JP6042205B2 - Distribution system - Google Patents

Description

  The present invention relates to a distribution system that transmits data from a distribution device to a reception device via a network.

  As a method for distributing the same file to a plurality of receiving apparatuses, there are multicast by UDP (User Datagram Protocol) and unicast by TCP (Transmission Control Protocol).

  In the case of unicast, the timing of downloading a file depends on the receiving device side, and a TCP session is individually established and distributed between the distributing device and the receiving device. Since it is based on TCP, there is no worry of losing a part of the file, and the receiving apparatus can receive the entire file.

  In general, a large amount of access is concentrated immediately after a new file is registered in the distribution apparatus. After a while, the number of accesses decreases rapidly. In the case of a distribution system that uses only unicast, no matter how low the load during normal times is, the distribution apparatus side needs to be designed to withstand the number of sessions at the peak, leading to an increase in construction cost.

  On the other hand, in the case of multicast, since the same data is simultaneously transmitted to a plurality of receiving devices, it is possible to reduce the load on the distribution device, but a receiving device whose reception timing is shifted cannot receive the entire file. . In addition, since the multicast communication protocol is UDP, it is not reliable and a part of the file may be lost. If the file to be delivered can accept incomplete reception, such as a video file or audio file, it is possible to allow some loss, but if the file requires complete reception, such as firmware, some loss is A distribution system that is not allowed and uses only multicast is not suitable.

  In recent years, a distribution system that combines multicast and unicast has been proposed in order to reduce the load on the distribution device and complement data that could not be received by multicast. In this type of distribution system, the distribution device basically distributes the file by multicast, and the reception device supplements the data that could not be received by multicast by unicast, and obtains the data obtained by multicast and unicast. A file can be restored using the data (for example, Patent Documents 1 to 3).

JP 2011-130277 A JP 2004-135239 A JP 2009-170985 A

  However, in this type of distribution system, the download start timing by multicast cannot be made consistent among the receiving apparatuses. This is because the timing of the file distribution request differs between the receiving devices or depends on the communication status between the distributing device and the receiving device. Further, when depending on the state of the internal timer of the receiving device such as downloading of firmware, there is a difference in the state of the internal timer between the receiving devices, which also causes a mismatch.

  As in Patent Document 3, if a receiving device that participates in the middle of multicasting is a system that complements data that has already been transmitted by halfway participation after the end of the multicasting of the participating times, a large amount of unicast data compensation occurs. However, there is a possibility of increasing the resources required for the distribution apparatus.

  Therefore, the problem to be solved by the present invention is to suppress unicast data supplementation while suppressing the peak load of the distribution device by multicast when distributing files in a system that combines multicast and unicast. .

The present invention that solves the above-described problem is a receiving apparatus in which the distribution apparatus includes a multicast distribution unit that is responsible for data transmission by multicast and a unicast distribution unit that is responsible for data transmission by unicast, and participates in the multicast However, it is premised on a distribution system that uses unicast to supplement unreceived file parts by multicast.
When the receiving device confirms the reception of all the files, the receiving device transmits a reception completion notification to the distribution device. Also, when participating in a multicast, the next multicast complement takes priority over the unicast complement.
The distribution apparatus monitors the number of distribution destinations: n, and updates the value of n when a new file distribution request or the reception completion notification is received. When a new file distribution request is received, the updated value of n is compared with the specified value: N. When n <N in the comparison, the receiving apparatus of the new distribution destination is instructed to receive by unicast. When n ≧ N in the comparison, the receiving apparatus of the new distribution destination is instructed to receive by multicast, and all the instructed unicasts are canceled. Instructing all of the receiving devices to be canceled by multicast reception. Multicast file transmission is repeated while the receiving device requiring multicast is present.
The receiving device to be canceled uses data received before the cancellation for file restoration in preference to complementing by unicast.
Here, the number of distribution destinations: n refers to the total number of receiving apparatuses that have responded to a file distribution request for the same distribution file and have not received a reception completion notification. The specified value: N is a threshold value. n and N are respectively held in the memory of the distribution apparatus. The administrator of the distribution apparatus can input N to the distribution apparatus in advance so that the peak load of the distribution apparatus does not become a problem, and can start receiving a new file.

According to the present invention, the number of distribution destinations: n can be grasped on the distribution apparatus side by a new file distribution request and reception completion notification from the reception apparatus. When n <N when there is no concern about the peak load, the distribution apparatus instructs the new distribution destination to receive data by unicast, and file reception without packet loss proceeds at this distribution destination. When n = N is satisfied while file distribution is being executed only by unicast, the distribution apparatus cancels all of the previously specified unicast file distribution (unicast sessions for up to N-1 units). After that, as long as n ≧ N is satisfied, a new distribution destination is instructed to receive by multicast. Therefore, even if the number of distribution destinations increases from N, new unicast file transmission occurs. There is no. Thereby, before the peak load of the unicast delivery part of a delivery apparatus becomes a problem, a peak load can be suppressed by multicast.
In addition, if all receiving devices that have been canceled and new receiving device satisfying n ≧ N participate in the middle of the multicast, the next multicast complement takes precedence over the unicast complement. The distribution device repeats multicast file transmission while there is a receiving device that requires multicast. Therefore, the receiving apparatus that has joined the multicast in the middle first tries to complement the next multicast, and still complements only the unreceived file part by unicast. Thereby, under the situation where the peak load is suppressed by multicast, it is possible to suppress data complementation by unicast due to halfway participation in multicast.
In addition, when the maximum number (N-1) of cancellation targets that start to suppress the peak load by multicast occurs, it can be expected that the data received before the cancellation and the data already distributed by multicast that has joined in the middle will overlap. . Because the receiving device that is the target of the cancellation, which has been duplicated, uses the received data for file restoration in preference to the unicast complement, the unicast complement is used in this situation where the peak load is suppressed by multicast. It is also possible to suppress this.

  The multicast delivery unit transmits in order from one of the beginning or end of the file, and the receiving device instructed to receive by unicast from the delivery device is the unicast in order from the other opposite to the one at the beginning or end of the file. A request may be made to the distribution unit, and the receiving device to be canceled may use data received by the cancellation prior to multicasting for file restoration. In this case, since the file transmission by unicast and the file transmission by multicast proceed from both ends of the file, in the receiving device to be canceled, the data received by unicast before the cancellation, the data received by multicast, Can be prevented from overlapping. Therefore, the receiving device to be canceled can finish file restoration or start unicast complementing without participating in the next multicast to the end.

  As described above, the present invention suppresses the peak load by multicast based on the setting of a specified value when distributing files in a system that combines multicast and unicast, and receives a file by repeated multicast under this suppression situation. Unicast data supplementation due to halfway participation in multicast can be suppressed by file restoration that prioritizes data and prioritizing data received by unicast before multicast start.

(A) is an operation flow diagram when the data transmission control unit of the distribution system according to the embodiment receives a new distribution request, and (b) is an operation flow diagram when the data transmission control unit receives a reception completion notification. The conceptual diagram which shows the network structure of the delivery system which concerns on embodiment Functional block diagram of distribution system according to embodiment Conceptual diagram of the distribution information management table of FIG. FIG. 3 is a flowchart of the operation of the data reception control unit when transmitting a new distribution request. The block diagram which shows the outline | summary of the file delivery by the unicast of the delivery system which concerns on embodiment (A) is an operation flow diagram of the multicast receiving unit of FIG. 3, and (b) is an operation flow diagram of the multicast distribution unit of FIG. The block diagram which shows the outline | summary of the file delivery by the multicast of the delivery system which concerns on embodiment Operation flow diagram of the received data management unit of FIG. Operation flow diagram at the time of complementation in unicast of the distribution system according to the embodiment FIG. 3 is a flowchart illustrating the operation of the data reception control unit when file reception is completed. Conceptual diagram showing an example of changing the multicast transmission order according to the embodiment

  Hereinafter, an embodiment of a distribution system according to the present invention (hereinafter simply referred to as “this distribution system”) will be described with reference to the accompanying drawings. As shown in FIG. 2, this system includes a distribution device 10, a plurality of reception devices 20, and a network 30 for connecting the distribution device 10 and the plurality of reception devices 20.

  The distribution apparatus 10 includes one or more computer devices that manage resources provided to the reception apparatus 20. The receiving device 20 includes computer equipment that uses the resources of the distribution device 10 via the network 30. Examples of the receiving device 20 serving as a client for the distribution device 10 include a communication device such as a home gateway (HGW), a relay device such as a router, a mobile communication terminal, and a PC terminal of an end user. The network 30 includes one or a plurality of IP networks such as an NGN (Next Generation Network), a backbone communication network, and an ISP network, regardless of whether it is a closed network or the Internet.

  As shown in FIGS. 3 and 4, the distribution device 10 stores distribution files (A, B, C...) In the distribution data storage unit 11 and manages them in the distribution information management table 12. The file for distribution may be either a program executed on the receiving device 20 side or a program other than a program processed by the program on the receiving device 20 side. For example, as a program executed on the receiving device 20 side, firmware incorporated in the HGW can be cited.

  The distribution information management table 12 manages a multicast address, a unicast address, and a file size used for distributing a file specified based on a file identifier in a distribution request from the receiving device 20. The unicast address may be an IP address, a combination of an IP address and a port number, or a URL. Further, the unicast address or multicast address may be uniquely specified in advance for the file identifier. Each time a file distribution request is generated, the distribution information management table 12 selects and assigns an unused address. May be.

  The distribution device 10 includes a multicast distribution unit 13 in charge of data transmission by multicast, a unicast distribution unit 14 in charge of data transmission by unicast, and data transmission control instructing multicast or unicast to a file distribution request source. Unit 15 and a multicast distribution data generation unit 16 that generates a multicast data frame from the file stored in the distribution data storage unit 11.

  The receiving device 20 includes a multicast receiving unit 21 in charge of data reception by multicast, a unicast reception unit 22 in charge of data reception by unicast, a data reception control unit 23 in communication with the data transmission control unit 15, A multicast data receiving buffer 24 that stores data received by the multicast receiving unit 21, a unicast data receiving buffer 25 that stores data received by the unicast receiving unit 22, and data stored in these buffers 24 and 25 are used. And a received data management unit 26 for restoring the distribution target file.

  The distribution data storage unit 11 to the multicast distribution data generation unit 16 and the multicast reception unit 21 to the reception data management unit 26 execute the computer program on the arithmetic processing unit of the corresponding distribution device 10 and the reception device 20, thereby The distribution device 10 and the reception device 20 are configured on hardware resources such as an arithmetic processing device, a storage device, and a network interface.

  The data transmission control unit 15 monitors the number of distribution destinations: n while the distribution apparatus 10 is in operation. The data transmission control unit 15 sets the initial value of n to zero and holds it in a predetermined subordinate memory area. n is the total number of receiving devices 20 in which the data transmission control unit 15 responds to the file distribution request for the same file and has not received the reception completion notification. This total number is held separately for each distribution file (A, B, C...) Managed by the distribution information management table 12.

  As shown in FIGS. 1A and 1B, when the data transmission control unit 15 receives a new file distribution request or a file reception completion notification from the data reception control unit 23 (S1, S2), it updates n. (S3, S4). The new file distribution request includes the identifier of the file to be distributed. The file reception completion notification is a signal indicating that one receiving device 20 that has received the file distribution request by the data transmission control unit 15 and has received the distribution request has received all the files requested for distribution. Yes.

  When receiving a new file distribution request (S1), the data transmission control unit 15 compares the updated value of n with the specified value: N (S5). N is stored in advance in a memory area under the data transmission control unit 15. When a new distribution file is registered in the distribution data storage unit 11, N is input to the data transmission control unit 15 in association with the file.

  When n <N (YES) in this comparison, the data transmission control unit 15 instructs the data reception control unit 23 of the new distribution destination that has triggered the update to receive data by unicast (S6). This instruction is included in the response to the new file delivery request. In this instruction, a unicast address for accessing the unicast delivery unit 14 is included. The data transmission control unit 15 acquires the unicast address from the distribution information management table 12.

  On the other hand, when n ≧ N (No) in the comparison of (S5), the data transmission control unit 15 determines whether the file to be distributed is being multicast (S7). For this determination, for example, the data transmission control unit 15 obtains a multicast address designated for the file to be distributed from the distribution information management table 12, inquires of the multicast distribution unit 13 whether or not there is transmission to the multicast address, and responds to this response. To do.

  When the multicast is not in progress at (S7) (No), the data transmission control unit 15 instructs the data reception control unit 23 of the new distribution destination to receive the multicast (S8). This instruction is included in the response to the new file delivery request. In this instruction, a multicast address for accessing the multicast distribution unit 13, a unicast address for accessing the unicast distribution unit 14, and a file size to be distributed are included. The data transmission control unit 15 acquires a multicast address and the like from the distribution information management table 12. The unicast address is used when it is necessary to complement the unicast after the receiving apparatus 20 performs a predetermined participation in the multicast.

