If set to 1, TCP always sends SYN segment with the timestamp option. Note that if TCP receives a SYN segment with the timestamp option, TCP responds with a SYN segment with the timestamp option even if the parameter is set to 0.
0 (disabled), 1 (enabled)
In summary, if an accurate measurement of round trip time (RTT) and TCP sequence number wraparound is a problem, enable it.
Refer to RFC 1323 for more reasons to enable this option.