session relay apparatuses which relay session control messages used for peer-to-peer communication between communication terminals;

edge nodes, in a network coupling the communication terminals, accommodating the communication terminals to the network; and

a core node which executes a packet relay process in the network,

wherein a first session relay apparatus receives a session control message from a first communication terminal and a second session relay apparatus receives a session control message from a second communication terminal;

wherein when the first session relay apparatus receives a session establishment request from the first communication terminal as a communication source:

the first session relay apparatus transfers the session establishment request to the second session reply apparatus;

the second session relay apparatus transfers the session establishment request to the second communication terminal;

if the second communication terminal is available to communicate, the second communication terminal transfers a message representing that the communication is available, to the second session relay apparatus;

after the second session relay apparatus transfers the message representing that the communication is available, to the first session relay apparatus, the first session relay apparatus generates a packet relay processing policy for a peer-to-peer communication packet, distributes the policy to a first edge node accommodating the first communication terminal, and causes the first edge node to register the policy, and the second session relay apparatus generates a packet relay process policy to the peer-to-peer communication packet, distributes the policy to a second edge node accommodating the second communication terminal, and causes the second edge node to register the policy to finish a policy setting process to the edge nodes; and

the peer-to-peer communication packet from the first communication terminal is set for a next relay node based on the policy in the first edge node to select a network to be relayed,

wherein if the second session relay apparatus receives a session end request from the second communication terminal:

the second session relay apparatus transfers the session end request to the first session relay apparatus;

the first session relay apparatus transfers the session end request to the first communication terminal; and

after the first communication terminal transfers an OK message to the first session relay apparatus in response to the session end request, the first session relay apparatus causes the first edge node accommodating the first communication terminal to delete the policy distributed to the first edge node and the second session relay apparatus causes the second edge node accommodating the second communication terminal to delete the policy distributed to the second edge node,

wherein upon receiving a session establishment request, the session relay apparatuses refer to the session establishment request, generate a packet relay processing policy including information for uniquely identifying a session, and manage a packet relay processing policy per session, and

wherein upon receiving an OK message, the session relay apparatuses search a packet relay processing policy based on the information for uniquely identifying the session, and delete the packet relay processing policy related to the received OK message.