Date: Thu, 6 Mar 2025 10:50:09 -0500 From: Cheng Cui <cc@freebsd.org> To: jaeyong yoo <y.jaeyong@gmail.com> Cc: freebsd-net@freebsd.org Subject: Re: Sending empty segment upon receiving partial ACK Message-ID: <979E9D00-755F-4E4D-9687-CAB957F4C8C8@freebsd.org> In-Reply-To: <CANud0TGXtjt1x_gFJxYMH1VhW6eWehHDszBn3DaBe0AhV8=Wfw@mail.gmail.com> References: <CANud0THEOnkWbuOn413AV_auSrY7-SysXThrTyigZMxujEdqEg@mail.gmail.com> <38B72ADC-B796-4BFC-8F94-2BD6E40C4231@freebsd.org> <CANud0TEUTakZkHj39J%2BJRyS9DHRgPr4FKxpgvjHcJao_Si01FQ@mail.gmail.com> <AB5BD54B-8CB0-4E71-92CE-83EBEAD9B46E@freebsd.org> <CANud0TGXtjt1x_gFJxYMH1VhW6eWehHDszBn3DaBe0AhV8=Wfw@mail.gmail.com>
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[-- Attachment #1 --] I see Bug 285158 <https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=285158>; is created. Let's talk/track it there. thanks > On Mar 5, 2025, at 16:58, jaeyong yoo <y.jaeyong@gmail.com> wrote: > > Yes it is data retransmission but my concern is that the > retransmission packet has the segment length of zero. > If there is nothing to send, why don't we just not send it. > > What I meant by "no packets going out" is, that zero-length-segment > can be considered as ACK to acknowledge some received packets but the > sender of "zero-length-segment" did not receive any packets hence > nothing to ACK. That said, those retransmission packets are the pure > purpose of retransmissions and its segment length is zero, which seems > pure overhead. > Hope this makes it clear. > > Thanks, > Jaeyong > > 2025년 3월 5일 (수) 오후 12:30, Cheng Cui <cc@freebsd.org>님이 작성: >> >> >> >> On Feb 26, 2025, at 10:21, jaeyong yoo <y.jaeyong@gmail.com> wrote: >> >> Yes that behavior was observed during recovery phase and during that >> time frame, there were no packets going out to the other direction so >> there is no reason to send pure ACK (and the ack number for those 3 >> acks are the same and no possibility of challenge ack as well). >> >> >> Isn't loss recovery phase used for data retransmission? There should be retransmitting packets. But what do you mean "no packets going out"? >> >> Best Regards, >> Cheng Cui >> >> >> Best Regards, Cheng Cui [-- Attachment #2 --] <html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;">I see <a href="https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=285158"><b>Bug 285158</b></a><span style="font-family: -webkit-standard; font-size: medium;"></span> is created. Let's talk/track it there. thanks<br id="lineBreakAtBeginningOfMessage"><div><br><blockquote type="cite"><div>On Mar 5, 2025, at 16:58, jaeyong yoo <y.jaeyong@gmail.com> wrote:</div><br class="Apple-interchange-newline"><div><div>Yes it is data retransmission but my concern is that the<br>retransmission packet has the segment length of zero.<br>If there is nothing to send, why don't we just not send it.<br><br>What I meant by "no packets going out" is, that zero-length-segment<br>can be considered as ACK to acknowledge some received packets but the<br>sender of "zero-length-segment" did not receive any packets hence<br>nothing to ACK. That said, those retransmission packets are the pure<br>purpose of retransmissions and its segment length is zero, which seems<br>pure overhead.<br>Hope this makes it clear.<br><br>Thanks,<br>Jaeyong<br><br>2025년 3월 5일 (수) 오후 12:30, Cheng Cui <cc@freebsd.org>님이 작성:<br><blockquote type="cite"><br><br><br>On Feb 26, 2025, at 10:21, jaeyong yoo <y.jaeyong@gmail.com> wrote:<br><br>Yes that behavior was observed during recovery phase and during that<br>time frame, there were no packets going out to the other direction so<br>there is no reason to send pure ACK (and the ack number for those 3<br>acks are the same and no possibility of challenge ack as well).<br><br><br>Isn't loss recovery phase used for data retransmission? There should be retransmitting packets. But what do you mean "no packets going out"?<br><br>Best Regards,<br>Cheng Cui<br><br><br><br></blockquote></div></div></blockquote></div><br><div> <div>Best Regards,<br>Cheng Cui</div><div><br></div><br class="Apple-interchange-newline"> </div> <br></body></html>
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