JP2010226447A - Content distribution system and content distribution method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a quality of distribution contents by efficiently re-distributing a missed packet when distributing contents from a high-order server in a VOD (Video On Demand) system to a low-order server. <P>SOLUTION: A management server 10 creates a packet by adding information on a packet SEQ number and the total number of packets to fragment data obtained by dividing held contents with a predetermined data length and distributes contents to a plurality of distribution servers 20 by multicasting. Each distribution server 20 then analyzes the received contents for the unit of a packet, creates missing information representing presence of packet missing in an order of packet SEQ numbers and transmits it to the management server 10. The management server 10 then determines presence of a missed packet to be retransmitted, a retransmission destination and a distribution method based on the received missing information and retransmits the missed packet to each distribution server 20 by multicasting or unicasting based on results of the determination. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a content distribution system and a content distribution method for distributing distribution content to a distribution server disposed at each site.

  A VOD (Video On Demand) system is a system that distributes content in response to a request from a user. For example, when a user wants to watch a movie, the user can view the movie at a desired time zone by selecting a title at a home viewing terminal (a personal computer or a television connected to a dedicated device).

  In general, content distributed by a VOD service provider is managed by a higher-level server and is distributed to a lower-level distribution server (relay server) arranged at each site as needed. For example, each distribution server distributes content that is expected to be viewed according to the contract contents of users in the distribution area, past viewing history, etc. from a higher-level server in advance, thereby improving the efficiency of distribution requests from users. Distribution processing can be performed.

  Further, unicast and multicast can be cited as communication methods for distributing content. Unicast is a one-to-one two-way communication between a sender and a receiver, and retransmission is performed when a transmitted packet is lost, so that communication reliability is high. On the other hand, when content is distributed from a higher-level server to a plurality of distribution servers, the same packet must be individually sent to each distribution server, which increases the load on the higher-level server and the network.

  On the other hand, multicast is a one-to-N one-way communication between a sender and a receiver, and a packet transmitted from one sender is transmitted while being copied by a relay device (router) on the network. Deliver to recipients. Therefore, it is preferable to distribute the content from the upper server to the distribution server by multicast. However, in the case of multicast, there is a possibility that some packets are lost in the relay device (router) on the network.

  In order to solve such a problem, a technique is known in which, when a packet is lost due to multicast, the lost packet is retransmitted by multicast (see, for example, Patent Document 1).

JP 2002-84239 A

  However, in the above-described prior art, even in the case of retransmission by multicast, content is transmitted almost in real time because it is transmitted at a constant bit rate in consideration of the network load. In addition, there is a problem that there is no missing packet and the lost packet is delivered to a delivery server that originally does not need to be retransmitted, resulting in a time loss and an extra load on the network, which is inefficient. .

  Therefore, in view of the above-mentioned problems of the conventional technology, the present invention can efficiently redistribute packets lost during distribution processing of distribution content performed between servers during the VOD service and improve the quality of distribution content. An object is to provide a content distribution system and a content distribution method.

  A content distribution system according to the present invention is connected to a management server that distributes owned content to a lower server, a viewing terminal for viewing the content, and a management server via a network, and distributes the content distributed from the management server. A plurality of distribution servers that distribute in response to a viewing request from the viewing terminal, wherein the management server includes a content storage unit that stores the content, and a fragment obtained by dividing the stored content by a predetermined data length A content distribution unit that creates a packet in which information of a packet SEQ number and the total number of packets is added to data, and distributes the content to the distribution server by a multicast or unicast distribution method, and whether or not data is missing in the distributed content In the order of the packet SEQ numbers. The received missing information is received from each of the plurality of distribution servers, and the missing information totaling unit for summing up, analyzing the tabulated missing information, whether there is a missing packet that needs to be retransmitted, the retransmission destination, and the multicast or the A content retransmission determination unit that determines a unicast distribution method and retransmits the missing packet from the content distribution unit according to the determination result, and the distribution server receives the content distributed from the management server. A distribution content receiving unit for receiving, a distribution content storage unit for storing content to be distributed to the viewing terminal, and a distribution registered and managed in the distribution content storage unit for content received by the distribution content receiving unit Content received by the content management unit and the distribution content receiving unit Create the missing information by analyzing a packet basis, based on the packet SEQ number and the total number of packets, characterized in that it comprises the missing information creation unit for transmitting it to the management server, the.