  When the multicast transmission unit 13 notifies the multicast transmission unit 13 of the start of multicasting for the multicast address instructed in (S8), the data transmission control unit 15 sends all the receiving devices 20 instructed in (S7) for the same distribution target file. Cancel unicast. Further, the data transmission control unit 15 instructs the data reception control unit 23 of the receiving device 20 to be canceled to receive data by multicast (S9). In this instruction, a multicast address for accessing the multicast distribution unit 13 and a file size to be distributed are included. The data transmission control unit 15 acquires a multicast address and the like from the distribution information management table 12. This cancellation is performed by, for example, instructing the unicast distribution unit 14 to disconnect all the persistent sessions established with the corresponding unicast address. For example, this instruction is transmitted to the unicast receiving unit 22 using the session before the session is disconnected, and the unicast receiving unit 22 notifies the data reception control unit 23 of the instruction.

  On the other hand, when the multicast is in progress in (S7) (Yes), the data transmission control unit 15 instructs the data reception control unit 23 of the new distribution destination to receive in the ongoing multicast (S10). This instruction is included in the response to the new file delivery request. In this instruction, a multicast address for accessing the multicast distribution unit 13, a unicast address for accessing the unicast distribution unit 14, and a file size to be distributed are included. The data transmission control unit 15 acquires a multicast address and the like from the distribution information management table 12. The unicast address is used when it is necessary to complement the unicast after the receiving apparatus 20 performs a predetermined participation in the multicast.

  As shown in FIG. 5, the data reception control unit 23 generates a new file delivery request specifying the file identifier by a trigger dependent on the receiving device such as user input, internal timer operation, etc., and transmits it to the data transmission control unit 15. (S21). Note that an address for the data reception control unit 23 to access the data transmission control unit 15 via the network 30 is given to the data reception control unit 23 in advance by notification from the distribution device 10, user input, or the like.

  The data reception control unit 23 reads an instruction in response from the data transmission control unit 15 to the file distribution request (S22). Here, when an instruction to receive by unicast is given, a file receiving process by unicast is started (S23). Thereafter, it is determined whether or not an instruction to stop unicast and reception by multicast is given (S24). If No, file reception by unicast is continued (S25), and the process returns to (S24). On the other hand, in the case of Yes, the multicast file reception process is started (S26). In addition, when it is instructed to receive by multicast in (S22), the data reception control unit 23 starts a file reception process by multicast (S27). File reception processing (S23), (S26), and (S27) are requested to the reception data management unit 26. Receiving this, the received data management unit 26 acquires the corresponding address, file size, etc., and requests the corresponding multicast receiving unit 21 or unicast receiving unit 22 to start reception.

  When the reception data management unit 26 requests the unicast reception unit 22 to start reception in (S23), the unicast reception unit 22 starts unicast file reception. That is, as shown in FIG. 6, the unicast delivery part 14 and the persistent session according to HTTP1.1 are established. Thereafter, the unicast receiving unit 22 supplies the identifier of the file to be distributed, an offset (offset) for specifying the number of bytes and after from the head of the file, and the requested data size (length). Send to. The unicast distribution unit 14 transmits the requested file data. The unicast receiving unit 22 advances data reception in the order of offset from data 1 having the file head offset 1 and data length 1, and writes the received data offset, data length, and data to the unicast data reception buffer 25. If all offset data can be received, the session is disconnected and the unicast reception process is terminated.

  As shown in FIGS. 7A and 8, when the multicast reception unit 21 is requested to start reception from the reception data management unit 26 based on the above (S26) and (S27), the multicast file reception is performed. To start. That is, the multicast receiving unit 21 acquires the multicast address, the identifier of the file to be distributed, and the file size from the received data management unit 26 (S31), and issues a multicast reception start request including at least one of the multicast address and the file identifier. It transmits to the multicast delivery part 13 (S32).

