JP2010154161A - Data distribution method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently and highly reliably perform the broadcast distribution of data. <P>SOLUTION: Retransmission control is attained under the initiative of a client concerning one-to-many data distribution by broadcast (multicast). That is, the attribute of data to be distributed is previously reported to a client terminal from a file server 4d, the client terminal determines the presence/absence of a missing data block based on the attribute, and then, a retransmission request is outputted to the file server 4d at an appropriate timing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a data distribution method and a program for causing a computer to execute the method.

  Most of recent data communications are performed on an IP (Internet Protocol) network, and TCP (Transmission Control Protocol) or UDP (Use Datagram protocol) is properly used according to the purpose. The former is compatible with communication that places importance on reliability and the latter on communication that emphasizes real-time performance. For example, in patent document 1, the suitable application to the road traffic information communication system is aimed at by using UDP.

  Patent Document 1 assumes peer-to-peer communication, and HTTP (HyperText Transfer Protocol) or FTP (File Transfer Protocol) is used for file transfer in such a form. However, the communication on the network is not limited to a one-to-one connection between the client and the server, and a one-to-many or many-to-many communication form can frequently occur. Neither HTTP nor FTP is suitable for data transfer in such a form. Therefore, multicast (IP multicast) or broadcast is used.

Multicast is effective for distributing the same data from a server to a plurality of network nodes. For example, an application that downloads a virus pattern file of anti-virus software from a server to a client uses multicast capable of specifying a transfer destination.
JP 2001-339434 A

  The existing multicast or broadcast involves server-led retransmission control, so it is necessary to manage responses from all data distribution destinations. In particular, although the sliding window method employed in TCP can distribute data efficiently by peer-to-peer, if the same method is applied to broadcast, a device that cannot confirm response generates a time lag and the window cannot slide smoothly. There is a need to provide a technology capable of efficiently distributing relatively large data to a large number of clients with high reliability.

  The present invention has been made under the circumstances described above, and an object thereof is to provide a data distribution method capable of distributing data efficiently and with high reliability, and a program for realizing the data distribution method.

  In order to achieve the above object, according to one aspect of the present invention, in a data distribution method for broadcasting data from a distribution source server to a plurality of distribution destination clients, the server includes the data A plurality of data blocks are transmitted to each of the clients without waiting for delivery confirmation for each data block, and each of the clients retransmits the unreachable data block to the server within a certain period of time. The data distribution method is provided, wherein the server retransmits only the data block requested to be retransmitted to the requesting client.

  By taking such a measure, delivery confirmation for each data block is omitted in the data broadcast transmission processing such as multicast or broadcast. Instead, unreachable data blocks within a certain period are managed in each client, and for example, the server is requested to retransmit unreachable data blocks at each timing period. The client can determine the presence or absence of unreachable data blocks based on data attributes (such as the total number of data blocks) notified from the server in advance. According to such a method, retransmission control led by the client is realized in the broadcast transmission, the time required for message transmission and reception for delivery confirmation can be shortened and the efficiency can be improved, and retransmission for undelivered data can be achieved. Since control is performed, it becomes possible to improve reliability.

  According to the present invention, it is possible to provide a data distribution method capable of distributing data efficiently and with high reliability, and a program for realizing the data distribution method.

  FIG. 1 is a diagram showing an example of a communication system in which a data distribution method according to the present invention is implemented. In FIG. 1, different networks 1c, 2c, 3c, and 4c are connected to the Internet via routers 1a, 2a, 3a, and 4a, respectively. Among these, the network 4c includes a plurality of client terminals provided on a LAN (Local Area Network) and a file server 3d in these terminals. The other networks 1c, 2c, 3c also include a plurality of client terminals.

  In the following, a case is considered in which a data file from the file server 4d is distributed by broadcast to the client terminal 4b belonging to the network 4c and the client terminal 3b belonging to the network 3c. A part of the broadcast or multicast method can be used for this distribution.

  FIG. 2 is a functional block diagram showing an embodiment of the file server 4d and the client terminal 3b in FIG. In FIG. 2, the file server 4d is connected to the Internet via the communication interface 15, and communicates with each client terminal in both directions. The file server 4 d includes a program memory 10, a storage unit 11, and a CPU (Central Processing Unit) 16. The CPU 16 processes instructions described in the program stored in the program memory 10 and realizes various processing functions necessary for this embodiment. The storage unit 11 is a recording medium such as a hard disk drive (HDD) and stores a data file 11a to be sent to the client terminal. It is assumed that the size of the data file 11a is so large that it cannot be transmitted in one packet. Therefore, the file server divides the data file 11a into a plurality of data blocks, and assigns a serial number to each to generate a broadcast packet. By using broadcast packets, it is possible to distribute to multiple clients at the same time.

  The program memory 10 includes a transmission processing block 12, a retransmission processing block 13, and a notification processing block 14 as program blocks according to this embodiment. These processing blocks are loaded into a file server 4d as a computer and executed by the CPU 16, whereby the CPU 16 provides a processing function as a file server.

  The transmission processing block 12 transmits a plurality of data blocks obtained by dividing the data file 11a to each of the client terminals (here, 3b and 4b). Normally, a delivery confirmation sequence is required for each individual data block. Here, however, the transmission processing block 12 transmits each data block in a drip manner without waiting for delivery confirmation.

  The retransmission processing block 13 retransmits the requested data block to the requesting client terminal only in response to a retransmission request notified from the client terminal at regular intervals, for example. The notification processing block 14 notifies each of the client terminals of the distribution destination of the attribute of the data file 11a in a sequence that is initially performed for data distribution. The attributes of the data file 11a include, for example, its size, extension, data type, total number of divided data blocks, serial number, and the like.

  The client terminal 3b in FIG. 2 is also a computer terminal, and receives a plurality of data blocks distributed from the file server 4d and reproduces the data file. The client terminal 3b is connected to the Internet via the communication interface 30 and includes a display unit 31, a keyboard 32, a mouse 33, a control unit 34, and a memory 35. The display unit 31 is a liquid crystal display, for example.

The memory 35 includes a retransmission request processing block 35a and a determination processing block 35b as program blocks according to this embodiment. When these processing blocks are loaded into the control unit 34 and executed, the control unit 34 provides a processing function as a client.
For example, the retransmission request processing block 35a monitors the presence or absence of unreachable data blocks within a certain period of time, and requests unsuccessful data blocks from the file server 4d. Alternatively, when the number of undelivered data blocks reaches a certain number, the retransmission request processing block 35a requests the file server 4d to retransmit those unreachable data blocks. At that time, the retransmission request processing block 35a transmits a retransmission request message addressed to the file server 4d at a random timing different from that of other client terminals.

  The determination processing block 35b determines the presence / absence of a non-delivery data block based on the attribute of the data file 11a notified from the file server 4d. Specifically, it is possible to detect the presence or absence of unreachable data blocks due to, for example, missing serial numbers. The other client terminals including the client terminal 4b have the same configuration as the client terminal 4b. Next, the operation of the above configuration will be described.

  FIG. 3 is a sequence diagram showing a processing procedure performed between the file server 4d and the client terminals 3b and 4b in FIG. In FIG. 3, prior to the distribution of the data file 11a, the file server 4d broadcasts information indicating the attribute of the data file 11a to the client terminals 3b and 4b by an information notification message. Next, the file server 4d waits for the receipt confirmation message for the information notification message from each of the client terminals 3b and 4b. If a time-out occurs without receiving a receipt confirmation message, the file server 4d sends an information notification message again, and repeats this process until it is confirmed that this message has arrived at the destination client terminal. Up to this point, in order to cope with the existence of a large number of clients, the file server 4d mainly performs retransmission control.

  Next, when receiving a receipt confirmation message from the client terminals 3b and 4b, the file server 4d starts distributing data blocks. That is, the file server 4d sequentially distributes the data block to which the serial number is assigned from the top number. At this time, the file server 4d transmits data blocks one after another without waiting for a response from the client terminal.

  The client terminals 3b and 4b monitor the lack of serial numbers in the received data blocks and determine the presence or absence of undelivered data blocks. If there is a non-reachable data block within a certain period (for example, 10 seconds), the client terminal that detects this does not immediately issue a retransmission request for that data block, but accumulates only that serial number. When a certain period of time elapses, a retransmission request message including the accumulated serial number is transmitted to the file server 4d.

  FIG. 3 shows that the client terminal 3b has detected a non-delivery data block and has sent a retransmission request message. Receiving this, the file server 4d sets a retransmission flag for the data block of the notified serial number, returns this data block to the requesting client terminal 3b, and then continues to distribute the data block.

