Edge-Core ECS4660-28F, Руководство по управлению, Страница: 597 / 2020

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HAPTER
14
| Basic Administration Protocols
PTP Configuration
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Variance – A clock's estimate of its stability based on
observation of its performance against the PTP reference.
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Quality – Clock quality based on expected timing deviation,
technology used to implement the clock, or location in a stratum
schema.
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Identifier – A universally unique numeric identifier for the clock.
This is typically constructed based on a device's MAC address.
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PTP uses a hierarchical selection algorithm based on the following
properties in the order indicated.
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Priority 1
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Class
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Accuracy
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Variance
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Priority 2
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Unique identifier (tie breaker)
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Priority2 – Sets a secondary preference level used by slave devices in
selecting the master clock. (Range: 0-255; Default: 128)
The Priority2 preference is only considered when it not possible to use
Priority1 and other clock attributes to select a best master clock.
◆
Domain Number – Specifies the PTP clock synchronization domain to
which the switch belongs. (Range: 0-255; Default: 0)
A domain is a set of clocks that synchronize to one another using PTP.
Multiple independent PTP clocking domains can be configured on a
single network, but a device can only belong to one domain.
◆
Ingress Latency – The ingress latency is added to the actual
timestamp of ingress PTP messages. Failure to make this correction will
result in a time offset between the slave and master clocks.
(Range: 0-1000000 nanoseconds; Default: 0 nanoseconds)
◆
Egress Latency – The egress latency is added to the actual timestamp
of egress PTP messages. Failure to make this correction will result in a
time offset between the slave and master clocks. (Range: 0-1000000
nanoseconds; Default: 0 nanoseconds)
W
EB
I
NTERFACE
To configure global settings for PTP:
1.
Click Sync, PTP.
2.
Select Configure Global from the Step list.
3.
Select the mode to the required clock type, enable local adjustment of
received timing information, configure the priorities used in selecting
the best master clock, and then specify the PTP domain to which this
switch is assigned.