X-Recipient: archive-cygwin@delorie.com X-SWARE-Spam-Status: No, hits=-1.6 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM X-Spam-Check-By: sourceware.org MIME-Version: 1.0 In-Reply-To: References: Date: Wed, 14 Dec 2011 13:25:05 -0500 Message-ID: Subject: Re: Issues with TCP Window Scaling Factor and Cygwin Daemons From: Jon Clugston To: cygwin@cygwin.com Content-Type: text/plain; charset=ISO-8859-1 X-IsSubscribed: yes Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Delivered-To: mailing list cygwin@cygwin.com Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by delorie.com id pBEIPUGD027140 On Wed, Dec 14, 2011 at 12:58 PM, David Groves wrote: > I am having some issues with cygwin applications (specifically sshd) > and TCP Window Scaling Factors. I am using OpenSSH client on either a > Debian Linux or FreeBSD machine to connect to sshd on a Windows 2k8 R2 > server. > > My SYN from the client has a non-zero WSF (16 for Debian, 8 for > FreeBSD), but the SYNACK response from the windows box has 0 as the > WSF. This means I will have a maximum of 64Kbytes of traffic allowed > to be unacknowledged in the TCP window. This is causing me > considerable performance problems in transfers from Europe to the US > West Coast and Australia. > > To try and decide if cygwin was a factor in this, I tried to replicate > this with Apache2 and pure-ftpd on cygwin, and in both cases, the WSF > was 0. I then tried a non-cygwin Apache2 install, and it returned a > non-zero WSF. > > TCP settings is clearly a function of the OS, but I'm a little unsure > where the line is drawn between the OS with cygwin, and it is > interesting I can reproduce this with multiple cygwin apps, and I > cannot reproduce it with non-cygwin apps, I'm thinking cygwin is at > least somewhat involved as part of the problem. > > Anyone have any ideas/pointers ? > > -- > Problem reports:       http://cygwin.com/problems.html > FAQ:                   http://cygwin.com/faq/ > Documentation:         http://cygwin.com/docs.html > Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple > Did you do all these tests w/ the same Windows machine? I believe that Windows XP always sets the WSF to zero, but newer versions support scaling. -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple