JP3999061B2 - Node device, terminal device, program, and recording medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for effectively using a communication band.
[0002]
[Prior art]
Conventionally, many communications performed on a communication network such as the Internet involve a personal computer (hereinafter referred to as “PC”) and a workstation (hereinafter referred to as “PC”) used by a data sender to transmit the data. WS ”) and other terminal devices such as PCs, mobile phones, and PDAs (Personal Digital Assistance) used by receivers of the data to receive the data (Hereinafter referred to as “reception device”) in a one-to-one communication mode (hereinafter, such communication mode is referred to as “unicast”). As another communication mode of this unicast, there is a communication mode in which a transmission device and a reception device perform one-to-many or many-to-many communication (hereinafter, this communication mode is referred to as “multicast”).
[0003]
As an example of multicast, IP multicast that realizes multicast using IP (Internet Protocol) widely used in the Internet or the like as a communication protocol in the network layer is widely known. In IP multicast, a multicast group is configured by assigning a multicast IP address to a group of receiving apparatuses that receive the same data. An IP address assigned to this multicast group is unique to the group. A receiving device that receives data to be multicast addressed to a multicast group first has a node device (for example, a router) that manages the communication network to which the receiving device belongs to a receiving device that belongs to the multicast group in the communication network. Information indicating that it exists is stored. That is, the receiving device first joins the multicast group. When the data transmitted from the transmitting device to the IP address of the multicast group is routed to the node device, the node device transmits the data to the receiving device participating in the multicast group under its own device. Multicast is realized by copying the required number of data and transmitting the data to each receiving device.
[0004]
When the transmitting apparatus actually transmits data, the transmitting apparatus divides the data into a plurality of data blocks (hereinafter referred to as “packets”) and transmits the data. Each of the plurality of packets includes data divided into data sizes in communication units (hereinafter referred to as “divided data”) and information indicating the destination of the packet (for example, the IP address of the receiving device). Has been. On the other hand, when the receiving device receives the plurality of packets, the receiving device acquires the divided data included in each of the plurality of packets, and assembles the plurality of divided data to transmit from the transmitting device. Get the data that has been done. When data is transmitted by multicast as described above, data is transmitted / received and copied in units of packets.
[0005]
The multicast described above can be realized not only in a wired communication network but also in a wireless communication network such as a wireless LAN (Local Area Network) defined by IEEE (Institute of Electrical and Electronic Engineers) 802.11b. In a wireless LAN, communication radio waves transmitted from a wireless access point device can be received by all the receiving devices connected to the wireless access point device. Therefore, when a packet addressed to a multicast group is transmitted from the wireless access point device. Therefore, the wireless access point device does not need to copy the packet by the number of receiving devices and transmit the packet, and multicast can be realized by transmitting one packet to the multicast group.
[0006]
As described above, when the same packet is transmitted to a plurality of receiving devices by multicast, the transmitting device need only transmit the packet once to the multicast group to which the plurality of receiving devices belong. The load on the transmission apparatus does not increase even if the number of the transmissions increases. In addition, since the transmission apparatus transmits only one packet to the node apparatus for one multicast group, the communication band necessary for transmission of the packet does not increase even if the number of reception apparatuses increases. On the other hand, when the same data is transmitted to a plurality of receiving apparatuses by unicast, the transmitting apparatus must transmit the same data for each receiving apparatus, and is proportional to the increase in the number of receiving apparatuses. As a result, the load on the transmission apparatus increases. Also, between the transmitting device and the node device, the number of packets transmitted by the transmitting device increases in proportion to the increase in the number of receiving devices, so it is necessary for packet transmission in proportion to the increase in the number of receiving devices. Wide communication bandwidth.
In summary, when the same packet is transmitted to a plurality of receiving devices, using multicast reduces the load on the transmitting device compared to using unicast, and can effectively use the communication band. There are advantages such as. In wireless LAN, wireless access point devices that transmit data addressed to a multicast group do not need to copy and transmit packets as many as the number of receiving devices participating in the multicast group. become.
[0007]
[Problems to be solved by the invention]
In the case of transmitting the same packet to a plurality of receiving apparatuses, unicast has been widely used in the past, although there are advantages to using multicast rather than using unicast. The reason for this is that the above-mentioned advantage of multicast is only for the data sender and the communication carrier managing the communication network, and that there is no advantage for the receiver to receive the multicast data. Can be mentioned. The following explains why there is no advantage to using multicast for the receiver.
[0008]
As described above, data transmitted from the transmission device is divided into a plurality of packets and transmitted to the reception device. In general, a flow of packets from a transmission device to a reception device in a communication network (hereinafter, a flow of packets having the same destination is referred to as a “communication flow”, and a destination of packets constituting the communication flow is referred to as a “communication flow destination”. ), A sufficient communication speed is not secured, and packets do not reach the receiving device (hereinafter referred to as “packet loss”). When such a packet loss occurs, the receiving device cannot correctly assemble the data transmitted from the transmitting device. In the case of unicast, even if a packet loss occurs, only one recipient is affected, but in the case of multicast, if a packet loss occurs, multiple recipients participating in the multicast group Will all be affected. Therefore, a communication flow whose destination is a multicast group in which a plurality of receiving devices participate (hereinafter referred to as “multicast communication flow”) is a communication flow whose destination is a single receiving device (hereinafter referred to as “unicast”). A wider communication bandwidth should be allocated.
[0009]
However, when a conventional node device allocates a communication band to a communication flow in a communication network managed by itself (hereinafter, such a communication network is referred to as a “local network”), the communication flow is a multicast communication flow. Regardless of whether it is a unicast communication flow or not, a communication band of the same width is allocated. For this reason, for the receiver, there is no difference between the case of receiving unicast data and the case of receiving multicast data, and there is no advantage of actively using multicast. Not only that, but the same bandwidth is allocated to the unicast communication flow and the multicast communication flow, so the packet loss occurs with the same probability in both the unicast communication flow and the multicast communication flow, and the There is a problem that the greater the number of participating recipients, the greater the number of recipients affected by this packet loss.
[0010]
To solve this problem, when a node device allocates a communication band to a multicast communication flow in the local network, the width is proportional to the number of receiving devices participating in the multicast group that is the destination of the multicast communication flow. It has been proposed to allocate a communication band.
