A cartridge assembly includes a plurality of ink cartridges each having a cartridge case that holds ink therein, and at least one connecting member that connects the plurality of ink cartridges together in a connection direction. This method involves incorporating, in a second apparatus, at least one primary calibration algorithm that is developed using absorbances of samples from a primary calibration set. Recesses are provided in the upper end surface of the rebound cushion at regular angular intervals in order to provide working oil between the rod guide and the upper end surface, thereby ensuring smooth rotation of the rebound cushion with respect to the rod guide when the piston rod at the protruding limiting position and the cylinder relatively rotate. Congestion notification metadata can be copied from a header of a virtual network data packet to a header of a physical network data packet when the virtual network data packet is encapsulated into the physical network data packet.