Date: Tue, 08 Feb 2005 14:21:56 -0500 From: Mark Allman <mallman@icir.org> To: Mohan Srinivasan <mohan_srinivasan@yahoo.com> Cc: Daikichi Osuga <osuga@nim.yrp.nttdocomo.co.jp> Subject: Re: SACK retransmits multiple segments respond to single dupack Message-ID: <20050208192156.6262377A6A5@guns.icir.org> In-Reply-To: <20050208184834.24690.qmail@web80602.mail.yahoo.com>
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--=-=-= Content-Type: text/plain > Which release are you experimenting with ? There was a bug > in 5.3 that would cause SACK to burst multiple segments on > a dupack reception. But that was fixed both in -current > and in RELENG_5 (1.100.2.3 and 1.102). From what I see, > the fix was never MFC'ed to RELENG_5_3. > > Referencing the code in -current, > > dupack handling starts at line tcp_input.c:1797. When SACK > recovery is first set up, upon reception of 3 dupacks, we > set cwnd to 3 (line 1867) and call tcp_output(), which would > cause 3 segments from the scoreboard to be retransmitted. I do not understand why receiving 3 dupacks would cause a retransmit of 3 segments. One retransmit I can understand. But, then we shouldn't be in packet conservation for a bit while some of the segments drain from the network to effectively halve the sending rate (because we noted congestion). allman -- Mark Allman -- ICIR -- http://www.icir.org/mallman/ --=-=-= Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.3 (FreeBSD) iD8DBQFCCRFUWyrrWs4yIs4RApp5AJ9nMx9QcYy8sRegfzOLrv088TvDuwCePJSM tuM27qCnMhj1i/xJMEuhIdw= =IMBD -----END PGP SIGNATURE----- --=-=-=--
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