JP2009111746A - Communication system and method, relay device, terminal device and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent transfer of an unwanted multicast packet. <P>SOLUTION: Terminal devices 113B-2 and 113C-1 belonging to a multicast group B each transmit a multicast address notice packet in which a multicast address B corresponding to the multicast group B is set as a transmission source at a predetermined timing to a broadband router 111. The broadband router 111 and layer 2 switches 112A-112C each learn the multicast address B in a port at which the multicast address notice packet has been received. The packet of the multicast group B transmitted from a multicast server 251 is transferred through a port which has learned the multicast address B, and received by terminal devices 113B-2 and 113C-1. This system and method are applicable to a home network system, for example. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a communication system and method, a relay device, a terminal device, and a program, and more particularly, to a communication system and method, a relay device, a terminal device, and a program that suppress unnecessary transmission of multicast packets.

  Recently, the support of the IP (Internet Protocol) network backbone to the packet multicast specification has progressed, and multicast packets have flowed on the home network. In particular, in IPTV (Internet Protocol TV) service, multicast packets exceeding 20 Mbps (Bits Per Second) may flow on the home network.

  Many routers that support layer 3 (L3, network layer) and higher protocols support multicast specifications (see, for example, Patent Document 1), but are layer 2 (L2, data link layer) networks. Many conventional standard layer 2 switches (switching hubs) used in a home network do not sufficiently support the multicast specification, and process multicast packets in the same way as broadcast packets. That is, the layer 2 switch passes through all ports to which the network (other devices) is connected regardless of whether or not there are terminal devices belonging to the multicast group in the network connected to each port. , Send the received multicast packet.

  As a result, unnecessary multicast packets flow in the home network, packet congestion occurs, and communication unrelated to multicast may be hindered.

  Also, for example, when networks with different transfer rates are connected to the layer 2 switch, the network with the slowest transfer rate becomes a bottleneck when sending multicast packets, and packet congestion occurs in the layer 2 switch. Even if there is a margin in the network bandwidth, packet loss or the like may occur.

  Conventionally, in order to solve the above problem, a layer 2 switch having an IGMP (Internet Group Management Protocol) snooping function is used. The IGMP snooping function recognizes the port to which a terminal device belonging to a multicast group is connected by sniffing (snooping) an IGMP join message exchanged between the router and the terminal device, and the terminal device belonging to the multicast group This is a function for transmitting a multicast packet only from a port to which is connected. With this function, unnecessary forwarding of multicast packets can be suppressed.

Japanese Patent Laid-Open No. 2004-180023

  However, the layer 2 switch having the IGMP snooping function needs to monitor not only the information of layer 2 but also the information of layer 3 (L3, network layer) or higher, which makes the processing complicated and expensive.

  In addition, when a protocol related to multicast is newly implemented in layer 3 or higher, it is necessary to add a function corresponding to the newly implemented protocol even if the protocol related to multicast of layer 2 is not changed.

  The present invention has been made in view of such a situation, and makes it possible to easily suppress unnecessary forwarding of multicast packets.

  The communication system according to the first aspect of the present invention includes a relay device that relays packets via a plurality of ports based on a layer 2 protocol, and a terminal device that transmits and receives packets based on a layer 2 protocol. In the configured communication system, the relay device transmits a correspondence relationship between a layer 2 address, which is a layer 2 address of the terminal device connected directly or indirectly to the port, and the port via the port. Learning based on the layer 2 address set as the transmission source of the received packet, and when the layer 2 address is a multicast address, the same layer 2 address is associated with the plurality of ports. If the layer 2 address is a unicast address, the same layer When there is a learning unit that prohibits associating an address with a plurality of the ports, and the port associated with the layer 2 address that matches the layer 2 address set in the destination of the received packet, First transmitting means for transmitting the received packet through the port, and when the terminal device belongs to a multicast group, the terminal device for multicast corresponding to the multicast group to which the terminal device belongs A second transmission unit configured to transmit a multicast address notification packet, which is a packet in which a layer 2 address is set as a transmission source, at a predetermined timing;

  A communication method according to a first aspect of the present invention includes a relay device that relays packets through a plurality of ports based on a layer 2 protocol, and a terminal device that transmits and receives packets based on a layer 2 protocol. In the communication method of the configured communication system, a correspondence relationship between a layer 2 address, which is a layer 2 address of the terminal device directly or indirectly connected to the port, executed by the relay device and the port Is learned based on the layer 2 address set in the transmission source of the packet received through the port, and when the layer 2 address is a multicast address, the same layer 2 address is Permits associating with the port, and the layer 2 address is a unicast address The same layer 2 address is prohibited from being associated with a plurality of the ports, and the port associated with the layer 2 address that matches the layer 2 address set as the destination of the received packet is If there is, the step of controlling packet transmission so as to transmit the received packet through the port, and the terminal device executed by the terminal device, if the terminal device belongs to a multicast group, Controlling transmission of packets so that a multicast address notification packet, which is a packet in which the multicast layer 2 address corresponding to the group is set as a transmission source, is transmitted at a predetermined timing.

  The relay device according to the second aspect of the present invention is a relay device that relays a packet via a plurality of ports based on a layer 2 protocol, and is a layer of a terminal device that is directly or indirectly connected to the port. 2 is learned based on the layer 2 address set in the transmission source of the packet received via the port, and the layer 2 address is multicast. The same layer 2 address is allowed to be associated with a plurality of the ports, and when the layer 2 address is a unicast address, the same layer 2 address is assigned to the plurality of ports. A learning means for prohibiting association, and the layer 2 address set as the destination of the received packet. If the layer 2 address that matches the less there are the ports that are associated, and transmission means for transmitting via its said port the received packet.

  If the learning means does not receive the packet set with the layer 2 address associated with the port as the transmission source through the port for a predetermined period, the learning unit The correspondence with the layer 2 address can be canceled.

  If the transmission means does not have the port associated with the layer 2 address that matches the layer 2 address set as the destination of the received packet, the received packet can be flooded.

  The communication method or program according to the second aspect of the present invention includes a communication method for a relay apparatus that relays a packet via a plurality of ports based on a layer 2 protocol, or a plurality of programs based on a layer 2 protocol. Correspondence between a layer 2 address, which is a layer 2 address of a terminal device directly or indirectly connected to the port, and the port in a program for causing a computer to execute a process of relaying a packet via a port of The relationship is learned based on the layer 2 address set in the transmission source of the packet received via the port, and when the layer 2 address is a multicast address, the same layer 2 address is The layer 2 address for unicast If the address is an address, it is prohibited to associate the same layer 2 address with a plurality of the ports, and the layer 2 address that matches the layer 2 address set as the destination of the received packet is associated If the port is present, the method includes controlling the transmission of the packet so as to transmit the received packet through the port.

