[REQ] Airlines and ATSOs participating in LINK 2000+ shall assign ATN application entity titles and ATN addresses in accordance with the data link services they decided to support.
Table 6 summarizes for each data link service which ATN application entity titles and addresses have to be defined.
Table 6 : Required LINK 2000+ ATN AE Titles and Addresses
[REQ] All air or ground ATC entities participating in LINK 2000+ shall be identified by a 24-bit address or an ICAO Facility Designator.
9.2.2CM Service related Requirements
[REQ] States participating in LINK 2000+ shall define the organisation of their ground space in terms of application addressing areas, or CM contexts4.
A "CM context" is the basic naming and addressing reporting unit to the aircraft: it identifies which ATN applications are available on the ground and the application protocol version operated. It may contain in addition the ATN application address, when used by the peer to establish a dialogue with this application.
The definition of the ground topology should follow the following basic rules:
There should be a single CM application per CM context, responsible to send to peer systems the context through the CM-logon and CM-update data exchanges.
Except for the CM application itself, an ATN Application may belong to more than one CM context; this may be the case for an DFIS Application shared by several States.
Several instances of the same version of an ATN application can be operated in the same CM context as far they are hosted in separate systems; for instance, the data link services DCL and ACL could be supported in an ATCC by 2 different CPDLC applications. In that case, the initiator system shall be able to know which system it needs to contact.
Note. Although several CM contexts may in theory be supported in the aircraft, it is supposed that aircraft in LINK 2000+ will represent a single CM context.
Figure 6 : Exanples of CM contexts
Any aircraft entering the LINK 2000+ area or departing from an airport of the LINK 2000+ area will establish communication with the appropriate CM addressing server to initiate the data link capability with the ground.
[REQ] A procedure shall be defined by each ATSO to make the aircrew aware of which CM server to contact first when entering the ATSO's airspace and for the purpose of initiating Data Link Service..
The addresses of the initial CM servers available in this area should have been previously loaded in the avionics system by the aircraft operators.
[REQ] Each ATSO participating in LINK 2000+ shall register at least one ATN address corresponding to a CM application operated in its data link domain.
Note1. These addresses could be published in [ICAO_9705] Edition 3 - Sub-Volume IX "ATN Identifier Registration" in section 9.3.1 "State Addresses".
Note 2 . Because the ICAO publication process is long and not flexible, it is recommended that a LINK 2000+ registration authority be established to maintain this CM Address data base and interface with ICAO when required.
An ATSO can operate more than one CM server in its data link area.
[REQ] The procedure by which the aircraft identifies the appropriate CM server when entering the area of an ATSO shall be clearly defined by the ATSO.
[REQ] The ATSO is responsible for providing the aircraft with the addressing information required to initiate the data link capability with the next ATSOs along the flight path, if the CPDLC Transfer of Communications function is not available or fails to transfer the aircraft to the next ATSO.
