Server time protocol (STP) messages and methods of exchange thereof are provided for facilitating synchronization of processing units of a timing network. The STP messages include exchange time parameters (XTP) commands and responses, and STP control (STC) commands and responses. XTP message exchange processing includes: generating an XTP message command at a first processing unit including a command transmit timestamp field set by the first processing unit and a command receive timestamp field which is unset by the first processing unit; transmitting the XTP message command to a second processing unit; setting the command receive timestamp field in the XTP command with the time the XTP command is received at the second processing unit; and generating an XTP message response at the second processing unit, the message response including the command transmit timestamp set by the first processing unit and the command receive timestamp set by the second processing unit.