  The content distribution method according to the present invention includes a management server that distributes owned content to a lower server, a viewing terminal that views the content, and a management server that are connected via a network, and that distributes the content distributed from the management server. A content distribution method in a computer system, comprising: a plurality of distribution servers that distribute in response to a viewing request from the viewing terminal, wherein the management server converts packet SEQ into fragment data obtained by dividing the content by a predetermined data length A content distribution step of creating a packet to which information on the number and the total number of packets is added and distributing the content to the distribution server by a multicast or unicast distribution method; and the content distributed by the distribution server in the content distribution step The Content registration step of registering in the database, and the distribution server analyzes the content distributed in the content distribution step in units of packets based on the packet SEQ number and the total number of packets, and the data missing in the content The missing information creation step of creating the missing information in which the presence / absence is represented in the order of the packet SEQ number and transmitting the information to the management server; and the management server creating the missing information created in the missing information creation step as the plurality of Missing information counting step for receiving and counting from each distribution server, and the management server analyzing the missing information tabulated in the missing information counting step, whether there is a missing packet that needs to be retransmitted, the retransmission destination, and the multicast Or how to distribute the unicast A content retransmission step for determining the content, a content retransmission step in which the management server retransmits the missing packet in accordance with a determination result in the content retransmission determination step, and the distribution server stores the content registered in the database A content update step of updating based on the lost packet retransmitted in the content retransmission step.

  According to the present invention, there are provided a content distribution system and a content distribution method capable of efficiently redistributing packets lost during distribution processing of distribution content performed between servers and improving the quality of distribution content. The

1 is a diagram showing an example of the overall configuration of a VOD system to which a content distribution system according to an embodiment of the present invention is applied. The figure which shows the structural example of the computer applied to the management server and distribution server which are shown in FIG. 1 is a block diagram showing an example of the overall configuration of a content distribution system according to an embodiment of the present invention. The figure explaining the transmission method of content data. The figure explaining the specific example of the totaling method of missing information. The figure explaining the format of the data stored in the delivery content storage part shown in FIG. The figure explaining the structural example of the transmission data containing missing information. The flowchart which shows the specific example of the process of the content distribution system which concerns on one Embodiment of this invention. The flowchart which shows the specific example of the process of the content distribution system which concerns on one Embodiment of this invention. The block diagram explaining the synchronization process of the content between delivery servers. The figure which shows the specific example of the delivery process of the content distribution system which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an example of the overall configuration of a VOD system to which a content distribution system according to an embodiment of the present invention is applied. As shown in the figure, the VOD system includes a management server 10, a distribution server 20, and a viewing terminal 30, and N (N ≧ 2) distribution servers 20 and distribution servers 20 with respect to the management server 10. N (n ≧ 2) viewing terminals 30 are connected via the network 40.

  The management server 10 is a computer that distributes owned content to lower servers. The distribution server 20 is a computer that is connected to the management server 10 and the viewing terminal 30 via the network 40 and distributes the content distributed from the management server 10. The viewing terminal 30 is a terminal such as a TV or a PC where a user views content distributed from the distribution server 20 in response to a viewing request made to the distribution server 20. The network 40 is a dedicated network for the VOD system.

  FIG. 2 is a diagram illustrating a configuration example of a computer applied to the management server 10 and the distribution server 20 illustrated in FIG. As shown in the figure, a computer applied to the management server 10 or the like includes a CPU (Central Processing Unit) 51, a ROM (Read Only Memory) 52, a RAM (Random Access Memory) 53, an interface 54, a system bus 55, an input. A device 56, a display device 57, an auxiliary storage device 58, and a communication device 59 are included.

  The CPU 51 is a processing device that executes various arithmetic processes using programs, data, and the like stored in the ROM 52 and the RAM 53. The ROM 52 is a read-only storage device that stores basic programs and environment files for causing the computer to function. The RAM 53 is a storage device that stores a program executed by the CPU 51 and data necessary for executing each program, and can be read and written at high speed. The interface 54 is a device and a program that mediate connections between various hardware and the system bus 55. The system bus 55 is an information transmission path shared by the CPU 51, ROM 52, RAM 53, and interface 54.

  In addition, hardware such as an input device 56, a display device 57, an auxiliary storage device 58, and a communication device 59 is connected to the interface 54. The input device 56 is a device that processes input from a user, and is, for example, a keyboard or a mouse. The display device 57 is a device that displays a calculation result, a creation screen, and the like to the user, and is a CRT, a liquid crystal display, a plasma display, or the like. The auxiliary storage device 58 is a large-capacity storage device that stores programs and data, and is, for example, a hard disk device.

