From 6c9ff979d1921e9fd05d89e1383121c2503759b9 Mon Sep 17 00:00:00 2001 From: Alex Bergmann Date: Fri, 31 Aug 2012 02:48:31 +0000 Subject: tcp: Increase timeout for SYN segments Commit 9ad7c049 ("tcp: RFC2988bis + taking RTT sample from 3WHS for the passive open side") changed the initRTO from 3secs to 1sec in accordance to RFC6298 (former RFC2988bis). This reduced the time till the last SYN retransmission packet gets sent from 93secs to 31secs. RFC1122 is stating that the retransmission should be done for at least 3 minutes, but this seems to be quite high. "However, the values of R1 and R2 may be different for SYN and data segments. In particular, R2 for a SYN segment MUST be set large enough to provide retransmission of the segment for at least 3 minutes. The application can close the connection (i.e., give up on the open attempt) sooner, of course." This patch increases the value of TCP_SYN_RETRIES to the value of 6, providing a retransmission window of 63secs. The comments for SYN and SYNACK retries have also been updated to describe the current settings. The same goes for the documentation file "Documentation/networking/ip-sysctl.txt". Signed-off-by: Alexander Bergmann Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- Documentation/networking/ip-sysctl.txt | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'Documentation/networking') diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index ca447b3..d64e531 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -439,7 +439,9 @@ tcp_stdurg - BOOLEAN tcp_synack_retries - INTEGER Number of times SYNACKs for a passive TCP connection attempt will be retransmitted. Should not be higher than 255. Default value - is 5, which corresponds to ~180seconds. + is 5, which corresponds to 31seconds till the last retransmission + with the current initial RTO of 1second. With this the final timeout + for a passive TCP connection will happen after 63seconds. tcp_syncookies - BOOLEAN Only valid when the kernel was compiled with CONFIG_SYNCOOKIES @@ -478,7 +480,9 @@ tcp_fastopen - INTEGER tcp_syn_retries - INTEGER Number of times initial SYNs for an active TCP connection attempt will be retransmitted. Should not be higher than 255. Default value - is 5, which corresponds to ~180seconds. + is 6, which corresponds to 63seconds till the last restransmission + with the current initial RTO of 1second. With this the final timeout + for an active TCP connection attempt will happen after 127seconds. tcp_timestamps - BOOLEAN Enable timestamps as defined in RFC1323. -- cgit v1.1