Network Clock FAQs

Q: What are Stratum?

A: The world of NTP is a hierarchy of reference clocks and time servers. At the top of the hierarchy are reference clocks known as stratum 0 time sources, which are typically atomic clocks or Global Positioning System (GPS) satellites.A server that is linked to a stratum 0 device is called a stratum 1 server. The link itself is provided by a direct connection to the stratum 0 device (not via a network link), such as via WWV (high-frequency radio waves from NIST), GPS, or dial-up modem connection. Stratum 1 servers are the top level NTP servers available over the Internet.Building on the NTP hierarchy, a stratum 2 server gets its time over the network from a stratum 1 server, a stratum 3 server from a stratum 2 server, and so on (up to stratum 15).In essence then, the stratum defines the number of steps that a server is from a primary time source. It’s also worth noting that NTP servers operating in the same stratum may be associated with one another in a peer-to-peer fashion. This is done so that a higher quality of time can be achieved and so that the servers can synchronize to the most accurate time setting amongst peers. 

Q: What is PoE?

A: Power over Ethernet technology is a network standard that allows various devices, such as Voice over IP (VoIP) telephones, wireless LAN access points, clocks, and digital signs to receive both power and data over existing LAN cabling.

Q: What is International Atomic Time?

A: International Atomic Time is an international time standard derived from 200 atomic clocks in 50 national laboratories from around the world. The readings from these clocks are used to form the standard for Coordinated Universal Time (UTC), which governs global time-keeping.  Atomic clocks represent the top-level stratum of the NTP hierarchy.

Q: How do I configure my PoE clock for SNTP?

A: When your clock ships, it is preconfigured to use the Inova Solutions time server at  Your clock should be reconfigured to point to your time server or one of the free available servers listed at: 

Q: How is SNTP used in OnTime PoE/IP Clocks?

A: By default, SNTP time synchronization is performed once per hour, which keeps the displayed time within 200 milliseconds of actual time. 

Q: What is SNTP?

A: Simple Network Time Protocol (SNTP) is a simplified version of NTP, which is used in cases where a full implementation of NTP is not required. Because SNTP uses the same packet format as NTP, SNTP clients can utilize NTP servers. 

Q: What is NTP?

A: Network Time Protocol (NTP) is a protocol that provides a reliable way of transmitting and receiving the time over TCP/IP networks. It has become the de facto standard for synchronizing Internet computers and other networked devices to Universal Coordinated Time (UTC), which is accomplished by having these devices reference a common time source – i.e., an atomic clock or a network time server (a.k.a. an “NTP server”).  NTP uses port 123, which must be opened on a firewall or router to ensure proper communication with the NTP server.