-Z Protocol

Because TLS versions older than TLS 1.2 are declared as "deprecated" by the IETF, TELNET now supports only version 1.2 or newer of the TLS protocol.

As the OpenSSL interface behind this option is declared as "deprecated", this option will be replaced in the future with the options -Z tlsMinProtocolVersion and -Z tlsMaxProtocolVersion.

-Z Protocol

=[+ | - ] { TLSv1.2 | TLSv1.3  |  ALL } ...

+

The protocol specified after this sign is permissible.

-

The protocol specified after this sign is not permissible.

If neither “+” nor “-” is specified, this has the same effect as specifying “+”.

TLSv1.2

TLS protocol version 1.2

TLSv1.3

TLS protocol version 1.3

ALL

All 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.