Marconi OMS 1200
Technical Product Description
221 02-ZAP 701 25/1 Rev C 2006-08-04
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The behaviour is such that the remote SNCP controller receives the RR use worker
channel and then determines the appropriate switching action according to request
priorities. It then sends the appropriate RR back to the local SNCP controller. It is at
this stage that the local node switches back to the worker channel, if so instructed by
the incoming RR.
Note:
With this behaviour there is a short period where the local node indicates No
Request - Traffic on Worker state, when in fact it is still switched to
protection.
7.5.2.4
SNC Persistency (Protection Switching Hold-Off)
You can configure persistency (or Hold-off) on SNC protection in the range zero - 20s
in 100ms (+/-20ms) increments, either on a global or per path basis. The default value
is 0ms.
You can only retrieve persistency values from the NE on an individual path basis.
This persistency is required if operating both 1+1 Linear MSP/MS-SPRING protection
schemes and SNC protection. It allows the MS layer protection scheme to react and
switch, and pre-empt SNCP switching, in the event that a detected fault leading to
switching actions is in fact an MS layer fault and not a specific VC-path layer fault.
SNCP switching can be triggered from failures detected at MS and HO path layers
(SNC/I monitoring), as well as failures detected at the specific protected VC-path layer
(SNC/N monitoring).
The persistency configuration is applied to the protection switch controller on the core
unit. It applies a hold-off to autonomous protection switching actions from received
SF/SD signalling flag requests.
Protection switching actions are only taken if the SF/SD flag has persisted for a period
greater than the configured hold-off time.
7.5.3 Protection
Switching Criteria for SNCP
SNC protection switching operates according to events received and detected by the
SMA in the network, which is terminating the protected SNC. These events comprise
locally detected VC-trail SNC failures, locally applied operator requests for switching
received via the NMI, and remotely signalled switching requests received from the
SMA at the far end of an end-to-end protected SNC.
Remote requests only apply to bi-directional switching modes and bi-directional
switching only operates on end-to-end protected SNCs. Remote requests are
signalled across the network via VC- POH bytes of the protected SNC.
7.5.3.1
Locally Detected VC Failure Events
The bearer SDH interface units of the SMA, which is receiving worker and protection
SNCs from the network, performs detection of VC-trail failures on a protected SNC.
The bearer SDH interface units are either STM-n interface units or VC-AM sub-STM-1
interface units.