JP2011171962A - Contents distribution system, and contents distribution method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve load resistance in a contents distribution system by dynamically controlling a contents distribution method. <P>SOLUTION: A distribution control server in the contents distribution system receives load information of a distribution server (S21), and, when the high load is determined (Yes in S22), determines a distribution method to perform a load distribution (a multicast or wide-range load distribution), based on the feature of contents (S24). When multicast is performed as the load distributing method (Yes in S27), the distribution control server performs congestion prediction so as to determine the probability of congestion (S31). When the probability of congestion is determined (Yes in S31), the distribution method for performing the load distribution is determined (S32). Besides, when it is determined that a load distribution release condition is satisfied (Yes in S28), the distribution control server determines the release of the load distribution (S29). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technology for increasing load resistance of a content distribution system by dynamically switching a content distribution method in accordance with the load status of the system in a content distribution system that distributes content via a network.

  In recent years, content distribution services for distributing content such as audio and video as continuous data using an IP (Internet Protocol) network have been provided. In general, when content is distributed by unicast, as the number of users of the service increases, the load of network resources that distribute the content increases, and normal distribution may not be possible. . In Patent Document 1, when distributing by unicast, the distribution status for a plurality of users is monitored, and a plurality of unicast distributions of the same content are changed to multicast distribution to reduce the load on the network equipment. Techniques to do this are disclosed.

JP 2004-80566 A

  However, the technology disclosed in Patent Document 1 may increase the load for managing the multicast tree in the nodes constituting the network for content with a short playback time. In other words, if multicast is applied to content with a short playback time, users will frequently join or leave the multicast group as the playback time starts and ends, increasing the load on the node. There is a risk of it.

Also, in content distribution, there are cases where a service is not established unless continuous data is transmitted from the beginning of the content, such as video on demand, and cases where a service is established even in the middle of the content, such as live broadcasting. is there. Therefore, it is necessary to use unicast distribution for video on demand, and there is no problem with multicast distribution for live broadcast. That is, there are contents that should use unicast distribution and those that should use multicast distribution, and Patent Document 1 does not consider such characteristics of the contents.
Therefore, an object of the present invention is to increase the load tolerance of a content distribution system by dynamically controlling the content distribution method while taking into consideration the load status of the content distribution system and the characteristics of the content.

  The present invention determines a distribution server and a distribution method for distributing content, a distribution control server for transmitting the determined distribution method to the distribution server, and a distribution server for distributing content based on the received distribution method. The distribution server includes a parameter indicating the server load of the distribution server and a parameter indicating the number of simultaneous connections indicating the number of contents simultaneously distributed by unicast as load parameters. , Means for measuring the value of the load parameter at a predetermined period, means for generating load information including at least the measured value of the load parameter, and transmitting the load information to the distribution control server; and the received from the distribution control server Means for distributing content based on a distribution method, wherein the distribution control server distributes the content. Storage means for storing distribution server load information storing the load information received from the distribution server for each server and content, and measurement values of the load parameters stored in the distribution server load information And a means for determining a distribution server and a distribution method for distributing contents according to the size and transmitting the determined distribution method to the distribution server.

  The present invention also determines a distribution server and a distribution method for distributing content, a distribution control server for transmitting the determined distribution method to the distribution server, and a distribution for distributing content based on the received distribution method. A content distribution method used in a content distribution system configured with a server, wherein the distribution server represents a parameter indicating its own server load and the number of simultaneous connections indicating the number of contents simultaneously distributed by unicast. A load parameter as a parameter, and a step of measuring a value of the load parameter at a predetermined period; a step of generating load information including at least the measurement value of the load parameter, and transmitting the load information to the distribution control server; Content based on the distribution method received from the distribution control server And a storage means for storing distribution server load information storing the load information received from the distribution server for each distribution server and content. Determining a distribution server and a distribution method for distributing content according to the magnitude of the measured value of the load parameter stored in the distribution server load information, and transmitting the determined distribution method to the distribution server; And executing the step of distributing the content based on the distribution method received from the distribution control server.

  According to such a configuration, the distribution control server can receive the load information of the distribution server, and dynamically control the content distribution method based on the load information. Therefore, it is possible to increase the load tolerance of the content distribution system by dynamically controlling the content distribution method while considering the load status of the content distribution system.

  In the present invention, the distribution server compares the measured value of the load parameter with a first threshold value stored in advance, and the measured value is equal to or greater than the first threshold value based on a comparison result. The high load identification information for identifying the high load is attached to the parameter of the measurement value, the measurement value and the high load identification information are included in the load information, and the distribution control server Means for transmitting the distribution server load information in which the distribution control server stores load information including the high load identification information, and a parameter to which the high load identification information is attached for each content. Content management information stored in association with a type of load distribution means for eliminating a high load, and the distribution server that has transmitted the load information When the load information includes the high load identification information, and the parameter to which the high load identification information is attached is a server load parameter, the most simultaneous connection within the distribution server with reference to the distribution server load information A method for identifying a large number of contents, referring to the content management information, determining a load distribution means associated with the content as a distribution method, and the distribution server that has transmitted the load information If the high load identification information exists in the server load information and the parameter to which the high load identification information is attached is a parameter indicating the number of simultaneous connections, the content having the parameter value to which the high load identification information is attached Referring to the content management information, the load distribution means associated with the content is determined as the distribution method. Characterized in that it comprises means for the.

