Question: In the context of Telecommunication Management Charging Data Record (CDR) file format, what is the implication for the CS domain (e.g., for Bc) regarding the file transfer mechanism as per the specifications?
Option 1: The CS domain must exclusively use a specified file transfer mechanism.
Option 2: The use of any file transfer mechanism is prohibited in the CS domain for Bc.
Option 3: For Bc in the CS domain, it is left to implementation choice whether to use the legacy interface, a newly specified interface, or both, with an alternative being another defined mechanism.
Option 4: The CS domain for Bc can only utilize file transfer mechanisms detailed in external specifications.
Explanation: This option correctly reflects the flexibility given to implementations in the CS domain for Bc, allowing a choice between legacy interfaces, a new interface, or both, while also acknowledging an alternative mechanism. This highlights the importance of implementation choices in telecom networks, especially concerning backward compatibility and the adoption of new standards.