  As described above, according to this embodiment, in one-to-many data distribution using broadcast (multicast), retransmission control is realized by the initiative of the client. That is, the file server 4d notifies the client terminal of the attribute of the data to be distributed in advance, the client terminal determines the presence or absence of a data block that has not been reached based on the attribute, and sends a resend request to the file server 4d at an appropriate timing. I try to put out.

  As described above, since retransmission control is performed under the initiative of the client, it is not necessary to manage responses on the file server side. Therefore, efficient data distribution can be realized without adopting the sliding window method. From these facts, it is possible to provide a data distribution method capable of broadcasting data efficiently and with high reliability, and a program for realizing the data distribution method.

  The present invention is not limited to the above embodiment. For example, the size of a broadcast packet generated by dividing a data file may be a fixed length or variable depending on a network state (mainly load). Which method is used may be switched according to the setting of the system operator. In order to measure the load on the network, for example, the functions of the routers 1a to 4a may be used.

The type of the data file may be any type, and may be multimedia data such as video and audio with relatively less restrictions in addition to data requiring reliability.
Furthermore, the present invention can be embodied by modifying the constituent elements without departing from the spirit of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment.

The figure which shows an example of the communication system with which the data delivery method concerning this invention is implemented. The functional block diagram which shows embodiment of the file server 4d of FIG. 1, and the client terminal 3b. The sequence diagram which shows the process sequence implemented between the file server 4d of FIG. 2, and the client terminal 3b.

Explanation of symbols

  1c, 2c, 3c, 4c ... network, 1a, 2a, 3a, 4a ... router, 3b, 4b ... client terminal, 11 ... storage unit, 11a ... data file, 10 ... program memory, 12 ... transmission processing block, 13 ... Retransmission processing block, 14 ... Notification processing block, 15 ... Communication interface, 16 ... CPU, 30 ... Communication interface, 31 ... Display unit, 32 ... Keyboard, 33 ... Mouse, 34 ... Control unit, 35 ... Memory, 35a ... Retransmission request Processing block, 35b ... determination processing block

Claims (10)

In a data distribution method for distributing data from a distribution source server to a plurality of distribution destination clients in a broadcast manner,
The server transmits a plurality of data blocks obtained by dividing the data to each of the clients without waiting for delivery confirmation for each data block,
Each of the clients requests the server to resend the unreachable data block within a certain period of time,
The server distributes only the data block requested to be retransmitted to the requesting client. In a data distribution method for distributing data from a distribution source server to a plurality of distribution destination clients in a broadcast manner,
The server transmits a plurality of data blocks obtained by dividing the data to each of the clients without waiting for delivery confirmation for each data block,
Each of the clients requests the server to resend those unreachable data blocks when a certain number of unreachable data blocks reaches a certain number,
The server distributes only the data block requested to be retransmitted to the requesting client. The server notifies each of the clients of an attribute of the data including a total number of the plurality of data blocks;
3. The data distribution method according to claim 1, wherein each of the clients determines the presence / absence of a non-delivery data block based on the notified attribute. 3. The data distribution method according to claim 1, wherein each of the clients requests the server to retransmit the undelivered data block at random timings. A program that is read by a server computer that broadcasts data to multiple clients,
In the server computer,
An instruction to execute a process of transmitting a plurality of data blocks obtained by dividing the data to each of the clients without waiting for delivery confirmation for each data block;
And a command for executing a process of retransmitting only a data block requested to be retransmitted to a requesting client. 6. The program according to claim 5, further comprising instructions for causing the server computer to execute a process of notifying each of the clients of the data attributes including the total number of the plurality of data blocks. A program that is read by a client computer that receives the data block from a server that broadcasts a plurality of data blocks into which data is divided,
On the client computer,
A program comprising an instruction for executing a process of requesting the server to retransmit a data block that has not been delivered within a certain period. A program that is read by a client computer that receives the data block from a server that broadcasts a plurality of data blocks into which data is divided,
On the client computer,
A program comprising: an instruction for executing a process for requesting the server to retransmit data blocks which have not been delivered when a certain number of data blocks have not been delivered. The system further comprises: an instruction for causing the client computer to execute a process of determining whether or not there is a non-deliverable data block based on an attribute of the data including the total number of the data blocks notified from the server. The program according to any one of 7 and 8. 9. The program according to claim 7, further comprising an instruction for causing the client computer to execute processing for requesting retransmission of the unreachable data block with another client computer at random timing. .

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