Encryption Types - Explicit SSL
Explicit SSL is used to provide access to a mixture of FTP clients. With Explicit
SSL, the connection starts out as any regular (unencrypted) FTP connection. The FTP
client has the option to continue unencrypted, as a regular FTP session, or issue
the AUTH command and switch to secure-FTP mode. Also, when a user requests sensitive
data, the server can then require the client to upgrade to a secure connection.
The advantage of Explicit SSL is that SSL is not required of the client, so older
clients will be able to access the server.