Differences between version 3 and revision by previous author of SysControls.
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| Newer page: | version 3 | Last edited on Tuesday, October 12, 2004 1:50:41 pm | by JohnMcPherson | Revert |
| Older page: | version 2 | Last edited on Tuesday, October 12, 2004 11:56:24 am | by PerryLorier | Revert |
@@ -1,15 +1,15 @@
This page describes the various linux syscontrols and what they do, these can be viewed/edited via the sysctl(8) command, or via /proc/sys/. eg, kernel.panic can be viewed by
- kernel.panic
+ /sbin/sysctl
kernel.panic
or
cat /proc/sys/kernel/panic
!!!kernel
!!kernel.panic
-This is the number of seconds to wait after a kernel has paniced
before the machine will reboot itself automatically. Very useful for unattended servers, or machines that are difficult to get physical access to.
+This is the number of seconds to wait after a kernel has panicked
before the machine will reboot itself automatically. Very useful for unattended servers, or machines that are difficult to get physical access to.
!!!net
-These sysctl's
control the networking. See also http://bec.at/support/ipsysctl-tutorial/tcpvariables.html
+These sysctls
control the networking. See also http://bec.at/support/ipsysctl-tutorial/tcpvariables.html
!!net.ipv4
These control most of the IPv4 options
!net.ipv4.ip_forwarding
@@ -18,12 +18,12 @@
!net.ipv4.tcp_fack
Enable __F__orward __Ack__nowledgement congestion avoidance and fast retransmission. The value is not used, if net.ipv4.tcp_sack is not enabled. See http://www.psc.edu/networking/papers/fack_abstract.html for details on how this option works. Basically it seems to assume that missing sequence ranges are dropped (ie, implies no reordering). Linux will disable fack on a per connection basis if it detects reordering.
!net.ipv4.tcp_vegas_cong_avoid (0)
-Enable tcp vegas congestion avoidance. TCP Vegas is another
congestion control algorithm like westwood
that mostly these days is not considered to be particularly useful. TCP Vegas is a sender side change and causes TCP to back off when it detects the [RTT] changing (ie, queuing is occuring). It works well when there is only a few flows using the bottleneck link.
+Enable tcp vegas congestion avoidance. TCP Vegas is a
congestion control algorithm
that mostly these days is not considered to be particularly useful (see TCP Westward, below)
. TCP Vegas is a sender side (ie only used by the machine initiating the TCP connection)
change and causes TCP to back off when it detects the [RTT] changing (ie, queuing is occuring). It works well when there is only a few flows using the bottleneck link.
!net.ipv4.tcp_westwood (0)
-Enable TCP Westwood+ congestion control algorithm. This is a sender side change where
estimates of throughput are kept to try and make sure that the stack uses the optimum amount of bandwidth at all times. Very useful, defaults off should probably be enabled for many sites.
+Enable TCP Westwood+ congestion control algorithm. This is a sender side change (like TCP Vegas) and
estimates of throughput are kept to try and make sure that the stack uses the optimum amount of bandwidth at all times. Very useful, defaults off should probably be enabled for many sites.
!net.ipv4.tcp_low_latency (0)
"If set, the TCP stack makes decisions that prefer lower latency as opposed to higher throughput" This seems to disable a function called tcp_prequeue, no idea what it does.
