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>
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1 changed files with 26 additions and 11 deletions
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@ -311,9 +311,12 @@ tcp_no_metrics_save - BOOLEAN
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connections.
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tcp_orphan_retries - INTEGER
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How may times to retry before killing TCP connection, closed
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by our side. Default value 7 corresponds to ~50sec-16min
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depending on RTO. If you machine is loaded WEB server,
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This value influences the timeout of a locally closed TCP connection,
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when RTO retransmissions remain unacknowledged.
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See tcp_retries2 for more details.
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The default value is 7.
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If your machine is a loaded WEB server,
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you should think about lowering this value, such sockets
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may consume significant resources. Cf. tcp_max_orphans.
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@ -327,16 +330,28 @@ tcp_retrans_collapse - BOOLEAN
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certain TCP stacks.
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tcp_retries1 - INTEGER
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How many times to retry before deciding that something is wrong
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and it is necessary to report this suspicion to network layer.
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Minimal RFC value is 3, it is default, which corresponds
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to ~3sec-8min depending on RTO.
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This value influences the time, after which TCP decides, that
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something is wrong due to unacknowledged RTO retransmissions,
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and reports this suspicion to the network layer.
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See tcp_retries2 for more details.
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RFC 1122 recommends at least 3 retransmissions, which is the
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default.
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tcp_retries2 - INTEGER
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How may times to retry before killing alive TCP connection.
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RFC1122 says that the limit should be longer than 100 sec.
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It is too small number. Default value 15 corresponds to ~13-30min
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depending on RTO.
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This value influences the timeout of an alive TCP connection,
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when RTO retransmissions remain unacknowledged.
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Given a value of N, a hypothetical TCP connection following
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exponential backoff with an initial RTO of TCP_RTO_MIN would
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retransmit N times before killing the connection at the (N+1)th RTO.
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The default value of 15 yields a hypothetical timeout of 924.6
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seconds and is a lower bound for the effective timeout.
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TCP will effectively time out at the first RTO which exceeds the
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hypothetical timeout.
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RFC 1122 recommends at least 100 seconds for the timeout,
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which corresponds to a value of at least 8.
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tcp_rfc1337 - BOOLEAN
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If set, the TCP stack behaves conforming to RFC1337. If unset,
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