JP2005276079A - Data distribution server and data distribution system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a data distribution server and a data distribution system that enable efficient data distribution even when data distribution requests from a large number of terminals are generated to the data distribution server.
A data distribution server distributes corresponding data among content managed by a content management unit that manages one or a plurality of contents and content managed by a content management unit in response to a data distribution request from a terminal. Unicast delivery means, multicast delivery means for delivering the corresponding data among the contents managed by the content management means in response to a data delivery request from the terminal, and terminal information being delivered Based on the distribution status management means managed as data and the distribution status data managed by the distribution status management means, it is determined whether data distribution to each terminal is performed via unicast distribution means or multicast distribution means Distribution method control means.
[Selection] Figure 1

Description

  The present invention relates to a data distribution server and a data distribution system that distribute data to terminals connected via a network.

  Data distribution services for distributing movies, music, and other contents to terminals connected via a network such as the Internet are being implemented. On the terminal side, when receiving a data distribution service of various contents, for example, an Internet connection by TCP / IP is performed, and desired data is downloaded by using a file transfer protocol such as FTP or HTTP.

  Computers installed in ordinary homes usually use digital telephone lines such as analog telephone lines and ISDN, and the data transfer speed is generally low, so that large-capacity content such as movies can be downloaded. Has a problem that it takes a long time.

  High-capacity lines that can be used for data transfer between a computer and a network include a digital dedicated line, a CATV line using a coaxial cable, and a satellite broadcast line using a broadcasting satellite. The digital leased line is a high-speed digital line installed separately from the public line network, and can be used by a user who individually contracts with a communication carrier. The CATV line is a dedicated line for broadcasting program distribution installed between each home and the broadcaster, and allows two-way communication between the broadcaster and the home. The satellite broadcast line is a one-way line for distributing a broadcast program from a single broadcast satellite to a large number of viewers.

In Patent Document 1, in order to efficiently perform download in response to a data distribution request from the terminal side, a small-band line such as a modem is used when the size of response data to the data distribution request received from the terminal by the server is small. There is described a communication path control device that selects via and selects a large-band line such as a satellite line when the size of response data is large, and performs data distribution.
Japanese Patent Laid-Open No. 10-257098

  Although the invention described in the cited document 1 proposes a method for selecting an appropriate line for each data distribution request from a terminal, it does not consider the load on the data distribution server or line, and data distribution When the number of terminals that make data distribution requests to a server that provides a service increases, there is a possibility that problems such as a line down may occur due to an increase in the load on the server and the line and a slow download speed.

  In recent years, xDSL technology represented by ADSL that performs data communication using a high-frequency band not used for voice transmission on a normal telephone line has become widespread. On the user side, various data can be downloaded at high speed by using such xDSL technology, but on the data distribution server side, the load on the server and line is increasing due to data distribution requests from multiple terminals. Become.

  It is also conceivable to perform multicast data transfer from a data distribution server to a plurality of terminals via a TCP / IP network. In this case, data such as voice and moving images is distributed using a protocol such as a multicast protocol. Such multicast data transfer is efficient when there are many terminals to be distributed, but has a problem that network resources are wasted when there are few terminals to be distributed.

  In the present invention, in view of such a problem, a data distribution server and a data distribution system that enable efficient data distribution even when data distribution requests from a large number of terminals are generated to the data distribution server. Propose.

  A data distribution server according to claim 1 of the present invention is a content management unit that stores one or a plurality of contents, and corresponding data among contents managed by the content management unit in response to a data distribution request from a terminal. Unicast distribution means for distributing by unicast, multicast distribution means for distributing the corresponding data among the contents managed by the content management means in response to a data distribution request from the terminal, and a terminal that is currently distributing data Distribution status management means for managing information as distribution status data, and based on the distribution status data managed by the distribution status management means, data distribution to each terminal is performed via unicast distribution means or via multicast distribution means Distribution method control means for determining whether or not to perform.

  In this case, with reference to the distribution status data managed by the distribution status management means, based on the current distribution status data, the data distribution by the unicast distribution means and the data distribution by the multicast distribution means are selected to increase the data distribution efficiency. Can be improved.