  In the present invention, the distribution server compares the measured value of the load parameter with a first threshold value stored in advance, and the measured value is equal to or greater than the first threshold value based on a comparison result. In this case, it is determined that the load is high, high load identification information for identifying the high load is attached to the parameter of the measurement value, the measurement value and the high load identification information are included in the load information, and the distribution control is performed. Transmitting to a server, and the distribution control server is attached with the distribution server load information storing load information including the high load identification information and the high load identification information for each content. Content management information associated with the type of load distribution means for eliminating the high load of the stored parameters and the storage means for storing the information, to the distribution server that has transmitted the load information When the distribution server load information includes the high load identification information and the parameter to which the high load identification information is attached is a server load parameter, the distribution server load information is referred to and the distribution server load information is referred to. Determining the content with the largest number of simultaneous connections, determining the load distribution means associated with the content as a distribution method with reference to the content management information, and the distribution that has transmitted the load information For a server, when the high load identification information exists in the distribution server load information and the parameter to which the high load identification information is attached is a parameter indicating the number of simultaneous connections, the parameter to which the high load identification information is attached The content having the value of is identified, the content management information is referred to, and the load associated with the content And to execute determining means as the delivery method, the.

  According to such a configuration, in order to increase the load distribution effect most, it is possible to select content to which load distribution is applied by determining the type of parameter determined to be high load. Therefore, it is possible to increase the load tolerance of the content distribution system by dynamically controlling the content distribution method while considering the load status of the content distribution system.

  According to the present invention, one of the types of the load distribution means is multicast, and the other of the types of the load distribution means distributes content from a distribution server different from the distribution server determined to be high load. It is characterized by being.

  According to such a configuration, it is possible to apply load distribution means that considers the characteristics of the content. Therefore, it is possible to increase the load tolerance of the content distribution system by dynamically controlling the content distribution method in consideration of the characteristics of the content.

  The present invention provides means for measuring the number of distribution requests for content distributed by the multicast every predetermined unit time when the distribution control server is performing multicast distribution in a distribution server that has not been determined to have a high load. Means for determining whether the rate of change in the number of distribution requests per unit time measured within a predetermined period is greater than a predetermined rate; and the rate of change in the number of distribution requests per unit time over time When it is determined that the content is not larger than a predetermined ratio, the content management information is referred to, a means for searching for another distribution server that stores the same content as the content that is being multicast-distributed, and based on the search result Means for determining a delivery method indicating delivery of content from the other delivery server when the other delivery server exists; Wherein the distribution server, the distribution control by receiving the distribution method determined by the server, characterized in that it comprises means for delivering content based on the delivery method.

  In the present invention, when the distribution control server is performing multicast distribution in a distribution server that is not determined to have a high load, the distribution control server measures the number of distribution requests for content distributed by the multicast every predetermined unit time. Determining whether the rate of change in the number of distribution requests per unit time measured during a predetermined period is greater than a predetermined rate; and determining the time change in the number of distribution requests per unit time When it is determined that the ratio is not greater than a predetermined ratio, the content management information is referred to search for another distribution server that stores the same content as the content that is being multicast-distributed; Based on the delivery method, the delivery method indicates that the content is delivered from the other delivery server when the other delivery server exists. Perform the steps of determining, wherein the distribution server receives the distribution method determined by the distribution control server, and executes the step of delivering content based on the delivery method.

  According to such a configuration, in the case of multicast distribution, it becomes impossible to manage whether or not the load is high depending on the number of simultaneous connections. Therefore, the distribution control server is based on the number of distribution requests accepted after switching to multicast distribution. Thus, congestion prediction can be performed so that the server load does not become high. Therefore, it is possible to increase the load tolerance of the content distribution system by dynamically controlling the content distribution method while considering the load status of the content distribution system.

  The present invention provides means for measuring the number of distribution requests for content distributed by the multicast every predetermined unit time when the distribution control server is performing multicast distribution in a distribution server that has not been determined to have a high load. , The number of distribution requests per unit time measured within a predetermined period, and individual values in time series of measured values of the load parameters stored in the distribution server load information, and respective values stored in advance And the number of distribution requests per unit time within the predetermined period and the measured values of the load parameter are all less than or equal to the second threshold based on the comparison result A means for transmitting instruction information for canceling the multicast distribution to the distribution server, wherein the distribution server includes the multicast distribution. Receives instruction information for releasing, characterized in that it comprises means for changing the unicast distribution to stop the multicast distribution instructed to release by the instruction information.