  The terminal device according to the third aspect of the present invention is a terminal device that transmits and receives packets based on a layer 2 protocol. When the terminal device belongs to a multicast group, the terminal device for multicast corresponding to the multicast group to which the terminal device belongs Transmission means for transmitting a multicast address notification packet, which is a packet in which the layer 2 address is set as a transmission source, at a predetermined timing.

  When the multicast server that transmits a packet addressed to the multicast group belongs to a layer 2 network to which the terminal device belongs, the transmission means can transmit the multicast address notification packet to the multicast server. .

  In the transmission means, when a multicast server that transmits a packet addressed to the multicast group belongs to a second layer 2 network different from the first layer 2 network to which the terminal device belongs, The multicast address notification packet can be transmitted to the gateway of the layer 2 network.

  The communication method or program according to the third aspect of the present invention performs a communication method of a terminal device that transmits and receives packets based on a layer 2 protocol or a process that transmits and receives packets based on a layer 2 protocol. In the program to be executed by the computer of the terminal device, when the terminal device belongs to a multicast group, a multicast address notification which is a packet in which a multicast layer 2 address corresponding to the multicast group to which the terminal device belongs is set as a transmission source Controlling the transmission of the packet to transmit the packet at a predetermined timing.

  In the first aspect of the present invention, a correspondence relationship between a layer 2 address, which is a layer 2 address of a terminal device connected directly or indirectly to a port by a relay device, and the port is set via the port. And learning based on the layer 2 address set as the transmission source of the received packet, and when the layer 2 address is a multicast address, the same layer 2 address is associated with the plurality of ports. When the layer 2 address is a unicast address, it is prohibited to associate the same layer 2 address with a plurality of the ports, and the layer 2 set as the destination of the received packet If there is the port associated with the layer 2 address that matches the address, When transmission of a packet is controlled to transmit a packet through the port, and the terminal device belongs to a multicast group, the layer 2 for multicast corresponding to the multicast group to which the terminal device belongs. Packet transmission is controlled such that a multicast address notification packet, which is a packet with an address set as a transmission source, is transmitted at a predetermined timing.

  In the second aspect of the present invention, a packet in which a correspondence relationship between a layer 2 address, which is a layer 2 address of a terminal device directly or indirectly connected to a port, and the port is received via the port. Is learned on the basis of the layer 2 address set as the transmission source, and if the layer 2 address is a multicast address, it is permitted to associate the same layer 2 address with a plurality of the ports. When the layer 2 address is a unicast address, it is prohibited to associate the same layer 2 address with a plurality of the ports, and matches the layer 2 address set as the destination of the received packet If there is the port associated with the layer 2 address, the received packet is Transmission of packets is controlled to transmit via the serial port.

  In the third aspect of the present invention, when a terminal device belongs to a multicast group, a multicast address notification packet that is a packet in which a multicast layer 2 address corresponding to the multicast group to which the terminal device belongs is set as a transmission source Packet transmission is controlled so as to be transmitted at a predetermined timing.

  According to the first to third aspects of the present invention, learning of the layer 2 address for multicast can be performed. In particular, according to the first to third aspects of the present invention, unnecessary forwarding of multicast packets can be easily suppressed.

  Embodiments of the present invention will be described below. Correspondences between the constituent elements of the present invention and the embodiments described in the specification or the drawings are exemplified as follows. This description is intended to confirm that the embodiments supporting the present invention are described in the specification or the drawings. Therefore, even if there is an embodiment which is described in the specification or the drawings but is not described here as an embodiment corresponding to the constituent elements of the present invention, that is not the case. It does not mean that the form does not correspond to the constituent requirements. Conversely, even if an embodiment is described herein as corresponding to a configuration requirement, that means that the embodiment does not correspond to a configuration requirement other than the configuration requirement. It's not something to do.

  The communication system according to the first aspect of the present invention includes a relay device (for example, the broadband router 111 and the layer 2 switches 112A to 112C in FIG. 1) that relays a packet through a plurality of ports based on a layer 2 protocol. In a communication system (for example, the network system 101 in FIG. 1) configured with a terminal device (for example, the terminal devices 113A to 113C-2 in FIG. 1) that transmits and receives packets based on the layer 2 protocol, the relay The device sets the correspondence between the layer 2 address, which is the layer 2 address of the terminal device connected directly or indirectly to the port, and the port to the transmission source of the packet received through the port Learning based on the layer 2 address that has been set, and the layer 2 address The same layer 2 address is allowed to be associated with a plurality of the ports, and when the layer 2 address is a unicast address, the same layer 2 address is assigned to the plurality of ports. The learning means (for example, the address learning unit 143 in FIG. 2) prohibiting association with the layer 2 address corresponding to the layer 2 address set as the destination of the received packet is associated with When there is a port, the terminal device includes first transmission means (for example, the transmission control unit 145 in FIG. 2) that transmits the received packet through the port, and the terminal device belongs to the multicast group. The layer 2 address for multicast corresponding to the multicast group to which it belongs Comprising a second transmission means for transmitting a multicast address notification packet is set to the source packet at a predetermined timing (e.g., the packet transmission unit 172 of FIG. 3).

  A communication method according to the first aspect of the present invention includes a relay device (for example, the broadband router 111 and the layer 2 switches 112A to 112C in FIG. 1) that relays a packet through a plurality of ports based on a layer 2 protocol. In a communication method of a communication system (for example, the network system 101 in FIG. 1) configured with a terminal device (for example, the terminal devices 113A to 113C-2 in FIG. 1) that transmits and receives packets based on the layer 2 protocol. The correspondence between the layer 2 address, which is the layer 2 address of the terminal device directly or indirectly connected to the port, executed by the relay device and the port is received via the port. Learning based on the layer 2 address set in the packet source, When the ear 2 address is an address for multicast, the same layer 2 address is allowed to be associated with a plurality of the ports. When the layer 2 address is a unicast address, the same layer 2 address is Correspondence to a plurality of the ports is prohibited (for example, steps S22 to S25 in FIG. 6), and the layer 2 address that matches the layer 2 address set as the destination of the received packet is associated. If there is the port, a step of controlling transmission of the packet so that the received packet is transmitted through the port (for example, steps S53 and S54 in FIG. 17), and the terminal executed by the terminal device If the device belongs to a multicast group, the multicast to which it belongs Packet transmission is controlled such that a multicast address notification packet, which is a packet in which the layer 2 address for multicast corresponding to the loop is set as a transmission source, is transmitted at a predetermined timing (for example, steps S1 and S2 in FIG. 4). Steps.

