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Created 02 May 2004
Modified 07 Feb 2016

Article 189

What is the difference between Implicit TLS and Explicit TLS?

FTP over TLS (Explicit)

Explicit security requires that the FTP client issues a specific command to the FTP server after establishing a connection to establish the SSL link. In explicit TLS the FTP client needs to send an explicit command (i.e. "AUTH TLS") to the FTP server to initiate a secure control connection. The default FTP server port is used. This formal method is documented in RFC 4217.

FTP over TLS (Implicit) - Deprecated

Implicit security is a mechanism by which security is automatically turned on as soon as the FTP client makes a connection to an FTP server. In this case, the FTP server defines a specific port for the client (990) to be used for secure connections. FTP over TLS Implicit has been deprecated and should no longer be used.

Keywords
TLS, SSL, Implicit, Explicit