Abstract: In a switch supporting a multiple spanning tree protocol and a bridged network formed of such a switch, the switch includes a default spanning tree in a multiple spanning tree, transmits, upon receipt of a frame having an individual destination address from a terminal side, an inquiry frame to a destination terminal of the individual destination address through the default spanning tree, transmits inquiry response frames to all of the spanning trees in the multiple spanning tree if the destination terminal is connected to the switch, and selects an optimum spanning tree based on information in the inquiry response frames from all of the spanning trees.

Abstract: A router suitable for use, for example, in a user site receiving an L2-VPN service, which constructs a network in which the communication efficiency does not degrade even in the case of the employment of a virtual private network which does not have a frame abandonment notification function or an abandonment function based on priority. The router, connected through a bridge unit to a transit network constituting a virtual private network, is made up of a reception traffic volume measuring unit for measuring a reception traffic volume on data received from all next hop routers forming other communication parties connected through the transit network and a measurement result notifying unit for notifying a measurement result on the measured reception traffic volume to all the next hop routers.

Abstract: A network system which automatically reconfigures its virtual LAN (VLAN) topology when a terminal station is relocated or newly added. When a terminal is relocated from one switch's local group to another switch's, the latter switch examines incoming frames from the relocated terminal, consulting its VLAN configuration table stored in a first storage unit. If this terminal turns out to be unknown to the switch, a query unit in the switch will request information about the unknown terminal by sending a query message to a server that manages the configuration of the network system. In response to the query, a searching unit in the server scans data records in a second storage unit, thus recognizing that the terminal in question has been relocated. The server then identifies to which VLAN the terminal is supposed to belong. A transmission unit in the server sends this information back to the requesting switch.

Abstract: In a switch supporting a multiple spanning tree protocol and a bridged network formed of such a switch, the switch includes a default spanning tree in a multiple spanning tree, transmits, upon receipt of a frame having an individual destination address from a terminal side, an inquiry frame to a destination terminal of the individual destination address through the default spanning tree, transmits inquiry response frames to all of the spanning trees in the multiple spanning tree if the destination terminal is connected to the switch, and selects an optimum spanning tree based on information in the inquiry response frames from all of the spanning trees.