  The relay device (for example, the broadband router 111 and the layer 2 switches 112A to 112C in FIG. 1) of the second aspect of the present invention is a relay device that relays packets via a plurality of ports based on the layer 2 protocol. The correspondence relationship between the port and the layer 2 address, which is the layer 2 address of the terminal device directly or indirectly connected to the port, is set as the transmission source of the packet received through the port When learning based on the layer 2 address and the layer 2 address is an address for multicasting, the same layer 2 address is allowed to be associated with a plurality of ports, and the layer 2 address is used for unicast The same layer 2 address is associated with a plurality of the ports. Learning means (for example, the address learning unit 143 in FIG. 2) that prohibits the port from being associated with the layer 2 address that matches the layer 2 address set as the destination of the received packet. In some cases, transmission means (for example, the transmission control unit 145 in FIG. 2) for transmitting the received packet via the port is included.

  The communication method or program according to the second aspect of the present invention is a relay device that relays packets via a plurality of ports based on a layer 2 protocol (for example, the broadband router 111 and the layer 2 switches 112A to 112C in FIG. 1). ) Or a terminal device connected directly or indirectly to the port in a program that causes a computer to execute a packet relay process via a plurality of ports based on a layer 2 protocol. The correspondence between the layer 2 address, which is a layer 2 address of the packet, and the port is learned based on the layer 2 address set in the transmission source of the packet received via the port, and the layer 2 address Is the multicast address, the same layer 2 address is used. If the layer 2 address is a unicast address, it is prohibited to associate the same layer 2 address with a plurality of ports (for example, step of FIG. 6). S22 to S25), when there is the port associated with the layer 2 address that matches the layer 2 address set as the destination of the received packet, the received packet is transmitted through the port. The packet transmission is controlled (for example, steps S53 and S54 in FIG. 17).

  The terminal device according to the third aspect of the present invention (for example, the terminal devices 113A to 113C-2 in FIG. 1) is a terminal device that transmits and receives packets based on a layer 2 protocol, and the terminal device belongs to a multicast group. If so, a transmission means for transmitting a multicast address notification packet, which is a packet in which the multicast layer 2 address corresponding to the multicast group to which it belongs is set as a transmission source at a predetermined timing (for example, the packet transmission unit in FIG. 3) 172).

  The communication method or program according to the second aspect of the present invention is a communication method of a terminal device (for example, the terminal devices 113A to 113C-2 in FIG. 1) that transmits and receives packets based on a layer 2 protocol, or a layer 2 In a program for causing a computer of a terminal device (for example, the terminal devices 113A to 113C-2 in FIG. 1) to execute processing for transmitting and receiving packets based on the protocol of the terminal device, if the terminal device belongs to a multicast group, The packet transmission is controlled so as to transmit a multicast address notification packet, which is a packet in which a multicast layer 2 address corresponding to the multicast group being set is set as a transmission source (for example, step S1 in FIG. 4). And S2) step.

  Embodiments to which the present invention is applied will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing an embodiment of a network system to which the present invention is applied. A network system 101 in FIG. 1 constitutes a layer 2 network, for example, a general home network system. A network system 101 is connected to an external network such as the Internet or a carrier network such as a CDN (Content Delivery Network), and is a broadband router 111 that relays packets based on at least layer 2 and layer 3 protocols. Layer 2 switches 112A to 112C, which are relay devices that relay packets based on the protocol of, and network compatible devices such as information processing devices, AV (Audio / Visual) devices, home appliances, etc. It is configured to include terminal devices 113A, 113B-1, 113B-2, 113C-1 and 113C-2 that transmit and receive packets based on the protocol.

  The broadband router 111 is connected to an external network via the port P1, is connected to the port P11 of the layer 2 switch 112A via the port P2, and is connected to the port P21 of the layer 2 switch 112B via the port P3. ing. The layer 2 switch 112A is connected to the port P31 of the layer 2 switch 112C via the port P12, and is connected to the terminal device 113A via the port P13. The layer 2 switch 112B is connected to the terminal device 113B-1 via the port P22, and is connected to the terminal device 113B-2 via the port P23. The layer 2 switch 112C is connected to the terminal device 113C-1 via the port P32 and is connected to the terminal device 113C-2 via the port P33.

  Hereinafter, the layer 2 switches 112A to 112C are simply referred to as the layer 2 switch 112 when it is not necessary to individually distinguish them. Hereinafter, the terminal devices 113 </ b> A to 113 </ b> C- 2 are simply referred to as the terminal device 113 when it is not necessary to distinguish them individually.

  FIG. 2 is a block diagram showing a functional configuration of a layer 2 communication unit that is a part that realizes a communication function based on the layer 2 protocol of the broadband router 111 and the layer 2 switch 112. The layer 2 communication unit 131 in FIG. 2 includes a reception control unit 141, a buffer 142, an address learning unit 143, a learning table storage unit 144, and a transmission control unit 145.

  The reception control unit 141 accumulates packets received from the outside via the ports 132-1 to 132-n in the buffer 142. The reception control unit 141 notifies the address learning unit 143 of the port that received the packet and the source MAC (Media Access Control) address (Source Address) of the received packet.

  In addition, the reception control unit 141 detects disconnection of a device (hereinafter also referred to as link disconnection) based on a signal indicating whether or not the device is connected supplied from the ports 132-1 to 132-n. When the link break is detected, the address learning unit 143 is notified of the port where the link break is detected.

  Hereinafter, when it is not necessary to distinguish the ports 132-1 to 132-n, they are simply referred to as ports 132. Further, the ports P1 to P33 in FIG. 1 correspond to the ports 132 of each device, respectively.

  As will be described later with reference to FIG. 6 and the like, the address learning unit 143 directly or indirectly to each port 132 based on the information notified from the reception control unit 141 or through another layer 2 switch 112 or the like. The MAC address of the connected terminal device 113 is learned. Based on the learning result, the address learning unit 143 generates or updates a learning table indicating the correspondence between the MAC address of the terminal device 113 directly or indirectly connected to each port 132 and each port 132, and learns The data is stored in the table storage unit 144.

