Address generator, address generation method, and encapsulation-decapsulation device

An encapsulation-decapsulation device disposed, in a network system in which a plurality of stub networks each of which uses a first protocol family are connected to one another via a backbone network which uses a second protocol family, at a boundary between each of the plurality of stub networks and the backbone network, the encapsulation-decapsulation device comprising:

• a storage device in which one or more second-protocol-family address prefixes based on the second protocol family are stored, the one or more second-protocol-family address prefixes each corresponding to a corresponding combination of at least a multiplexing identifier and a first-protocol-family address based on the first protocol family;
• and
• a controller configured to, upon receiving, from a source stub network to which the encapsulation-decapsulation device is connected among the plurality of sub networks, a data block addressed to a destination stub network, the data block including both a first-protocol-family source address and a first-protocol-family destination address,
• read, from the storage device, a second-protocol-family address prefix corresponding to a combination of at least a multiplexing identifier and a first-protocol-family destination address contained in the data block, the read second-protocol-family prefix serving as an address prefix for a network that is overlaid with the destination stub network,
• encapsulate the data block with a header including a second-protocol-family address which contains only the first-protocol-family destination address among the first-protocol-family source address and the first-protocol-family destination address, the multiplexing ID, and the read second-protocol-family address prefix, and
• transmit the encapsulated data block to the backbone network.