Hi All, Just to let people know, there are now new versions of the iptables tutorial, and the ipsysctl tutorial available. The iptables-tutorial was released the 24th in. store these parameters for use at boot time. For a deeper reference into the matter and use of sysctl see the IP Sysctl tutorial, maintained by Oskar Andreasson. For more information on TCP variables see: tutorial/#TCPVARIABLES. Starting in Linux (and.
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Ipsysctl < Wikilearn < TWiki
There are a lot of differences between Linux version 2. Like all operating systems, the default maximum Linux TCP buffer sizes are way too small.
I suggest changing them to the following settings:. Another thing you can try that may help increase TCP throughput is to increase the size of the interface queue. To do this, do the following:.
I’ve seen increases in bandwidth of up to 8x by doing this on some long, fast paths. This is only a good idea for Gigabit Ethernet connected hosts, and may have other side effects such as uneven sharing between multiple streams. Starting with Linux 2. This assumes you have set large buffers on the recieve side, as the sending buffer will not grow beyond the size of the recieve buffer.
The value for ssthresh for a given path is cached in the routing table.
This means that if a connection has has a retransmition and reduces its window, then all connections to that host for the next 10 minutes will use a reduced window size, and not even try to increase its window.
The only way to disable this behavior is to do the following before all new connections you must be root:. More information on various tuning parameters for Linux 2. Starting in Linux 2. A BIC implementation bug was discovered, but this was fixed in Linux 2. There is also a setting to fix the ssthresh caching weirdness described above. Starting with version 2.
The congestion control algorithm used is set using the sysctl variable net. Apparently they decided that BIC was not quite ready for prime time. The current set of congestion control options are:. To set this, do the following:.
More information on each of these algorithms and some results can be found here. This problem was fixed in version 2. A workaround for this problem is to use ethtool to disable segmentation offload:. More information on tuning parameters and defaults for Linux 2.
And finally a warning for both 2. Restricting the TCP buffer size to about 12 MB seems to avoid this problem, but clearly limits your total tuttorial. Another solution is to disable SACK. If you are still running Linux 2. FreeBSD version before 4.
Lpsysctl should upgrade to 4. The tuutorial for Tcp is “No value”; the default behavior is do not initiate options, but if requested provide them. You can ipsysdtl setsockopt in your program to set your buffers to any size up to GlobalMaxTcpWindowSize, or you can use TcpWindowSize to set the default send and receive buffers for ALL sockets to this size.
Its probably not a good idea to set this too large, but setting it up to K should be OK.