  In the present invention, when the distribution control server is performing multicast distribution in a distribution server that is not determined to have a high load, the distribution control server measures the number of distribution requests for content distributed by the multicast every predetermined unit time. Steps, the number of distribution requests per unit time measured within a predetermined period, and individual values in time series of measured values of the load parameters stored in the distribution server load information, respectively, stored in advance Comparing the second threshold value corresponding to the value of the second threshold value, and based on the comparison result, the number of distribution requests per unit time within the predetermined period and the measured value of the load parameter are all the second threshold value. In the following cases, the instruction information for canceling the multicast distribution is transmitted to the distribution server, and the distribution server It receives instruction information for releasing the multicast distribution, and executes the step of changing the unicast distribution to stop the multicast distribution instructed to release by the instruction information.

  According to such a configuration, it is possible to switch the distribution server that is performing multicast distribution to normal unicast distribution that can easily manage the load situation while considering the load situation of the content distribution system. Load tolerance can be increased.

  The present invention provides a time series of measured values of load parameters within a predetermined period read from the distribution server load information when the distribution control server is executing wide area load distribution distribution in a distribution server that is not determined to be high load. Means for comparing the individual values of the second value and the second threshold value corresponding to each value stored in advance, and based on the comparison result, all the measured values of the load parameter within the predetermined period are all 2 or less, when the distribution server receives the instruction information for canceling the wide area load distribution distribution, and a means for transmitting the instruction information for canceling the wide area load distribution distribution to the distribution server, Means for stopping the wide area load distribution distribution instructed to release by the instruction information.

In the present invention, when the distribution control server is performing wide-area load distribution distribution in a distribution server that is not determined to have a high load, the measured value of the load parameter within a predetermined period read from the distribution server load information A step of comparing each time-series individual value with a second threshold value corresponding to each value stored in advance, and based on the comparison result, all the measured values of the load parameter within the predetermined period are all If it is equal to or smaller than the second threshold value, the step of transmitting instruction information for canceling the wide area load distribution distribution to the distribution server is executed, and the distribution server receives the instruction information for canceling the wide area load distribution distribution. Then, the step of stopping the wide area load distribution distribution instructed to be released by the instruction information is performed.

  According to such a configuration, it is possible to stop the distribution by the distribution server that is executing the wide area load distribution distribution while considering the load status of the content distribution system, and the duplicated content is deleted. Therefore, a margin can be made for the resources of the content distribution system, and the load tolerance of the content distribution system can be increased.

  ADVANTAGE OF THE INVENTION According to this invention, the load tolerance of a content delivery system can be improved by controlling the delivery method of a content dynamically, considering the load condition of a content delivery system, and the characteristic of a content.

It is a figure which shows the structural example and operation example of a content delivery system. It is a figure which shows the example of the flow of the main processes in a delivery control server. It is a figure which shows the structural example and function example of a delivery server. It is a figure which shows an example of content DB. It is a figure which shows an example of simultaneous connection number DB. It is a figure which shows an example of load DB. It is a figure which shows an example of threshold value DB. It is a figure which shows the structural example and function example of a delivery control server. It is a figure which shows an example of distribution server load DB. It is a figure which shows an example of content management DB. It is a figure which shows an example of user registration DB. It is a figure which shows the example of the flow of a process when a delivery server is highly loaded. (A) is a figure which shows the example of the flow of the load distribution cancellation | release process in the case of multicast, (b) is a figure which shows the example of the flow of the load distribution | release cancellation | release process in the case of wide area load distribution. It is a figure which shows the example of the flow of the load distribution process based on congestion prediction.

  Next, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail with reference to the drawings as appropriate.

(Outline of content distribution system)
A configuration example of the content distribution system in this embodiment will be described with reference to FIG. As shown in FIG. 1, the content distribution system 100 includes a distribution control server 1, a distribution server 2, a connection control server 3, a terminal 4, and a network 5. The network 5 is configured by connecting one or more routers 6 as nodes and connecting the routers 6 so as to communicate with each other. The router 6 transmits the content to the destination by routing the data. The terminal 4 is a portable terminal such as a personal computer, a television with a communication function, or a mobile phone. The connection control server 3 receives a content distribution request (also referred to as a distribution request) from the terminal 4 and transfers the content distribution request to the distribution control server 1. The distribution control server 1 determines a distribution server 2 and a distribution method for distributing content based on the content distribution request, and transmits the determined distribution method to the distribution server 2. The distribution server 2 transmits the content to the terminal 4 based on the distribution method determined by the distribution control server 1. In FIG. 1, only one distribution control server 1, distribution server 2, connection server 3, and terminal 4 are shown, but two or more may be provided. Further, although three routers 6 are illustrated in FIG. 1, the number is not limited to three.