  Hereinafter, a case where a learning table is provided for each port 132 will be described as an example. That is, a learning table corresponding to each port 132 is individually provided, and each learning table includes a port 132 corresponding to the learning table and a MAC of the terminal device 113 directly or indirectly connected to the port 132. It is assumed that data indicating a correspondence relationship with an address (hereinafter also referred to as an entry) is registered.

  Each entry in the learning table includes at least a learned MAC address, that is, a MAC address of the terminal device 113 directly or indirectly connected to the port 132 corresponding to the learning table, and an aging timer. . The aging timer is a timer that is updated at a predetermined interval and indicates the valid period of each entry. As will be described later with reference to FIG. 20, the entry for which the aging timer has timed out is discarded.

  As will be described later with reference to FIG. 17 and the like, the transmission control unit 145 stores the destination MAC address (Destination Address) of the packet stored in the buffer 142 and the learning table stored in the learning table storage unit 144. Based on this, the port 132 for transmitting the received packet is selected, and the packet is transmitted to the outside through the selected port 132.

  FIG. 3 is a block diagram illustrating a functional configuration of a multicast address notification unit that is a part that realizes a function of notifying the multicast address of the terminal device 113. The multicast address notification unit 161 in FIG. 3 is configured to include a MAC address storage unit 171 and a packet transmission unit 172.

  When the terminal device 113 performs an operation for joining a multicast group, the MAC address storage unit 171 stores a multicast MAC address (hereinafter also referred to as a multicast address) corresponding to the multicast group. The terminal device 113 can participate in a plurality of multicast groups, and the MAC address storage unit 171 stores multicast MAC addresses corresponding to all multicast groups to which the terminal device 113 belongs.

  As will be described later with reference to FIG. 4, the packet transmission unit 172 notifies a multicast address stored in the MAC address storage unit 171 at a predetermined timing (hereinafter also referred to as a multicast address notification packet). Generate and send.

  Next, multicast address notification processing executed by the terminal device 113 will be described with reference to the flowchart of FIG. This process is executed, for example, at a predetermined timing (for example, a predetermined interval, a predetermined time, or a timing when a predetermined process is performed in the terminal device 113).

  In step S1, the packet transmission unit 172 determines whether a multicast MAC address is set. If the multicast address is stored in the MAC address storage unit 171, the packet transmission unit 172 determines that the multicast MAC address is set, and the process proceeds to step S2.

  As shown in FIG. 5, for the multicast address, 0x01005E is set in the first 3 bytes (1st to 24th bits), 1 is set in the 25th bit, and the lower 23 bits indicate the multicast group. This is the MAC address where the ID is set.

  In step S2, the packet transmission unit 172 transmits a packet in which a multicast MAC address is set as the transmission source, and the multicast address notification process ends. Specifically, the packet transmission unit 172 generates a packet of a ping (Packet Internet Groper) command in which the MAC address stored in the MAC address storage unit 171 is set as a transmission source MAC address, and the generated packet is a multicast address. Sent as a notification packet.

  When the terminal device 113 belongs to a plurality of multicast groups and a plurality of multicast addresses corresponding to each multicast group are set, the packet transmission unit 172 generates a multicast address notification packet for each multicast address. ,Send.

  On the other hand, in step S1, when the MAC address storage unit 171 does not store the multicast MAC address, the packet transmission unit 172 determines that the multicast MAC address is not set, and the multicast address notification process ends. To do.

  Next, packet reception processing executed by the broadband router 111 and the layer 2 switch 112 will be described with reference to the flowchart of FIG. This process is started when, for example, the broadband router 111 or the reception control unit 141 of the layer 2 switch 112 receives a packet from the outside via any port 132.

  In step S21, the reception control unit 141 accumulates packets. Specifically, the reception control unit 141 stores received packets in the buffer 142. Further, the reception control unit 141 notifies the address learning unit 143 of the port 132 that has received the packet and the transmission source MAC address of the received packet.

  In step S22, the address learning unit 143 determines whether the source MAC address of the received packet is a multicast address. If it is determined that the source MAC address of the received packet is not a multicast address, that is, if it is determined that the source MAC address of the received packet is a unicast address, the process proceeds to step S23.

  In step S23, the address learning unit 143 determines whether the transmission source MAC address has been learned in another port. Specifically, the address learning unit 143 targets the learning table of the port 132 other than the port 132 that receives the packet (hereinafter also referred to as a receiving port) among the learning tables stored in the learning table storage unit 144. Search for an entry that includes a MAC address that matches the source MAC address of the received packet. If the address learning unit 143 detects an entry including a MAC address that matches the transmission source MAC address of the received packet, the address learning unit 143 determines that the transmission source MAC address has been learned in another port, and the process proceeds to step S24. .

  In step S24, the address learning unit 143 discards entries with duplicate MAC addresses. Specifically, the address learning unit 143 deletes the entry including the MAC address that matches the source MAC address of the received packet detected in step S23 from the learning table. As a result, it is prohibited to register duplicate entries including the same unicast address in the learning table of the plurality of ports 132. That is, it is prohibited to associate the same unicast address with a plurality of ports.

  On the other hand, if it is determined in step S23 that the source MAC address has not been learned in another port, the process of step S24 is skipped, and the process proceeds to step S25.

  If it is determined in step S22 that the source MAC address of the received packet is a multicast address, the processes in steps S23 and S24 are skipped, and the process proceeds to step S25.

  In step S25, the address learning unit 143 updates the reception port learning table, and the packet reception process ends. Specifically, the address learning unit 143 determines the source MAC address of the received packet when the entry including the MAC address that matches the source MAC address of the received packet is not registered in the learning table of the reception port. The new entry is added to the learning table, and the aging timer of the added entry is set to the initial value. Further, when an entry including a MAC address that matches the transmission source MAC address of the received packet is registered in the learning table of the reception port, the address learning unit 143 returns the aging timer of the entry to the initial value.

  In this way, received packets are accumulated in the buffer 142, and learning of the MAC address of the terminal device 113 connected directly or indirectly to each port 132 is performed.

  Here, with reference to FIG. 7 and FIG. 8, a specific example of processing in the case of learning a multicast address will be described.

  FIGS. 7 and 8 are diagrams illustrating the states of the learning tables of the ports 0 to 3 of the layer 2 switch 201 having the same configuration as the layer 2 switch 112 of FIG.

  For example, as shown in FIG. 7, first, when the layer 2 switch 201 receives a packet in which the multicast address A is set in the source MAC address (MAC SA) via the port 0, the multicast address A is included. The entry is registered in the learning table for port 0.