  As shown in FIGS. 7B and 8, upon receiving the multicast reception start request in (S32), the multicast distribution unit 13 stores the receiving device 20 that is the multicast request source (S41), and the multicast address It is confirmed whether a file is being transmitted to (S42). Here, in the case of No, a file identifier corresponding to the multicast address in the multicast reception start request is acquired from the distribution information management table 12, and a frame generation request including the file identifier is passed to the multicast distribution data generation unit 16 (S43). ). If only the file identifier is included in the multicast reception start request, the file identifier is read and the frame generation request is passed.

  The multicast distribution data generation unit 16 takes out the file corresponding to the file identifier in the frame generation request from the distribution data storage unit 11, divides it into packet units, gives an offset, and passes the generated frame to the multicast distribution unit 13 ( S44). The offset is information indicating the number of bytes after the start of the distribution target file. The offset and data length are shared with unicast.

  The multicast distribution unit 13 determines whether or not a multicast reception end request has been received from all the receiving devices 20 of the multicast request source (S45). Here, in the case of No, the multicast distribution unit 13 transmits the frames obtained in (S44) in the order of offset, that is, in order from the beginning of the file (S46), and distributes all the offsets every time the frame is transmitted. It is determined whether or not it is finished (S47). Here, if No, the process returns to (S45), and if Yes, the next multicast is started (S48). This means that one multicast is completed and transmission is performed in the order of offset from the frame of offset 1 which is the head of the file again.

  When (S48) is executed, the process returns to (S45). In the case of Yes in (S45), the multicast for the multicast address is terminated (S49). When receiving the multicast reception end request, the multicast distribution unit 13 deletes the requesting receiving device 20 from the storage in (S41).

  As shown in FIGS. 7A and 8, the multicast receiver 21 determines whether or not a packet has not been received for a predetermined time or more after (S32) (S33). Here, in the case of No, after receiving the multicast packet (S34), the offset in the received packet is acquired (S35), and the data length and data are written in the multicast data reception buffer 24 (S36). Next, the multicast receiver 21 determines whether or not it has participated in one round of multicast (S37). One round is a packet including an offset (referred to as a reference offset) acquired in (S35) of a multicast packet first received after (S32) and an offset immediately before the reference offset, or an offset greater than or equal to the reference offset This is equivalent to the first reception of a packet containing the. The determination in (S37) can be made by appropriately utilizing the offset accumulated in the multicast data reception buffer 24 and the file size acquired from the reception data management unit 26, and there is no halfway participation in the multicast or packet loss. Even if it occurs, it may be any means that guarantees participation for at least one round. For example, the offset stored in the multicast data reception buffer 24 may be browsed and determined by searching for one of the previous offset and the second offset, or using the offset, data length, and file size. You may judge based on the calculated. The calculation method includes offset + data length ≧ file size. If No in (S37), the process returns to (S33). In the case of Yes in (S37) or (S33), the multicast reception unit 21 transmits a multicast reception end request to the multicast distribution unit 13, and notifies the reception data management unit 26 of the end of multicast reception (S38). The file reception by multicast is terminated.

  The reception data management unit 26 requested to start reception by unicast or multicast from the data reception control unit 23 in the above (S23), (S26), and (S27) is necessary for reception as shown in FIG. An appropriate address, file size, and the like are acquired from the data reception control unit 23 (S51). Next, the reception data management unit 26 clears the multicast data reception buffer 24 and the unicast data reception buffer 25 (S52), and then requests the corresponding multicast reception unit 21 or unicast reception unit 22 to start reception (S53). ).

  Thereafter, the reception data management unit 26 determines whether or not reception is being performed by multicast (S54). Here, the reception data management unit 26 determines Yes when the multicast reception unit 21 is requested to start reception in (S53), and the reception end in (S38) is not notified from the multicast reception unit 21. , (S54) is repeated. On the other hand, the reception data management unit 26 requests the unicast reception unit 22 to start reception in (S53), or requests the multicast reception unit 21 to start reception in (S53) and (S38) described above. If the end of reception is notified from the multicast receiver 21, the determination is No, and the offset and data length of unreceived data that does not exist in either the multicast data reception buffer 24 or the unicast data reception buffer 25 are searched. (S55).

  Next, the received data management unit 26 determines whether all data necessary for file restoration has been received from the presence / absence of unreceived data (S56). Here, in the case of No, the reception data management unit 26 requests the unicast reception unit 22 to receive data having a data length designated from an unreceived offset (S57), and returns to (S55). On the other hand, in the case of Yes in (S56), the reception data management unit 26 restores the distribution target file by combining in the order of offset, notifies the data reception control unit 23 of the completion of reception of all data of the file, and ends (S58). ).

