# US 2021/0243052 A1 · Communication system and server switching method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0243052 A1 - Document ID: US20210243052A1 - Status: Published application - Kind: A1 - Application number: 16/967,576 - Filed: 2019-02-13 - Published: 2021-08-05 - Earliest claimed: 2018-02-14 - Assignees: Nippon Telegraph and Telephone Corporation - Applicants: Nippon Telegraph and Telephone Corporation - Inventors: Takehiro Kitano - Web page: https://patentgrep.com/patent/US20210243052A1 ## CPC - H04L 12/2856: {Access arrangements, e.g. Internet access (asynchronous transfer mode networks H04L12/5601; broadband local area networks H04L12/2801; optical access or distribution networks H04Q11/0067; access to open networks H04L12/5691; digital subscriber line end-user equipment and bit-level processing of data on a PSTN-based network H04M11/00; home network gateways H04L12/2834; wireless access networks H04W)} - H04L 12/4675: {Dynamic sharing of VLAN information amongst network nodes (configuration of the network or of network elements H04L41/08)} - G06F 13/00: Interconnection of, or transfer of information or other signals between, memories, input/output devices or central processing units (interface circuits for specific input/output devices G06F3/00 {; multiprogram control therefor G06F9/46}; multiprocessor systems G06F15/16 ) - H04L 41/042: comprising distributed management centres cooperatively managing the network - H04L 41/045: comprising client-server management architectures - H04L 41/0663: Performing the actions predefined by failover planning, e.g. switching to standby network elements - H04L 41/0668: by dynamic selection of recovery network elements, e.g. replacement by the most appropriate element after failure - H04L 41/0816: the condition being an adaptation, e.g. in response to network events - H04L 61/103: across network layers, e.g. resolution of network layer into physical layer addresses or address resolution protocol [ARP] - H04L 67/1034: Reaction to server failures by a load balancer - H04L 67/563: Data redirection of data network streams - H04L 67/61: taking into account QoS or priority requirements - H04L 41/0895: Configuration of virtualised networks or elements, e.g. virtualised network function or OpenFlow elements - H04L 61/58: Caching of addresses or names - H04L 2101/622: Layer-2 addresses, e.g. medium access control [MAC] addresses - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) ## Abstract A service interruption time of a client terminal is shortened. A communication system (100) includes a plurality of servers 10 (10a and 10b) each functioning as an active system or a standby system and a relay device (20) that relays communication between a server of the active system and one or more client terminals (30) operated by clients. Each of the servers includes a priority level determining unit that determines a priority level of each of the clients, a virtual port creating unit that creates, in the server, a virtual port corresponding to a virtual LAN assigned to each of the client terminals, and a communication processing unit that instructs the relay device to change a destination of communication performed between the client terminal and the server to the virtual port. The communication processing unit gives an instruction of change of the destination of the communication in order of highest to lowest priority level of the client when a malfunction occurs in another server of the active system. ## Claims ### Claim 1 A communication system comprising: a plurality of servers each functioning as an active system or a standby system; and a relay device that relays communication between a server of the active system and one or more client terminals operated by clients, wherein each of the servers includes: a priority level determining unit that determines a priority level of each of the clients, a virtual port creating unit that creates, in the server, a virtual port corresponding to a virtual local area network (LAN) assigned to each of the clients, and a communication processing unit that instructs the relay device to change a destination of communication performed between the client terminal and the server to the virtual port, and wherein the communication processing unit gives an instruction to change the destination of the communication in order of highest to lowest priority level of each of the clients when a malfunction occurs in another server of the active system. ### Claim 2 (depends on 1) The communication system according to claim 1, wherein the server repeatedly creates the virtual port by using the virtual port creating unit and gives the instruction of change of the destination of the communication by using the communication processing unit, in order of highest to lowest priority level of each of the clients when a malfunction occurs in another server of the active system. ### Claim 3 (depends on 1) The communication system according to claim 1, wherein the instruction of change of the destination of the communication by using the communication processing unit is given by transmitting a Gratuitous Address Resolution Protocol (G-ARP) packet including a virtual internet protocol (IP) address corresponding to the virtual LAN and a media access control (MAC) address corresponding to the virtual IP address to the relay device. ### Claim 4 (depends on 1) The communication system according to any one of claim 1, wherein the priority level determining unit determines the priority level of each of the clients based on a usage frequency of the virtual LAN assigned to each of the clients. ### Claim 5 A server switching method comprising: determining, by using a server of a standby system, a priority level of each of clients when a malfunction occurs in a server of an active system among a plurality of servers arranged to be able to communicate with one or more client terminals operated by the clients through a relay device; creating, in the server and by using the server of the standby system, a virtual port corresponding to a virtual local area network (LAN) assigned to each of the clients; and instructing, by using the server of the standby system, the relay device to change a destination of communication performed between the client terminal and the server to the virtual port in order of highest to lowest priority level of the client.