
PTP Operational Overview
PTP Introduction
PRISM MPI2-10-MPX2-10 User Manual
294
PTP Introduction
PTP Master Selection
In a PTP network, all the masters on the network are evaluated by the Best Master Clock
Algorithm (BMCA). The BMCA runs on all devices, and chooses a master based on
several parameters. Some of the parameters relate to clock quality; conversely the
Priority 1 and Priority 2 parameters are set by the user to influence the choice of a
master:
Note:
The PRISM monitor has no role in setting the priority parameters or in
providing information to the BMCA.
•
Priority 1: This parameter defines which clocks are allowed to be considered as
masters. To be considered as a master, the value should be set to 128 or less. Priority
1 is the first criteria in the BMCA, so if Priority 1 is set to a lower value than other
devices on the system, then it is chosen even if the clock quality is poor. Typically, all
the masters in a domain should have the same value for the Priority 1 parameter.
•
Priority 2: This parameter is used to break the tie between masters that have the
same clock quality. Several values may be used to define a hierarchy of devices.
Most profiles use 128 as a default, so a value of 127 or lower would indicate a
preferred master.
•
The final tie-breaker in the BMCA is the clock ID. This is usually the MAC address so
it provides a unique value by which the BMCA can choose.
Network Topology
In a typical IEEE1588 PTP network, many devices may be either masters or slaves. If the
current master stops working, all the devices that are capable of being a master
broadcast their clock quality and a new master is selected.
For video networks it may make sense to depart from the telecom-style PTP topology
and dedicate devices to be only masters or slaves. This is the approach supported by
the PRISM monitor, which allows for a more traditional primary and backup master
structure controlling a range of slave devices. The BMCA is still used to select the active
master and the network still takes the place of the ECO in the legacy Black-burst/Tri-
level network. The PRISM monitor is a slave-only device.
Содержание PRISM MPI2-10
Страница 1: ...PRISM MPI2 10 and MPX2 10 SDI IP Waveform Monitor User Manual April 2021 D00010021C...
Страница 6: ...6 PRISM MPI2 10 MPX2 10 User Manual...
Страница 52: ...Getting Started Activity Center PRISM MPI2 10 MPX2 10 User Manual 54...
Страница 74: ...Methods of Operation Remote Control through API Commands PRISM MPI2 10 MPX2 10 User Manual 76...
Страница 302: ...PTP Operational Overview Compensating for Causes of Asymmetric Delay PRISM MPI2 10 MPX2 10 User Manual 304...