Abstract: In a network system formed by one or a plurality of hosts having a function for accessing Internet, and a router for connecting each host and the Internet through an accessing communication path of a provider, two types of IP address including first type IP addresses and second type IP addresses are generated and selectively used by each host, according to two types of prefix including first type prefixes and second type prefixes that have shorter valid periods than the first type prefixes, which are advertised from the router periodically.

Abstract: In a network system formed by one or a plurality of hosts having a function for accessing Internet, and a router for connecting each host and the Internet through an accessing communication path of a provider, two types of IP address including first type IP addresses and second type IP addresses are generated and selectively used by each host, according to two types of prefix including first type prefixes and second type prefixes that have shorter valid periods than the first type prefixes, which are advertised from the router periodically.

Abstract: In a source address selection system containing a router device connected to a plurality of Internet service providers, and a communication node connected to the router device, it becomes possible to utilize the multi-home environment effectively, by enabling the selection of the source address according to the egress router with respect to the Internet, by accounting for the state of connection with the Internet service provider.

Abstract: At a node device, after an exchange procedure for exchanging a security association information is carried out, the security association information is stored in a memory unit while a management information including the destination address, the identification information, and an information regarding a valid period of the security association information is stored in a non-volatile medium, such that it is possible to recover the normal state quickly without damaging the safety, when a temporary operation trouble occurs at one node under an environment in which a plurality of nodes are carrying out communications safely by using a prescribed security protocol.

Abstract: At a node device, after an exchange procedure for exchanging a security association information is carried out, the security association information is stored in a memory unit while a management information including the destination address, the identification information, and an information regarding a valid period of the security association information is stored in a non-volatile medium, such that it is possible to recover the normal state quickly without damaging the safety, when a temporary operation trouble occurs at one node under an environment in which a plurality of nodes are carrying out communications safely by using a prescribed security protocol.

Abstract: The host name to be used in responding to the reverse look-up request from the correspondent is generated at the name server side and returned as a response, and/or the IP address to be used in responding to the normal look-up request from the correspondent is generated at the name server side and returned as a response, so that the communications can be carried out without exposing the privacy of the communication host or the user to danger.

Abstract: The host name to be used in responding to the reverse look-up request from the correspondent is generated at the name server side and returned as a response, and/or the IP address to be used in responding to the normal look-up request from the correspondent is generated at the name server side and returned as a response, so that the communications can be carried out without exposing the privacy of the communication host or the user to danger.

Abstract: In a network system formed by one or a plurality of hosts having a function for accessing Internet, and a router for connecting each host and the Internet through an accessing communication path of a provider, two types of IP address including first type IP addresses and second type IP addresses are generated and selectively used by each host, according to two types of prefix including first type prefixes and second type prefixes that have shorter valid periods than the first type prefixes, which are advertised from the router periodically.

Abstract: In a network system formed by one or a plurality of hosts having a function for accessing Internet, and a router for connecting each host and the Internet through an accessing communication path of a provider, two types of IP address including first type IP addresses and second type IP addresses are generated and selectively used by each host, according to two types of prefix including first type prefixes and second type prefixes that have shorter valid periods than the first type prefixes, which are advertised from the router periodically.

Abstract: In a network system formed by one or a plurality of hosts having a function for accessing Internet, and a router for connecting each host and the Internet through an accessing communication path of a provider, two types of IP address including first type IP addresses and second type IP addresses are generated and selectively used by each host, according to two types of prefix including first type prefixes and second type prefixes that have shorter valid periods than the first type prefixes, which are advertised from the router periodically.

Abstract: In a source address selection system containing a router device connected to a plurality of Internet service providers, and a communication node connected to the router device, it becomes possible to utilize the multi-home environment effectively, by enabling the selection of the source address according to the egress router with respect to the Internet, by accounting for the state of connection with the Internet service provider.

Abstract: The host name to be used in responding to the reverse look-up request from the correspondent is generated at the name server side and returned as a response, and/or the IP address to be used in responding to the normal look-up request from the correspondent is generated at the name server side and returned as a response, so that the communications can be carried out without exposing the privacy of the communication host or the user to danger.

Abstract: In order to search for an IPv4 address of an IPv4 host H2 connected to an IPv4 network from the logical name of the IPv4 host H2 by an IPv6 host H1 connected to an IPv6 network and provided with an IPv6 address, a query is made via a cache server to a name server installed in the IPv4 network and configured to manage DNS information of the IPv4 host H2. The integrity of the IPv4 address obtained as a response to this query is verified by using DNSSEC. A pseudo IPv6 address is generated by using a translation prefix obtained from a router R1. By using the pseudo IPv6 address as a destination address, connection to the IPv4 address is established via a translator.

Abstract: A server apparatus capable of concealing the present location of a mobile terminal in Mobile IPv6 is to be provided. A server assigns an address for location concealment to be used as a pseudo care-of address to a mobile terminal to conceal a care-of address acquired at its present location. The mobile terminal creates and sends an encapsulated packet in which an IP packet containing the acquired address for location concealment as a source address, the address of a correspondent terminal as a determination address and its own home address is encapsulated where its care-of address is a source address and the address of the server is a determination address. The server decapsulates the received encapsulated packet, extracts the IP packet, and sends the extracted IP packet. The IP packet is received by the correspondent terminal.

Abstract: At a router device capable of accessing a plurality of Internet service providers that provide services for accessing Internet, a probe packet destined to a prescribed address on the Internet is transmitted via each Internet service provider, a response packet in response to the probe packet is received, and accessibility of each Internet service provider is judged according to a result of receiving the response packet. Then, information indicating the accessibility of each Internet service provider is stored, and one of the Internet service providers through which a received packet should be routed is selected according to the information indicating the accessibility, upon receiving a packet that can be routed via more than one Internet service providers.

Abstract: At a node device, after an exchange procedure for exchanging a security association information is carried out, the security association information is stored in a memory unit while a management information including the destination address, the identification information, and an information regarding a valid period of the security association information is stored in a non-volatile medium, such that it is possible to recover the normal state quickly without damaging the safety, when a temporary operation trouble occurs at one node under an environment in which a plurality of nodes are carrying out communications safely by using a prescribed security protocol.

Abstract: In a network system formed by one or a plurality of hosts having a function for accessing Internet, and a router for connecting each host and the Internet through an accessing communication path of a provider, two types of IP address including first type IP addresses and second type IP addresses are generated and selectively used by each host, according to two types of prefix including first type prefixes and second type prefixes that have shorter valid periods than the first type prefixes, which are advertised from the router periodically.