Nokia 7705 - 6.4.6.13 ITU-T G.8275.1

Basic System Configuration Guide System Management
Edition: 01 3HE 11010 AAAC TQZZA 251
When a PTP clock is configured for Ethernet encapsulation, there are two profiles
available: ieee1588-2008 or g8275dot1-2014. When the profile configuration is
ieee1588-2008, the PTP clock’s priority1 and priority2 settings are used by the
BMCA to help determine which clock should provide timing for the network. When
the profile configuration is g8275dot1-2014, the local-priority value is used to
choose between PTP masters in the BMCA. See ITU-T G.8275.1 for information
about the g8275dot1-2014 profile.
6.4.6.13 ITU-T G.8275.1
The 7705 SAR implements Recommendation ITU-T G.8275.1, which specifies the
architecture that allows the distribution of time/phase with full timing support from the
network. The Recommendation details the profile for using IEEE 1588 to distribute
time in an environment where every node is either a grand master, boundary, or
ordinary clock. When configured for the G.8275.1 profile, the 7705 SAR can operate
as boundary clock, an ordinary master clock, or an ordinary slave clock.
When the 7705 SAR is configured for the G.8275.1 profile, it uses an alternate BMCA
for best master clock selection. This BMCA includes a PTP dataset comparison that
is defined in IEEE 1588-2008, but with the following differences:
•the priority1 attribute value is removed from the dataset comparison
•the master-only parameter value must be considered
• multiple active grand master clocks are allowed; therefore, the BMCA will select
the nearest clock of equal quality
• a port-level local-priority attribute value is used to select a slave port if two ports
receive an Announce message. This attribute is used as a tie-breaker in the
dataset comparison algorithm if all other previous attributes of the datasets
being compared are equal.
•the local-priority parameter value is considered for the default dataset
The ITU-T G.8275.1 profile has the following characteristics.
• The default domain setting is 24; the allowed range is 24 to 43.
• Both one-step and two-step clocks are supported.
• Both IP encapsulation and Ethernet encapsulation are supported. When
Ethernet encapsulation is used, the following points apply.
Note: The local-priority parameter is only supported for Ethernet-encapsulated ports; it is
not supported for IP-encapsulated ports.