Next, an outline of an operation example of the content distribution system 100 according to the present embodiment will be described with reference to FIG.
In step S <b> 11, the terminal 4 used by the user transmits a content distribution request for requesting content distribution to the connection control server 3. The content distribution request includes at least a content ID for identifying the content and terminal identification information for identifying the terminal 4 of the transmission source (for example, the IP address of the terminal 4).

  In step S12, the connection control server 3 transfers the content distribution request to the distribution control server 1. The connection control server 3 accepts a connection request from the terminal 4 for requesting connection to another terminal 4 or a server (not shown) other than the content distribution request. Therefore, the connection control server 3 determines whether or not the connection request is a content distribution request by using the content distribution request identification information that identifies the content distribution request. When the connection control server 3 determines that the connection request is a content distribution request, the connection control server 3 transfers the content distribution request to the distribution control server 1.

In step S13, the distribution control server 1 determines a distribution server 2 and a distribution method for distributing contents based on the received content distribution request and load information (described later) of the distribution server received from the distribution server 2.
The delivery method includes unicast delivery used for normal delivery as a default and multicast delivery used as load balancing means for distributing the load when the delivery server 2 is heavily loaded (to eliminate the high load). And wide area load distribution. Changing the unicast distribution to the multicast distribution by applying the load distribution means can combine a plurality of unicast packets into one multicast packet, so that not only the bandwidth used for the line but also the distribution server 1 processing load can be reduced. However, if the distribution destination is branched, a copy of the data must be generated on the network or the like, and the processing load may increase. Further, in the wide area load distribution, a new distribution server 2 that distributes the same content can be provided separately so that the processing load of the distribution server 2 that is heavily loaded can be prevented from further increasing. In wide area load distribution, content is transmitted by unicast distribution.

In step S14, the distribution control server 1 transmits the determined distribution server 2 and distribution method to the terminal 4 as connection response information corresponding to the content distribution request. The connection response information stores at least a content ID and connection destination information. The connection destination information is a multicast address in the case of multicast distribution, and is an address of the distribution server 2 in the case of unicast distribution.
In step S15, the terminal 4 transmits to the distribution server 2 a content distribution start instruction for instructing start of content distribution based on the received connection response information. The content distribution start instruction stores at least a content ID, connection destination information, and terminal identification information of a transmission source.
In step S16, the distribution server 2 receives the content distribution start instruction, and distributes the content to the terminal 4 based on the distribution method received from the distribution control server 1 in step S18.

In step S17, the distribution server 2 simultaneously distributes at least each parameter representing the server load (for example, the CPU usage rate, the memory usage rate, the usage bandwidth) and the content ID of the content stored in itself in a unicast manner. A parameter indicating the number of simultaneous connections indicating the number of connections is set as a load parameter, and the load parameter is measured at a predetermined period DX. The distribution server 2 compares the measured value of the load parameter with a threshold value (first threshold value), and determines that the load is high when the measured value is equal to or greater than the threshold value (first threshold value). Then, the distribution server 2 attaches high load identification information for identifying the high load to the parameter of the measurement value determined to be high load, and distributes the load information including the measurement value and the high load identification information to the distribution control server. 1 to send. Note that the transmission timing of the load information to the distribution control server 1 is a predetermined cycle DY (≧ DX) and a high load.
In step S18, the distribution control server 1 determines the distribution server 2 and the distribution method based on the load information received from the distribution server 2, and transmits the determined distribution method to the distribution server 2 as a distribution method instruction.

(Outline of distribution control server)
Next, the main processing flow of distribution control in the distribution control server 1 will be described with reference to FIG.
In step S21, the distribution control server 1 receives load information from the distribution server 2 at a predetermined cycle or when the distribution server 2 determines that the load is high. It is assumed that a server ID for identifying the distribution server 2 that transmitted the load information is associated with the load information.
In step S22, the distribution control server 1 determines whether or not the distribution server 2 has a high load based on the high load identification information included in the received load information. That is, the distribution control server 1 determines that the load is high if high load identification information exists. If it is determined in step S22 that the load is high (Yes in step S22), the process proceeds to step S23.

In step S23, the distribution control server 1 determines whether or not the distribution server 2 associated with the load information is a distribution server that is executing the load distribution means. If the distribution server is executing the load distribution means (Yes in step S23), the process returns to step S21. If the distribution server is not executing the load distribution means (No in step S23), the process proceeds to step S24.
In step S24, the distribution control server 1 selects content to be load-distributed by a method described later, and determines a distribution method for performing load distribution based on the characteristics of the content. Details of the process for determining the distribution method in step S24 will be described later.
In step S25, the distribution control server 1 transmits the determined distribution method to the distribution server 2 as a distribution method instruction. And the process after step S25 returns to step S21, and repeats the process after step S22 using the newly received load information (step S21).

