To implement more appropriate QoS control by compressing contents data distributed via a network taking into consideration meaning of contents and preferences of users.A network system comprises a content provider that provides content and client that acquires the content. The content provider attaches information on communication priorities to the content based on the content's importance which is determined from the meaning of the content's and sends the content to the client using a protocol which controls quality of service based on the priority and the client receives the content transmitted by the content provider.