Abstract: A translator is connected to a first network for transferring data in a first protocol, to a second network for transferring data in a second protocol, and to a translation server to which other translators are connected, for retaining translation information for a protocol translation between the first protocol and the second protocol. The translator generates a second address in the first protocol corresponding to a first address in the second protocol provided to a terminal accommodated in the second network. It retains a correspondence between the first address and the second address as the translation information and registers the correspondence at the translation server.

Abstract: The invention provides a method for selecting a communication IP address whereby traffic of a network can be reduced and a session with the partner of communication can be maintained even when the mobile node has moved. The method prescribes provision of means for judging a state of a foreign network to which the mobile node is connected, and means of monitoring an IP address that an application having been started by the mobile node is using for communication, and enables selection of the mobile IP address so that the mobile node can maintain the session surely even in a visited foreign network.

Abstract: Communication between a caller client system and a callee client system is based on selection of a suitable communication program from a list of communication programs. The list of communication programs is determined based on the callee's communication environment.

Abstract: An IPv6 mobile packet communication network in which mobile VPN service can be provided without having to use a mobile tunnel. A control signal for enabling packet data transmission and reception is sent from a mobile terminal to a gateway node. Using destination-of-connection information contained in the control signal, the gateway node checks whether mobile VPN service is requested or not. Upon detection of a mobile VPN service request, the gateway node returns IP address information of the gateway node to the mobile terminal via a subscriber node. The mobile terminal then assembles an IPv6 header (210) and an IPv6 routing header (220) so that packet data will be unexceptionally transferred through the gateway node.

Abstract: Communication between a caller client system and a callee client system is based on selection of a suitable communication program from a list of communication programs. The list of communication programs is determined based on the callee's communication environment.

Abstract: A translator is connected to a first network for transferring data in a first protocol, to a second network for transferring data in a second protocol, and to a translation server to which other translators are connected, for retaining translation information for a protocol translation between the first protocol and the second protocol. The translator generates a second address in the first protocol corresponding to a first address in the second protocol provided to a terminal accommodated in the second network. It retains a correspondence between the first address and the second address as the translation information and registers the correspondence at the translation server.

Abstract: The invention provides a method for selecting a communication IP address whereby traffic of a network can be reduced and a session with the partner of communication can be maintained even when the mobile node has moved. The method prescribes provision of means for judging a state of a foreign network to which the mobile node is connected, and means of monitoring an IP address that an application having been started by the mobile node is using for communication, and enables selection of the mobile IP address so that the mobile node can maintain the session surely even in a visited foreign network.

Abstract: A roaming service covering a plurality of telecommunications carriers in mobile data communication is provided. In a communication system including a wireless terminal, two or more terminal-side networks communicating with the wireless terminal, and a backbone-side network connected to the terminal-side networks and connecting the wireless terminal with a backbone network, the wireless terminal traveling between the terminal-side networks during communication, wherein each of the terminal-side networks has a relay device for relaying communication between the wireless terminal and the backbone-side network and wherein the backbone-side network has a position management device for managing positional information of the wireless terminal and an authentication device for authenticating the wireless terminal according to contract information of the wireless terminal.

Abstract: The disclosed invention provides a network system that achieves connecting a terminal to a plurality of networks simultaneously and forwarding packets correctly. The network system is built such that an access node connected with a terminal and a network are connected by a relay node and includes an authentication node with which the terminal can communicate and which assigns the terminal an address associated with the network. The address assigned to the terminal is mapped to identification code of the relay node and stored on the access node.

Abstract: A translator is connected to a first network for transferring data in a first protocol, to a second network for transferring data in a second protocol, and to a translation server to which other translators are connected, for retaining translation information for a protocol translation between the first protocol and the second protocol. The translator generates a second address in the first protocol corresponding to a first address in the second protocol provided to a terminal accommodated in the second network. It retains a correspondence between the first address and the second address as the translation information and registers the correspondence at the translation server.

Abstract: An IPv6 mobile packet communication network in which mobile VPN service can be provided without having to use a mobile tunnel. A control signal for enabling packet data transmission and reception is sent from a mobile terminal to a gateway node. Using destination-of-connection information contained in the control signal, the gateway node checks whether mobile VPN service is requested or not. Upon detection of a mobile VPN service request, the gateway node returns IP address information of the gateway node to the mobile terminal via a subscriber node. The mobile terminal then assembles an IPv6 header (210) and an IPv6 routing header (220) so that packet data will be unexceptionally transferred through the gateway node.