Precision Time Protocol; Description Of Ptp Functions - Hirschmann RS20 User Manual

Synchronizing the System Time in the
Network

7.3 Precision Time Protocol

7.3.1

Description of PTP Functions

Precise time management is required for running time-critical applications via
a LAN.
The IEEE 1588 standard with the Precision Time Protocol (PTP) describes a
procedure that determines the best master clock in a LAN and thus enables
precise synchronization of the clocks in this LAN.
This procedure enable the synchronization of the clocks involved to an
accuracy of a few 100 ns. The synchronization messages have virtually no
effect on the network load. PTP uses Multicast communication.
Factors influencing precision are:

Accuracy of the reference clock
IEEE 1588 classifies clocks according to their accuracy. An algorithm that
measures the accuracy of the clocks available in the network specifies the
most accurate clock as the "Grandmaster" clock.
PTPv1 PTPv2
Stratum Clock class
number
0 – (priority 1 =
0)
1 6
2 6
Table 6: Stratum – classifying the clocks
UM BasicConfig L2E
Release 8.0 05/2013
Specification
For temporary, special purposes, in order to assign a higher
accuracy to one clock than to all other clocks in the network.
Indicates the reference clock with the highest degree of
accuracy. The clock can be both a boundary clock and an
ordinary clock. Stratum 1/ clock class 6 clocks include GPS
clocks and calibrated atomic clocks. A stratum 1 clock cannot be
synchronized using the PTP from another clock in the PTP
system.
Indicates the second-choice reference clock.
7.3 Precision Time Protocol
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