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Chapter 5
Setup and Configuration
Section 5.12
Managing Time Synchronization Functions
RUGGEDCOM ROX II uses version 4 of the Network Time Protocol (NTP) to synchronize the internal clock with a
time source.
NOTE
For more information about version 4 of NTP, refer to
NTP is a fault-tolerant protocol that allows an NTP daemon to automatically select the best of several available
reference clocks to synchronize with. Multiple candidates can be combined to minimize the accumulated error.
The NTP daemon can also detect and avoid reference clocks that are temporarily or permanently advertising the
wrong time.
The NTP daemon achieves synchronization by making small and frequent changes to the internal clock. It
operates in a client-server mode, which allows it to synchronize the internal clock with NTP servers and act as an
NTP server for peer devices.
If multiple NTP servers are available to choose from, the NTP daemon will synchronize with the server that has
the lowest stratum. The stratum is a rating of the server compared to the server with the reference clock. The
reference clock itself appears at stratum 0. A server synchronized with a stratum n server will be running at
stratum n+1.
NTP hosts with a lower stratum are typically configured as NTP servers, while NTP hosts with higher stratums
are configured at the same stratum as their peers. If each NTP server fails, a configured peer will help in
providing the NTP time. It is recommended that at least one server and one peer be configured.
The NTP daemon knows which NTP servers and peers to use in three ways:
• The daemon is configured manually with list of servers to poll
• The daemon is configured manually with a list of peers to send to
• NTP servers issue advertisements to the daemon on broadcast or multicast address
NOTE
If a firewall is enabled, make sure UDP port 123 is open to send (if the router is an NTP client) or
receive (if the router is an NTP server).
NTP uses UDP/IP packets for data transfer, as UDP offers fast connections and response times, and transfers
them through UDP port 123.
The following sections describe how to configure and manage time synchronization functions:
•
Section 5.12.1, "Configuring the Time Synchronization Settings"
•
Section 5.12.2, "Configuring the System Time and Date"
•
Section 5.12.3, "Configuring the System Time Zone"
•
Section 5.12.4, "Configuring the Local Time Settings"
•
Section 5.12.5, "Configuring NTP Multicast Clients"
•
Section 5.12.6, "Configuring NTP Broadcast Clients"
•
Section 5.12.7, "Enabling/Disabling the NTP Service"
•
Section 5.12.8, "Viewing the NTP Service Status"
•
Section 5.12.9, "Viewing the Status of Reference Clocks"
•
Section 5.12.10, "Monitoring Subscribers"
216
RFC 5905
[http://tools.ietf.org/html/rfc5905].
Managing Time Synchronization Functions
RUGGEDCOM ROX II
CLI User Guide
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Troubleshooting