  Next, as shown in FIG. 8, when the layer 2 switch 201 receives a packet in which the multicast MAC address A is set in the source MAC address (MAC SA) through the port 1, the entry including the multicast address A is entered. Is registered in the learning table of port 1. At this time, as described above, since the processing of steps S23 and S24 in FIG. 6 is skipped, the entry including the same multicast address A as the source MAC address of the received packet is not deleted from the learning table of port 0. .

  In this way, it is permitted that entries including the same multicast address are registered in duplicate in the learning tables of a plurality of ports. That is, the same multicast address is permitted to be associated with a plurality of ports.

  Next, an example of the transmission destination of the multicast address notification packet will be described with reference to FIGS.

  Hereinafter, the unicast MAC address of the broadband router 111 is MAC_GW, the IP address is IP_GW, the unicast MAC address of the terminal device 113B-2 is MAC_E, the IP address is IP_E, and the terminal device 113C- The MAC address for 1 unicast is MAC_A, and the IP address is IP_A. Hereinafter, a MAC address for multicast (multicast address) corresponding to multicast group 1 is referred to as MAC_M.

  First, consider a case where the terminal device 113C-1 belongs to the multicast group 1 and the multicast server that transmits the multicast packet addressed to the multicast group 1 belongs to a layer 2 network different from the network system 101. In this case, for example, as illustrated in FIG. 9, the terminal device 113 </ b> C- 1 transmits a multicast address notification packet to the broadband router 111 that is a gateway of the network system 101.

  FIG. 10 shows an example of the configuration of a multicast address notification packet transmitted at this time. In the Ethernet header part of the multicast address notification packet of FIG. 10, MAC_GW which is the MAC address of the broadband router 111 is set as the destination MAC address (MAC DA), and the terminal device 113C-1 is set as the source MAC address (MAC SA). MAC_M, which is the multicast address of multicast group 1 to which is assigned, is set, and the value 0x0800 indicating that the corresponding protocol is IP is set in the Ethernet type (Type). Further, in the IP header part, a value 0x01 indicating that the upper protocol is ICMP (Internet Control Message Protocol) is set in the protocol field (Protocol), and the source IP address (IP SA) of the terminal device 113C-1 is set. IP_A that is an IP address is set, and IP_GW that is the IP address of the broadband router 111 is set as the destination IP address (IP DA). Furthermore, an IP payload (IP Payload) and a CRC (Cyclic Redundancy Check) code are added after the IP header.

  In this case, the multicast address notification packet of FIG. 10 transmitted from the packet transmission unit 172 of the terminal device 113C-1 includes the port P32 and the port P31 of the layer 2 switch 112C, the port P12 and the port P11 of the layer 2 switch 112A, and Received by the broadband router 111 via the port P2. As a result, the multicast set in the terminal device 113C-1 at the port P32 of the layer 2 switch 112C, the port P12 of the layer 2 switch 112A, and the port P2 of the broadband router 111, which are ports that have received the multicast address notification packet. The address MAC_M is learned.

  Next, consider a case where the terminal device 113C-1 belongs to the multicast group 1 and the multicast server that transmits the multicast packet addressed to the multicast group 1 is the terminal device 113B-2 in the network system 101. In this case, for example, as illustrated in FIG. 11, the terminal device 113C-1 transmits a multicast address notification packet to the terminal device 113B-2.

  FIG. 12 shows an example of the configuration of a multicast address notification packet transmitted at this time. Compared with the multicast address notification packet of FIG. 10, the multicast address notification packet of FIG. 12 is set with the MAC_E that is the MAC address of the terminal device 113B-2 set as the destination MAC address (MAC DA) and the destination IP address (IP DA ) Is set to IP_E which is the IP address of the terminal device 113B-2.

  In this case, the multicast address notification packet of FIG. 12 transmitted from the packet transmission unit 172 of the terminal device 113C-1 includes the port P32 and port P31 of the layer 2 switch 112C, the port P12 and port P11 of the layer 2 switch 112A, the broadband router The data is received by the terminal device 113B-2 via the port P2 and port P3 of 111 and the port P21 and port P23 of the layer 2 switch 112B. As a result, the terminal device 113C at the port P32 of the layer 2 switch 112C, the port P12 of the layer 2 switch 112A, the port P2 of the broadband router 111, and the port P21 of the layer 2 switch 112B that are ports that have received the multicast address notification packet. MAC_M, which is a multicast address set to -1, is learned.

  Further, when the terminal device 113C-1 belongs to the multicast group 1, it is conceivable that the terminal device 113C-1 broadcasts a multicast address notification packet in the network system 101 as shown in FIG.

  FIG. 14 shows an example of the configuration of a multicast address notification packet transmitted at this time. Compared with the multicast address notification packet of FIG. 10, the multicast address notification packet of FIG. The difference is that IP_A, which is the IP address of the terminal device 113C-1, is set in the IP address (IP DA).

  In this case, the multicast address notification packet of FIG. 14 transmitted from the packet transmission unit 172 of the terminal device 113C-1 is received by the terminal device 113C-1 via the port P32 of the layer 2 switch 112C, and the layer 2 switch 112C Received by the terminal device 113C-2 via the port P32 and the port P33 of the second port, and received by the terminal device 113A via the port P32 and the port P31 of the layer 2 switch 112C and the port P12 and the port P13 of the layer 2 switch 112A. The port P32 and port P31 of the layer 2 switch 112C, the port P12 and port P11 of the layer 2 switch 112A, the port P2 and port P3 of the broadband router 111, and the layer 2 switch 112B are received. Received by the terminal device 113B-1 via the port P21 and the port P22, the port P32 and the port P31 of the layer 2 switch 112C, the port P12 and the port P11 of the layer 2 switch 112A, the port P2 and the port P3 of the broadband router 111, In addition, the data is received by the terminal device 113B-2 via the port P21 and the port P23 of the layer 2 switch 112B.

  As a result, the terminal device 113C at the port P32 of the layer 2 switch 112C, the port P12 of the layer 2 switch 112A, the port P2 of the broadband router 111, and the port P21 of the layer 2 switch 112B that are ports that have received the multicast address notification packet. MAC_M, which is a multicast address set to -1, is learned.

  Further, when the terminal device 113C-1 belongs to the multicast group 1, it is considered that the terminal device 113C-1 transmits a multicast address notification packet to itself as shown in FIG.

