188.8.131.52 Status and Error Handling
SSTP MUST attempt to delineate the SSTP frames that are contained in the HTTPS stream. If the delineation fails because of an unsupported or unrecognized packet format, then the connection MUST be forcefully aborted without any SSTP message being sent to the SSTP far end. This is done to avoid the use of unreliable streams.
If an invalid SSTP message is received, the SSTP state machine aborts processing using the following procedure.
Change CurrentState to Call_Abort_In_Progress_1.
Start the TIMER_VAL_ABORT_STATE_TIMER_1 timer (section 184.108.40.206).
Change CurrentState to Call_Abort_Pending.
For the attribute parameters that are received from the Call Connect Request message, the server MAY respond with a negative acknowledgment. In the negative acknowledgment message, the server MUST include the list of attributes that are not acceptable and the reason that they were not accepted.
For a list of status acknowledgments, see section 2.2.8.