In the CUCM traces , you can find a lot of StationInit and StationD .
What are they corresponding ?
It is simple , the StationInit represents a message from an endpoint to the CUCM. Meanwhile , the StationD represents a message from the CUCM to the endpoint.
If you want to follow the discussion between the endpoint and the CUCM , then you need to follow the TCP handle in the message which identifies the IP Phone.