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author | Damian Lukowski <damian@tvk.rwth-aachen.de> | 2009-09-01 10:24:04 +0000 |
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committer | David S. Miller <davem@davemloft.net> | 2009-09-01 17:40:50 -0700 |
commit | 5d7892298a819743b3892df08bb496992fe85951 (patch) | |
tree | 88314aa52496de008b06958358c38c05f250ec24 | |
parent | 5152fc7de3ae31b46692022ea63ce0501280f5b1 (diff) | |
download | op-kernel-dev-5d7892298a819743b3892df08bb496992fe85951.zip op-kernel-dev-5d7892298a819743b3892df08bb496992fe85951.tar.gz |
RTO connection timeout: sysctl documentation update
This patch updates the sysctl documentation concerning the interpretation
of tcp_retries{1,2} and tcp_orphan_retries.
Signed-off-by: Damian Lukowski <damian@tvk.rwth-aachen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r-- | Documentation/networking/ip-sysctl.txt | 37 |
1 files changed, 26 insertions, 11 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index 8be7623..4e9c6d7 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -311,9 +311,12 @@ tcp_no_metrics_save - BOOLEAN connections. tcp_orphan_retries - INTEGER - How may times to retry before killing TCP connection, closed - by our side. Default value 7 corresponds to ~50sec-16min - depending on RTO. If you machine is loaded WEB server, + This value influences the timeout of a locally closed TCP connection, + when RTO retransmissions remain unacknowledged. + See tcp_retries2 for more details. + + The default value is 7. + If your machine is a loaded WEB server, you should think about lowering this value, such sockets may consume significant resources. Cf. tcp_max_orphans. @@ -327,16 +330,28 @@ tcp_retrans_collapse - BOOLEAN certain TCP stacks. tcp_retries1 - INTEGER - How many times to retry before deciding that something is wrong - and it is necessary to report this suspicion to network layer. - Minimal RFC value is 3, it is default, which corresponds - to ~3sec-8min depending on RTO. + This value influences the time, after which TCP decides, that + something is wrong due to unacknowledged RTO retransmissions, + and reports this suspicion to the network layer. + See tcp_retries2 for more details. + + RFC 1122 recommends at least 3 retransmissions, which is the + default. tcp_retries2 - INTEGER - How may times to retry before killing alive TCP connection. - RFC1122 says that the limit should be longer than 100 sec. - It is too small number. Default value 15 corresponds to ~13-30min - depending on RTO. + This value influences the timeout of an alive TCP connection, + when RTO retransmissions remain unacknowledged. + Given a value of N, a hypothetical TCP connection following + exponential backoff with an initial RTO of TCP_RTO_MIN would + retransmit N times before killing the connection at the (N+1)th RTO. + + The default value of 15 yields a hypothetical timeout of 924.6 + seconds and is a lower bound for the effective timeout. + TCP will effectively time out at the first RTO which exceeds the + hypothetical timeout. + + RFC 1122 recommends at least 100 seconds for the timeout, + which corresponds to a value of at least 8. tcp_rfc1337 - BOOLEAN If set, the TCP stack behaves conforming to RFC1337. If unset, |