[0011]
In order to allow a node device to assign a communication bandwidth of a width proportional to the number of receiving devices participating in each multicast group to each multicast communication flow, for example, the node device can be assigned within the local network. A maximum value (hereinafter referred to as “maximum communication band”) of the communication bandwidth is stored in advance, and the node device is caused to acquire the number of receiving devices participating in each multicast group in the local network, and It is assumed that a communication band obtained by dividing the maximum communication band by a width proportional to the number of receiving devices participating in each multicast group is assigned to each multicast communication flow. In an actual communication network, a plurality of small sub-networks are included in one local network, and node devices (hereinafter referred to as “lower-level node devices”) that manage the sub-networks are installed in each sub-network. It is often done. Even in such a network form, each lower node device acquires the number of receiving devices participating in the multicast group in the subnetwork, and notifies the upper node device of the acquired number of receiving devices, The upper node apparatus can acquire the number of receiving apparatuses participating in each multicast group, and can allocate a communication band having a width proportional to the number of receiving apparatuses participating in the multicast group to each multicast communication flow. it can. That is, a node device (hereinafter referred to as an “edge node device”) that is placed closest to the receiving device and directly manages the receiving device accurately obtains the number of receiving devices participating in each multicast group. If it is possible, it becomes possible to grasp the number of receiving apparatuses participating in each multicast group under the control of the own apparatus in all node apparatuses communicating with the transmitting apparatus.
[0012]
A multicast router is generally known as a node device having a special function for grasping that there is a receiving device participating in a multicast group in a local network. The multicast router realizes the above functions by performing an operation in conformity with IGMP (Internet Group Management Protocol) standardized by IETF (Internet Engineering Task Force). More specifically, the multicast router transmits an IGMP-Query to a receiving device in the local network. The receiving apparatus that has received the IGMP-Query waits for a random time and then transmits an IGMP-Report to the IP address of the multicast group to which the receiving apparatus participates. By receiving the IGMP-Report, the multicast router can know that there is at least one receiving device participating in the multicast group in the local network, and transmits a packet addressed to the multicast group to the local network. . The reason why the receiving apparatus waits for a random time is to prevent itself from transmitting an IGMP-Report when another receiving apparatus has already transmitted the IGMP-Report. Even if the number of receiving devices becomes very large by this mechanism, the number of IGMP-Reports can be suppressed. In this way, a multicast router that performs an operation compliant with IGMP can determine whether or not there is a receiving device participating in the multicast group in the local network, but the receiving device that is participating in each multicast group The number of can't be obtained accurately.
[0013]
ECMP (Express Count Management Protocol) has been proposed as a technique for causing a node device to acquire the number of receiving devices participating in the multicast group for each multicast group in the local network. A node device that performs an operation conforming to the ECMP periodically transmits an inquiry packet inquiring the number of receiving devices to the multicast group to which the device itself is transmitting a packet. When the receiving device participating in the multicast group receives this inquiry packet, the receiving device transmits a response packet notifying that it is participating in the multicast group to the node device. A node device that performs an operation conforming to the ECMP receives this response packet, and can count the number of received response packets to obtain the number of receiving devices participating in each multicast group. In ECMP, whether or not a receiving device participating in a multicast group is a legitimate receiving device by causing each receiving device to transmit a response packet with information indicating that it is a legitimate receiving device. It can also be determined whether or not.
[0014]
In the following, a flow of an operation in which a node device that performs an operation based on ECMP allocates a communication band having a width proportional to the number of receiving devices participating in a multicast group to each multicast communication flow will be described with reference to FIG. . The communication system shown in FIG. 1 includes transmission devices 10A, 10B, and 10C, the Internet 100, a node device 20, a network switch 30, wireless access point devices 40A and 40B, and reception devices 50A, 50B, 50C, and 50D. have. In the following description, when it is not necessary to distinguish each of the transmission devices 10A, 10B, and 10C, they are referred to as “transmission device 10”. Further, when it is not necessary to distinguish between the wireless access point devices 40A and 40B, they are described as “wireless access point device 40”. Further, when it is not necessary to distinguish each of the receiving devices 50A, 50B, 50C, and 50D, the receiving devices 50A, 50B, 50C, and 50D are referred to as “receiving device 50”.
[0015]
The transmission device 10 is connected to the Internet 100 and transmits a packet to a multicast group. More specifically, the transmitting apparatus 10A transmits a packet addressed to a multicast group (hereinafter, “multicast group 1”) to which the IP address 239.10.1.1 is assigned. In addition, the transmitting apparatus 10B transmits a packet addressed to a multicast group (hereinafter, “multicast group 2”) to which the IP address 239.1.1.2 is assigned. Further, the transmitting apparatus 10C transmits a packet addressed to a multicast group (hereinafter, “multicast group 3”) to which the IP address 239.10.1.3 is assigned.
[0016]
The network switch 30 includes a plurality of interfaces (hereinafter referred to as “communication ports”) for connecting the node device 20 and the wireless access point device 40, and each of the plurality of communication ports has a unique number (hereinafter referred to as “communication port”). , “Port number”). In the communication system shown in FIG. 1, a wireless access point device 40A is connected to a communication port assigned port number 1, and a wireless access point device 40B is connected to a communication port assigned port number 2. It is assumed that the node device 20 is connected to the communication port to which the port number 3 is assigned. When the destination of the packet received from the node device 20 is a multicast group, the network switch 30 transmits this packet to the wireless access point device 40A and generates one copy of this packet. It is transmitted to the point device 40B.
[0017]
The wireless access point device 40A is assigned an IP address 10.0.1.41 and the wireless access point device 40B is assigned an IP address 10.0.1.42. Each of the wireless access point device 40A and the wireless access point device 40B forms cells 200A and 200B having the same area, and is connected to the receiving device 50 in the cell to perform wireless communication. It is assumed that the maximum communication band in the cells 200A and 200B is 11 Mbps.
[0018]
The receiving device 50 is connected to the wireless access point device 40 for wireless communication. In the communication system shown in FIG. 1, the receiving devices 50A and 50B exist in the cell 200A and are connected to the wireless access point device 40A. On the other hand, it is assumed that receiving devices 50C and 50D exist in cell 200B and are connected to wireless access point device 40B. The receiving devices 50A and 50B are participating in the multicast group 1, the receiving device 50C is participating in the multicast group 2, and the receiving device 50D is participating in the multicast group 3.
