Alcatel-Lucent 9500 MXC User Manual page 647

Ring
3DB 23063 ADAA - Rev 004 July 2007
• The Rx protection switch function is contained within the RACs and is
transferred between RACs to always be with the online Rx RAC (bus
driving RAC).
• Changing the online status from one RAC to the other using the locks in the
System/Controls screen, or withdrawing the online Rx RAC, transfers the
online protection switch function to the partner RAC, which causes a service
interruption.
• Switching is not restorative, which means that when a fault condition has been
cleared there is no automatic return to the pre-fault online Rx or online Tx
RACs. To change online status use the commands in System/Controls, or
withdraw an online RAC to effect a switch to its partner RAC. Except for a
single antenna hot-standby link where an unequal coupler has been installed,
there is no operational need to always return to the default online RACs
(low-loss side should be with the online Tx).
• Where testing involves disconnection and re-connection of the ODU cable at
RAC front panels, such action is only recommended for protection switch
testing for the reason connector mating surfaces can be damaged by arcing, and
the arcing may cause errors on other traffic transiting the Node. For all other
situations, either withdraw the RAC from its backplane, or disconnect the -48
Vdc power supply before ODU cable disconnection and re-connection.
A ring comprises a closed network of nodes where RACs at each node are
assigned in an East and West direction in the Protection screen. Within this ring
there are two traffic rings:
• One is designated primary, where traffic comes in on the West RAC and leaves
on the East RAC (clockwise direction). Under normal no-fault conditions, all
traffic flows just on this primary ring.
• The other is designated the secondary, where traffic comes in on the East RAC
and leaves on the West RAC (anti-clockwise direction). This secondary ring is
only used in the event of a fault; traffic is diverted from the primary ring onto
the secondary ring at the break point, where it travels around the ring (East to
West, anti-clockwise direction) to meet up with the primary ring at the other
side of the break. This process is called 'wrapping'.
Unlike hot-standby and diversity protection, ring protection is restorative; once a
fault condition has cleared, the ring automatically unwraps so that only the
primary ring is carrying traffic.
NMS visibility is maintained to all Nodes on a ring for a single break. Visibility
is only lost where a Node or Nodes are isolated due to a double/multiple break.
Auxiliary data traffic is not protected on a ring.
Alarm I/O event mapping follows NMS visibility; providing NMS contact is
maintained to Nodes, Alarm I/O event signalling is maintained.
9500 MXC User Manual
Vol. V-1-9