  As shown in FIG. 10A, the unicast receiving unit 22 that has received the request of (S57) starts complementing by unicast, and includes the unicast address, the specified offset, and the data length included in the request. (S61), specify the unicast delivery unit 14 from the obtained unicast address (S62), establish a session with the unicast delivery unit 14 (S63), specify the offset and data length, and send the data. A request is made (S64). As shown in FIG. 10B, when the unicast distribution unit 14 establishes the session of (S63) (S71), the unicast distribution unit 14 acquires the file identifier corresponding to the destination unicast address of this session from the distribution information management table 12. (S72). When the data request for the offset and data length requested in (S64) is received (S73), the data after the offset is extracted from the file corresponding to the file identifier by the data length (S74). The data is transmitted to the unicast receiving unit 22 (S75), and the session is disconnected. On the other hand, as shown in FIG. 10A, the unicast receiving unit 22 receives the requested data from the unicast distribution unit 14 after (S64) (S65), disconnects the session (S66), Writing to the unicast data reception buffer 25 (S67), and completion of one unreceived data is terminated.

  As shown in FIG. 11, when receiving the notification (S58) (S81), the data reception control unit 23 transmits a reception completion notification to the data transmission control unit 15 (S82).

  According to the distribution system of this embodiment, the distribution apparatus 10 side grasps the number of distribution destinations: n based on a new file distribution request (S21, S1) and a reception completion notification (S82, S2) from the reception apparatus 20. (S3, S4). When n <N when there is no concern about peak load (S5), the distribution device 10 instructs the new distribution destination to receive data by unicast (S6). Reception proceeds (S23, S24, S25, FIG. 6). When a new file distribution request satisfying n = N is received in a state where file distribution is being executed only by unicast (S21, S1, S5, S7), the distribution apparatus 10 receives the unicast instructed earlier. All file distributions (up to N-1 unicast sessions) are canceled (S9), and thereafter, as long as n ≧ N is satisfied, a new distribution destination is instructed to receive multicast (S8, S10). ) Since all the corresponding receiving devices 20 follow this (S22, S24, S26, S27), no new unicast file transmission occurs even if the number of distribution destinations increases from N. Thereby, before the peak load of the unicast delivery part 14 of the delivery apparatus 10 becomes a problem, a peak load can be suppressed by multicast.

  In addition, all receiving devices 20 (S9) that are subject to cancellation and new receiving device 20 (S8, S10) satisfying n ≧ N must participate in one round when participating in multicast halfway. (S37, S38), the next multicast supplement is prioritized over the unicast complement (S54 to S57), and the distribution device 10 performs file transmission by multicast while the receiver 20 requiring multicast exists. Repeat (S37, S38, S41, S42, S45 to S48). Therefore, the receiving device 20 that has joined the multicast in the middle is to complement only the file portion (that is, the packet loss during one round of multicast) that has not been received even if the supplement is attempted in the next multicast by unicast. Become. Thereby, under the situation where the peak load is suppressed by multicast, it is possible to suppress data complementation by unicast due to halfway participation in multicast.

  In addition, when the maximum number of units (N-1) to be canceled that starts to suppress the peak load by multicast occurs, data that has been received by the time of cancellation, data that has already been distributed in the middle of the multicast, and cannot be supplemented by the next multicast It can be expected that the data will overlap. Since the receiving device to be canceled in which duplication has occurred uses the received data for file restoration in preference to complementing by unicast (S55 to S57), under this situation, the peak load is suppressed by multicast. Unicast completion can also be suppressed.

  For example, in this embodiment, the file reception by the previous unicast proceeds from the beginning of the file (S23, FIG. 6), and the file transmission by multicast is as shown by the arrow in the transmission order (1) in FIG. Since data is transmitted in order from the data 1 at the head of the file to the data at the end (Z), the data that has already been transmitted by the multicast at the participation time and the data that has already been received by unicast overlap before midway participation. Therefore, if the multicast has not progressed beyond the range already received by the previous unicast at the time of participation, it is only necessary to supplement the packet loss during the multicast (S54 to S57). Moreover, even if the multicast has progressed beyond the range already received by the previous unicast at the time of participation in the middle, all the data received by the previous unicast can be used for complementation (S54 to S57). No need to complete with unicast. Accordingly, it is possible to suppress unicast complementation due to mid-way participation for all receiving apparatuses 20 in which the previous unicast has been canceled. In order to suppress the peak load of the distribution apparatus 10, this is particularly suitable when it is desired to suppress the occurrence of unicast complementation itself and the amount of supplementary data.