  FIG. 3 is a block diagram showing an example of the overall configuration of a content distribution system according to an embodiment of the present invention. As shown in the figure, the management server 10 functions as a content storage unit 101, a server management information storage unit 102, a distribution notification unit 103, a content distribution unit 104, a missing information totaling unit 105, and a content retransmission determination unit 106. Have.

The content storage unit 101 is a storage device that stores content to be distributed to the distribution server 20.
The server management information storage unit 102 is a storage device that stores server management information such as the identification name, IP address, and group information of the distribution server 20 connected to the network 40. In the present embodiment, it is assumed that the distribution servers 20 are distributed at the bases of the VOD service provider, and the distribution servers 20 are classified into a plurality of groups based on a predetermined rule. In addition, rules for classifying groups can be arbitrarily defined. However, in consideration of a tendency of data loss at the time of multicasting, it is preferable that servers that pass through the same relay device (router) be the same group. Further, in the group, one server (hereinafter referred to as “representative distribution server”) that communicates with the management server 10 on behalf of the group is selected in advance, and another server (hereinafter referred to as “representative distribution server”). And “affiliated distribution server”) and group information.

The distribution notification unit 103 is a program that outputs a prior notification from the communication device 59 to the distribution destination before performing content distribution processing from the content distribution unit 104.
The content distribution unit 104 creates a packet in which information on the packet SEQ number and the total number of packets is added to fragment data obtained by dividing the stored content by a predetermined data length, and the packet related to the content is transmitted by a multicast or unicast distribution method. It is a program distributed to the distribution server 20.

  FIG. 4 is a diagram for explaining a content data transmission method. Here, the content data to be distributed is divided into fragment data of a predetermined data length, and the TCP header and IP header are added to the data that uses the packet SEQ number indicating the packet order and the total number of packets as a header and the fragment data as a payload. It is shown that an IP packet is created, and header information (preamble, SFD, MAC header) corresponding to the physical layer is added to this IP packet as transmission data. This transmission data is further converted in the relay device (router) and transmitted over the network 40. Further, it is indicated that the maximum length of an IP packet is an MTU (Maximum Transmission Unit) that is the maximum value of data that can be transmitted in one transfer in the network 40. In this embodiment, since there are a plurality of distribution servers 20, the distribution method when the content is first distributed from the management server 10 is multicast, and the second and subsequent distribution methods are from the content retransmission determination unit 106 described later. It shall be based on the instructions.

  The missing information totaling unit 105 is a program that receives and totals missing information representing the presence or absence of data loss in the distributed content in order of packet SEQ numbers from a plurality of distribution servers 20 (representative distribution servers). FIG. 5 is a diagram illustrating a specific example of a method for counting missing information. Here, as a result of analyzing the packet relating to the contents, “0” is set when the packet is received, and “1” is set when the packet is missing. 20 is received as missing information at 20, and a plurality of missing information is totaled for each bit, and it is shown that total information including weighting indicating whether or not a packet is missing and the number of missing servers is created. For example, when the third column from the left of the total information corresponds to a packet of “packet SEQ number = 3”, the packet is missing on the network 40, and the number of distribution servers 20 is four. I understand.

  The content retransmission determination unit 106 analyzes the aggregated missing information, determines the presence / absence of a missing packet that needs to be retransmitted, a retransmission destination, and a distribution method, and retransmits the lost packet to the content distribution unit 104 according to the determination result. It is a program to let you. Specifically, the optimal distribution method (multicast / unicast) is selected after calculating the load of the management server 10 and the total amount of data sent to the network 40. It should be noted that an optimal value is previously calculated and set as a threshold value as a determination criterion based on past statistics, experimental results, and the like, but it is preferable that the administrator can arbitrarily change it.

  As shown in FIG. 3, the distribution server 20 includes a distribution notification receiving unit 201, a distribution content receiving unit 202, a distribution content management unit 203, a distribution content storage unit 204, a missing information creation unit 205, and a missing information totaling unit 206. , A distribution content retransmission determination unit 207, a group information storage unit 208, a distribution notification unit 209, a distribution content synchronization unit 210, a distribution request reception unit 211, and an RTP distribution unit 212 are included as functions.

  The distribution notification receiving unit 201 is a program that receives a distribution notification (preliminary notification) transmitted from the management server 10 or the representative distribution server and outputs the distribution notification to the distribution content receiving unit 202.