If it is not determined in step S22 that the load is high (No in step S22), the process proceeds to step S26.
In step S26, the distribution control server 1 determines whether or not the distribution server that has transmitted the load information is a distribution server that is executing load distribution means (load distribution is being performed). If the distribution server is not executing load distribution (No in step S26), the process returns to step S21. If the distribution server is executing load distribution (Yes in step S26), the process proceeds to step S27.
In step S27, the distribution control server 1 determines whether or not the load distribution means is multicast distribution. If the load distribution means is not multicast distribution (No in step S27), the process proceeds to step S28.

In step S28, the distribution control server 1 determines whether or not the load distribution cancellation condition is satisfied. Details of this cancellation condition will be described later. If the load distribution cancellation condition is not satisfied (No in step S28), the process returns to step S21. When the load distribution cancellation condition is satisfied (Yes in step S28), the process proceeds to step S29.
In step S29, the distribution control server 1 determines release of load distribution. Details of the process for determining the cancellation of load balancing will be described later.
In step S30, the distribution control server 1 transmits the determined distribution method to the distribution server 2 as a distribution method instruction (release). And the process after step S30 returns to step S21, and repeats the process after step S22 using the newly received load information.

In step S27, when the load distribution means is multicast distribution (Yes in step S27), the process proceeds to step S31.
In step S31, the distribution control server 1 determines whether there is a possibility of congestion. The process of step S31 is performed on the content distributed by multicast. This is because when the load distribution means changes from unicast distribution to multicast distribution, the distribution data is bundled into one, so the distribution server 2 measures the number of simultaneous connections as in unicast distribution. It is because it becomes impossible. That is, the load information transmitted from the distribution server 2 to the distribution control server 1 does not include the number of simultaneous connections. Therefore, the distribution control server 1 measures the number of new distribution requests for the content being multicast distributed every predetermined period. Next, the distribution control server 1 calculates a temporal change tendency of the number of distribution requests within a predetermined period. And the delivery control server 1 determines whether a time change tendency is a decreasing tendency. When it is determined that the temporal change tendency is a decreasing tendency larger than a predetermined ratio, it is determined that there is no possibility of congestion.
If it is determined in step S31 that there is no possibility of congestion (No in step S31), the process proceeds to step S28. If it is determined that there is a possibility of congestion (Yes in step S31), the process proceeds to step S32.

In step S32, the distribution control server 1 determines a distribution method for performing load distribution. Details of the process for determining the distribution method in step S32 will be described later.
In step S33, the distribution control server 1 transmits the determined distribution method to the distribution server 2 as a distribution method instruction. And the process after step S33 returns to step S21, and repeats the process after step S22 using the newly received load information (step S21).

(Distribution server)
Next, a configuration example and a function example of the distribution server 2 will be described with reference to FIG. The distribution server 2 includes a processing unit 21, a communication unit 22, and a storage unit 23. The processing unit 21 includes a CPU of a computer and a main memory. The processing unit 21 develops an application program stored in the storage unit 23 in the main memory, and loads a load measurement unit 211, a load determination unit 212, a load information notification unit 213, The delivery destination changing unit 214 and the content copy deleting unit 215 are implemented.

  The load measuring unit 211 measures the number of simultaneous connections for each content ID with a predetermined period DX. Further, the load measuring unit 211 measures its own server load at a predetermined period DX. For example, the server load includes a CPU usage rate, a memory usage rate, and a usage band. The load measurement unit 211 transmits the measurement result to the load determination unit 212 at a predetermined period DX.

  The load determination unit 212 has individual threshold values in which values of individual load parameters (CPU usage rate, memory usage rate, usage band, number of simultaneous connections) included in the measurement result received from the load measurement unit 211 are set in advance. Determine if greater than. When the load determination unit 212 determines that the value of the load parameter is greater than the threshold value, the load determination unit 212 attaches high load identification information for identifying the high load to the load parameter, and the load parameter value and the high load identification information are loaded. It transmits to the notification part 213.

  The load information notification unit 213 transmits the load parameter value and the high load identification information received from the load determination unit 212 as load information to the distribution control server 1 at a predetermined cycle DY. However, the predetermined cycle is DY ≧ DX. In addition, when the high load identification information is detected, the load information notification unit 213 transmits the load information at that time to the distribution control server 1 even if it is not in a predetermined cycle.

  When the distribution method instruction received from the distribution control server 1 via the communication unit 22 is a multicast distribution instruction, the distribution destination changing unit 214 changes the distribution of the instructed content from unicast distribution to multicast distribution. Also, after changing to multicast distribution, the content is not unicasted until load distribution (multicast distribution) is canceled.

The content copy deletion unit 215 performs content management for managing the content when the distribution method instruction received from the distribution control server 1 via the communication unit 22 is execution of wide area load distribution and content replication is instructed. The content is downloaded from a server (not shown) or the like, and a copy is generated. The content copy deletion unit 215 deletes the content when the distribution method instruction received from the distribution control server 1 via the communication unit 22 is cancellation of load distribution and the deletion of the copied content is instructed. To do.
The processing unit 21 controls the communication unit 22 and the storage unit 23 to transmit and receive information.

