The SoftLayer_Container_Authentication_Request_Common data type contains common information for requests to the getPortalLogin API. This is an abstract class that serves as a base that more specialized classes will derive from. For example, a request class specific to SoftLayer Native IMS Login (username and password).
The answer to your security question.
A security question you wish to answer when authenticating to the SoftLayer customer portal. This parameter isn't required if no security questions are set on your portal account or if your account is configured to not require answering a security account upon login.