A data distribution server according to claim 2 of the present invention is the data distribution server according to claim 1, wherein the distribution status management means manages distribution at the time of starting distribution to the terminal and at the time of ending distribution to the terminal. The distribution status data is updated so that the fact is reflected in the status data.
In this case, the current distribution status can be reliably grasped, and the data distribution efficiency can be improved.

  The data distribution server according to claim 3 of the present invention is the data distribution server according to claim 2, wherein the distribution method control means manages the distribution status managed by the distribution status management means when there is a data distribution request from the terminal. Refers to the data, and if the number of terminals that are delivering the corresponding content by unicast is less than the predetermined number, the contents are delivered by unicast delivery means, and the number of terminals that are delivering the relevant content by unicast Is determined to be distributed by the multicast distribution means.

  In this case, when the number of terminals being distributed by unicast that increases the load on the server or the line exceeds a certain number, the load can be reduced by performing data distribution by multicast. In addition, when the number of terminals that are performing unicast data distribution is less than a predetermined number, it is efficient by performing unicast data distribution with high data transfer efficiency in one-to-one data distribution. Data distribution can be performed.

A data distribution server according to claim 4 of the present invention is the data distribution server according to any one of claims 1 to 3, wherein the distribution method control means dynamically distributes according to the number of terminals during data distribution. A switching determination unit for determining switching, a switching notification unit for notifying a terminal that switches the distribution method based on the determination at the switching determination unit, and a unicast based on the determination at the switching determination unit A switching control unit that instructs the distribution unit and the multicast distribution unit to switch data distribution.
In this case, by switching the distribution method based on the current distribution status data, efficient data distribution can be performed by the data distribution method according to the occasion.

A data distribution server according to claim 5 of the present invention is the data distribution server according to any one of claims 1 to 4, wherein the distribution status management means receives a download end notification from a terminal during data distribution Update delivery status data.
In this case, when there is a terminal for which data distribution has been completed, that fact is reliably reflected in the distribution status data, and efficient data distribution can always be performed.

  The data distribution server according to claim 6 of the present invention is the data distribution server according to claim 5, wherein the distribution status management means receives a download end notification from a terminal that has started data distribution even after a predetermined time has elapsed. If not, it is determined that the download on the terminal has ended.

  In this case, even if the download has not been completed due to a communication error or terminal error, it is considered that the data distribution to the terminal has been completed after a certain period of time. Therefore, it is possible to improve the efficiency of data distribution because data of terminals that are not currently being distributed are not left forever.

  A data distribution system according to claim 7 of the present invention is a data distribution system that performs data distribution from a data distribution server in response to a data distribution request from a terminal, and the data distribution server stores one or more contents. Content management means, unicast delivery means for delivering the corresponding data among the contents managed by the content management means in response to a data delivery request from the terminal, and in response to a data delivery request from the terminal Managed by multicast distribution means for multicasting the corresponding data among the contents managed by the content management means, distribution status management means for managing terminal information being distributed as distribution status data, and distribution status management means Data distribution to each terminal based on the distribution status data And a distribution method control means for determining whether to perform the data distribution via the unicast distribution means or the multicast distribution means, and the terminal transmits a data distribution request to the data distribution server and from the data distribution server Download means for receiving data distributed by unicast or multicast, and download instruction means for selecting content to be downloaded from the data distribution server and causing the download means to receive data from the data distribution server.

  By adopting such a configuration, it is possible to select data distribution by unicast and data distribution by multicast according to the current distribution status data to increase the efficiency of data distribution.

  A data download terminal according to claim 8 of the present invention transmits a data distribution request to a data distribution server in order to download content managed by the data distribution server, and receives data distributed from the data distribution server by unicast or multicast. Downloading means to receive, and when receiving a switching notification of the distribution method from the data distribution server during execution of data download by the downloading means, the download means temporarily stops receiving data and continues the data downloaded so far A download control unit for downloading in a designated manner.

  In the data distribution server, when the number of accesses from the terminal increases and the load due to data distribution increases, the load can be reduced by switching to multicast data distribution. In addition, when the number of accesses from the terminal is reduced and the load is relatively reduced during data distribution by multicast, switching to data distribution by unicast with good quality can be considered. When the data download terminal as described above is configured, it is possible to realize efficient data download corresponding to such switching of the distribution method in the data distribution server.

According to the present invention, even when there are data distribution requests from a large number of terminals to the data distribution server, the load on the server and the line is reduced and efficient data distribution is enabled.

An embodiment of a data distribution system according to the present invention will be described with reference to the drawings.
The data distribution system according to the present invention is a system in which a data distribution server that receives a data distribution request from a terminal selects unicast distribution or multicast distribution according to the current distribution status and distributes data to the terminal. Here, transmission of data from the server to the terminal is referred to as data distribution, and reception of data transmitted from the data distribution server is referred to as download.

FIG. 1 is a functional block diagram showing a schematic configuration of a data distribution system in which one embodiment of the present invention is adopted.
The data distribution server 100 receives access requests from a plurality of terminals 101 via a network such as the Internet, and distributes data requested by the terminals 101. The data distribution server 100 includes a multicast distribution unit 111 and a distribution method control unit 110. Unicast distribution means 112, distribution status management means 113, and content management means 114.

  The content management means 114 stores moving image data, music data, and other various contents. The unicast distribution unit 112 distributes the corresponding data among the contents managed by the content management unit 114 by unicast in response to a data distribution request from the terminal 120.

  The multicast distribution unit 111 distributes the corresponding data among the contents managed by the content management unit 114 by multicast in response to a data distribution request from the terminal 120.

The distribution status management means 113 manages terminal information that is currently being distributed as distribution status data.
Based on the distribution status data managed by the distribution status management unit 113, the distribution method control unit 110 determines whether data distribution to each terminal 120 is performed via the unicast distribution unit 112 or the multicast distribution unit 111. decide.

A plurality of data distribution servers 100 may be provided in the system, and is not limited to a single configuration as illustrated.
The terminal 120 includes a download unit 121 and a download instruction unit 122. The download means 121 transmits a data distribution request to the data distribution server 100 and receives data distributed from the data distribution server 100 by unicast or multicast. The download instruction unit 122 selects content to be downloaded from the data distribution server 100 and causes the download unit 121 to receive data from the data distribution server 100. For example, the download instruction unit 122 notifies the download unit 121 of a download instruction, triggered by the download instruction received from the user of the terminal 120 or the detection of the arrival of the reserved time set by the user using a timer.

  When the download unit 121 receives the download instruction from the download instruction unit 122, the download unit 121 notifies the data distribution server 100 of a data distribution request, and downloads data distributed from the data distribution server 100. Here, it is assumed that the data distribution server 100 and the terminal 120 are connected by a network capable of bidirectional communication such as the Internet or a public line network. Further, the terminal 120 can use the downloaded data only for real-time reproduction, and can be configured to accumulate the downloaded data and reproduce it repeatedly.

  The data distribution request notified from the download unit 121 to the data distribution server 100 includes at least an identifier for identifying data to be downloaded, and can be transmitted and received using a general technique such as the TCP / IP protocol. It is feasible.

  The distribution status data managed by the distribution status management means 113 manages the data being distributed to the terminal 120, the distribution method of the data, the distribution start time, etc., for example, as shown in FIG. Consists of tables.

  In the example of the distribution status data 200 shown in FIG. 2, the distribution data column 201, the distributing terminal column 202, and the distribution start time column 203 constitute a table, and movie A is distributed to three terminals by multicasting. It shows that drama B is being distributed to two terminals by unicast. In the distribution status data shown in the figure, the title of each content is input in the distribution data column 201. However, the data is not particularly limited to the title as long as it is data for identifying the content.