The communication unit 22 has a function of controlling communication.
The storage unit 23 stores a content DB 231, a simultaneous connection number DB 232, a load DB 233, and a threshold value DB 234.
As shown in FIG. 4, the content DB 231 stores a content ID assigned to content stored in the distribution server 2 and a flag attached in the case of copying. The flag is displayed as “1” when it represents that it has been copied. The flag is not limited to “1”, and may be a symbol that can be identified as duplicated. The copied content is deleted when the load distribution is canceled, and the flag “1” is deleted accordingly.

As shown in FIG. 5, the simultaneous connection number DB 232 stores the content ID, the maximum number of simultaneous connections, and the current number of simultaneous connections in association with each other. The maximum number of simultaneous connections is preset and represents the maximum number of connections that can be connected simultaneously. The current number of simultaneous connections represents a value measured in a predetermined period DX.
As shown in FIG. 6, the load DB 233 stores time, a CPU usage rate, a memory usage rate, and a usage band (Mbit) in association with each other. In FIG. 6, the time is shown in increments of 1 minute (unit), but the present invention is not limited to this.
As illustrated in FIG. 7, the threshold DB 234 stores each parameter of the server load and a threshold for determining a high load in association with each other. Further, although not shown in FIG. 7, for the number of simultaneous connections, a threshold (for example, the maximum number of simultaneous connections shown in FIG. 5) is stored for each content. The threshold shown in FIG. 7 is an example, and may be determined as appropriate according to the processing capability of the distribution server.

(Delivery control server)
Next, a configuration example and a function example of the distribution control server 1 will be described with reference to FIG. The distribution control server 1 includes a processing unit 11, a communication unit 12, and a storage unit 13. The processing unit 11 includes a computer CPU and a main memory. The processing unit 11 develops an application program stored in the storage unit 13 in the main memory, and loads a load information collection unit 111, a load distribution determination unit 112, and a load distribution release unit. 113, the content management unit 114, and the distribution request receiving unit 115 are embodied. In addition, the processing unit 11 controls the communication unit 12 and the storage unit 13 and transmits and receives each piece of information.

  The load information collection unit 111 executes the process of step S21 in FIG. That is, the load information collection unit 111 collects load information from the distribution server 2. In addition, the load information collection unit 111 measures the number of distribution requests per predetermined unit time. Then, the load information collection unit 111 stores the collected load information and the number of distribution requests for each predetermined unit time in the distribution server load DB 131 (described later) as a time series.

  The load distribution determining unit 112 executes the processes of steps S22 to S27 and S31 to S33 in FIG. That is, when the load distribution determination unit 112 detects that the load information collected from the distribution server includes a parameter with high load identification information, the load distribution determination unit 112 sets the value of the parameter with the high load identification information. The content distribution ID is extracted, and the load distribution unit is determined by reading the load distribution unit associated with the content ID with reference to the content management DB 132 (described later). Then, the load distribution determination unit 112 transmits the determined load distribution unit to the distribution server 2 as a distribution method instruction. Also, the load distribution determination unit 112 determines a distribution method for performing load distribution based on the number of distribution requests stored in the distribution server load DB 131 (described later), and sends the distribution method to the distribution server 2 as a distribution method instruction. Send. Details of the determination of the load distribution means will be described later.

  The load distribution canceling unit 113 executes the processes of steps S28 to S30 in FIG. That is, when the load distribution cancellation unit 113 refers to the distribution server load DB 131 and monitors the load information of the distribution server to which the load distribution unit is applied, and determines that the load is not high even if the load distribution unit is not applied. The load distribution means (load distribution) is canceled. Details of canceling load balancing will be described later.

  The content management unit 114 determines a load distribution unit based on the feature of the content. Further, the content management unit 114 generates connection destination information indicating a connection destination to be accessed by the terminal 4 in order to receive content distribution, based on the processing results of the load distribution determination unit 112 and the load distribution cancellation unit 113. . Since the connection destination information is unicast distribution in the case of normal distribution to which load distribution is not applied, the distribution server address is applied, and when multicast distribution is applied, the multicast address and wide area load distribution distribution are applied. If there is a distribution server address. Then, the content management unit 114 associates, for each content ID, the server ID storing the content, the load distribution means, the parameter with the high load identification information, the presence / absence of content duplication, and the connection destination information. And stored in the content management DB 132.

The distribution request receiving unit 115 receives a content distribution request. Then, the distribution request receiving unit 115 refers to the content management DB 132 and transmits connection response information (content ID, connection destination information) to the terminal 4 via the connection control server 3. In addition, the distribution request receiving unit 115 measures the number of distribution requests every predetermined unit time and stores it in the distribution server load DB 131 (described later).
When a user is registered in advance when providing a content distribution service, the distribution request receiving unit 115 receives a content distribution request including a user ID for identifying the user. Then, the distribution request receiving unit 115 refers to the user registration DB 133 (described later), attaches a priority when determining the distribution server 2 to the default distribution server 2 associated with the user ID, You may transmit to the load distribution determination part 112. FIG. When there is no difference in load information, the load distribution determining unit 112 may determine the distribution server 2 in consideration of the priority order.

