User Manual
COGE5, COGE5-F
page 44 of 110
© KEYMILE December 2015
EN/LZTBU 372 144/3 RA
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Functional Description
Timing transfer over most Ethernet interfaces operates without restrictions.
Timing transfer over 1000BASE-T operates only in unidirectional direction,
from the clock master to the clock slave. Two 1000BASE-T ports autono-
mously negotiate which port will be the clock master and which port will be
the clock slave. The procedure is as follows:
• At start up both ports of an Ethernet point-to-point link have the preferred
clock mode “master”. The negotiation process arbitrarily selects one of
the ports as “slave”.
• If one of the Ethernet ports is used as synchronization source for the
PETS, it gets the preferred clock mode “slave”. If necessary the master/
slave roles are re-negotiated and the link is restarted.
Risk of operating trouble!
The selection of a synchronous Ethernet port as PETS clock source can lead
to a short traffic interruption.
• If both ports of an Ethernet point-to-point link are configured as synchro-
nization source for the PETS, both get the preferred clock mode “slave”.
The negotiation process arbitrarily selects one of the ports as “master”.
− The alarm CLKMIS (Clock Mismatch) is activated on the “master” port.
− Timing transfer is only possible in one direction.
5.4.3
Precision Time Protocol
The COGE5 front ports port-1 to port-5 support the Precision Time Protocol
(PTP) according to IEEE 1588v2.
Synchronization via PTP is supported for the following Ethernet port speeds:
• 100BASE-x,
• 1000BASE-x,
• 10GBASE-x.
Risk of operating trouble!
The SFP-based 1 GbE interfaces port-1 and port-2 on the COGE5 unit are
not operable as PTP timing sources.
→ The port-1 and port-2 must use the 10 GbE mode to be usable as PTP
timing source.
In a PTP Boundary Clock the received PTP packets in an Ethernet signal
can be used to synchronize the PETS. The forwarded PTP packets are syn-
chronized to the PETS timing. See section
5.4.3.1 Boundary Clock Applica-
In a PTP Ordinary Clock the received PTP packets in an Ethernet signal can
be used to synchronize the PETS. There are no forwarding PTP packets.
See section
5.4.3.2 Ordinary Clock Application
Please note:
A PTP port must be in the administrative status “up” to be selectable as PTP
source at the AP: /ne, Configuration - PTP.
In a PTP Transparent Clock the received PTP packets in an Ethernet signal
are forwarded, with a transit delay correction, as transmit PTP packets.
