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authorDamian Lukowski <damian@tvk.rwth-aachen.de>2009-09-01 10:24:04 (GMT)
committerDavid S. Miller <davem@davemloft.net>2009-09-02 00:40:50 (GMT)
commit5d7892298a819743b3892df08bb496992fe85951 (patch)
tree88314aa52496de008b06958358c38c05f250ec24 /Documentation/networking
parent5152fc7de3ae31b46692022ea63ce0501280f5b1 (diff)
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>
Diffstat (limited to 'Documentation/networking')
-rw-r--r--Documentation/networking/ip-sysctl.txt37
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,

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