The storage unit 13 stores a distribution server load DB 131, a content management DB 132, and a user registration DB 133.
As shown in FIG. 9, the distribution server load DB 131 includes parameters with server ID, content ID, server load parameters, application / non-application of load balancing means, number of simultaneous connections, number of distribution requests, and high load identification information. Is associated with and stored. Each parameter of the server load, the number of simultaneous connections, and the number of distribution requests are stored in time series. The number of distribution requests is a value measured by the distribution request receiving unit 115 every predetermined unit time. The column of whether or not load balancing means is applied stores the type of load balancing means (multicast or wide area load balancing), “Yes” when applied, and “No” when not applied. Yes. The parameter column with high load identification information represents the case where “server load (memory usage rate)” and “number of simultaneous connections” are stored as examples of parameters determined to be high load. .

  As shown in FIG. 10, the content management DB 132 stores a content ID, a server ID, a load distribution unit, a parameter with high load identification information, a copy, and connection destination information. The load distribution means is determined based on the characteristics of the content. That is, the load distribution means performs multicast distribution when the content has a playback time longer than a predetermined time and / or when the content is live relayed. Further, load distribution means that is not multicast distribution is assumed to be wide area load distribution distribution. The duplicate column stores a flag “1” when duplicated. The connection destination information column stores a multicast address when the load distribution means is multicast, and stores a distribution server address when the load distribution means is wide area load distribution. In the case of normal distribution to which load balancing is not applied, the distribution server address is stored in the connection destination information column.

  As shown in FIG. 11, the user registration DB 133 stores a user ID and a server ID in association with each other. In the server ID column, server IDs are stored in the order of priority selected when there is no difference in load information.

(Processing flow when the distribution server is under heavy load)
The flow of processing when the distribution server 2 is heavily loaded will be described with reference to FIG. 12 (see FIGS. 8 to 10 as appropriate). Note that the processes in steps S41 to S49 shown in FIG. 12 represent the processes in steps S24 to S25 in FIG. 2 in detail.

  In step S41, the load distribution determining unit 112 refers to the distribution server load DB 131, and extracts a parameter (high load parameter) stored in a parameter column with high load identification information. Then, the load distribution determining unit 112 determines whether the extracted high load parameter is one or both of the server load parameter and the number of simultaneous connections. If the high load parameter is a server load parameter, the process proceeds to step S42. If the high load parameter is the number of simultaneous connections, the process proceeds to step S43. If the high load parameter is both the server load parameter and the number of simultaneous connections, the process proceeds to step S42.

In step S <b> 42, the load distribution determining unit 112 refers to the distribution server load DB 131 and identifies the content ID having the largest number of simultaneous connections in the distribution server 2.
In step S43, when the parameter to which the high load identification information is attached is a parameter indicating the number of simultaneous connections, the load distribution determining unit 112 specifies the content ID having the parameter value to which the high load identification information is attached. To do. Then, the load distribution determining unit 112 uses the content ID specified in step S42 or step S43, refers to the content management DB 132, extracts the load distribution means associated with the content ID, and loads the load Decide to apply the distribution means. If the load distribution means is wide area load distribution, the process proceeds to step S44.
In step S44, the load distribution determining unit 112 refers to the content management DB 132 and searches for another distribution server that distributes the same content. If there is no other distribution server that distributes the same content, the process proceeds to step S45.

In step S45, the load distribution determination unit 112 refers to the distribution server load DB 131, selects a distribution server with the lowest server load, and transmits a distribution method instruction that instructs the distribution server to copy the target content. The distribution server 2 having the lowest server load is selected based on a value calculated by a predetermined function having variables of the CPU usage rate, the memory usage rate, and the usage bandwidth.
In step S50, when receiving a new distribution request, the distribution request receiving unit 115 transmits the connection destination information of the distribution server 2 that copied the content to the terminal 4 and connects to the distribution server 2 that copied the content. Instruct.

If there is one or more distribution servers that distribute the content with the same content ID in the search result of step S44, the process proceeds to step S46. In step S46, the load distribution determining unit 112 refers to the distribution server load DB 131 and selects the distribution server 2 with the lowest server load.
In step S51, when receiving a new distribution request, the distribution request receiving unit 115 transmits connection destination information with the selected distribution server 2 as a connection destination to the terminal 4, and connects to the selected distribution server 2. Instruct.

In step S43, if the load distribution means is multicast, the process proceeds to step S47. In step S47, the load distribution determination unit 112 refers to the content management DB 132 and searches for another distribution server that stores the same content (content ID). If there are one or more other distribution servers storing the same content, the process proceeds to step S48.
In step S48, the load distribution determining unit 112 transmits a distribution method instruction to the distribution server 2 having the smallest server load. It should be noted that when determining the size of the server load, since there are three parameters, a CPU usage rate, a memory usage rate, and a usage band, the determination is based on a weighted average of these parameters.

