The priority control for specified communication was difficult because the design concept of the Internet was best effort, but QoS technology such as Diffserv has realized the priority control. In this paper, we propose a new priority control mechanism. that the policy of the behavior of the packets is described using metadata. The metadata is structured data about data and is able to describe policy. We use the emergency communications as an implementation of the proposed mechanism. In an emergency, the Internet is important as a communication infrastructure for getting information about victim and disaster areas. Metadata is able to describe that this information is emergency. Diffserv is able to transport information managed by a priority control mechanism. This mechanism is going to be included in ITU-T F.706 recommendation.