•
Follow-up
•
Delay-request
•
Delay-Response
•
Management
Unicast and Multicast Messages
PTP supports the following options for unicast and multicast:
•
Unicast mode: In this mode, all PTP messages are sent as unicast messages. This is the default behavior.
•
Mixed mode: (Not supported for ASR 9000 series routers)In this mode, Announce and Sync messages
are sent as multicast messages, while Signaling, Delay-Request, and Delay-Response messages are sent
as unicast messages.
•
Multicast mode: In this mode, all packets are sent as multicast messages.
Frequency and Time Selection
The selection of the source to synchronize the backplane clock frequency is made by frequency synchronization,
and is outside of the scope of PTP. The Announce, Sync and Delay-Request frequencies must be the same on
the master and slave.
Delay-Response Mechanism
The Delay Request-Response Mechanism, defined in section 11.3 of IEEE Std 1588-2008, is a mechanism
which allows a slave ports to estimate to a good degree of accuracy the difference between its own clock-time,
and the clock-time of its master. The following options are supported:
•
One-step mechanism - The timestamp for the Sync message is sent in the Sync message itself.
•
Two-step mechanism - The timestamp for the Sync message in a later Follow-Up message.
When running a port in Slave state, a router can send Delay-Request messages and handle incoming Sync,
Follow-Up and Delay-Response messages. The timeout periods for both Sync and Delay-Response messages
are individually configurable.
PTP Interface and Profile Configuration
If a global PTP profile is attached to an interface, its values are used as the default settings for that interface.
If additional settings are configured under the interface itself, these override the defaults in the profile. If no
profile is attached to an interface, the configuration on the interface is used to determine the PTP settings for
the interface.
You can use either of the following approaches when configuring PTP:
•
Create a profile (or multiple profiles) containing all the default settings to use on all PTP interfaces.
Override any settings that differ for particular interfaces by using the interface configuration under the
interfaces themselves.
•
Configure all settings separately for each interface, without using any global profiles. Use this approach
if the interfaces do not have consistent settings, or if you are configuring only a small number of PTP
interfaces.
Cisco ASR 9000 Series Aggregation Services Router System Management Configuration Guide, Release 5.1.x
235
Configuring PTP
PTP Implementation
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