1. Field of the Invention
The present invention relates to a technical field of an overlay network system. Especially, the technical field is a peer-to-peer (P2P) communication system comprising a plurality of node devices capable of mutually communicating via a network.
2. Description of the Related Art
In recent years, a peer-to-peer communication system is paid attention. In the peer-to-peer communication system, one content is divided into a plurality of items of data to be distributed and stored in a plurality of node devices. Each divided data is called “division data.” For example, in the conventional technique, when a node device acquires a content, the node device requesting the content requests division data constituting the content from another node device. A node device receiving the request uploads the requested division data on the requesting node device each time. When downloading and storing the division data, the node device performs a processing of publicizing that it is storing the division data. Accordingly, even before the acquisition of the entire content is completed, another node device can acquire the division data from the node device storing the division data therein. In this manner, a load for uploading the content is distributed in a plurality of node devices. All the division data constituting the content is acquired so that the acquisition of the entire content is completed.