  The distribution content receiving unit 202 is a program that prepares to receive content when the distribution notification receiving unit 201 receives the distribution notification and receives the content distributed from the management server 10 or the representative distribution server.

  The distribution content management unit 203 is a program that registers and manages the content received by the distribution content reception unit 202 in the distribution content storage unit 204.

  The distribution content storage unit 204 is a storage device that stores content to be distributed to the viewing terminal 30. FIG. 6 is a diagram for explaining the format of data stored in the distribution content storage unit 204 shown in FIG. Here, when the distribution content receiving unit 202 receives packets with packet SEQ numbers 3, 5, and 7 missing, it is referred to as a missing packet in the distribution content storage unit 204 (hereinafter referred to as “missing packet”). It is shown that NULL is set in the storage area corresponding to) and is stored in a form that can be complemented using the packet SEQ number as a key when it is retransmitted. Note that the storage format in the distribution content storage unit 204 is not limited to the storage format shown in FIG. 5, and a value (space, symbol, etc.) other than NULL may be set in the storage area corresponding to the missing packet.

  The missing information creation unit 205 is a program that analyzes the content received by the distribution content receiving unit 202 in units of packets based on the packet SEQ number and the total number of packets, creates missing information, and transmits this to the management server 10. . FIG. 7 is a diagram illustrating the configuration of transmission data including missing information. Here, as a result of analyzing the packet related to the content, the bit string set in the order of the packet SEQ number is “0” when the packet is received and “1” when the packet is missing. It is shown that missing information is set in the data portion.

  The missing information totaling unit 206 is a program that receives and totals the missing information at the time of distribution from the management server 10 or the representative distribution server from the belonging distribution server of the same group, similarly to the above-described missing information totaling unit 105. .

  Similarly to the content retransmission determination unit 106 described above, the distribution content retransmission determination unit 207 analyzes the missing information collected by the missing information totaling unit 206, and determines whether there is a missing packet that needs to be retransmitted, the retransmission destination, and the distribution method. It is a program to judge.

  The group information storage unit 208 is a storage device that stores group information such as the identification name, IP address, group identification name, and identification name of the representative distribution server belonging to the same group on the network 40.

  The distribution notification unit 209 is a program that outputs a prior notification from the communication device 59 to the distribution destination before performing distribution processing (synchronization processing) of missing packets from the distribution content synchronization unit 210.

  The distribution content synchronization unit 210 is a program that retransmits the missing packet to the affiliated distribution servers in the same group based on the determination result in the distribution content retransmission determination unit 207, and synchronizes the distribution content storage unit 204 between the servers. is there.

  The distribution request receiving unit 211 is a program that receives a viewing request transmitted from the viewing terminal 30 by the communication device 59 and outputs it to the RTP distributing unit 212.

  When the distribution request receiving unit 211 receives the viewing request, the RTP distribution unit 212 acquires the content related to the viewing request from the distribution content storage unit 204 and distributes it from the communication device 59 based on RTP (Real-time Transport Protocol). It is a program.

  The functions of the missing information totaling unit 206, the distribution content retransmission determination unit 207, the group information storage unit 208, the distribution notification unit 209, and the distribution content synchronization unit 210 are sufficient to have only the representative distribution server. Since it may be necessary to change from the affiliated distribution server to the representative distribution server, such as when the distribution server fails, it is preferable that all the distribution servers 20 have the same function.

8 and 9 are flowcharts showing specific examples of processing of the content distribution system according to the embodiment of the present invention. Also,
In step S <b> 801, the distribution notification unit 103 of the management server 10 transmits a prior notification of content distribution to all the distribution servers 20.
In step S <b> 802, the content distribution unit 104 of the management server 10 multicasts the content to all the distribution servers 20.
In step S <b> 803, the content distribution unit 104 of the management server 10 requests the representative distribution server 20 to transmit missing information.

In step S804, the missing information creation unit 205 of the representative delivery server creates missing content information.
In step S <b> 805, the missing information creation unit 205 of the representative delivery server transmits missing information to the management server 10.
In step S806, the missing information totaling unit 105 of the management server 10 totals missing information from the representative distribution server.
In step S <b> 807, the content retransmission determination unit 106 of the management server 10 determines whether there is a missing packet. If it is determined that there is a missing packet, the process proceeds to S808. On the other hand, if it is determined that there is no missing packet, the process proceeds to S812.

