additional choices may be available based on kernel configuration.
Default is set as part of kernel configuration.
+tcp_cookie_size - INTEGER
+ Default size of TCP Cookie Transactions (TCPCT) option, that may be
+ overridden on a per socket basis by the TCPCT socket option.
+ Values greater than the maximum (16) are interpreted as the maximum.
+ Values greater than zero and less than the minimum (8) are interpreted
+ as the minimum. Odd values are interpreted as the next even value.
+ Default: 0 (off).
+
tcp_dsack - BOOLEAN
Allows TCP to send "duplicate" SACKs.