Nortel Optical Multiservice Edge 6130 Planning Manual page 195

Note: In the Route-Diversity-Disabled option, no DCN configuration is
allowed on the configured protected port of the MSP pair.
"Route diversity disabled" mode uses a single DCC channel which is switched
with the traffic for management, which is unlike the "route diversity enabled"
mode where each interface of the 1+1 MSP link has a separate DCC channel
that is not switched with the MSP protected traffic.
In the Route-Diversity-Enabled option, the DCN operation on the configured
working and configured protected ports belonging to MSP are treated
independently. The transmit and receive data of the two layer 1 interfaces
(belonging to the configured working and configured protected ports
belonging of MSP pair) is independently presented to the layer 2 termination
protocol as two independent interfaces. The layer 2 and above are presented
with two independent network interfaces.
Note: In the Route-Diversity-Enabled option, DCN configuration is
allowed on the configured protected port of the MSP pair.
If OME6130 NE is interworking with another network element (e.g OM4000)
which has its interface set to bi-directional MSP switching mode, route
diversity should be provisioned to the same at the OME6130 NE and the
far-end NE. Otherwise, DCC alarms may be raised on the non-OME6130 NE
which can be ignored or disabled.
When an OME6130 NE, which has its DCC route diversity disabled, is
interworking in a 1+1 MSP uni-directional switching mode with other NE (e.g.
OM4000) with route diversity enabled, a single fibre break in the Rx direction
of the non-OME6130 NE in working path can result in lost of communication
between the two NEs because the OME6130 NE can still receive traffic on the
working interface which the transmit has failed, therefore bi-directional LAPD
adjacency can not be established on neither the working path nor the protection
path, and hence loss of communication. There will no loss of communication
if both fibres (Tx and Rx) on the working path fail at the same time so that
bi-directional LAPD adjacency can be establish on the protection path.
Bi-directional switching mode is the recommended protection scheme used for
1+1 MSP in order to guarantee full data communication between interworking
network elements.
SNCP or unprotected system
In this configuration, each STM-1/4 link is considered as an individual port,
allowing the DCC to be configured independently. The following are the
supported combinations for each DCC:
• STM port with DCC disabled
• STM port with PPP/IP or cHDLC/IP
Planning Guide NT6Q92MA Rel 1.0 Iss 1 Standard September 2006
Appendix A: Data communications planning 10-9