The handling of localhost  on Unix depends on the type of transport protocol. Connections using classic MySQL protocol handle localhost  the same way as other MySQL clients, which means that localhost is assumed to be for socket-based connections. For connections using X Protocol, the behavior of localhost  differs in that it is assumed to represent the loopback address, for example, IPv4 address 127.0.0.1. 

## Additional Connection parameters 

You can specify options for the connection, either as attributes in a URI-like string by appending ? attribute=value , or as key-value pairs. The following options are available: 

• ssl-mode : The desired security state for the connection. The following modes are permissible: 

• DISABLED 

• PREFERRED 

• REQUIRED 

• VERIFY_CA 

• VERIFY_IDENTITY 

For information about these modes, see the --ssl-mode  option description in Command Options for Encrypted Connections. 

• ssl-ca : The path to the X.509 certificate authority file in PEM format. 

• ssl-capath : The path to the directory that contains the X.509 certificates authority files in PEM format. 

• ssl-cert : The path to the X.509 certificate file in PEM format. 

• ssl-cipher : The encryption cipher to use for connections that use TLS protocols up through TLSv1.2. 

• ssl-crl : The path to the file that contains certificate revocation lists in PEM format. 

• ssl-crlpath : The path to the directory that contains certificate revocation-list files in PEM format. 

• ssl-key : The path to the X.509 key file in PEM format. 

• tls-version : The TLS protocols permitted for classic MySQL protocol encrypted connections. This option is supported by MySQL Shell only. The value of tls-version  (singular) is a comma separated list, for example TLSv1.1,TLSv1.2 . For details, see Section 6.3.2, “Encrypted Connection TLS Protocols and Ciphers” . This option depends on the ssl-mode  option not being set to DISABLED . 

• tls-versions : The permissible TLS protocols for encrypted X Protocol connections. The value of tls-versions  (plural) is an array such as [TLSv1.2,TLSv1.3] . For details, see Section 6.3.2, “Encrypted Connection TLS Protocols and Ciphers” . This option depends on the ssl-mode  option not being set to DISABLED . 

• tls-ciphersuites : The permitted TLS cipher suites. The value of tls-ciphersuites  is a list of IANA cipher suite names as listed at TLS Ciphersuites. For details, see Section 6.3.2, “Encrypted Connection TLS Protocols and Ciphers” . This option depends on the ssl-mode  option not being set to DISABLED . 

• auth-method : The authentication method to use for the connection. The default is AUTO , meaning that the server attempts to guess. The following methods are permissible: 