  The terminal being delivered column 202 shows information on terminals that are currently delivering data. In the illustrated example, the IP address of the terminal currently delivering data is stored in the delivering terminal column 202, and for movie A, the IP addresses are 'aaa.aaa.aaa.aaa', 'bbb.bbb. It is being distributed to the terminals bbb.bbb 'and' ccc.ccc.ccc.ccc '. For drama B, the IP address is' ddd.ddd.ddd.ddd', 'eee.eee.eee.eee' It is showing that it is delivering to the terminal which is. The data stored in the delivering terminal column 202 is for identifying the terminal that is delivering data. In addition to the IP address, the MAC address (Media Access Control address) of the network card installed in the terminal is used. ) Or the serial number of the terminal can be used.

  The data stored in the distribution start time column 203 represents the time when distribution to the terminal is started. In this example, the distribution start time of movie A to the terminal with IP address 'aaa.aaa.aaa.aaa' is time 15:30:00, and movie A to the terminal with IP address 'bbb.bbb.bbb.bbb'. Distribution start time of the movie A to the terminal of the IP address' ccc.ccc.ccc.ccc 'is 15:32:40, and the IP address' ddd.ddd Drama B distribution start time for the terminal of “.ddd.ddd” is 15:25:00, and drama B distribution start time for the terminal of the IP address “eee.eee.eee.eee” is time 15:29: It means that it is 00. In this example, only the time is indicated, but it is also possible to display the date as necessary.

  Distribution status data managed by the distribution status management means 113 is received by the distribution method control means 110 from the data distribution request from the terminal 120, and data distribution is started by either the multicast distribution means 111 or the unicast distribution means 112. In this case, the information is recorded in the table managed by the distribution status management unit 113 by the distribution method control unit 110.

  In the case of data distribution by unicast, it is possible to completely grasp terminal information during connection by using KeepAlive for connection between the data distribution server 100 and the terminal 120, and distribution status management means 113 The distribution status data managed in FIG. 5 may be only information on how many terminals 120 are being distributed for each content.

  In addition, when performing data distribution by multicast, it is possible to manage the distribution information such as session information during data distribution by the multicast address or unicast by the distribution status management means 113.

  Processing for determining which of the multicast distribution means 111 and the unicast distribution means 112 performs distribution when the distribution method control means 110 receives a data distribution request from the terminal 120 will be described based on the flowchart of FIG. .

  When receiving the data distribution request from the terminal 120, the distribution method control means 110 determines whether or not the data for which the distribution request has been made is a content that is being distributed by the server (step S300). If the distribution method control unit 110 determines that the data requested to be distributed is not a service target, the distribution method control unit 110 proceeds to step S306. In step S306, the distribution method control means 110 notifies the terminal 120 that has requested data distribution that the corresponding content distribution service is not being performed, and ends the process.

  In step S300, when the distribution method control unit 110 determines that the content requested to be distributed is a distribution target, the process proceeds to step S301. In step S301, the distribution method control unit 110 refers to the distribution status data managed by the distribution status management unit 113, and determines the number of terminals (number of sessions) that are distributing the content requested for data distribution by unicast. It is determined whether it is less than a predetermined number N. If it is determined that the number of sessions by unicast is less than N, the process proceeds to step S307. If not, the process proceeds to step S302.

  In step S307, the distribution method control unit 110 instructs the terminal 120 that has transmitted the data distribution request from the unicast distribution unit 112 to distribute the corresponding data. The distribution method control means 110 notifies the terminal 120 that has made a data distribution request of unicast distribution information. Receiving this, the terminal 120 starts downloading data transmitted from the unicast distribution means 112 based on the received unicast distribution information. The data distribution method can be performed using FTP (File Transfer Protocol), HTTP (Hyper Text Transfer Protocol), and other known techniques.

  Thereafter, the process proceeds to step S305, where the distribution method control unit 110 adds the information of the terminal that has newly started data distribution by unicast to the distribution status data managed by the distribution status management unit 113, and ends the process.

  If it is determined in step S301 that the number of unicast sessions (number of terminals) is N or more, the process proceeds to step S302, and the distribution method control means 110 is distributing data of the corresponding content by multicast. Determine whether or not. The distribution method control unit 110 proceeds to step S304 when it is determined that the content requested to be distributed is already being distributed by multicast, and otherwise proceeds to step S303.

