Bug#401435: debian-installer: sometimes net install does not work because of networking change in Linux 2.6.17 or later
On Sunday 01 April 2007 15:20, Josip Rodin wrote: I'm willing to add that info, especially for the installed system. Do values in tcp_wmem also need to be modified or is modifying tcp_rmem sufficient? What's the difference between the two? The r stands for read, w stands for write. tcp_rmem affects the downloads, tcp_wmem affects the uploads. Thanks a lot for the additional info. I've just updated the errata to include the values you suggested. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Bug#401435: debian-installer: sometimes net install does not work because of networking change in Linux 2.6.17 or later
On Tuesday 20 March 2007 15:50, Josip Rodin wrote: TCP window scaling as such was by default enabled in earlier Linux kernel versions, too, but the default window *sizes* were different, much smaller. These are set in the tcp_rmem/tcp_wmem pseudo-files in the same directory; you could just run something like echo 4096 65536 65536 /proc/sys/net/ipv4/tcp_rmem to reset them to values supported by just about anything. I'm willing to add that info, especially for the installed system. Do values in tcp_wmem also need to be modified or is modifying tcp_rmem sufficient? What's the difference between the two? pgpx9rMg2xpQ3.pgp Description: PGP signature
Bug#401435: debian-installer: sometimes net install does not work because of networking change in Linux 2.6.17 or later
On Sun, Apr 01, 2007 at 09:30:16AM +0200, Frans Pop wrote: TCP window scaling as such was by default enabled in earlier Linux kernel versions, too, but the default window *sizes* were different, much smaller. These are set in the tcp_rmem/tcp_wmem pseudo-files in the same directory; you could just run something like echo 4096 65536 65536 /proc/sys/net/ipv4/tcp_rmem to reset them to values supported by just about anything. I'm willing to add that info, especially for the installed system. Do values in tcp_wmem also need to be modified or is modifying tcp_rmem sufficient? What's the difference between the two? The r stands for read, w stands for write. tcp_rmem affects the downloads, tcp_wmem affects the uploads. I'm not sure how the broken routers react, but I'd guess that the tcp_rmem is the culprit because most non-advanced users do more download than upload. The first value in those files is the minimum window size, the middle is the default, and the third value is the maximum. TCP window size can (and should) be stretched as allowed by the hardware; if you enlarge it, you make more bytes go through the pipe in the same time intervals, so you need to have CPU power to process it and memory to hold it. And so do all hops on the packet path (routers and switches alike). The thing that happened was that the kernel developers got tired of the years-old fixated default maximum, and made it vary according to local hardware parameters. Here's an example default from a 2.4.31 machine: % cat /proc/sys/net/ipv4/tcp_{r,w}mem 409687380 174760 409616384 131072 (You can see there how killing off TCP window scaling altogether would have been a bad idea - no packets would have been allowed to grow even a little bit past the default size, as they were allowed in the old kernel versions, even if by a fairly small amount.) Here's an example default from a 2.6.18 on a machine with 384 MB RAM: % cat /proc/sys/net/ipv4/tcp_{r,w}mem 409687380 524288 409616384 524288 And here's an example default from a 2.6.18 on a 2 GB RAM machine: % cat /proc/sys/net/ipv4/tcp_{r,w}mem 409687380 4194304 409616384 4194304 I never checked exactly what the parameters for this new variation are, but AFAIR RAM size is one of them. This worked out well for the vast majority of people, but as always, there are machines that don't follow protocols and can't handle these variations. This is somewhat similar to the TCP ECN situation; Linux kernel using features and finding a few bumps in the wild. -- 2. That which causes joy or happiness. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Bug#401435: debian-installer: sometimes net install does not work because of networking change in Linux 2.6.17 or later
On Sun, Dec 03, 2006 at 03:14:02PM +0100, Santiago Vila wrote: Short summary: A change introduced in Linux 2.6.17 makes the network not to work properly in some cases, due to buggy routers. There is a trivial workaround: echo 0 /proc/sys/net/ipv4/tcp_window_scaling However, I had to spend several afternoons to *diagnose* this problem and realize what exactly the nature of the problem was. I saw this linked from the d-i web page, so I feel I should point out a bit of an injustice - that workaround is way too severe, as it kills off TCP window scaling altogether. TCP window scaling as such was by default enabled in earlier Linux kernel versions, too, but the default window *sizes* were different, much smaller. These are set in the tcp_rmem/tcp_wmem pseudo-files in the same directory; you could just run something like echo 4096 65536 65536 /proc/sys/net/ipv4/tcp_rmem to reset them to values supported by just about anything. -- 2. That which causes joy or happiness. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]
Bug#401435: debian-installer: sometimes net install does not work because of networking change in Linux 2.6.17 or later
Package: debian-installer Version: 20061102 Severity: important This is really a feature more than a bug, but the adverse effects are so devastating that it would be nice to have a workaround in debian-installer, or have it properly documented in the install manual. It seems there is a buggy router between me and the Internet. As a result, apt-get does not work at all (it hangs, waiting for who knows what). Needless to say, this is very bad if one wants to install Debian via the Internet. I found a thread in the linux kernel mailing list which explains *exactly* my problem: http://www.gatago.com/linux/kernel/9440712.html Short summary: A change introduced in Linux 2.6.17 makes the network not to work properly in some cases, due to buggy routers. There is a trivial workaround: echo 0 /proc/sys/net/ipv4/tcp_window_scaling However, I had to spend several afternoons to *diagnose* this problem and realize what exactly the nature of the problem was. Considering that the number of systems potentially affected is very big, it would be nice if this were at least documented somewhere. Thanks. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of unsubscribe. Trouble? Contact [EMAIL PROTECTED]