From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Furniss Subject: Re: Port-forwarding Perfomance Date: Tue, 08 Mar 2005 11:12:48 +0000 Message-ID: <422D88B0.9070905@dsl.pipex.com> References: <421D2F04.8090100@wildcash.com> <1109156169.11713.2.camel@nostromo.bgsecm.com> <421DE4AF.6040702@wildcash.com> <20050223211053.GA12107@bender.817west.com> <421E6E14.5020905@wildcash.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit In-Reply-To: <421E6E14.5020905@wildcash.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: netfilter-bounces@lists.netfilter.org Errors-To: netfilter-bounces@lists.netfilter.org Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Rudi Starcevic Cc: "netfilter@lists.netfilter.org" Rudi Starcevic wrote: > Hi, > > > I'm still seeing slow performance with my port-forwarding but > have found something interesting that may be problematic. > > Just to re-cap: > > I have one Linux 66.283.12.21 box and one Windows box 192.168.0.10 > I can download a file of the linux box at around 140K/s > That very same file download on the Windows machine is around 15K/s > using DNAT and Masq/Forwarding. > > However we can upload to the Windows box at 140k/s. > > So it is only slow, 15K/s, when the data is coming from Windows then > through the Linux Iptables Masq/Forwarding Firewall. > > I contacted an earlier Admin for the Windows machine and was informed > the TCP window size has been manually increased. > > Could this affect Forwarding in Iptables ? > > The default maximum TCP window size in Win2000 is 17520 bytes (12 > segments). > The current value is set at 131400. Max window size is 64k without scaling - so I assume they have turned scaling on aswell - there have been problems with scaling, one of the linux kernel releases set it to 7 which confused buggy peers. AIUI they turned it back down to workaround. You could tcpdump so you can can see what's going on. > > 90% of the traffic being port-forwarded are Digital video files. > These range in size from 2MB to 200MB. > > So I assume with large files like these Windows would opt for it's > largest TCP window size. > > I guess the next step is to lower these to their default values and see > if it affect bandwidth. > > Your thoughts on that would be much appreciated. > > Thanks. > Regards, > Rudi > > > >