Using CDC (Clear Data Channel) speeds up transfers with SSL sites. A clear data channel encrypts the connection process, but files are transferred without encryption. You can add more speed to your transfers by using a clear command channel as well.
Click on a site in the Site Manager.
On the menu bar, click File > Properties. The Site Properties dialog box appears.
Click the Type tab.
In the Protocol list, make sure FTP with SSL (Implicit encryption), or FTP with SSL (Explicit encryption) is selected.
Select the Clear Data channel check box.
Click OK or Connect.
The Clear Data channel option is only available with SSL connections.
Using a clear command channel with SSL