What requirements must be satisfied for the conversation between ONUs connected to the MA5680T?
1. Ensure that the ONUs can ping the softswitch in the network.
2. Ensure that ONUs can ping each other.
3. Ensure that the network-side VLANs for the voice services of the ONUs must be different.
4. Ensure that the voice data packets of the ONUs must be forwarded through the upstream device.