What’s common for FTP, POP3, IMAP, SMTP, HTTP? All those protocols share same method for encryption of communication between client and server – the TLS/SSL. TLS is just a new name for SSL version 3.1 (for details see KB article about Secure FTP).
The TLS/SSL comes in two common flavors:
- TLS/SSL Explicit
- TLS/SSL Implicit
What’s the difference?
Detailed description can be found at KB article about TLS/SSL implicit and explicit modes difference. Simplified explanation follows:
- Runs on the same port as plain (unencrypted) protocol.
- Client must ask the server to switch the encryption on.
- Runs on a different port than plain (unencrypted) protocol.
- Encryption is turned on automatically.
How to choose which one to use?
You may have received a hostname and port from you admin and you are wondering which version of TLS/SSL security should be used. A general rule of thumb seems to be simple:
- If the port is the same as standard port for this protocol use the TLS/SSL Explicit
- If the port is different use the TLS/SSL Implicit
See following KB article for standard and TLS/SSL Explicit ports for FTP, POP3, IMAP, SMTP and HTTP.
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