A first edge node in an MPLS network system includes a generation module generating a key value for determining an allocating destination link in a way that uses, as input values, a piece of source identifying information and a piece of destination identifying information contained in a header of a forwarding target frame before being attached with an MPLS header enabling the frame to be forwarded across an MPLS network on the basis of an MPLS protocol, an embedding module embedding the key value generated by the generation module into a specified field in the MPLS header, and a transmitting module transmitting the MPLS frame containing the key value embedded into the specified field in its MPLS header to the MPLS network.