A shield holder has a manually-engageable handle on its lower end and a spoon-shaped panel on its upper end. The porous ceramics according to the present invention, having the closed pores homogeneously diffusing at a high ratio, exhibits excellent characteristics when applied to an electronic circuit board or the like requiring moisture absorption resistance, low permittivity and low dielectric loss as well as mechanical strength. A mobile host must add an inner encapsulation header to inbound DHCP packets with the source IP address set to 0 to indicate that the packet is from a mobile host that does not have a registered home IP address. The pole or the zero point of the feedback loop is determined based on the response parameter and the ratio parameter in such a way that the ratio of a response frequency which is quotient of the loop gain divided by an inertia value of the controlled object to a frequency corresponding to the pole or the zero point of the feedback loop is the value determined by the ratio parameter.