  In step S808, the content retransmission determination unit 106 of the management server 10 determines whether the number of retransmission target servers is equal to or greater than a threshold value. If it is determined that the value is equal to or greater than the threshold value, the process proceeds to S809. On the other hand, if it is determined that it is less than the threshold value, the process proceeds to S811.

  In step S809, the content retransmission determination unit 106 of the management server 10 determines whether the number of missing packets is equal to or greater than a threshold value. Here, if it is determined that the threshold value is exceeded, the process proceeds to S810. On the other hand, if it is determined that it is less than the threshold value, the process proceeds to S811.

In S810, the content distribution unit 104 of the management server 10 multicasts the missing packet to the representative distribution server.
In S811, the content distribution unit 104 of the management server 10 unicasts the lost packet only to the representative distribution server in which the packet is lost. Through the processes in S801 to S811, first, the lack of content in the representative distribution server is complemented by retransmission, and preparation for synchronization processing between the distribution servers 20 described later is completed. FIG. 10 is a block diagram illustrating content synchronization processing between the distribution servers 20. Here, the representative distribution server aggregates and retransmits the missing information transmitted from the affiliated distribution server in the group (*), and synchronizes by distributing the content (missing packet) to the affiliated distribution server according to this result. The flow in which is performed is shown.

In S812, the distribution content synchronization unit 210 of the representative distribution server makes a transmission request for missing content information to the affiliated distribution server belonging to the same group.
In step S813, the missing information creation unit 205 of the affiliated distribution server creates missing content information.
In S814, the missing information creation unit 205 of the affiliated distribution server transmits the missing information to the representative distribution server.
In S815, the missing information totaling unit 206 of the representative distribution server totals the missing information from the affiliated distribution server.

  In step S816, the distribution content retransmission determination unit 207 of the representative distribution server determines whether there is a missing packet. If it is determined that there is a missing packet, the process proceeds to S817. On the other hand, if it is determined that there is no missing packet, the process proceeds to S821.

  In step S817, the representative distribution server distribution content retransmission determination unit 207 determines whether or not the number of retransmission target servers is equal to or greater than a threshold value. If it is determined that the value is equal to or greater than the threshold value, the process proceeds to S818. On the other hand, if it is determined that it is less than the threshold, the process proceeds to S820.

  In step S818, the representative delivery server delivery content retransmission determination unit 207 determines whether the number of missing packets is equal to or greater than a threshold value. Here, if it is determined that the value is equal to or greater than the threshold value, the process proceeds to S819. On the other hand, if it is determined that it is less than the threshold, the process proceeds to S820.

In S819, the distribution content synchronization unit 210 of the representative distribution server multicasts the missing packet to the affiliated distribution server.
In S820, the representative distribution server unicasts the lost packet only to the affiliated distribution server in which the packet is lost.
In step S <b> 821, the content distribution unit 104 of the management server 10 determines whether distribution of content to the distribution server 20 has been completed. If it is determined that the content distribution has been completed, the process ends. On the other hand, if it is determined that the content distribution has not been completed, the process returns to S802, and the processes of S802 to S821 are repeated until the content distribution is completed, and the process ends.

  FIG. 11 is a diagram showing a specific example of distribution processing of the content distribution system according to the embodiment of the present invention. As shown in the figure, first, content is distributed from the management server 10 to all distribution servers 20 (distribution servers (1) to (8)) by multicast (distribution pattern A). Next, the management server 10 analyzes the missing information transmitted from the representative distribution servers (distribution servers (1) and (5)), and calculates the load of the management server 10 and the total amount of data transmitted to the network 40. An optimum distribution method (multicast / unicast) is selected and a retransmission process is performed to the representative distribution server (distribution pattern B). Then, the distribution server 20 on the network 40 is classified into a plurality of groups in advance and a representative distribution server is defined, and a synchronization process (distribution pattern C) is performed between the representative distribution server and the affiliated distribution server in the group and missing. Complement the packet. For this reason, since the minimum necessary data is transmitted and received between the servers, the load on the server and the network 40 can be reduced, and the quality of the content finally provided to the user can be improved. Further, compared to the case where missing information is transmitted from each distribution server 20 to the management server 10, less access to the management server 10 is required, so that the processing efficiency is good.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment.