[0019]
The node device 20 is a multicast router that performs an operation based on ECMP, and is connected to the Internet 100 and the network switch 30. The node device 20 stores the maximum communication bandwidth (11 Mbps) described above, and the maximum communication bandwidth and the reception devices participating in each multicast group acquired by performing an operation in conformity with the ECMP. A communication band is assigned to each multicast communication flow based on the number of units. Specifically, the node device 20 performs an operation conforming to the above-described ECMP, and acquires the number of receiving devices participating in each multicast group. In the communication system shown in FIG. 1, there are two receiving devices (receiving devices 50A and 50B) participating in multicast group 1, and the number of receiving devices participating in multicast group 2 and multicast group 3 is one. (Only the receiving device 50C participates in the multicast group 2 and only the receiving device 50D participates in the multicast group 3). Then, the node device 20 allocates a communication band in which the maximum communication band is distributed to each multicast communication flow at a ratio of the number of receiving devices participating in each multicast group. That is, the node device 20 allocates a communication band of 5.5 Mbps to the multicast communication flow addressed to the multicast group 1, and allocates a communication band of 2.75 Mbps to the multicast communication flows addressed to the multicast groups 2 and 3.
[0020]
As described above, when the node device 20 performs an operation conforming to ECMP, it becomes possible to allocate a communication band having a width proportional to the number of receiving devices participating in the multicast group to each multicast communication flow.
[0021]
However, in the communication system shown in FIG. 1, since both the wireless access point devices 40A and 40B transmit the packet transmitted from the network switch 30 as it is, the wireless access point device 40A is connected to its own device. Although the receiving device is not participating in the multicast groups 2 and 3, the packet is transmitted to each of the multicast groups 2 and 3 in the communication band of 2.75 Mbps. Even though the receiving device connected to the device does not participate in the multicast group 1, the packet addressed to the multicast group 1 is transmitted in the communication band of 5.5 Mbps. That is, the communication system shown in FIG. 1 has a problem that both the wireless access point devices 40A and 40B transmit useless packets.
[0022]
IGMP-Snooping is generally known as a technique for eliminating such useless packet transmission. The function of the network switch having the IGMP-Snooping function will be described below. The network switch having the IGMP-Snooping function monitors the presence / absence of reception of the IGMP-Report for each communication port, and determines the port number of the communication port that has received the IGMP-Report and the IP address of the multicast group that has transmitted the IGMP-Report. The correspondence is stored (hereinafter, this correspondence is referred to as “communication port information”). Based on this communication port information, such a network switch is configured not to transfer IGMP-Report other than the communication port to which the node device 20 is connected (communication port that has received IGMP-Query). By performing such an operation, the communication port in which the receiving device exists is recognized, and the packet addressed to the multicast group is transmitted only to the communication port to which the receiving device participating in the multicast group is connected. Packets addressed to the multicast group are not transmitted to a communication port that is not connected to a receiving device participating in.
[0023]
In the communication system shown in FIG. 1, it is conceivable to give the above-described IGMP-Snooping function to the network switch 30 so that each wireless access point device 40 does not transmit useless packets. When the IGMP-Snooping function is given to the network switch 30, the network switch 30 stores communication port information as shown in FIG. 2, and only the packets addressed to the multicast group 1 are stored in the wireless access point device 40A based on this communication port information. And only the packets addressed to the multicast groups 2 and 3 are transmitted to the wireless access point device 40B. As described above, by providing the network switch 30 with the IGMP-Snooping function, useless packets are not transmitted from the wireless access point devices 40A and 40B.
[0024]
However, since the maximum communication band in each cell 200 is 11 Mbps, the wireless access point device 40A transmits only the packet addressed to the multicast group 1 in the 5.5 Mbps communication band, so that it corresponds to 5.5 Mbps. Communication bandwidth is unused and free. Further, since the wireless access point device 40B transmits packets with a communication band of 2.75 Mbps (total of 5.5 Mbps) to each of the multicast groups 2 and 3, the communication band corresponding to 5.5 Mbps is still available. Unused and empty.
[0025]
That is, when the node device 20 that performs an operation conforming to ECMP and the network switch 30 having the IGMP-Snooping function are combined, useless packet transmission by the wireless access point devices 40A and 40B is eliminated. However, the communication band used for transmitting useless packets is not effectively used. In the end, even if an existing technology such as ECMP or IGMP-Snooping is used, a communication band cannot be allocated to a multicast communication flow without waste.
[0026]
The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a technique for allocating a communication band to a multicast communication flow without waste while ensuring the benefit of a receiver participating in a multicast group.
[0027]
[Means for Solving the Problems]
In order to solve the above-mentioned object, the present invention has a plurality of wireless access point devices that receive a data block containing destination information indicating a destination and wirelessly transmit it to a terminal device under the control, and receive the data block A network switch that transmits the data block only to a wireless access point device that has a destination terminal device indicated by the destination information of the data block among the plurality of wireless access point devices. A node device having the data block, and transmitting the data block to the network switch only when the destination indicated by the destination information of the data block is a terminal device subordinate to the plurality of wireless access point devices Means and the plurality of wireless access points Information indicating a wireless access point device subordinate to the terminal device and information indicating a multicast group to which the terminal device participates from terminal devices participating in the multicast group among terminal devices subordinate to the remote device. Based on the acquisition means to acquire and the information acquired by the acquisition means, Each wireless access point device The number of terminal devices participating in the multicast group For each wireless access point device Tally In each wireless access point device, the total of the terminal device Large number The data block addressed to the multicast group Data block Send And a control means for controlling the transmission means so as to communicate.
[0028]
In order to achieve the above object, the present invention provides a plurality of wireless access units connected to a network switch that receives a data block containing a destination transmitted from a node device and transmits the data block only to the destination. A terminal device that receives the data block transmitted wirelessly from the wireless access point device under the control of any one of the point devices determines whether the device is participating in a multicast group And only when participating in a multicast group, a wireless access point having information about the wireless access point device under its control and information indicating a multicast group with which the device is in control as a subordinate Transmitting means for transmitting to the node device via a device; and A communication band to be allocated to the transmission of the data block addressed to the multicast group to which the node device is participating in the own apparatus based on the information transmitted by the signal unit, The data block addressed to a multicast group with a large participation number of terminal devices under the control of a wireless access point device under its own device There is provided a terminal device comprising receiving means for receiving the data block transmitted in a wide communication band.
