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Message-Id: <1399196499-8449-2-git-send-email-vincent@bernat.im> Date: Sun, 4 May 2014 11:41:39 +0200 From: Vincent Bernat <vincent@...nat.im> To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, linux-doc@...r.kernel.org, netdev <netdev@...r.kernel.org> Cc: Vincent Bernat <vincent@...nat.im> Subject: [PATCH] tcp: more documentation for tcp_tw_reuse and tcp_tw_recycle The documentation is not very helpful about what those settings affect. We find numerous tuning guides advising to set both these settings to 1 to reduce the number of entries in the TIME-WAIT state. However, enabling tcp_tw_recycle will cause massive problems when working with NAT. The documentation is completed a bit to explain quickly what kind of connections both those settings will affect and to encourage the use of tcp_tw_reuse instead of tcp_tw_recycle for outgoing connections. --- Documentation/networking/ip-sysctl.txt | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index ab42c95f9985..d771aa064af8 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -532,14 +532,18 @@ 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 + Enable fast recycling TIME-WAIT sockets. Default value is + 0. Enabling this option will cause problems when incoming + connections originate from NAT devices. For outgoing + connections, prefer the use of tcp_tw_reuse which is safer. It + should not be changed without advice/request of technical experts. 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 + Allow to reuse TIME-WAIT sockets for new outgoing connections + when it is safe from protocol viewpoint. Default value is + 0. This parameter has no effect on incoming connections. It + should not be changed without advice/request of technical experts. tcp_window_scaling - BOOLEAN -- 2.0.0.rc0 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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