  In step S303, the distribution method control unit 110 instructs the multicast distribution unit 111 to start data distribution by multicast of the corresponding data. Multicast data distribution methods can use multicast over TCP / IP networks (Internet), satellite broadcasting, etc., DSMCC carousel transmission method (see ISO / IEC13818-6), and other well-known It is possible to use the transmission method. The multicast distribution means 111 starts data distribution of content corresponding to the data distribution request using such a method.

  In step S304, the distribution method control means 110 notifies the multicast address that distributes the corresponding data to the terminal 120 that has transmitted the data distribution request. The multicast address can be multicast address information on a TCP / IP network indicating a URL for downloading data, channel information in broadcasting, or the like. The terminal 120 that has received the notification of the multicast address from the distribution method control means 110 can download the corresponding content by accessing the multicast address. Thereafter, the process proceeds to step S305, where the distribution method control unit 110 adds the information of the terminal that has newly started data distribution by multicast to the distribution status data managed by the distribution status management unit 113, and ends the process.

  Processing when a data distribution request is received at the data distribution server will be further described based on a specific example. Consider a case where the distribution status data 200 is in a state as shown in FIG. 2 and there is a data distribution request for drama B from a terminal whose IP address is 'fff.fff.fff.fff'.

  Since the received data distribution request relates to the drama B, the distribution method control means 110 determines that the data is the distribution target data in step S300, and proceeds to step S301.

  In step S301, the distribution method control means 110 refers to the distribution status data 200 managed by the distribution status management means 113, and counts the number of terminals (number of sessions) that are distributing the drama B. As shown in FIG. 2, since the number of terminals that are delivering drama B is 2, the delivery method control means 110 counts the number of sessions that are currently delivering drama B as 2. Next, when it is assumed that the predetermined number N for determining that data distribution by multicast is performed when a distribution request is made is 2, the current number of sessions by unicast is 2, so the predetermined number N or more Thus, the process proceeds from step S301 to step S302.

  Drama B is in the process of distributing data by unicast to two terminals, and does not perform data distribution by multicast, so the process moves from step S302 to step S303.

  The distribution method control means 110 instructs the multicast distribution means 111 to start multicast distribution of drama B data to the terminal 120 that has newly requested data distribution. The multicast distribution unit 111 starts distributing the data of the drama B by multicast according to the instruction of the distribution method control unit 110.

  In step S304, the distribution method control means 110 notifies the terminal 120 that has made a data distribution request of the multicast address where distribution of the drama B is started. The terminal 120 that has received the notification of the multicast address from the distribution method control means 110 can receive the data of the drama B that has requested the data distribution by accessing this multicast address.

  In step S305, the distribution method control unit 110 updates the contents of the distribution status data 200 managed by the distribution status management unit 113 based on a series of processes. In this example, since the distribution of the drama B by multicast is newly started to the IP address 'fff.fff.fff.fff', the distribution status data 200 managed by the distribution status management means 113 is shown in FIG. The state is as shown.

  The predetermined number N in step S301 can be set to a different value for each data to be distributed according to the data size, popularity, and other parameters. For example, for movie A, N is set to 10. For drama B, N can be set to 100.

A process for deleting information of terminals for which data distribution has been completed from the distribution status data will be described based on the flowchart shown in FIG.
In step S500, when the distribution method control unit 110 receives a download completion notification from the terminal 120 that is distributing data, the distribution method control unit 110 proceeds to step S501.

In step S501, the distribution method control unit 110 deletes the information of the terminal that has received the notification of the end of download from the distribution status data managed by the distribution status management unit 113.
In step S502, the delivery method control unit 110 determines whether or not the delivery status data managed by the delivery status management unit 113 includes terminal information being delivered whose timeout period has passed. If the distribution method control unit 110 determines that the distribution status data managed by the distribution status management unit 113 includes terminal information whose preset timeout period has passed, the process proceeds to step S503. If not, the process proceeds to step S500.

In step S503, the distribution method control unit 110 deletes terminal information that has passed a predetermined timeout period in the distribution status data managed by the distribution status management unit 113.
A process for deleting terminal information from distribution status data will be described below based on a specific example. Here, it is assumed that the preset timeout period is set to 10 minutes.

