All SOCKS implementations should support the GSSAPI (RFC 1961) and Username/Password (RFC 1929) methods.

If the selected authentication method supports encapsulation for the purposes of integrity, authentication and/or confidentiality, the data are encapsulated using the method-dependent encapsulation.

Similarly, when data arrives at the SOCKS server for the client, the server MUST encapsulate the data as appropriate for the authentication method in use.