10 ... Management server,
20 ... distribution server,
30 ... viewing terminal,
40 ... Network,
51 ... CPU,
52 ... ROM,
53 ... RAM,
54 ... Interface,
55 ... System bus,
56 ... Input device,
57 ... display device,
58. Auxiliary storage device,
59. Communication device,
101 ... content storage unit,
102 ... Server management information storage unit,
103 ... distribution notification part,
104 ... content distribution section,
105. Missing information totaling unit,
106: Content retransmission determination unit,
201 ... distribution notification reception part,
202 ... a distribution content receiving unit,
203 ... distribution content management unit,
204: Distribution content storage unit,
205 ... missing information creation unit,
206 ... Missing information totaling unit,
207 ... Distribution content retransmission determination unit,
208 ... Group information storage unit,
209 ... Distribution notification section,
210 ... distribution content synchronization unit,
211 ... Distribution request accepting unit,
212 ... RTP distribution unit.

Claims (5)

A management server that distributes the content held to lower servers;
A plurality of distribution servers connected to a viewing terminal for viewing the content and a management server via a network, and distributing the content distributed from the management server in response to a viewing request from the viewing terminal;
Consists of
The management server
A content storage unit for storing the content;
Content that creates a packet by adding packet SEQ number and packet total information to fragmented data obtained by dividing the stored content by a predetermined data length, and distributes the content to the distribution server by a multicast or unicast distribution method A distribution department;
A missing information totaling unit that receives and totals the missing information that represents the presence or absence of data loss in the distributed content in the order of the packet SEQ numbers from the plurality of distribution servers;
Analyzing the aggregated missing information, determining the presence / absence of a missing packet that needs to be retransmitted, the retransmission destination, and the multicast or unicast delivery method, and from the content delivery unit according to the judgment result A content retransmission determination unit for retransmitting
With
The distribution server
A distribution content receiving unit that receives the content distributed from the management server;
A distribution content storage unit for storing content to be distributed to the viewing terminal;
A distribution content management unit that registers and manages content received in the distribution content receiving unit in the distribution content storage unit;
Analyzing the content received in the distribution content receiving unit in units of packets based on the packet SEQ number and the total number of packets to create the missing information, and transmitting the missing information to the management server;
A content distribution system comprising:   The distribution server is classified into a plurality of groups on the network, and a representative distribution server selected in advance from the group displays the missing information created by the missing information creation unit on behalf of the group. The content distribution system according to claim 1, wherein the content distribution system transmits the received packet and retransmits the missing packet. The representative distribution server further includes:
A second missing information totaling unit that receives and totals the missing information related to the content delivered from the management server or the representative delivery server from other delivery servers belonging to the group;
A distribution content retransmission determination unit that analyzes the missing information collected in the second missing information aggregation unit and determines the presence / absence of a missing packet that needs to be retransmitted, a retransmission destination, and the distribution method;
A distribution content synchronization unit that retransmits the missing packet to the other distribution server based on a determination result in the distribution content retransmission determination unit, and performs synchronization processing of the distribution content storage unit between the servers;
The content distribution system according to claim 2, further comprising: A management server that distributes content held to a lower server, a viewing terminal that views the content, and a management server that are connected via a network, and that responds to a viewing request from the viewing terminal for the content distributed from the management server A content distribution method in a computer system comprising a plurality of distribution servers for distribution,
The management server creates a packet obtained by adding packet SEQ number and packet total information to fragment data obtained by dividing the content by a predetermined data length, and distributes the content to the distribution server by a multicast or unicast distribution method. Content delivery step to
A content registration step in which the distribution server receives the content distributed in the content distribution step and registers it in a database;
The distribution server analyzes the content distributed in the content distribution step in units of packets based on the packet SEQ number and the total number of packets, and indicates missing information indicating the presence or absence of data loss in the content in the order of the packet SEQ number Creating missing information and sending this to the management server;
The management server receives the missing information created in the missing information creation step from each of the plurality of delivery servers, and totals the missing information,
A content retransmission determination step in which the management server analyzes the missing information aggregated in the missing information aggregation step and determines whether there is a missing packet that needs to be retransmitted, a retransmission destination, and a multicast or unicast distribution method; ,
A content retransmission step in which the management server retransmits the missing packet according to a determination result in the content retransmission determination step;
A content updating step in which the distribution server updates the content registered in the database based on the missing packet retransmitted in the content retransmission step;
A content distribution method characterized by comprising:   The distribution server is classified into a plurality of groups on the network, and a representative distribution server selected in advance from the group sends the missing information to the management server on behalf of the group in the missing information creation step. The content distribution method according to claim 4, further comprising: retransmitting the lost packet from the management server.

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