></blockquote></blockquote></div></blockquot= e></div><br class=3D""></body></html>= --Apple-Mail=_0987CBA6-7ECA-4B84-BEC7-7256BD5AFCA9--
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