User's Manual

ALFOplus 24GHz (North America) - Release 01.05.0x - MN.00395.E - 004 65
b. Radio with quality SSUT (Priority 2)
In case the sources have equal quality, the SIAE equipment will switch the source of synchronization
with higher priority, in this case (a) the LAN1 with Priority 1 and quality SSUT. However, if a DNU quality
would be received on LAN1, the SIAE equipment will switch the synch source to Radio port.
The quality of the synchronism has to be enabled for each SIAE equipment and can be transported on the
following interfaces:
• On the Ethernet Interfaces through a standard protocol (according to ITU-T G.8264)
• Radio interface with Local/Remote Telemetry: Depending on the MW link configuration (1+0) the
SSM messages are passed to the remote SIAE equipment in different ways.
- 1+0 Configuration: In this case there is one Local/Remote Telemetry passing the SSM messages
Within this configuration table there are also some maintenance configurations such as:
• Forced Switch: this command allows the operator to force the SETS to lock to a predetermined
source. This command is above all other configurations. This means that the SETS will be locked
onto this source even if the cable is unplugged
• Preferential switch: In case two sources have equal priority it is possible to set a Preferential Source.
In any case the quality is the main parameter of choice, then when two sources have the same pri-
ority, the preferential source is chosen.
In relation to the SSM, it is possible to:
• Visualize the quality of the clock signal received and transmitted (Rx Quality and Tx Quality)
• Overwrite the Quality received or transmitted (Ovw Rx Qlty and Ovw Tx Quality) and the choices
are:
- PRC: Primary reference Clock – Best quality clock reachable (Cesium Clock)
- SSUT: Synchronization Supply Unit Transit (Rubidium Clock)
- SSUL: Synchronization Supply Unit Local
- SEC: SDH Equipment Clock (Crystal Clock)
- DNU: Do not Use – This signal informs the receiver to do not use this clock
The Overwrite of the Quality of the Clock is configurable by the user and simply forces in input or output
the quality.
7.15.1 SSM on Ethernet Interfaces
In order to propagate the clock signal through the Ethernet 1GE Electrical interface it is necessary to set
correctly the master and slave option for each interface. It is possible to assign the roles (Master or Slave)
statically (as set up for source LAN) or dynamically (according to Synch direction).
This because the Master interface transmits the clock to the Slave interface and in case the direction of
propagation of the clock has to be changed (line failure, insufficient quality, etc..), the master and slave
assignment has to be re-negotiated with a consequent loss of traffic. This re-negotiation implies an inter-
ruption of the traffic from 2.4 to 2.6 seconds.
SIAE equipment allows to set the role of the interfaces to “According to synch direction” (dynamic), the
flow of the propagation of the clock signal is automatically changed depending on the transferring direction
of the CK.
If the role of the interfaces is set to “As set up for source LAN” (Static), the flow of the propagation of the
clock signal is fixed (see Fig.29
).
Fig.29 - LAN synchronisation method