From owner-freebsd-net@FreeBSD.ORG Wed Mar 16 12:57:06 2005 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id B046616A4CE for ; Wed, 16 Mar 2005 12:57:06 +0000 (GMT) Received: from r-dd.iij4u.or.jp (r-dd.iij4u.or.jp [210.130.0.70]) by mx1.FreeBSD.org (Postfix) with ESMTP id EAB5143D41 for ; Wed, 16 Mar 2005 12:57:05 +0000 (GMT) (envelope-from demizu@dd.iij4u.or.jp) Received: from localhost (h178.p057.iij4u.or.jp [210.130.57.178]) by r-dd.iij4u.or.jp (8.11.6+IIJ/8.11.6) with ESMTP id j2GCv2W11122; Wed, 16 Mar 2005 21:57:03 +0900 (JST) Date: Wed, 16 Mar 2005 21:57:30 +0900 (JST) Message-Id: <20050316.215730.84382579.Noritoshi@Demizu.ORG> From: Noritoshi Demizu To: freebsd-net@freebsd.org X-Mailer: Mew version 4.1 on Emacs 21 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Subject: TCP SACK of FreeBSD stable X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 16 Mar 2005 12:57:06 -0000 I am observing the TCP SACK behavior of FreeBSD stale. I found the followings: o After the third duplicate ACK, i.e., it enters recovery mode, it seems that the outstanding window size may not be halved. It sends one data segment for each duplicate ACK received. If the number of lost data and ACK segment was small, the outstanding window size would not be reduced enough. o In recovery mode, it retransmits data when the first SACK block above the data is received. It would be weak in reordering of data or ACK segments. I put the results of my experiments at http://www.dd.iij4u.or.jp/~demizu/memo/2005-0316/ Any comments are welcome. Thank you. Regards, Noritoshi Demizu