[2] RFC 781 - Specification of the Internet Protocol (IP) timestamp option, , https://tools.ietf.org/html/rfc781
[1] RFC 792 - Internet Control Message Protocol, , https://tools.ietf.org/html/rfc792#page-16
[4] RFC 3252 - Binary Lexical Octet Ad-hoc Transport, , https://tools.ietf.org/html/rfc3252#page-11
[3] TCP Timestamps とは違います。