SNTPD is a TCP/IP daemon that is used to synchronize time between a client and a server. SNTP (Simple Network Time Protocol) is a protocol for synchronizing clocks across a WAN or a LAN through a specific formatted message.
An External Time Reference (ETR) named stratum 0, is chosen as the highest timer reference. A stratum 1 server is a server attached to a stratum 0 timer. For example, the z/OS® sysplex timer could be a stratum 0 timer and z/OS Communications Server would be a stratum 1 server. A client attached to stratum 1 server can also be a stratum 2 server, and so on. SNTP uses UDP packets for data transfer with the well-known port number 123. RFC 2030 (Mills 1996) describes SNTP. You can start SNTPD from the z/OS UNIX shell or as a started procedure. Each of these methods is described in the z/OS Communications Server: IP Configuration Reference.