Date: Wed, 1 Aug 2007 18:38:01 +1000 From: Peter Jeremy <peterjeremy@optushome.com.au> To: Peter Wemm <peter@freebsd.org> Cc: cvs-src@freebsd.org, src-committers@freebsd.org, cvs-all@freebsd.org Subject: Re: cvs commit: src/sys/netinet tcp_subr.c tcp_timer.h Message-ID: <20070801083801.GI1152@turion.vk2pj.dyndns.org> In-Reply-To: <200707312211.l6VMBupO010347@repoman.freebsd.org> References: <200707312211.l6VMBupO010347@repoman.freebsd.org>
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--45Z9DzgjV8m4Oswq Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 2007-Jul-31 22:11:56 +0000, Peter Wemm <peter@freebsd.org> wrote: > To demonstrate, boot with kern.hz=3D100. ssh to a box on local ethernet > and establish a reliable round-trip-time (ie: type a few commands). > Then unplug the ethernet and press a key. Time how long it takes to > drop the connection. I've bumped into this problem as well but chose a slightly different solution. I've left the TCPTV_MIN/tcp_rexmit_min code alone (because I believed the bit about it being scaled to hz). Instead I added a new sysctl "Minimum Retransmission Period before Dropping Connection" and require that a connection's t_rxtshift remain at TCP_MAXRXTSHIFT until that time has expired. My gut feeling is that putting an artifical lower bound on the RTT is a hackish way to control the retransmit timeout - I thought the TCP algorithms relied on knowing the real RTT to correctly handle retransmissions. A variable that explicitly controls the retransmit timeout would seem easier to understand. I thought I'd PR'd the patch but it looks like I haven't. If anyone is interested, I'll submit it. --=20 Peter Jeremy --45Z9DzgjV8m4Oswq Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (FreeBSD) iD8DBQFGsEZp/opHv/APuIcRAgKQAJ0dKeCye/rmjTcrRro2Y+R+U5sd9QCfb/xH +r97Lu7+2eE7Vcub9vM3Xd8= =qFMq -----END PGP SIGNATURE----- --45Z9DzgjV8m4Oswq--
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