A method, medium, and system for connecting to a communication system in a network having a plurality of nodes capable of communicating with each other. The node requests an identifier to a foreign network when a router advertise (RA) message is received from the foreign network, and then the node connects to the communication system, via the foreign network, by use of the received identifier. A method, medium, and system for delegating a network identifier (prefix) from a server of a foreign network, in a network having a plurality of nodes capable of communicating with each other, so that a node can communicate with the foreign network. The prefix to be used by the nodes in the network is transmitted from the server of the foreign network to the node.