Ericsson MINI-LINK TN R3 ETSI, Technical Description, Page: 58 / 150

MINI-LINK TN R3 ETSI
3.10 Synchronization
3.10.1 Overview
MINI-LINK TN is by default working in Free Running mode. In this mode the
node is not a part of the synchronization network, and does not maintain a
SEC. The node behavior can be described by how the different protocols are
processed:
• Unstructured primary rate PDH channels are passed transparently except
for timing recovery and jitter attenuation. This is also valid for robbed
timeslot DCN channels.
• STM/STS interfaces are configured to take outgoing synch from local
oscillator or loop timing. If SSM is enabled “Do Not Use” is transmitted.
• PDH primary rate channels terminated in an AAU/ATM switch are
configured to take outgoing synch from local oscillator or loop timing.
• PDH primary rate channels used for Ethernet over PDH will have outgoing
synch generated by the local oscillators.
MINI-LINK TN ETSI can from release 3.1 also be configured to Network
Synchronized mode where the node maintains a SEC and distributes
synchronization and synchronization quality level status on cross connected
PDH channels (ITU-T G.813).
Note that unstructured primary rate PDH channels are still passed transparently
as in the Free Running mode, but now with reduced jitter. This is also valid for
PDH connections that are used for DCN including robbed timeslot DCN.
With Network Synchronized mode it possible to build a synchronized network
where all the NEs are synchronized to the same source. Figure 50 on page
53 shows an example of a network where the synchronization information is
carried to all the NEs through an assigned path. In case of link failures the
synchronization may be reestablished using the unassigned synchronization
paths.
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