  FIG. 16 shows an example of the configuration of a multicast address notification packet transmitted at this time. In the multicast address notification packet of FIG. 16, compared to the multicast address notification packet of FIG. 10, MAC_A that is the MAC address of the terminal device 113C-1 is set as the destination MAC address (MAC DA), and the destination IP address (IP DA ) Is set to IP_A which is the IP address of the terminal device 113C-1.

  In this case, the multicast address notification packet of FIG. 16 transmitted from the packet transmission unit 172 of the terminal device 113C-1 is received by the terminal device 113C-1 via the port P32 of the layer 2 switch 112C. As a result, the MAC_M that is the multicast address set in the terminal device 113C-1 is learned at the port P32 of the layer 2 switch 112C that is the port that has received the multicast address notification packet.

  Next, packet transmission processing executed by the broadband router 111 and the layer 2 switch 112 will be described with reference to the flowchart of FIG.

  In step S <b> 51, the transmission control unit 145 determines whether packets are stored in the buffer 142. The determination process in step S51 is repeatedly executed at predetermined intervals until it is determined that packets are accumulated in the buffer 142. If it is determined that packets are accumulated in the buffer 142, the process proceeds to step S52. .

  In step S52, the transmission control unit 145 determines whether the destination MAC address is a broadcast address. Specifically, the transmission control unit 145 sets the packet accumulated most recently in the buffer 142 as a packet to be transmitted next, and refers to the destination MAC address of the packet. If the transmission control unit 145 determines that the destination MAC address of the next packet to be transmitted is not a broadcast address, that is, determines that it is a multicast address or a unicast address, the process proceeds to step S53.

  In step S53, the transmission control unit 145 determines whether the destination MAC address has been learned. Specifically, the transmission control unit 145 searches all learning tables stored in the learning table storage unit 144 for an entry including a MAC address that matches the destination MAC address of the packet to be transmitted next. If the transmission control unit 145 detects an entry including a MAC address that matches the destination MAC address of the next packet to be transmitted, the transmission control unit 145 determines that the destination MAC address has been learned, and the process proceeds to step S54.

  In step S54, the transmission control unit 145 transmits the packet to the set destination. Specifically, the transmission control unit 145 copies the packet to be transmitted, and matches the port 132 corresponding to the learning table in which the entry detected in step S53 is registered, that is, the destination MAC address of the packet to be transmitted. The copied packet is transmitted from the port 132 associated with the MAC address.

  If a multicast address is set as the destination MAC address of the packet to be transmitted and there are a plurality of ports 132 associated with the MAC address that matches the multicast address, the transmission control unit 145 determines that all of those ports For 132, a process of copying the packet to be transmitted and transmitting the copied packet from the port 132 is executed. Thereby, the received packet is multicast.

  For example, as illustrated in FIG. 18, consider a case where the layer 2 switch 201 having the same learning table as in FIG. 8 described above receives a packet in which the multicast address A is set as the destination MAC address from the port 3. In this case, the layer 2 switch 201 transmits the received packet from the port 0 and the port 1 in which the entry including the multicast address A is registered in the learning table, and the entry including the multicast address A is registered in the learning table. The received packet is not transmitted from the port 2 that does not exist.

  That is, all the ports that have learned the multicast address A, in other words, the packets received from all the ports that are associated with the multicast address A are transmitted, in other words, the ports that have not learned the multicast address A. The received packet is not transmitted from the port not associated with the multicast address A.

  Thereafter, the process proceeds to step S56.

  On the other hand, in step S53, the transmission control unit 145 determines that the destination MAC address has not been learned when the entry including the MAC address that matches the destination MAC address of the packet to be transmitted next cannot be detected, and the processing is performed. Proceed to step S55.

  If it is determined in step S52 that the destination MAC address is a broadcast address, the process proceeds to step S55.

  In step S55, the transmission control unit 145 floods the packet. That is, the transmission control unit 145 transmits the received packet from all the ports 132 connected to other devices among the ports 132 other than the port 132 that has received the packet. More specifically, the transmission control unit 145 copies the packet to be transmitted to all the ports 132 to which other devices are connected among the ports 132 other than the port 132 that has received the packet. Execute the process to send. Thereafter, the process proceeds to step S56.

  In step S <b> 56, the transmission control unit 145 deletes the transmitted packet from the buffer 142.

  Thereafter, the process returns to step S51, and the processes after step S51 are executed.

  As described above, packet multicasting can be easily realized using only layer 2 information, and unnecessary forwarding of multicast packets can be suppressed.

  For example, as shown in FIG. 19, the multicast server 251 is connected to the network system 101 via the port P1 of the broadband router 111, and the terminal device 113B is connected to the multicast group B that receives the multicast packet transmitted from the multicast server 251. -2 and 113C-1 are considered. Hereinafter, the multicast MAC address of multicast group B is referred to as multicast address B.

  In this case, first, the terminal device 113C-1 transmits a multicast address notification packet to the broadband router 111, whereby the port P32 of the layer 2 switch 112C, the port P12 of the layer 2 switch 112A, and the port of the broadband router 111 In P2, the multicast address B is learned. In addition, when the terminal device 113B-2 transmits a multicast address notification packet to the broadband router 111, the multicast address B is learned at the port P23 of the layer 2 switch 112B and the port P3 of the broadband router 111.

  When a multicast packet having the multicast address B set as the destination MAC address is transmitted from the multicast server 251, the broadband router 111 receives the multicast packet via the port P1, and the multicast address B is associated with it. Multicast packets are transmitted via the ports P2 and P3.

  The layer 2 switch 112A receives the multicast packet via the port P11, transmits the multicast packet via the port P12 associated with the multicast address B, and starts from the port P13 not associated with the multicast address B. Do not send multicast packets.

  The layer 2 switch 112B receives the multicast packet via the port P21, transmits the multicast packet via the port P23 associated with the multicast address B, and the terminal device 113B-2 receives the multicast packet. The layer 2 switch 112B does not transmit a multicast packet from the port P22 to which the multicast address B is not associated.

  The layer 2 switch 112C receives the multicast packet via the port P31, transmits the multicast packet via the port P32 associated with the multicast address B, and the terminal device 113C-1 receives the multicast packet. Further, the layer 2 switch 112C does not transmit a multicast packet from the port P33 to which the multicast address B is not associated.

  In this way, the multicast packet transmitted from the multicast server 251 is transferred only to the terminal devices 113B-2 and 113C-1 belonging to the multicast group B.

