1588 Packet Types
•
Announce : Used to announce the existence of PTP clocks throughout the network. Sent by ports in
MASTER state.
•
Sync/Follow-Up/Delay-Req/Delay-Resp: Used to exchange timestamps between master and slave, to
synchronize time.
•
Signalling Messages: Used to negotiate unicast grants.
PTP Hybrid Mode
Your router allows the ability to select separate sources for frequency and time-of-day (ToD). Frequency
selection can be between any source of frequency available to the router, such as: BITS, GPS, SyncE or IEEE
1588 PTP. The ToD selection is between the source selected for frequency and PTP, if available (ToD selection
is from GPS, DTI or PTP). This is known as hybrid mode, where a physical frequency source (BITS or SyncE)
is used to provide frequency synchronization, while PTP is used to provide ToD synchronization.
Frequency selection uses the algorithm described in ITU-T recommendation G.871, and is described in the
Configuring Frequency Synchronization module in this document. The ToD selection is controlled using the
time-of-day priority configuration. This configuration is found under the source interface frequency
synchronization configuration mode and under the global PTP configuration mode. It controls the order for
which sources are selected for ToD. Values in the range of 1 to 254 are allowed, with lower numbers indicating
higher priority.
Related Topics
Configuring PTP Hybrid Mode, on page 250
PTP Hybrid Mode: Example, on page 258
Configuring Frequency Synchronization, on page 191
ITU-T Telecom Profiles for PTP
Cisco IOS XR software supports ITU-T Telecom Profiles for PTP as defined in the ITU-T recommendation.
A profile consists of PTP configuration options applicable only to a specific application.
Separate profiles can be defined to incorporate PTP in different scenarios based on the IEEE 1588-2008
standard. A telecom profile differs in several ways from the default behavior defined in the IEEE 1588-2008
standard and the key differences are mentioned in the subsequent sections.
The following sections describe the ITU-T Telecom Profiles that are supported for PTP.
G.8265.1 Profile
G.8265.1 profile fulfills specific frequency-distribution requirements in telecom networks. Features of G.8265.1
profile are:
•
Clock advertisement: G.8265.1 profile specifies changes to values used in Announce messages for
advertising PTP clocks. The clock class value is used to advertise the quality level of the clock, while
the other values are not used.
Cisco ASR 9000 Series Aggregation Services Router System Management Configuration Guide, Release 5.1.x
236
Configuring PTP
1588 Packet Types
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