An integrated circuit structure includes a semiconductor substrate having a front surface and a back surface; a conductive via passing through the semiconductor substrate; and a metal feature on the back surface of the semiconductor substrate. A request-to-establish message is sent from the client terminal, supplemented with a checksum generated for available SDP information. The distribution map generating unit includes a representative vector calculating unit and a representative vector arrangement determining unit, and generates a distribution map that represents an overall trend of the group of sequential images.