# US 7,609,656 B2 · Bridge device, method of controlling bridge device, and control program > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,656 B2 - Document ID: US7609656B2 - Status: Granted - Kind: B2 - Application number: 11/498,387 - Filed: 2006-08-03 - Published: 2007-10-04 - Granted: 2009-10-27 - Earliest claimed: 2006-03-31 - Assignees: Fujitsu Limited - Inventors: Ko Takatori - Web page: https://patentgrep.com/patent/US7609656B2 ## CPC - H04L 12/4625: {Single bridge functionality, e.g. connection of two networks over a single bridge} - H04L 12/185: {with management of multicast group membership} - H04L 45/16: Multipoint routing - H04L 45/48: Routing tree calculation - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract The bridge device is connected to a layer-2 network. The Query message distribution unit discriminates, distributes, and outputs the normal Query messages and abnormal Query messages among the received Query messages. The abnormal message processing unit counts the number of received abnormal Query messages, and the normal message processing unit counts the number of normal Query messages. The router connection state judgment unit judges that the bridge device is a bridge device that is adjacent to the router when only the number of normal Query messages is counted and outputs an instruction to change the bridge ID to the STP processing unit. The STP processing unit establishes the bridge ID as a minimum value and renders the bridge device a root bridge. ## Claims ### Claim 1 A bridge device in a layer-2 network, comprising: a setting unit which sets the bridge device as a root bridge by making a bridge ID of the bridge device smaller than the bridge IDs of other bridge devices when the bridge device is adjacent to a router connected to the layer-2 network; and a router connection state judgment unit which judges whether or not the bridge device is adjacent to the router by comparing, with respect to a Query message representing a message for confirming whether or not there is participation in a multicast group that is sent by the router, a first reception number indicating the number of normal Query messages received and a second reception number indicating the number of abnormal Query messages received, and which outputs an instruction to change the bridge ID when judged that the bridge device is adjacent to the router. ### Claim 2 (depends on 1) The bridge device according to claim 1, further comprising: a message transmission unit which transmits the abnormal Query message together with the normal Query message to the other bridge devices, with respect to the Query message representing a message for confirming whether or not there is participation in a multicast group that is sent by the router. ### Claim 3 (depends on 2) The bridge device according to claim 2, wherein the message transmission unit transmits a control message that is used in order to judge whether or not the bridge device is adjacent to the router, instead of the abnormal Query message. ### Claim 4 (depends on 1) The bridge device according to claim 1, wherein the router connection state judgment unit judges that the bridge device is adjacent to the router when only the first reception number is counted. ### Claim 5 (depends on 1) The bridge device according to claim 1, wherein the router connection state judgment unit judges that the bridge device is not adjacent to the router when the first reception number and the second reception number are counted as having the same count number. ### Claim 6 (depends on 1) The bridge device according to claim 1, further comprising: a router connection state judgment unit which judges whether or not the bridge device is adjacent to the router on the basis of the reception history of a BPDU which is transferred between the bridge devices and represents a control packet that stores data including the bridge ID. ### Claim 7 (depends on 6) The bridge device according to claim 6, wherein the router connection state judgment unit receives only a Query message representing a message for confirming whether or not there is participation in a multicast group that is sent from the router and judges that the bridge device is adjacent to the router when the BPDU is not received from the reception history. ### Claim 8 (depends on 6) The bridge device according to claim 6, wherein the router connection state judgment unit judges that the bridge device is not adjacent to the router when both a Query message and the BPDU are received. ### Claim 9 A layer-2 network, comprising: a router; and a plurality of bridge devices, wherein the bridge device that is adjacent to the router among the plurality of bridge devices is set as a root bridge by making a bridge ID of the bridge device smaller than the bridge IDs of other bridge devices; and the bridge device comprising: a router connection state judgment unit which judges whether or not the bridge device is adjacent to the router by comparing, with respect to a Query message representing a message for confirming whether or not there is participation in a multicast group that is sent by the router, a first reception number indicating the number of normal Query messages received and a second reception number indicating the number of abnormal Query messages received, and which outputs an instruction to change the bridge ID when judged that the bridge device is adjacent to the router. ### Claim 10 A bridge device in a layer-2 network, comprising: a setting unit which sets the bridge device as a root bridge by storing an ID that is smaller than the bridge IDs of other bridge devices in a region where a root ID of a BPDU is stored when the bridge device is adjacent to a router connected to the layer-2 network; and a router connection state judgment unit which judges whether or not the bridge device is adjacent to the router by comparing, with respect to a Query message representing a message for confirming whether or not there is participation in a multicast group that is sent by the router, a first reception number indicating the number of normal Query messages received and a second reception number indicating the number of abnormal Query messages received, and which outputs an instruction to change the bridge ID when judged that the bridge device is adjacent to the router. ### Claim 11 A layer-2 network, comprising: a router; and a plurality of bridge devices, wherein the bridge device that is adjacent to the router among the plurality of bridge devices is set as a root bridge by storing an ID that is smaller than the bridge IDs of other bridge devices in a region where a root ID of a BPDU is stored, wherein the bridge device comprising: a router connection state judgment unit which judges whether or not the bridge device is adjacent to the router by comparing, with respect to a Query message representing a message for confirming whether or not there is participation in a multicast group that is sent by the router, a first reception number indicating the number of normal Query messages received and a second reception number indicating the number of abnormal Query messages received, and which outputs an instruction to change the bridge ID when judged that the bridge device is adjacent to the router.