Refer to figures.
Controller-pilot data link communications (CPDLC). A means of communication between controller and pilot, using data link for ATC communications.

ICAO Doc 10037 Global Operational Data Link (GOLD) Manual
1.2.3. CPDLC connection management

1.2.3.1.1. The purpose of a CPDLC connection is to allow the exchange of CPDLC messages between an aircraft and an ATS unit (active connection), and also to provide an advance connection with the next ATS unit (inactive connection). An aircraft can have a maximum of two CPDLC connections established concurrently, each with a different ATS unit. Only one CPDLC connection can be active at any given time; any second connection is inactive.

1.2.3.3.2. The ATS unit initiates a CPDLC connection by sending a CPDLC connection request to the aircraft as shown in Figure 1-11.

1.2.3.3.3. Provided there is no existing CPDLC connection, the aircraft system:

a) accepts the connection request;

b) establishes this CPDLC connection as the active connection; and

c) responds with a CPDLC connection confirm.

1.2.3.5. Transferring CPDLC connections

1.2.3.5.1. Under normal circumstances, the CDA will initiate a CPDLC transfer to an adjacent ATS unit as the aircraft transits from the current ATS unit to another CPDLC-capable ATS unit. These transfers are normally automatic, without flight crew action.

“Disconnected from LOVV. Connecting to LOVL”: This transmission indicates that the aircraft's CPDLC system has autonomously managed the transition between the CPDLC ground stations. LOVV refers to the control center that the aircraft was previously connected to, and LOVL is the new control center it has connected to. This automatic handover is a standard process in CPDLC to maintain continuous communication as the aircraft moves through different airspace sectors.