188.8.131.52.6 Receiving an SSTP_MSG_CALL_DISCONNECT_ACK Message
If CurrentState is set to Call_Disconnect_Ack_Pending, the server MUST:
Immediately clear the connection state to clean up the connection.
Change CurrentState to Server_Call_Disconnected.
Else if CurrentState is set to Call_Abort_Pending, Call_Abort_Timeout_Pending, or Call_Disconnect_Timeout_Pending:
Ignore the message.
Change CurrentState to Call_Abort_In_Progress_1.
Send an SSTP_MSG_CALL_ABORT (section 2.2.13) message.
Start the TIMER_VAL_ABORT_STATE_TIMER_1 timer (section 184.108.40.206).
Change CurrentState to Call_Abort_Pending.
The HTTPS listener MUST continue to function as it did before the cleanup process. The cleanup of the connection MUST NOT affect other existing HTTPS connections and MUST NOT affect the ability of the HTTPS listener to accept new connections.