[0029]
In order to achieve the above object, the present invention has a plurality of wireless access point devices under the control of receiving a data block containing destination information indicating a destination and wirelessly transmitting it to a terminal device under the control. A network switch that transmits the data block only to a wireless access point device subordinate to a destination terminal device indicated by the destination information of the data block among the plurality of wireless access point devices. The data block is received by the subordinate computer device, and the data block is transmitted to the network switch only when the destination indicated by the destination information of the data block is a terminal device subordinate to the plurality of wireless access point devices. And a plurality of wireless access means From the terminal devices participating in the multicast group among the terminal devices subordinate to the point device, information indicating the wireless access point device subordinate to the terminal device and information indicating the multicast group in which the terminal device is participating Based on the acquisition means to acquire and the information acquired by the acquisition means, Each wireless access point device The number of terminal devices participating in the multicast group For each wireless access point device Tally In each wireless access point device, the total of the terminal device Large number The data block addressed to the multicast group Data block Send There are provided a program for realizing a control means for controlling the transmission means so as to communicate and a computer-readable recording medium on which the program is recorded.
[0030]
In order to achieve the above object, the present invention provides a plurality of wireless access units connected to a network switch that receives a data block containing a destination transmitted from a node device and transmits the data block only to the destination. Whether a computer device that receives the data block transmitted wirelessly from the wireless access point device under any one wireless access point of the point devices participates in a multicast group Only when the computer apparatus determines and participates in the multicast group, information indicating the wireless access point apparatus subordinate to the computer apparatus and information indicating the multicast group in which the computer apparatus participates are subordinate to the computer apparatus. Wireless access point Transmitting means for transmitting to the node device via the remote device, and communication assigned by the node device for transmission of the data block addressed to the multicast group to which the computer device participates based on the information transmitted by the transmitting device Bandwidth, A data block addressed to a multicast group with a large participation number of computer devices under the control of a wireless access point device under the control of the computer device. Provided are a program for realizing receiving means for receiving the data block transmitted in a wide communication band, and a computer-readable recording medium storing the program.
[0031]
When such a node device, terminal device, program, and recording medium are used, when a data block addressed to the multicast group is transmitted from the node device to the network switch, each wireless access point device participates in each multicast group. As the number of terminal devices is larger, a wider communication band is allocated and transmitted.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments according to the present invention will be described below with reference to the drawings.
(1) Overall configuration
FIG. 3 is a diagram showing an example of the overall configuration of a communication system having a node device and a terminal device according to the present invention. As shown in this figure, the overall configuration of this communication system is different from the communication system shown in FIG. 1 in that a node device 60 is provided instead of the node device 20 and the receiving devices 50A, 50B, and 50C. And 50D instead of receiving devices 70A, 70B, 70C and 70D. In addition, when it is not necessary to distinguish each of the receiving devices 70A, 70B, 70C, and 70D, it is expressed as “receiving device 70”.
[0033]
The receiving device 70 is different from the receiving device 50 in that the IP address of the wireless access point device 40 to which the own device is connected in response to a request from the node device 60 and the IP of the multicast group to which the own device participates. The connection information including the address is transmitted to the node device 60. An example of connection information when the receiving device 70 is connected to the wireless access point device 40A and participates in the multicast group 1 is shown in FIG.
[0034]
The node device 60 is different from the node device 20 in that a bandwidth management table (to be described later) is stored instead of the maximum communication bandwidth of a cell formed by the wireless access point device 40, and each wireless access point device 40 A point of requesting transmission of connection information to the reception device 70 connected to the network, and a point of updating the storage content of the bandwidth management table described above based on the content of the connection information transmitted from each of the reception devices 70 The communication bandwidth is allocated to each multicast communication flow based on the stored contents of the bandwidth management table. An example of the bandwidth management table is shown in FIG. As shown in FIG. 5, the bandwidth management table includes the IP address of each wireless access point device 40, the maximum communication bandwidth of the cell 200 formed by the wireless access point device 40, and the wireless access point device 40 transmitting a packet. This table stores the IP address of a multicast group, the number of receiving devices participating in the multicast group, and the value of the communication band assigned to the communication flow addressed to the multicast group in association with each other.
[0035]
(2) Configuration of the node device 60
FIG. 6 is a block diagram illustrating a configuration example of the node device 60. As shown in this figure, the node device 60 includes a first communication interface unit (hereinafter referred to as “first communication IF unit”) 61, a second communication IF unit 62, a routing control unit 63, and information holding. Section 64, queue control section 65, and bandwidth control section 66.
[0036]
The first communication IF unit 61 receives a packet transmitted from the transmission device 10 via the Internet 100, passes this packet to the routing control unit 63, and transmits the packet passed from the routing control unit 63 to the Internet. It has a function. The second communication IF unit 62 has a function of receiving the packet transmitted from the network switch 30, passing the packet to the routing control unit 63, and transmitting the packet passed from the routing control unit 63 to the network switch 30. is doing. The first communication IF unit 61 performs an operation according to a multicast protocol such as PIM-SM (Protocol Independent Multicast-Sparse Mode) or DVMRP (Distance Vector Multicast Routing Protocol), and the second communication IF unit 62 The first communication IF unit 61 and the second communication IF unit 62 that perform operations in accordance with IGMP perform such operations, whereby a multicast communication flow path from the transmission device 10 to the reception device 70 Is established.
[0037]
The routing control unit 63 determines whether to transmit the packet to the local network or the Internet based on the destination of the packet passed from the first communication IF unit 61 or the second communication IF unit 62, and to the local network. If it is determined that the packet is to be transmitted, the packet is transferred to the second communication IF unit 62. Conversely, if the packet is determined to be transmitted to the Internet, the packet is transferred to the first communication IF unit 61. .
[0038]
The information holding unit 64 is a storage device that stores information such as a hard disk in a nonvolatile manner, and stores the above-described bandwidth management table (see FIG. 5).
[0039]
The queue control unit 65 causes the second communication IF unit 62 to send packets addressed to the multicast group in the communication band stored in the band management table (see FIG. 5) in association with the IP address of the multicast group. It has a function to control.
[0040]
The bandwidth control unit 66 has a function of periodically updating the storage contents of the bandwidth management table described above. As will be described in detail later, the bandwidth control unit 66 has a timekeeping function for acquiring the current time, and only when the current time acquired by this timekeeping function matches a predetermined time, A message requesting transmission is generated, and this message is transmitted to all the receiving devices 70 via the second communication IF unit 62. Then, the bandwidth control unit 66 receives the connection information transmitted from each receiving device 70 via the second communication IF unit 62, and updates the storage content of the bandwidth management table described above based on the content of the received connection information. To do.
