System Management
7210 SAS D, E, K OS Basic System Configuration Guide Page 185
Network Time Protocol (NTP)
NTP is the Network Time Protocol defined in RFC 1305, Network Time Protocol (Version 3)
Specification, Implementation and Analysis. It allows for the participating network nodes to keep
time more accurately and more importantly they can maintain time in a more synchronized fashion
between all participating network nodes.
NTP uses stratum levels to define the number of hops from a reference clock. The reference clock
is considered to be 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 as a
network connection to an NTP server is required.
The higher stratum levels are separated from the stratum-1 server over a network path, thus, 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.
The internal PTP process is to be used as a source of time for System Time and OAM time then it
must be specified as a server for NTP. If PTP is specified then the prefer parameter must also be
specified. Once PTP has established a UTC traceable time from an external grandmaster then it
shall always be the source for time into NTP even if PTP goes into time holdover.
Note: Use of the internal PTP time source for NTP will promote the internal NTP server to stratum
1 level. This may impact the NTP network topology.
The following NTP elements are supported:
• Server mode — In this mode, the node advertises the ability to act as a clock source for
other network elements. In this mode, the node will, by default, transmit NTP packets in
NTP version 4 mode.
• Authentication keys — Increased security support in carrier and other network has been
implemented. Both DES and MD5 authentication are supported as well as multiple keys.
• Operation in symmetric active mode — This capability requires that NTP be synchronized
with a specific node that is considered more trustworthy or accurate than other nodes
carrying NTP in the system. This mode requires that a specific peer is set.
• Broadcast modes —When operating in this mode, the node will receive or send using a
broadcast address.
• Alert when NTP server is not available — When none of the configured servers are
reachable on the node, the system reverts to manual timekeeping and issues a critical
alarm. When a server becomes available, a trap is issued indicating that standard operation
has resumed.
To Next Page
Loading...
Need help?
General
