According to ITU-T recommendations, the requirement that the MSP switching time should be within 50 ms is conditional. For example, the number of NEs on an entire ring network is less than 16.

When setting the LCAS mode, follow the following principles:

1. If devices at the two ends are both Huawei devices, set them to the "Standard Mode".

2. If a Huawei device is interconnected with a third-party device, set the interconnected devices to the same mode according to the mode supported by the third-party device.

Which of the following statements about the multiplex section remote error indication (MS-REI) is correct?

1. The B2 byte indicates the transmission channel.

2. The Ml byte indicates the transmission channel.

3. MS-REI is transmitted from the sink to the source.

4. MS-REI is transmitted from the source to the sink.

5. Indicates the number of detected bit errors after the sink receives the MS signals.