Sub-Network Connection Protection

Sub - Network Connection Protection ( SNCP, German subnetwork connection protection) is a protective mechanism for interconnection in telecommunications.

This protection mechanism is used in the synchronous digital hierarchy (for example, VC -12) to switch VC paths in case of failure of the active path to a pre- defined backup path. If ( for example, by cable defect ), so is automatically switched to another route within the subnet route. This alternate route ties together the same endpoints as the failed route before.

A distinction is made between SNCP -I ( inherent ) and SNCP -N ( nonintrusive ). The difference between the two is the type of error, which can trigger a switching of the connection on the backup path. The SNCP -I trigger the error loss of pointer (LOP ) and Alarm Indication Signal (AIS ). SNCP -N can also be triggered by the error signal Degraded (SD), Trace Identifier Mismatch (TIM ) and excessive Error Bit Rate ( exBER ). For this purpose, a monitoring of the path overhead of the VC is necessary because the information contained in this overhead allow only monitoring for these errors.

Older network elements that do not have a Path Monitoring, also do not have SNCP -N functionality, so that then only SNCP -I may be used.

The next higher - level Protection for SNCP is the Multiplex Section Protection ( MSP), are protected when not individual VCs, but a whole section with many VCs.

Equivalent of the SNCP in the SONET technology, also known as UPSR.

• Multiplexing technique