[0041]
(3) Example of operation
In the communication system shown in FIG. 3, the operation of the node device 60 assigning a communication band to each multicast communication flow will be described with reference to FIG.
[0042]
(3-1) Operation example 1
First, as a premise of this operation example, it is assumed that the receiving devices 70A and 70B are in the cell 200A, are connected to the wireless access point device 40A, and participate in the multicast group 1. In addition, it is assumed that the receiving devices 70C and 70D are in the cell 200B and are connected to the wireless access point device 40B. It is assumed that the receiving device 70C participates in the multicast group 2 and the receiving device 70D participates in the multicast group 3. The information holding unit 64 of the node device 60 stores the bandwidth management table shown in FIG. 5. As shown in FIG. 5, the communication flow addressed to the multicast group 1 has a communication bandwidth of 5.5 Mbps. It is assumed that a communication band of 2.75 Mbps is assigned to the communication flows addressed to multicast groups 2 and 3.
[0043]
FIG. 7 is a flowchart showing the flow of bandwidth allocation processing executed by the bandwidth controller 66 of the node device 60. As shown in this figure, the band control unit 66 first obtains the current time using a time measuring function (step SA1), and determines whether or not the current time matches a predetermined time ( Step SA2). If the bandwidth control unit 66 determines that the current time does not match the predetermined time, the band control unit 66 repeatedly executes the processes after step SA1, and conversely, if the current time matches the predetermined time. If it is determined, the processes after step SA3 are performed. In this operation example, a case will be described in which the current time acquired by the bandwidth control unit 66 matches a predetermined time.
[0044]
In step SA3, the bandwidth control unit 66 generates a request message for requesting transmission of connection information, and transmits this request message to the IP address 224.0.0.1. This IP address 224.0.0.1 is a special IP address that means that all receiving devices in the local network are destinations. Then, the bandwidth control unit 66 that has completed the transmission of the request message assigns the IP address of the multicast group stored in the bandwidth management table, the number of receiving devices participating in the multicast group, and each multicast group. The communication band is deleted and the band management table is initialized (step SA4).
[0045]
The request message transmitted from the node device 60 reaches the network switch 30 via the communication line. Upon receiving this request message, the network switch 30 transmits the request message to the wireless access point device 40A, generates one copy of the request message, and transmits the copy to the wireless access point device 40B.
[0046]
The two request messages transmitted from the network switch 30 reach the wireless access point devices 40A and 40B via individual communication lines. When this request message is received, each of the wireless access point devices 40A and 40B transmits this request message to a cell formed by the wireless access point device 40A and 40B.
[0047]
The request message sent to the cells 200A and 200B is received by the receiving device 70 connected to each wireless access point device 40 in each cell 200. Receiving device 70 that has received this request message reads the connection information stored in its own device, and transmits a response message including this connection information to node device 60. The response message transmitted from each receiving device 70 reaches the node device 60 via the wireless access point device 40 and the network switch 30 to which each receiving device 70 is connected in order.
[0048]
The bandwidth control unit 66 of the node device 60 receives the response message transmitted from each receiving device 70 via the second communication IF unit 62, and acquires connection information included in each response message (step SA5). . Then, the bandwidth control unit 66 updates the storage contents of the bandwidth management table stored in the information holding unit 64 based on the connection information (step SA6).
[0049]
More specifically, in this operation example, the bandwidth control unit 66 acquires a total of four pieces of connection information transmitted from each of the receiving devices 70A, 70B, 70C, and 70D. The bandwidth control unit 66 first classifies these four pieces of connection information according to the IP address of the wireless access point device 40 included in each connection information, and further includes the IP address of the same wireless access point device 40. Connection information is classified according to the IP address of the multicast group included in each connection information. In this operation example, the four connection information transmitted from each receiving device 70 is classified into the following three groups. The first group is a group of connection information including the IP address of the wireless access point device 40A and the IP address of the multicast group 1, and the connection information acquired from the receiving devices 70A and 70B belongs to this group. Yes. The second group is a group of connection information including the IP address of the wireless access point device 40B and the IP address of the multicast group 2, and the connection information acquired from the receiving device 70C belongs to this group. The third group is a group of connection information including the IP address of the wireless access point device 40B and the IP address of the multicast group 3, and the connection information acquired from the receiving device 70D belongs to this group. Then, the bandwidth control unit 66 associates the IP address of the wireless access point device 40 included in the connection information belonging to each group, the IP address of the multicast group, and the number of connection information belonging to each group. Store in the bandwidth management table.
[0050]
Next, the bandwidth control unit 66 sets the maximum communication bandwidth associated with each wireless access point device 40, the number of multicast groups to which the wireless access point device 40 is transmitting packets, and the wireless access point device 40. The communication band to be allocated to the communication flow addressed to each multicast group is determined based on the number of receiving apparatuses 70 connected to the multicast group and participating in each multicast group, and this communication band is stored in the band management table. Specifically, since the wireless access point device 40A transmits only the packet addressed to the multicast group 1 to the cell 200A, the bandwidth control unit 66 assigns 11 Mbps, which is the maximum communication bandwidth in the cell 200A, to the multicast group 1. In addition, since the wireless access point device 40B transmits packets to the multicast groups 2 and 3, and there is one receiving device participating in the multicast groups 2 and 3, the bandwidth control unit 66 in the cell 200B A communication band obtained by distributing the maximum communication band of 11 Mbps at a ratio of 1: 1 is assigned to multicast groups 2 and 3.
[0051]
As described above, when the bandwidth control unit 66 updates the storage content of the bandwidth management table based on the connection information acquired from the receiving device 70, the storage content of the bandwidth management table becomes the state shown in FIG. Thereafter, the queue control unit 65 of the node device 60 sends the packet addressed to each multicast group in the communication band stored in the band management table (see FIG. 8) in association with the IP address of the multicast group. By controlling the two-communication IF unit 62, a communication band of 11 Mbps is allocated to the communication flow addressed to the multicast group 1, and the communication flow addressed to the multicast group 2 and the communication flow addressed to the multicast group 3 are both 5.5 Mbps. A communication band is allocated.
