Overview - Interoperation with Network Time Protocol
Network Time Protocol (NTP) is an Internet-recommended standard. The NTP synchronization subnetwork is represented by a tree-structured graph with nodes representing time servers and edges representing the transmission paths between them. The root nodes of the tree are designated primary servers that synchronize to a radio broadcast or calibrated atomic clock. Remaining nodes are designated secondary servers that synchronize to other servers (primary and secondary).
The number of subnetwork hops between a particular server and a primary server determines the stratum of that server; that is, the smaller the number of hops, the lower the stratum. A lower-stratum server always has a higher accuracy than a higher-stratum server. All servers have identical functionality and can operate simultaneously as clients of the next lower stratum and servers for the next higher stratum.
Servers, both primary and secondary, typically run NTP with several other servers at the same or lower stratum. A selection algorithm attempts to select the most accurate and reliable server or set of servers from which to actually synchronize the local clock.
NTP and DTS both can be used in large computer networks that have embedded local nets (that is, those connected by routers, gateways, and bridges) and use both broadcast and point-to-point transmission media. DTS and NTP can run simultaneously on the same LAN. The following topics describe how to give time to and get time from local and remote NTP time sources, and how to prevent loops.