tcp_syn_retries

file: /proc/sys/net/ipv4/tcp_syn_retries
variable: net.ipv4.tcp_syn_retries
Official reference

Number of times initial SYNs for an active TCP connection attempt will be retransmitted. Should not be higher than 127. Default value is 6, which corresponds to 63seconds till the last retransmission with the current initial RTO of 1second. With this the final timeout for an active TCP connection attempt will happen after 127seconds.

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