  In the case of the distribution status data 200 as shown in FIG. 4, a notification indicating that the download of movie A has been completed is received from the terminal having the IP address “aaa.aaa.aaa.aaa” at 15 hours 34 minutes 30 seconds. Assuming that In this case, upon receiving the notification of the end of download from the terminal having the IP address' aaa.aaa.aaa.aaa ', the distribution method control means 110 moves from step S500 to step S501, and from the distribution status data 200 to the IP address' Delete the terminal information of aaa.aaa.aaa.aaa '. As a result, the distribution status data 200 shifts to a state as shown in FIG.

  Further, when the time elapses and 15 minutes and 35 minutes are reached, the terminal having the IP address “ddd.ddd.ddd.ddd” that distributes the data of drama B will exceed the timeout period. Therefore, the distribution method control unit 110 proceeds to step S503 based on the determination result in step S502.

  In step S503, the distribution method control unit 110 manages the information of the terminals whose timeout period has elapsed (here, the terminal whose IP address is 'ddd.ddd.ddd.ddd') by the distribution status management unit 113. Delete from delivery status data. As a result, the distribution status data 200 is in a state as shown in FIG.

  The notification of the end of download from the terminal 120 during data delivery is not configured to notify the delivery method control means 110, but to the unicast delivery means 112 and multicast delivery means 111, and the unicast delivery means 112 and multicast delivery means 111 are notified. It is also possible to configure so as to notify the distribution method control means 110 from the above. In addition, when data is distributed by the unicast distribution unit 112, the download completion notification from the terminal 120 is made because the unicast distribution unit 112 can recognize this when the download at the terminal 120 is completed. It is also possible to adopt a configuration without this.

  The distribution method control means 110, the multicast distribution means 111, and the unicast distribution means 112 can be mounted on one device, and each is mounted on another device, and each device is connected via a network to cooperate. The structure which operate | moves may be sufficient.

  The timeout period in step S502 of FIG. 5 can be set for each data to be distributed. For example, the timeout period is set to 30 minutes for movie A, and the timeout period is set to 10 minutes for drama B. Examples such as

  Also, the timeout period can be changed according to the bit rate at the time of data distribution. For example, the time-out period when drama B is distributed at 10 Mbit / sec is set to 10 minutes, and the time-out period when it is distributed at 20 Mbit / sec is set to 5 minutes.

  Instead of setting the time-out period for each data, it is possible to automatically calculate according to the data size. For example, when the data size of movie A is three times the data size of drama B, the timeout period of movie A can be set to be three times the timeout period of drama B. Further, it is possible to automatically calculate and set the timeout period according to the bit rate at the time of data distribution. For example, a configuration may be considered in which the timeout period is halved if the bit rate for data distribution is doubled.

<Other embodiments>
(A) When receiving a data distribution request from the terminal 120, if the number of terminals to be distributed by unicast exceeds the predetermined number N according to the data distribution request, in addition to the terminal that newly starts data distribution, It is also possible to configure the terminal that performs data distribution by casting to switch to data distribution by multicast.

A functional block diagram of the distribution method control means 110 in this case is shown in FIG.
As shown in FIG. 8, the distribution method control means 110 performs distribution based on the determination in the switching determination unit 115 and the switching determination unit 115 that dynamically determines the distribution method according to the number of terminals during data distribution. A switching notification unit 116 that notifies the terminal 120 that switches the method, and a switching instruction for data distribution to the unicast distribution unit 112 and the multicast distribution unit 111 based on the determination by the switching determination unit 115 And a switching control unit 117 for performing the above.

  In this case, when a new data distribution request is received, the switching determination unit 115 refers to the distribution status data managed by the distribution status management means 113, and counts the number of terminals that are distributing the corresponding data by unicast. It is then determined whether or not the predetermined number N is exceeded. When the switching determination unit 115 determines that the number of terminals that perform unicast data distribution exceeds a predetermined number N according to the data distribution request, the switching determination unit 115 notifies the switching notification unit 116 and the switching control unit 117 to that effect. Do.

