188.8.131.52 AUTH SSL Message Handling
The AUTH SSL message can be used with Explicit FTPS and does not apply to Implicit FTPS. When server receives an AUTH SSL message, it will interpret it as an AUTH TLS message and the rest of the execution will proceed as specified in [RFC4217]. There is no semantic difference between processing AUTH TLS and AUTH SSL messages. The AUTH SSL message is supported for the compatibility with legacy clients.