Customer had some doubt about the MSP switching time.
According to the ITU-T recommendation, the MSP switching time is less than 50 ms in order to ensure the normally running services. However it is true only on the
condition that (for ring network):
1. No additional services
2. All NEs on the ring are in idle state
3. The whole ring has a maximum of 16 NEs
4. The total length of the ring is less than 1200 kilometer
5. Signal Failure (SF) event occurs between adjacent NEs
If any of the requirements is not met, the MSP switching time can be more than 50 ms. The explaination for this is as below:
1. No additional services means no time to remove extra services
2. All NEs on the ring are in idle state means no detected failures, no external commands and receiving only idle K-byte.
3. The whole ring has a maximum of 16 NEs is required by MSP protocol
4. The total length of the ring is less than 1200 kilometer means the switch (ring and span) completion time for a failure on a single span shall be less than 50 ms.