  The switching notification unit 116 notifies all of the terminals that distribute the corresponding data by unicast to the multicast address at which the distribution is newly started, stops the download by unicast, and from the notified multicast address Request to switch to download.

In the switching control unit 117, distribution of the corresponding data by the unicast distribution unit 112 is stopped, and distribution of the corresponding data by the multicast distribution unit 111 is started.
The terminal 120 that received the request to cancel the download by unicast and to download by multicast, knows the data position received so far at the terminal, stops the download by unicast, and performs the multicast. Access the address and start multicast download. The terminal 120 can download the continuation of the data downloaded by unicast by multicast and combine the data to complete the data.

  In addition, when there is a download end notification from the terminal 120 that is distributing data, the total number of terminals that are distributing data by multicast and terminals that are distributing data by unicast by the download end notification is When the number becomes less than the predetermined number M, it is possible to switch from multicast data distribution to unicast data distribution.

  In this case, when the download end notification is received, the switching determination unit 115 refers to the distribution status data managed by the distribution status management means 113, counts the number of terminals that are distributing the corresponding data, and determines a predetermined number. It is determined whether or not it is less than M. Upon receiving the download completion notification from the terminal 120, the switching determination unit 115 deletes the corresponding terminal information from the distribution status data managed by the distribution status management means 113, and thereby the number of terminals being distributed by multicast and the unit. When it is determined that the total number with the number of terminals being distributed by casting is less than a predetermined number M, a notification to that effect is sent to the switching notification unit 116 and the switching control unit 117.

  The switching notification unit 116 requests all terminals that distribute the corresponding data by multicast to stop downloading by multicast and switch to downloading by unicast.

The switching control unit 117 stops the distribution of the corresponding data by the multicast distribution unit 111 and starts the distribution of the corresponding data by the unicast distribution unit 112.
The terminal 120 that received a request to stop downloading by multicast and download by unicast knows the data position received so far at the terminal, stops downloading by multicast, and then unicasts. Start downloading at. The terminal 120 can download the continuation of the data downloaded by multicast by unicast and combine the data to complete the data.

  For partial downloading of data, a method by http range specification or other known methods can be used. Further, the value of the predetermined number M can be a value equal to or less than the predetermined number N.

  As described above, switching between data distribution by unicast and data distribution by multicast can be applied to a case where data received at terminal 120 is temporarily stored and reproduced later.

  Note that the algorithm for determining whether data distribution is performed by the multicast distribution unit 111 or data distribution by the unicast distribution unit 112 depends on the state of the terminal that is performing data distribution when the data distribution request is received. Then, for example, an algorithm may be considered in which, without using the threshold value N for the number of terminals that are delivering each content, the content is distributed in order from the largest number of terminals that are currently delivering data to multicast delivery. . Therefore, it is possible to configure the process to be executed by an algorithm different from the flowchart shown in FIG.

  In addition, based on the sum of the number of terminals that are performing data distribution by unicast and the number of terminals that are performing data distribution by multicast, a distribution method is determined for a terminal that has requested data distribution next. be able to. As described above, when the number of terminals performing data distribution by unicast exceeds a predetermined number N, for terminals that have next requested data distribution in order to reduce the load, multicast is used. Start data distribution. After this, when the data download at the terminal that is distributing data by unicast is completed, the number of terminals that are distributing data by unicast in the distribution status data managed by the distribution status management means 113 Becomes a predetermined number N or less. Therefore, according to the flowchart as shown in FIG. 3, if there is a data distribution request for the same content next, the data distribution method for the terminal is based on unicast. On the other hand, in step S301, it is determined whether or not the total of the number of terminals performing data distribution by unicast and the number of terminals performing data distribution by multicast is less than a predetermined number N. If it is determined that the number is less than the predetermined number N, it is possible to proceed to step S307. If it is determined that the number is greater than or equal to the predetermined number N, the process can be shifted to step S302. In this case, when there are many data distribution requests from the terminal, the data distribution will be converged to the multicast data distribution, and the data distribution server 100 and the line load can be reduced to improve the data distribution efficiency. it can.

