Network Time Protocol (NTP)

The Network Time Protocol (NTP) is defined in RFC 1305, Network Time Protocol (Version 3) Specification, Implementation and Analysis. It allows participating network nodes to keep time more accurately and maintain time in a more synchronized manner between the participating network nodes.

NTP uses stratum levels to define the number of hops from a reference clock. The reference clock is treated as a stratum-0 device that is assumed to be accurate with little or no delay. Stratum-0 servers cannot be used in a network. However, they can be directly connected to devices that operate as stratum-1 servers. A stratum-1 server is an NTP server with a directly-connected device that provides Coordinated Universal Time (UTC), such as a GPS or atomic clock.

The 7210 SAS devices cannot act as stratum-1 servers but can act as stratum-2 devices because a network connection to an NTP server is required.

The higher stratum levels are separated from the stratum-1 server over a network path, therefore a stratum-2 server receives its time over a network link from a stratum-1 server. A stratum-3 server receives its time over a network link from a stratum-2 server.

If the internal PTP process is used as a time source for System Time and OAM, it must be specified as a server for NTP. If PTP is specified, the prefer parameter must also be specified. After PTP has established a UTC traceable time from an external grandmaster source, that clock is always the time source into NTP, even if PTP goes into time holdover.

Note:

Use of the internal PTP time source for NTP promotes the internal NTP server to stratum-1 level. This may impact the NTP network topology.

The following NTP elements are supported: