A communication system includes a host device and a network storage device interconnected via a network. The host device includes a data file request command issuing unit issuing a data file request command a data file receiving unit receiving a requested data file, a data file storing unit storing the requested data file, an attribute file request command issuing unit issuing an attribute file request command, an attribute file receiving unit receiving a requested attribute file, and an attribute updating unit updating attribute information of the requested data file with an original attribute information included in the attribute file. The network storage device includes a data file sending unit sending the data file to the host device, an attribute file creating unit creating the attribute file, and an attribute file sending unit sending the created attribute file to the host device.