Date: Wed, 5 Mar 2025 16:58:04 -0500 From: jaeyong yoo <y.jaeyong@gmail.com> To: Cheng Cui <cc@freebsd.org> Cc: freebsd-net@freebsd.org Subject: Re: Sending empty segment upon receiving partial ACK Message-ID: <CANud0TGXtjt1x_gFJxYMH1VhW6eWehHDszBn3DaBe0AhV8=Wfw@mail.gmail.com> In-Reply-To: <AB5BD54B-8CB0-4E71-92CE-83EBEAD9B46E@freebsd.org> 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>
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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 2025=EB=85=84 3=EC=9B=94 5=EC=9D=BC (=EC=88=98) =EC=98=A4=ED=9B=84 12:30, C= heng Cui <cc@freebsd.org>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1: > > > > 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 r= etransmitting packets. But what do you mean "no packets going out"? > > Best Regards, > Cheng Cui > > >
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