[0052]
(3-2) Operation example 2
Next, a bandwidth management table shown in FIG. 8 is stored in the information holding unit 64 of the node device 60. As shown in this figure, a communication bandwidth of 11 Mbps is assigned to the communication flow addressed to the multicast group 1. It is assumed that a communication band of 5.5 Mbps is assigned to the communication flows addressed to the multicast groups 2 and 3. Also, the receiving devices 70A and 70B are connected to the wireless access point device 40A and participate in the multicast group 1, the receiving devices 70C and 70D are connected to the wireless access point device 40B, and the receiving device 70C is in the multicast group 2. It is assumed that the receiver 70D is participating in the multicast group 3. Under such circumstances, only the receiving device 70B cancels the connection with the wireless access point device 40A, moves from the cell 200A to the cell 200B, connects to the wireless access point device 40B, and joins the multicast group 2. The operation will be described.
[0053]
Only when the current time acquired by the node device 60 using the time counting function matches a predetermined time, a request message for requesting transmission of connection information to the own device is transmitted to the receiving device 70, The operation of the node device 60 until the bandwidth management table is initialized is the same as the operation of Step SA1 to Step SA4 of the node device 60 in Operation Example 1 described above. Further, the operation of each device of the network switch 30, the wireless access point device 40, and the receiving device 70 until the response message to the request message reaches the node device 60 is the same as the operation of each device in the operation example 1. . Further, the bandwidth control unit 66 of the node device 60 acquires the connection information transmitted from each receiving device 70, and updates the storage content of the bandwidth management table stored in the information holding unit 64 based on the connection information. The operation is the same as the operation of step SA5 and step SA6 of the node device 60 in the operation example 1 described above.
[0054]
However, since the content of the connection information received from each receiving device 70 is different from the content of the connection information in the operation example 1, the storage content of the bandwidth management table is updated with the storage content different from that in the operation example 1. Specifically, since the wireless access point device 40A transmits only the packet addressed to the multicast group 1 to the cell 200A, the bandwidth control unit 66 transmits the maximum communication bandwidth of 11 Mbps in the cell 200A to the multicast group 1. Assign to. Further, the wireless access point device 40B transmits packets to the multicast groups 2 and 3, and there are two receiving devices (receiving devices 70B and 70C) participating in the multicast group 2, and participating in the multicast group 3. Since there is one receiving device (receiving device 70D), a communication band obtained by distributing 11 Mbps, which is the maximum communication band in the cell 200B, at a ratio of 2: 1 is allocated to the multicast groups 2 and 3. That is, the bandwidth control unit 66 allocates a communication band of 7.3 Mbps to the multicast group 2 and allocates a communication band of 3.7 Mbps to the multicast group 3.
[0055]
As described above, when the bandwidth control unit 66 updates the storage content of the bandwidth management table based on the connection information acquired from the receiving device 70, the storage content of the bandwidth management table becomes the state shown in FIG. Thereafter, the queue control unit 65 of the node device 60 sends the packet addressed to each multicast group in the communication band stored in the bandwidth management table (see FIG. 9) in association with the IP address of the multicast group. By controlling the two-communication IF unit 62, the communication flow addressed to the multicast group 1 is assigned a communication bandwidth of 11 Mbps, and the communication flow addressed to the multicast group 2 is assigned a communication bandwidth of 7.3 Mbps. The communication flow addressed to group 3 is assigned a communication band of 3.7 Mbps.
[0056]
(4) Modification
(4-1) Modification 1
In the above-described embodiment, the case where a packet is used as an example of a data block has been described. However, the data block transmitted and received by the node device according to the present invention is not limited to a packet, and may be a frame. In short, it may be a data block including divided data obtained by dividing data by the data size of the communication unit and information indicating the destination of the data.
[0057]
(4-2) Modification 2
Although the IP multicast has been described as an example of the multicast in the above-described embodiment, the multicast to which the node device according to the present invention allocates the communication band is not limited to the IP multicast. For example, it may be a multicast realized in a protocol layer lower than the network layer. Specifically, multicast using a MAC address which is a communication address in the data link layer may be used.
[0058]
(4-3) Modification 3
In the above-described embodiment, the case where the node device 60 controls the allocation of the communication band in the wireless LAN has been described. However, the network in which the node device according to the present invention controls the allocation of the communication band is limited to the wireless LAN. Instead, it may be a mobile packet communication network. The means for realizing multicast in the mobile packet communication network is realized by setting a packet transmission destination to a specific destination indicating a multicast group.
[0059]
(4-4) Modification 4
In the above-described embodiment, the node device 60 has been described with respect to the case where the communication band is allocated in the cell 200 formed by the wireless access point device 40 directly connected to the network switch 30 connected to the own device. The wireless access point device 40 that forms a cell in which the node device 60 manages the communication band may not be directly connected to the network switch 30. For example, a wireless access point device that forms a cell in which the node device 60 manages a communication band is a wireless access point device connected to a plurality of network switches connected to the network switch 30 connected to the node device 60 It may be.
[0060]
(4-5) Modification 5
In the above-described embodiment, the case where the bandwidth control unit 66 of the node device 60 has a timekeeping function and it is determined whether or not a certain time has elapsed using this timekeeping function has been described. Separately, a timer unit having a timer function may be provided. Specifically, it is determined whether or not a certain amount of time has elapsed in this timing unit, and only when it is determined that a certain amount of time has elapsed, a certain amount of time has passed from the timing unit to the bandwidth control unit 66. Notify me. Upon receiving this notification, the bandwidth control unit 66 may perform the processing after step SA3 of the bandwidth control processing described above.
[0061]
(4-6) Modification 6
In the above-described embodiment, the case where the bandwidth control unit 66 of the node device 60 initializes the bandwidth management table after transmitting a request message to all the receiving devices 70 under its own device has been described. The bandwidth management table may be initialized immediately before the unit 66 updates the storage contents of the bandwidth management table. Also, a work table having the same table format as the bandwidth management table is provided, and in this work table, the number of receiving devices for each wireless access point device and each multicast group calculated based on the connection information acquired from each receiving device 70 And the communication band assigned to each multicast group may be stored, and the stored contents of the work table may be overwritten on the band management table.
