From 25e131bc116d55eff8253ca1c17b4e8ce2477fdb Mon Sep 17 00:00:00 2001 From: Sami Kerola <kerolasa@xxxxxx> Date: Thu, 1 Oct 2009 16:54:33 +0200 Subject: [PATCH] networking/ip-sysctl.txt tcp_tw_recycle and tcp_tw_reuse Cc: kerolasa@xxxxxx IMHO technical experts need some hints to judge is changing tcp_tw_recycle and tcp_tw_reuse good idea in their environment. I believe that for the most values are simply too dangerous to be used in production systems, it is too difficult to be sure about network topology now and in future (when setting on some server can become a problem). Signed-off-by: Sami Kerola <kerolasa@xxxxxx> --- Documentation/networking/ip-sysctl.txt | 20 +++++++++++++------- 1 files changed, 13 insertions(+), 7 deletions(-) diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index fbe427a..24dde0e 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -436,15 +436,21 @@ tcp_tso_win_divisor - INTEGER Default: 3 tcp_tw_recycle - BOOLEAN - Enable fast recycling TIME-WAIT sockets. Default value is 0. - It should not be changed without advice/request of technical - experts. + Enable fast recycling TIME-WAIT sockets. See also caution wrote to + tcp_tw_reuse. Default value is 0. tcp_tw_reuse - BOOLEAN - Allow to reuse TIME-WAIT sockets for new connections when it is - safe from protocol viewpoint. Default value is 0. - It should not be changed without advice/request of technical - experts. + Allow to reuse TIME-WAIT sockets for new connections when it is safe + from protocol viewpoint. One should enable also tcp_timestamps when + this is enabled. Default value is 0. + + Caution. Both tcp_tw_recycle and tcp_tw_reuse can cause problems. + You should not enable either without understanding network topology + in between node(s) which are using or used by the node where the + parameter is enabled. Connections which go via nodes that are aware + of TCP connection states, such as firewall, NAT or load balancer may + start dropping frames because of the setting. The problem will + become visible when there is large enough number of connections. tcp_window_scaling - BOOLEAN Enable window scaling as defined in RFC1323. -- 1.6.2.5
