Ntp-Ptp Interworking - Cisco ASR 9000 Series User Configuration Manual

Implementing NTP
or receive broadcast or multicast messages. However, the accuracy of timekeeping is marginally reduced
because the information flow is one-way only.
An NTP broadcast client listens for broadcast messages sent by an NTP broadcast server at a designated IPv4
address. The client synchronizes the local clock using the first received broadcast message.
The time kept on a machine is a critical resource, so we strongly recommend that you use the security features
of NTP to avoid the accidental or malicious setting of incorrect time. Two mechanisms are available: an access
list-based restriction scheme and an encrypted authentication mechanism.
When multiple sources of time (VINES, hardware clock, manual configuration) are available, NTP is always
considered to be more authoritative. NTP time overrides the time set by any other method.

NTP-PTP Interworking

NTP-PTP interworking provides the ability to use PTP, as well as other valid time of day (TOD) sources such
as Data over Cable Service Interface Specification (DOCSIS) Timing Interface (DTI) and global positioning
system (GPS), as the time source for the operating system. Prior to the support of NTP-PTP interworking,
only backplane time was supported for the operating system time.
NTP-PTP interworking also provides the means to communicate status changes between PTP and NTP
processes. It also supports the unambiguous control of the operating system time and backplane time in the
event of bootup, switchovers or card and process failures.
Related Topics
Configuring NTP-PTP Interworking, on page 222
How to Implement NTP
Configuring Poll-Based Associations
No specific command enables NTP; the first NTP configuration command that you issue enables NTP.
Note
You can configure the following types of poll-based associations between the router and other devices (which
may also be routers):
• Client mode
• Symmetric active mode
The client and the symmetric active modes should be used when NTP is required to provide a high level of
time accuracy and reliability.
When a networking device is operating in the client mode, it polls its assigned time serving hosts for the
current time. The networking device then picks a host from all the polled time servers to synchronize with.
Because the relationship that is established in this case is a client-host relationship, the host does not capture
or use any time information sent by the local client device. This mode is most suited for file-server and
workstation clients that are not required to provide any form of time synchronization to other local clients.
Cisco ASR 9000 Series Aggregation Services Router System Management Configuration Guide, Release 5.1.x
NTP-PTP Interworking
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