[0062]
(4-7) Modification 7
In the above-described embodiment, the node device 60 stores the maximum communication band in the cell formed by each wireless access point device 40 in association with the IP address of the wireless access point device 40 that forms the cell. Although a case has been described in which a communication band divided by a width proportional to the number of receiving devices participating in each multicast group is assigned to each multicast communication flow, the node device 60 stores the maximum communication band. It does not have to be. For example, the greater the number of receiving devices participating in each multicast group for each wireless access point device calculated based on the connection information acquired from each receiving device 70, the more the node device 60 becomes a queue control unit within a unit time. 65 may be used to increase the amount of packets sent to each multicast group.
[0063]
(4-8) Modification 8
In the embodiment described above, the number of receiving devices participating in each multicast group for each wireless access point device calculated based on the connection information acquired from each receiving device 70 and the width of the communication bandwidth allocated to each multicast group However, the relationship between the number of receiving devices participating in each multicast group for each wireless access point device and the width of the communication bandwidth allocated to the multicast group is not limited to proportional. For example, the bandwidth of the communication band allocated to each multicast group may be proportional to the square of the number of receiving devices participating in each multicast group for each wireless access point device. You may make it proportional to a logarithm (for example, common logarithm). The point is that the larger the number of the receiving devices, the wider the communication band may be assigned to the multicast group.
[0064]
(4-9) Modification 9
In the embodiment described above, only the case where the node device 60 assigns the communication band to the multicast communication flow has been described. However, the node device 60 may assign the communication band to both the multicast communication flow and the unicast communication flow. Of course you can. Specifically, by regarding the unicast communication flow as a multicast communication flow addressed to a multicast group in which only one receiving device participates, the node device 60 can perform both the multicast communication flow and the unicast communication flow. A wider communication band can be allocated as the number of receiving devices that receive each communication flow for each wireless access point device increases.
[0065]
(4-10) Modification 10
In the above-described embodiment, the node device 60 acquires connection information including the IP address of the wireless access point device 40 connected from each receiving device 70 and the IP address of the participating multicast group, and In the above description, the storage contents of the bandwidth management table stored in the device are updated based on this connection information, and the communication bandwidth is assigned to each multicast communication flow. You may have the authentication function which judges sex.
[0066]
Specifically, information indicating the validity of the own device (for example, an electronic certificate issued by a trusted certificate authority) is stored in advance in the receiving device 70, and the receiving device 70 transmits connection information to the node device 60. When this is done, this electronic certificate is also sent. The node device 60 can determine the validity of the receiving device 70 by determining the presence or absence of the electronic certificate.
[0067]
In this way, by making the node device 60 determine the validity of each receiving device 70, the connection information is transmitted many times by impersonating another device, and whether many receiving devices 70 participate in the same multicast group. Thus, it is possible to prevent an illegal act such as causing the node device 60 to allocate a large communication band.
[0068]
(4-11) Modification 11
In the above-described embodiment, the node device 60 periodically requests that all the receiving devices 70 managed by the node device 60 transmit connection information, and the connection information transmitted from each receiving device 70 in response to this request. However, the mode in which the node device 60 acquires the connection information from each receiving device 70 is not limited to such a mode. For example, the receiving device 70 periodically transmits the connection information. The node device 60 may receive and acquire the connection information, and the node device 60 acquires the connection information when the receiving device 70 notifies the node device 60 of participation in the multicast group. There may be.
[0069]
First, a mode in which the node device 60 receives and acquires connection information periodically transmitted by the receiving device 70 will be described in detail. When the receiving device 70 is provided with a time measuring function for acquiring the current time, and the current time acquired by the time measuring function matches a predetermined time, the receiving device 70 displays the connection information stored in the own device. This aspect is realized by transmitting to the node device 60 and receiving and acquiring the connection information by the node device 60.
[0070]
Next, an aspect in which the node device 60 acquires connection information when the receiving device 70 notifies the node device 60 of participation in the multicast group will be specifically described. When the receiving device 70 notifies the node device 60 of participation in the multicast group, the receiving device 70 sets the connection information including the IP address of the participating multicast group and the IP address of the connected wireless access point device to the node. This aspect is realized by transmitting to the device 60 and receiving and acquiring the connection information by the node device 60.
[0071]
(4-12) Modification 12
In the above-described embodiment, the case where a multicast router is used as an example of the node device 60 according to the present invention has been described. However, for realizing a function of the node device according to the present invention in a general computer device such as a PC or WS. By executing the program, the same functions as those of the multicast router described above may be added to these computer devices.
[0072]
Specifically, a program for realizing the function of the node device according to the present invention is recorded on a computer-readable recording medium such as a CD-ROM (Compact Disk-Read Only Memory) or FD (Floppy Disk). In addition, a program recorded on the recording medium is read by a computer device equipped with a device (for example, a CD-ROM drive or an FD drive) that can read the information recorded on the recording medium. This is realized by causing the CPU (Central Processing Unit) of the computer apparatus to execute the read program.
[0073]
In addition, by causing a general computer device such as a mobile phone, PDA, or PC to execute a program for realizing the function of the terminal device according to the present invention, these computer devices have the same functions as the receiving device 70 described above. May be added.
[0074]
Specifically, it is possible to record a program for realizing the function of the terminal device according to the present invention on a computer-readable recording medium and read information recorded on such a recording medium. This is realized by causing a computer device provided with a device (for example, a CD-ROM drive or an FD drive) to read a program recorded on the recording medium and causing the CPU of the computer device to execute the read program.
[0075]
【The invention's effect】
According to the present invention, the width of the communication band allocated to the multicast communication flow becomes wider as the number of receiving devices participating in the multicast group that is the destination of the multicast communication flow increases. In a multicast communication flow addressed to a multicast group with a large number of packets, packet loss is less likely to occur, and the benefit of a receiver receiving multicast data is ensured.
[0076]
In addition, according to the present invention, a receiving device that participates in a multicast group in which the wireless access point device transmits data has a communication band that can be used when data is transmitted from the wireless access point device to each multicast group. Since the communication bandwidth divided by the width corresponding to the number of the communication bandwidths is assigned, it is possible to assign the communication bandwidth to each multicast communication flow without waste.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an example of the overall configuration of a communication system having a conventional node device 20. FIG.
2 is a diagram showing an example of communication port information stored in the network switch 30. FIG.
FIG. 3 is a block diagram showing an example of the overall configuration of a communication system having a node device 60 and a receiving device 70 according to the present invention.
FIG. 4 is a diagram showing an example of connection information stored in a receiving device 70 configuring the system.
FIG. 5 is a diagram showing an example of storage contents of a bandwidth management table stored in the node device 60;
6 is a diagram showing a configuration example of the node device 60. FIG.
