Alcatel-Lucent 9500 MXC User Manual page 871

Ring Protection
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The east, west, clockwise and anti-clockwise descriptors are conventions used to describe and configure
9500 MXC ring operation. The physical implementation of a ring may be quite different.
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Wrapping can occur at the east-facing or west-facing RAC connections to the TDM bus. In this way,
should a ring-break be due to a fault within a RAC/ODU, the failed RAC will not participate in the traffic
re-direction.
3DB 23063 ADAA - Rev 004 July 2007
East facing (primary) RAC/ODUs drive the clockwise, primary ring. The
reverse, secondary ring, is driven by the West facing (secondary) RAC/ODUs
Only nodes adjacent to the failure point are involved in the wrapping action; all
other nodes on the ring continue to transmit and receive data in the same pre-fault
clockwise direction. The wrapping action is performed on the TDM bus.
Figure F-7 on page F-16 illustrates a back-to-back configuration of a typical
east-west node. At Node B, the normal and fault scenarios shown are:
• For normal, no-fault situations, the east-facing RAC is online transmitting valid
traffic, and the west-facing RAC is online receiving, for a clockwise data flow.
There is no valid traffic sent in the opposite direction, from the west-facing Tx
and east-facing Rx (secondary ring).
• For a break between nodes C and D, there is no change to the operation of node
B, but the secondary ring passing through it is now carrying wrapped data from
node C.
• For a break between nodes B and C, node B wraps data from the primary to
secondary ring, and does so without involving its primary Tx RAC
drop-insert circuits remain intact.
9500 MXC User Manual
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Vol. VI-F-15