  In addition, participation in the multicast is limited to one lap (S37, S38), at the time of joining in the middle (S9, S26) or from the beginning (S10, S27). Just participate. Accordingly, since the receiving device 20 can start complementing the packet loss by unicast as quickly as possible while suppressing the peak load of the distribution device 10 (S54 to S57), it is unnecessary until reception of the entire file. Don't spend time on

  Note that the multicast start time may be started in response to a multicast distribution request from a receiving apparatus that first instructs n = N and instructed to receive the multicast as in this embodiment, or starts file distribution. Later, it may be triggered by the fact that n = N is first given and multicast is instructed. In these cases, unnecessary multicast can be prevented from occurring. Moreover, you may repeat from the beginning of the delivery which registers a file into a delivery information management table. In this case, the processes related to the multicast reception start request and the multicast reception end request can be omitted (S37, S38).

  In this embodiment, file transmission by unicast is started from the beginning of the file (data 1) (FIG. 6), and file transmission by multicast is indicated by an arrow in the transmission order (2) in FIG. The data may be changed so that data 1 is transmitted in order from the end of the file (data (Z)). In the case of the transmission order (2), since the file transmission by unicast and the file transmission by multicast proceed from both ends of the file, in the receiving apparatus to be canceled, the data already received by unicast before the cancellation and the multicast Can prevent duplication of data received. Therefore, the receiving device to be canceled can finish file restoration or start unicast complementing without participating in the next multicast to the end. This is particularly suitable when it is desired to suppress the concentration of complementation in unicast in order to suppress the peak load of the distribution apparatus. The technical scope of the present invention is not limited to the above-described embodiment, but includes all modifications within the scope of the technical idea based on the description of the scope of claims.

DESCRIPTION OF SYMBOLS 10 Distribution apparatus 11 Distribution data storage part 12 Distribution information management table 13 Multicast distribution part 14 Unicast distribution part 15 Data transmission control part 16 Multicast distribution data generation part 20 Receiving device 21 Multicast reception part 22 Unicast reception part 23 Data reception control part 24 Multicast data reception buffer 25 Unicast data reception buffer 26 Reception data management unit 30 Network

Claims (2)

The distribution device includes a multicast distribution unit that is responsible for data transmission by multicast and a unicast distribution unit that is responsible for data transmission by unicast. In a delivery system complemented by unicast,
When the reception device confirms reception of the entire file, a process of sending a reception completion notification to the distribution device, and a process that prioritizes complementation in the next multicast over complementation in unicast when participating in the middle of the multicast, When participating in multicast, be sure to participate in one round of multicast, and when the first round of participation , perform a process of sending a multicast reception end request to the distribution device and ending file reception in multicast ,
The distribution apparatus monitors the number of distribution destinations: n, receives a new file distribution request or the reception completion notification, updates the value of n, and receives a new file distribution request. The process of comparing the value of n with the specified value: N, the process of instructing the receiving device of the new distribution destination to receive in unicast when n <N, and n ≧ N in the comparison In this case, the receiving device of the new distribution destination is instructed to receive the multicast, and the processing of canceling all of the instructed unicasts and the reception of the multicast to all the receiving devices targeted for the cancellation are performed. a process of instructing, by determining whether or not it has received the multicast reception end request from all of the receiving device instructs the reception of a multicast, in the presence of the receiver that require multicast, Ma Run the process of repeating the file transmission in Chikyasuto,
The distribution system, wherein the receiving device to be canceled uses data received before the cancellation for file restoration in preference to complementing by unicast.   The multicast distribution unit sequentially transmits the divided data one by one from the beginning and end of the file to the other, and the receiving device instructed to receive by unicast from the distributing device is the file at the beginning or end of the file. The delivery according to claim 1, wherein the unicast delivery unit makes a request to the unicast delivery unit in order from the other side opposite to one side, and the receiving device to be canceled uses data received up to the cancellation in preference to multicast for file restoration. system.

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