  By suppressing unnecessary forwarding of multicast packets as described above, congestion of packets in the broadband router 111 or the layer 2 switch 112 is suppressed, and as a result, packet congestion of the entire network system 101 is reduced. Occurrence is suppressed.

  In addition, the multicast packet transfer process can be speeded up, the capacity of the buffer 142 can be reduced, and the delay time caused by the packet transfer can be shortened.

  Next, the learning table entry discarding process executed by the broadband router 111 and the layer 2 switch 112 will be described with reference to the flowchart of FIG.

  In step S71, the address learning unit 143 determines whether there is an entry for which the aging timer has timed out. If the address learning unit 143 determines that there is an entry for which the aging timer has timed out among the entries in the learning table stored in the learning table storage unit 144, the process proceeds to step S72.

  In step S72, the address learning unit 143 discards the time-out entry. As a result, when a packet in which a source MAC address that matches the MAC address associated with each port 132 is not received from the port 132 for a predetermined period, the learning table of the port 132 An entry including the MAC address is deleted, and processing for canceling the correspondence between the port 132 and the MAC address is performed.

  On the other hand, if it is determined in step S71 that there is no entry for which the aging timer has timed out, the process of step S72 is skipped, and the process proceeds to step S73.

  In step S73, the reception control unit 141 determines whether a link break has occurred. Specifically, if the reception control unit 141 determines that a link break has occurred based on a signal indicating the presence / absence of connection of a device supplied from each port 132, the process proceeds to step S74.

  In step S74, the address learning unit 143 discards the entry in the learning table of the port 132 in which the link break is detected. Specifically, the reception control unit 141 notifies the address learning unit 143 of the port 132 in which the link break has been detected. The address learning unit 143 deletes all entries from the learning table of the port 132 in which the link break is detected. Thereafter, the process returns to step S71, and the processes after step S71 are executed.

  On the other hand, if it is determined in step S73 that no ring break has occurred, the process returns to step S71, and the processes after step S71 are executed.

  Thus, for example, as shown in FIG. 21, the layer 2 switch 201 having the same learning table as FIG. 8 described above sends a multicast address notification packet in which the multicast address A is set to the source MAC address to the port 0. , The entry including the multicast address A is deleted from the learning table for port 0. When a link break is detected at port 1, all entries are deleted from the learning table for port 1.

  In the above description, the MAC address is used as the layer 2 address. However, the present invention can also be applied to the case where another layer 2 address capable of identifying the multicast address is used. is there.

  In the above description, an example of a network system that performs communication based on the Ethernet standard has been described. However, the present invention is also applicable to a case where communication is performed based on another layer 2 protocol having a multicast specification. Is possible.

  Further, in the above description, an example in which the learning table is individually managed for each port is shown. However, for example, one learning is performed by including information on the corresponding port in each entry or dividing the entry for each port. The correspondence between each port and the MAC address may be managed by a table.

  In the above description, an example in which a ping command packet is used as a multicast address notification packet has been described. However, other command packets may be used.

  The present invention can be applied to an apparatus having a function of transmitting / receiving or relaying a packet based on a layer 2 protocol. Therefore, for example, the present invention can be applied to a layer 3 or higher switch having a layer 2 switch function.

  The series of processes described above can be executed by hardware or can be executed by software. When a series of processing is executed by software, a program constituting the software executes various functions by installing a computer incorporated in dedicated hardware or various programs. For example, it is installed from a program recording medium in a general-purpose personal computer or the like.

  FIG. 22 is a block diagram illustrating an example of a hardware configuration of a computer that executes the above-described series of processes using a program.

  In a computer, a CPU (Central Processing Unit) 301, a ROM (Read Only Memory) 302, and a RAM (Random Access Memory) 303 are connected to each other by a bus 304.

  An input / output interface 305 is further connected to the bus 304. The input / output interface 305 includes an input unit 306 including a keyboard, a mouse, and a microphone, an output unit 307 including a display and a speaker, a storage unit 308 including a hard disk and a nonvolatile memory, and a communication unit 309 including a network interface. A drive 310 that drives a removable medium 311 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory is connected.

  In the computer configured as described above, the CPU 301 loads the program stored in the storage unit 308 to the RAM 303 via the input / output interface 305 and the bus 304 and executes the program, for example. Is performed.

  The program executed by the computer (CPU 301) is, for example, a magnetic disk (including a flexible disk), an optical disk (CD-ROM (Compact Disc-Read Only Memory), DVD (Digital Versatile Disc), etc.), a magneto-optical disk, or a semiconductor. It is recorded on a removable medium 311 which is a package medium composed of a memory or the like, or provided via a wired or wireless transmission medium such as a local area network, the Internet, or digital satellite broadcasting.

  The program can be installed in the storage unit 308 via the input / output interface 305 by attaching the removable medium 311 to the drive 310. Further, the program can be received by the communication unit 309 via a wired or wireless transmission medium and installed in the storage unit 308. In addition, the program can be installed in advance in the ROM 302 or the storage unit 308.

  The program executed by the computer may be a program that is processed in time series in the order described in this specification, or in parallel or at a necessary timing such as when a call is made. It may be a program for processing.

  In this specification, the term “system” refers to an overall device including a plurality of devices and means.

  The embodiment of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

It is a block diagram which shows one Embodiment of the network system to which this invention is applied. It is a block diagram which shows the functional structure of the layer 2 communication part which implement | achieves a layer 2 communication function. It is a block diagram which shows the functional structure of a multicast address notification part. It is a flowchart for demonstrating a multicast address notification process. It is a figure which shows the format of a multicast address. It is a flowchart for demonstrating a packet reception process. It is a figure for demonstrating the specific example of a process in the case of learning a multicast address. It is a figure for demonstrating the specific example of a process in the case of learning a multicast address. It is a figure which shows the example of the transmission destination of a multicast address notification packet. It is a figure which shows the example of a structure of a multicast address notification packet. It is a figure which shows the other example of the transmission destination of a multicast address notification packet. It is a figure which shows the other example of a structure of a multicast address notification packet. It is a figure which shows the further another example of the transmission destination of a multicast address notification packet. It is a figure which shows the further another example of a structure of a multicast address notification packet. It is a figure which shows the further another example of the transmission destination of a multicast address notification packet. It is a figure which shows the further another example of a structure of a multicast address notification packet. It is a flowchart for demonstrating a packet transmission process. It is a figure for demonstrating the specific example of a packet transmission process. It is a figure for demonstrating the specific example of the process which transfers a multicast packet. It is a flowchart for demonstrating a learning table entry discard process. It is a figure for demonstrating the specific example of a learning table entry discard process. It is a figure which shows the structural example of a computer.

