Because TLS versions older than TLS 1.2 are declared as "deprecated" by the IETF, TELNET now supports only TLS protocol version 1.2 or newer. The usage of the previous option values SSLv3, TLSv1 or TLSv1.1 leads to a warning message and ignoring the option value.
As the OpenSSL interface behind this option is declared as "deprecated", this option will be replaced in the future with the options -Z minProtocolVersion and -Z maxProtocolVersion.
-Z Protocol |
={+ | -} { TLSv1.2 | TLSv1.3 | ALL } ... |
+
The protocol specified after this sign is permissible.
-
The protocol specified after this sign is not permissible.
TLSv1.2
TLS protocol version 1.2.
TLSv1.3
TLS protocol version 1.3.
ALL
All supported protocols are to be enabled.
ALL is the default.
Example
The specifications -Z Protocol=ALL - TLSv1.2 and -Z Protocol=TLSv1.3 have the same effect.