  According to the configuration of the present invention as described above, even when access to specific content is concentrated. It becomes possible to realize efficient data distribution by reducing the load on the server and the line.

  The data distribution server and the data distribution system according to the present invention are useful for a content distribution system using the broadband Internet and the like, and in particular, access may be concentrated on the distribution start date and release date of movies and games. Useful when delivering content. Further, the present invention can be applied not only to the Internet but also to a data distribution system on an intranet.

1 is a block diagram showing a schematic configuration of a data distribution system in which one embodiment of the present invention is adopted. Explanatory drawing which shows an example of delivery status data. The flowchart which shows the process of a delivery method determination. Explanatory drawing which shows an example of delivery status data. The flowchart which shows the process at the time of completion | finish of delivery. Explanatory drawing which shows an example of delivery status data. Explanatory drawing which shows an example of delivery status data. The functional block diagram of a delivery method control means.

Claims (8)

Content management means for storing one or more contents;
Unicast distribution means for distributing the corresponding data by unicast among the contents managed by the content management means in response to a data distribution request from the terminal;
Multicast distribution means for distributing the corresponding data among the contents managed by the content management means in response to a data distribution request from the terminal by multicast;
Distribution status management means for managing terminal information that is currently being distributed as distribution status data;
A distribution method control means for determining whether data distribution to each terminal is performed via the unicast distribution means or the multicast distribution means based on distribution status data managed by the distribution status management means;
A data distribution server comprising:   The data according to claim 1, wherein the distribution status management means updates the distribution status data so that the status is reflected in the distribution status data managed at the start of distribution to the terminal and at the end of distribution to the terminal. Distribution server.   When there is a data distribution request from a terminal, the distribution method control means refers to the distribution status data managed by the distribution status management means, and the number of terminals that are distributing the corresponding content by unicast is less than a predetermined number. In some cases, the content is distributed by unicast distribution means, and when the number of terminals that are distributing the corresponding content by unicast is equal to or greater than a predetermined number, the content is determined to be distributed by multicast distribution means. Item 3. The data distribution server according to Item 2.   The distribution method control means includes a switching determination unit that dynamically determines a distribution method to be switched according to the number of terminals during data distribution, and a terminal that switches a distribution method based on the determination by the switching determination unit. And a switching control unit for instructing switching of data distribution to the unicast distribution unit and the multicast distribution unit based on the determination by the switching determination unit. The data delivery server in any one of -3.   The data distribution server according to any one of claims 1 to 4, wherein the distribution status management means updates the distribution status data when receiving a download end notification from a terminal during data distribution.   6. The data distribution server according to claim 5, wherein the distribution status management means determines that the download at the terminal is completed when a download completion notification is not received even after a predetermined time has elapsed from the terminal that started the data distribution. . A data delivery system for delivering data from a data delivery server in response to a data delivery request from a terminal,
The data distribution server is
Content management means for storing one or more contents;
Unicast distribution means for distributing the corresponding data by unicast among the contents managed by the content management means in response to a data distribution request from the terminal;
Multicast distribution means for distributing the corresponding data among the contents managed by the content management means in response to a data distribution request from the terminal by multicast;
Distribution status management means for managing terminal information being distributed as distribution status data;
A distribution method control means for determining whether data distribution to each terminal is performed via the unicast distribution means or the multicast distribution means based on distribution status data managed by the distribution status management means;
With
The terminal
Download means for transmitting a data distribution request to the data distribution server and receiving data distributed by unicast or multicast from the data distribution server;
Download instruction means for selecting content to be downloaded from the data distribution server and causing the download means to receive data from the data distribution server;
A data distribution system comprising: Download means for transmitting a data distribution request to the data distribution server in order to download content managed by the data distribution server, and receiving data distributed by unicast or multicast from the data distribution server;
When a download notification of distribution method is received from the data distribution server during execution of data download by the download means, the download means temporarily stops receiving data and the continuation of the data downloaded so far is designated. A download control unit for downloading by a method,
A data download terminal comprising:

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