Abstract: An edge router adds a tag specifying a VLAN, to which a receiver host belongs, for receiving a multicast packet and transmits the multicast packet to a subordinate router one by one, and the subordinate router receiving the multicast packet copies this multicast packet and transfers the copied multicast packet to each receiver host belonging to the VLAN, thereby reducing a line occupancy rate and improving band utilization efficiency.

Abstract: A plurality of routers are connected within the same network and are set in a relationship of a master and a backup according to the mounted VRRP, thereby to build up a virtual router. The virtual router transmits a packet that is input from the network or an external network, to a destination network. Substitute ports are provided in both routers, and these substitute ports are connected to each other. When a trouble has occurred on the route, a router in the backup state is changed to a master state, and a packet from a PC or the Internet is forwarded on the route via the substitute ports.

Abstract: In response to a participation application from a receiver host, the receiver host capable of participating in a multicast group is registered in a user authentication server in advance, if an IGMP membership report indicating a participation request is transmitted to a router from the receiver host, the receiver host is authenticated based on information in this report and a registration content of the user authentication server, and if the receiver host is authenticated, the receiver host is accepted to participate in the multicast group within accepted time, whereby a user can be accurately authenticated while a function of a receiver-side host remains as it is.

Abstract: A public key used for creating a session shared key is inserted into a packet transmitted by a wireless terminal to an access point based on a DHCP. A public key used for creating the session shared key is inserted into a packet transmitted by the access point to the wireless terminal based on the DHCP. The access point creates the session shared key based on the public key and the wireless terminal creates the session shared key based on the public key. As a result, it becomes possible to safely share the session shared key K for privacy and/or authentication between the wireless terminal and the access point.

Abstract: To transmit a data frame between different LANs, a connection is established, through a switching network, between routers respectively connected to the LAN's. The data frame is then forwarded from a source router to a destination router through the established connection. When a data frame is received from a LAN-side transmitter-receiver section in the source router, a network layer section samples from a routing table, according to the destination address included in the data frame, an address of the destination router, and samples a telephone number index corresponding to this gateway from a destination number table. A communication network line control section samples a telephone number corresponding to this index from a telephone number table, places a call in accordance with this telephone number, thereby connecting lines of the communication network, and automatically relays the frame from a LAN-side transmitter-receiver section to a destination LAN through the lines.