7 is a flowchart showing a flow of bandwidth allocation processing executed by the node device 60. FIG.
8 is a diagram showing an example of storage contents of a bandwidth management table stored in the node device 60. FIG.
FIG. 9 is a diagram showing an example of storage contents of a bandwidth management table stored in the node device 60;
[Explanation of symbols]
10A, 10B, 10C ... transmission device, 20, 60 ... node device, 30 ... network switch, 40A, 40B ... wireless access point device, 50A, 50B, 50C, 50D, 70A, 70B, 70C, 70D ... receiving device, 61 ... 1st communication IF part, 62 ... 2nd communication IF part, 63 ... Routing control part, 64 ... Information holding part, 65 ... Queue control part, 66 ... Band control part, 100 ... Internet, 200A, 200B ... Cell.

Claims (10)

A network switch that receives a data block that includes a plurality of wireless access point devices that receive a data block including destination information indicating a destination and wirelessly transmit the data block to a subordinate terminal device, the plurality of wireless access point devices, In a node device subordinate to a network switch that transmits the data block only to a wireless access point device subordinate to a destination terminal device indicated by the destination information of the data block among the access point devices,
Transmitting means for receiving the data block and transmitting the data block to the network switch only when the destination indicated by the destination information of the data block is a terminal device under the plurality of wireless access point devices;
Among the terminal devices subordinate to the plurality of wireless access point devices, from the terminal devices participating in the multicast group, information indicating the wireless access point device subordinate to the terminal device and the multicast group in which the terminal device is participating Acquisition means for acquiring information indicating
Based on the information acquired by the acquisition means, the number of terminal devices participating in each multicast group under the control of each wireless access point device is counted for each wireless access point device, and each wireless access point device , nodes; and a control means for controlling the transmission means so as to send the data block in a broad communication band as is the data block addressed to the multicast group number is large aggregate the said terminal apparatus. Storage means for storing information that uniquely identifies each of the plurality of wireless access point devices and the maximum communication bandwidth of the wireless access point device identified by the information in association with each other;
The control means totals the number of terminal devices participating in each multicast group for each wireless access point device, assigns a wider communication band as the number increases, and the sum of the communication bands corresponds to the wireless access point device. The node device according to claim 1, wherein the transmission unit is controlled so as not to exceed a maximum communication band stored in the storage unit. A timekeeping means for obtaining the current time;
Only when the current time obtained by the time measuring means is a predetermined time, the terminal device is connected to a terminal device participating in a multicast group among terminal devices under the plurality of wireless access point devices. Request means for requesting transmission of information indicating a wireless access point device under control and information indicating a multicast group in which the terminal device is participating, to the own device;
Further comprising
The node device according to claim 1, wherein the obtaining unit receives and obtains information transmitted from a terminal device that has requested transmission of information by the requesting unit. The acquisition means includes
A terminal device provided with a time measuring means for acquiring the current time, and having the terminal device periodically transmitted from the terminal devices participating in the multicast group under the plurality of wireless access point devices The node device according to claim 1, wherein the node device receives and acquires information indicating a wireless access point device and information indicating a multicast group in which the terminal device participates. The acquisition means includes
Receive and obtain information indicating a wireless access point device under the control of a terminal device transmitted from a terminal device instructed to join a multicast group and information indicating a multicast group instructed to join by the user The node device according to claim 1, wherein: Determining means for determining whether or not the terminal device that has transmitted the information indicating the wireless access point device having the own device and the information indicating the multicast group in which the own device participates is a valid terminal device Prepared,
The node device according to claim 1, wherein the acquisition unit receives and acquires only information transmitted from a terminal device determined to be a legitimate terminal device by the determination unit. A subordinate of one of the plurality of wireless access point devices connected to the network switch that receives the data block containing the destination transmitted from the node device and transmits the data block only to the destination In the terminal device that receives the data block transmitted wirelessly from the wireless access point device,
It is determined whether or not the own device is participating in the multicast group, and only when the own device is participating in the multicast group, information indicating the wireless access point device that owns the own device and the multicast group in which the own device is participating Transmitting means for transmitting the information indicating to the node device via a wireless access point device under its control,
A communication band that is allocated to transmission of the data block addressed to a multicast group in which the node device participates based on information transmitted by the transmission unit, and is a wireless access point device under its own device And a receiving unit configured to receive the data block transmitted in a wider communication band as the data block is addressed to a multicast group having a larger participation number of the terminal device. A network switch that receives a data block that includes a plurality of wireless access point devices that receive a data block including destination information indicating a destination and wirelessly transmit the data block to a subordinate terminal device, the plurality of wireless access point devices, To a computer device subordinate to a network switch that transmits the data block only to a wireless access point device subordinate to a destination terminal device indicated by the destination information of the data block among the access point devices,
Transmitting means for receiving the data block and transmitting the data block to the network switch only when the destination indicated by the destination information of the data block is a terminal device under the plurality of wireless access point devices;
Among the terminal devices subordinate to the plurality of wireless access point devices, from the terminal devices participating in the multicast group, information indicating the wireless access point device subordinate to the terminal device and the multicast group in which the terminal device is participating Acquisition means for acquiring information indicating
Based on the information acquired by the acquisition means, the number of terminal devices participating in each multicast group under the control of each wireless access point device is counted for each wireless access point device, and each wireless access point device a program for implementing a control means for controlling said transmission means to send the data block in a broad communication band as is the data block addressed to the multicast group number is large aggregate the said terminal device. A subordinate of one of the plurality of wireless access point devices connected to the network switch that receives the data block containing the destination transmitted from the node device and transmits the data block only to the destination In the computer device that receives the data block transmitted wirelessly from the wireless access point device,
It is determined whether or not the computer device is participating in the multicast group. Only when the computer device is participating in the multicast group, information indicating the wireless access point device under the computer device and the computer device are participating. Transmitting means for transmitting information indicating a multicast group to the node device via a wireless access point device under the control of the computer device;
A wireless access point which is a communication band assigned to transmission of the data block addressed to the multicast group in which the computer device participates based on the information transmitted by the transmission means and which has the computer device under control A program for realizing, under the device, a receiving means for receiving the data block transmitted in a wider communication band as the data block is addressed to the multicast group having a larger participation number of computer devices .   A computer-readable recording medium on which the program according to claim 8 is recorded.

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