Date: Fri, 18 Nov 2016 15:13:07 -0800 From: hiren panchasara <hiren@strugglingcoder.info> To: Michael Tuexen <tuexen@freebsd.org> Cc: freebsd-transport@freebsd.org Subject: Re: Loss recovery at tail Message-ID: <20161118231307.GN42586@strugglingcoder.info> In-Reply-To: <3A9A8225-A296-408F-BEC5-3E9CEFB65AF0@freebsd.org> References: <3A9A8225-A296-408F-BEC5-3E9CEFB65AF0@freebsd.org>
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--AKkMM/tm2Mk6Yn/s Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 11/18/16 at 09:20P, Michael Tuexen wrote: > Dear all, >=20 > in the last telco we discussed the behaviour when that last N packets are= dropped. > It was mentioned that multiple retransmission timers where used to recove= r. >=20 > I wrote a packetdrill script which > * Get the cwnd to 30 segments > * Sends 30 segments, which all get lost > * Observe how the 30 dropped segments are retransmitted. >=20 > It uses only a single timeout as one would expect. > So this script does NOT reproduce the problem, but I'm attaching it such = that > you can see how the stack behaves. > Tested with FreeBSD head r308802. Thanks for testing. https://reviews.freebsd.org/D8556 was the issue detecting a valid RTO as bad and resetting snd_nxt to snd_max (instead of snd_una as done by valid RTO) causing us to not trigger retransmit of missed packets but wait for RTO for all of lost packets. Cheers, Hiren --AKkMM/tm2Mk6Yn/s Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQF8BAABCgBmBQJYL4r+XxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w ZW5wZ3AuZmlmdGhob3JzZW1hbi5uZXRBNEUyMEZBMUQ4Nzg4RjNGMTdFNjZGMDI4 QjkyNTBFMTU2M0VERkU1AAoJEIuSUOFWPt/lITMH/jhFYHrRoMGSFVwgMZYVRJ6e WBxKaIu+TX8/Gthd3GLukcCJeQ9DUOCzbH6546VP8E0QChGgR8EQyditqhxwSkgS ow+vhrX4PLh1OmveN7/GRDxnFIS+fnBPUblfnQZ2sZVL7V1GIbL+oAwNR940y0qG Yim06Tj2rI0TolbK75FaPBvNyYFRshRQqKg2UNGtlxx3V4kD0UuALGQmGxuhiNVf sRH/zbQPhqjpcW4nOUj7RRL1BHnNKkL8fn4n2M2wMnHktFjbtS3bneXtYU3HuId4 uhdZr6h3f3Sjw4i57wK/EmB+WuHpNjDfbyZsPFlVDAA159se7iY+7bpz8jMK60U= =pNW2 -----END PGP SIGNATURE----- --AKkMM/tm2Mk6Yn/s--
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