How to implement a replication between different networks using FTP

Hi all,
I'm try to understand how implement a transitional replication between 2 different network.
I've create a Publication on SERVER A (type transitional) with  FTP activation.

I don't understand if is possible, for the subscriber, get updates via FTP or this way in only for the initial snapshot data.

Please someone can give a clearly feedback or some useful link.

Thanks ALEN, Italy