Explanation of symbols

  101 network system, 111 broadband router, 112 layer 2 switch, 113 terminal device, 131 layer 2 communication unit, 132 port, 141 reception control unit, 143 address learning unit, 144 learning table storage unit, 145 transmission control unit, 161 multicast address Notification unit, 171 MAC address storage unit, 172 Packet transmission unit

Claims (12)

In a communication system including a relay device that relays packets via a plurality of ports based on a layer 2 protocol, and a terminal device that transmits and receives packets based on a layer 2 protocol,
The relay device is
The correspondence between the layer 2 address, which is the layer 2 address of the terminal device connected directly or indirectly to the port, and the port is set in the transmission source of the packet received via the port When learning based on the layer 2 address and the layer 2 address is an address for multicasting, the same layer 2 address is allowed to be associated with a plurality of ports, and the layer 2 address is used for unicast Learning means for prohibiting associating the same layer 2 address with a plurality of the ports,
When there is the port associated with the layer 2 address that matches the layer 2 address set as the destination of the received packet, first transmission means for transmitting the received packet through the port Including and
The terminal device
When the terminal device belongs to a multicast group, a second multicast address notification packet that is a packet in which the layer 2 address for multicast corresponding to the multicast group to which the terminal device belongs is set as a transmission source is transmitted at a predetermined timing. A communication system including a transmission means. In a communication method of a communication system configured by a relay device that relays a packet via a plurality of ports based on a layer 2 protocol and a terminal device that transmits and receives a packet based on a layer 2 protocol,
Executed by the relay device;
The correspondence between the layer 2 address, which is the layer 2 address of the terminal device connected directly or indirectly to the port, and the port is set in the transmission source of the packet received via the port When learning based on the layer 2 address and the layer 2 address is an address for multicasting, the same layer 2 address is allowed to be associated with a plurality of ports, and the layer 2 address is used for unicast The same layer 2 address is prohibited from being associated with a plurality of the ports,
When there is the port associated with the layer 2 address that matches the layer 2 address set as the destination of the received packet, packet transmission is performed so that the received packet is transmitted through the port. Controlling the step,
Executed by the terminal device;
When the terminal device belongs to a multicast group, a packet is transmitted so that a multicast address notification packet that is a packet in which the layer 2 address for multicast corresponding to the multicast group to which the terminal device belongs is set as a transmission source is transmitted at a predetermined timing And a method for controlling the transmission of. In a relay device that relays packets via a plurality of ports based on a layer 2 protocol,
The correspondence between the layer 2 address, which is the layer 2 address of the terminal device directly or indirectly connected to the port, and the port is set in the transmission source of the packet received through the port When learning based on a layer 2 address and the layer 2 address is an address for multicast, the same layer 2 address is allowed to be associated with a plurality of ports, and the layer 2 address is used for unicast. If it is an address, a learning means for prohibiting associating the same layer 2 address with a plurality of the ports;
Transmitting means for transmitting the received packet through the port when there is the port associated with the layer 2 address that matches the layer 2 address set as the destination of the received packet. Relay device. If the learning means does not receive a packet in which the layer 2 address associated with the port is set as a transmission source through the port for a predetermined period, the learning unit and the port The relay apparatus according to claim 3, wherein the correspondence relationship with the layer 2 address is canceled. The said transmission means floods the received packet when there is no said port with which the said layer 2 address which matches the said layer 2 address set to the destination of the received packet is matched. Relay device. In a communication method of a relay apparatus that relays a packet through a plurality of ports based on a layer 2 protocol,
The correspondence between the layer 2 address, which is the layer 2 address of the terminal device directly or indirectly connected to the port, and the port is set in the transmission source of the packet received through the port When learning based on a layer 2 address and the layer 2 address is an address for multicast, the same layer 2 address is allowed to be associated with a plurality of ports, and the layer 2 address is used for unicast. If it is an address, it is prohibited to associate the same layer 2 address with a plurality of the ports,
When there is the port associated with the layer 2 address that matches the layer 2 address set as the destination of the received packet, packet transmission is performed so that the received packet is transmitted through the port. A communication method including the step of controlling. In a program for causing a computer to execute a process of relaying a packet through a plurality of ports based on a layer 2 protocol,
The correspondence between the layer 2 address, which is the layer 2 address of the terminal device directly or indirectly connected to the port, and the port is set in the transmission source of the packet received through the port When learning based on a layer 2 address and the layer 2 address is an address for multicast, the same layer 2 address is allowed to be associated with a plurality of ports, and the layer 2 address is used for unicast. If it is an address, it is prohibited to associate the same layer 2 address with a plurality of the ports,
When there is the port associated with the layer 2 address that matches the layer 2 address set as the destination of the received packet, packet transmission is performed so that the received packet is transmitted through the port. A program that executes processes including steps. In a terminal device that transmits and receives packets based on the layer 2 protocol,
When the terminal device belongs to a multicast group, transmission means for transmitting a multicast address notification packet, which is a packet in which a multicast layer 2 address corresponding to the multicast group to which the terminal device belongs is set as a transmission source at a predetermined timing, Including terminal device. The transmission means transmits the multicast address notification packet to the multicast server when the multicast server that transmits the packet addressed to the multicast group belongs to a layer 2 network to which the terminal device belongs. The terminal device described. When the multicast server that transmits a packet addressed to the multicast group belongs to a second layer 2 network different from the first layer 2 network to which the terminal device belongs, the transmission means The terminal device according to claim 8, wherein the multicast address notification packet is transmitted to a gateway of a layer 2 network. In a communication method of a terminal device that transmits and receives packets based on a layer 2 protocol,
When the terminal device belongs to a multicast group, a packet is transmitted so that a multicast address notification packet that is a packet in which a multicast layer 2 address corresponding to the multicast group to which the terminal device belongs is set as a transmission source is transmitted at a predetermined timing. A communication method including a step of controlling the transmission of a message. In a program for causing a computer of a terminal device to execute a process of transmitting and receiving a packet based on a layer 2 protocol,
When the terminal device belongs to a multicast group, a packet is transmitted so that a multicast address notification packet that is a packet in which a multicast layer 2 address corresponding to the multicast group to which the terminal device belongs is set as a transmission source is transmitted at a predetermined timing. A program for executing processing including a step for controlling transmission of a message.

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