Date: Tue, 20 Jun 2000 22:24:35 +0900 From: Noritoshi Demizu <demizu@acm.org> To: freebsd-net@FreeBSD.ORG Subject: question on tcp_xmit_timer() of FreeBSD 4.0R Message-ID: <20000620222435Z.demizu@dd.iij4u.or.jp>
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I have a question about the 2nd argument "rtt" of tcp_xmit_timer() of FreeBSD 4.0R. Why are the 2nd arguments in following code calculated differently ? i.e. for timestamp option, +1. l.1857, netinet/tcp_input.c, tcp_input() if (to.to_flag & TOF_TS) tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) tcp_xmit_timer(tp, ticks - tp->t_rtttime); Why is `1' subtracted from the 2nd argument "rtt" here ? l.2448, netinet/tcp_input.c, tcp_xmit_timer() delta = ((rtt - 1) << TCP_DELTA_SHIFT) - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); These codes works for 3.x and earlier versions. But I am not sure they are still OK for 4.0R. I could not explain to students, so,,, could somebody help us? Thank you very much. Noritoshi Demizu To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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