If there is no distribution server that stores the content of the same content ID in the search result of step S47, the process proceeds to step S49. In step S49, the load distribution determining unit 112 transmits a distribution method instruction to the high-load distribution server that is the processing target in step S41.
In step S52, when receiving a new connection request, the distribution request receiving unit 115 transmits connection destination information having the distribution server 2 that has transmitted the distribution method instruction as a connection destination to the terminal 4, and transmits the connection destination information to the distribution server 2. Instruct to connect.

(Flow of load balancing release processing)
The flow of processing for canceling load distribution will be described with reference to FIGS. FIG. 13A is a diagram showing a flow of load distribution cancellation processing in the case of multicast, and FIG. 13B is a diagram showing a flow of load distribution cancellation processing in the case of wide area load distribution. Note that the processing shown in FIGS. 13A and 13B represents the processing in steps S28 to S30 in FIG. 2 in detail.

As shown in FIG. 13 (a), when multicast distribution is being performed, in step S61, the load distribution canceling unit 113 refers to the distribution server load DB 131 for the distribution server 2 for each predetermined unit time. Get measured values for new delivery request count and server load parameters. Note that the load distribution releasing unit 113 may directly acquire the number of new distribution requests for each predetermined unit time measured by the distribution request receiving unit 115.
In step S62, the load distribution canceling unit 113 determines the number of new distribution requests for each predetermined unit time within a predetermined period (a length longer than the transmission cycle DY of the distribution server) for the content distributed in multimedia. It is determined whether the measured value of the server load parameter is equal to or less than the corresponding threshold value (second threshold value). Note that the threshold (second threshold) is determined in advance.

If it is determined in step S62 that any or all of them are larger than the threshold value (second threshold value), the process returns to step S61. If it is determined that all or less than the threshold value (second threshold value), the process returns to step S63. move on.
In step S63, the load distribution canceling unit 113 transmits a distribution method instruction (cancellation) indicating an instruction to cancel the load distribution means to the distribution server 2, and cancels the load distribution means being executed. Then, the distribution server 2 receives the distribution method instruction (cancellation) for canceling the load distribution unit, stops the load distribution unit that is performing the multicast distribution, and changes to the unicast distribution.

  Here, in multicast distribution, the reason for using the number of new distribution requests for release determination is that multicast distribution cannot grasp the number of users who stopped receiving distribution on the way, that is, know the number of simultaneous connections. This is because they cannot. The fact that the number of distribution requests per predetermined unit time within a predetermined period is equal to or less than the threshold (second threshold) assumes that the server load of the distribution server 2 is less likely to become high thereafter. ing. In addition, instead of comparing the number of distribution requests per predetermined unit time within a predetermined period with a threshold (second threshold), the possibility of high load is determined by the method used in step S82 of FIG. 14 to be described later. May be.

Next, as illustrated in FIG. 13B, when the wide area load distribution is being performed, in step S <b> 71, the load distribution cancellation unit 113 refers to the distribution server load DB 131 and loads parameters of the distribution server 2. Read the measured value.
In step S72, the load distribution canceling unit 113 determines that the measured value of the server load parameter and the number of simultaneous connections for a predetermined period (a length longer than the transmission cycle DY of the distribution server) for the content distributed over a wide area load distribution. , It is determined whether it is equal to or less than a threshold value (second threshold value) corresponding thereto. Note that the threshold (second threshold) is determined in advance.
In step S72, when it is determined that any or all of them are larger than the threshold (second threshold) (No in step S72), the process returns to step S71, and all are determined to be equal to or less than the threshold (second threshold). If yes (Yes in step S72), the process proceeds to step S73.

  In step S73, the load distribution canceling unit 113 transmits a distribution method instruction (cancellation) indicating an instruction to cancel the load distribution to the distribution server 2, and cancels the load distribution of the distribution server 2. Then, the distribution server 2 receives the distribution method instruction (cancellation) for canceling the load distribution unit, and stops the load distribution unit that is executing the wide area load distribution distribution. Further, the distribution server 2 refers to the content DB 231 to determine whether or not the content is duplicated. If the content is a duplicate, the distribution server 2 deletes the content.

(Congestion prediction processing flow)
The flow of the congestion prediction process when multicast distribution is being performed as the load distribution means in a distribution server that has not been determined to be highly loaded will be described with reference to FIG. As described above, in multicast distribution, it becomes impossible to manage whether or not the load is high depending on the number of simultaneous connections. Therefore, the distribution control server 1 performs congestion prediction so that the server load does not become high depending on the number of new distribution requests received after switching to multicast distribution. The process shown in FIG. 14 represents the process of steps S31 to S33 in FIG. 2 in detail.

In step S <b> 81, the load information collection unit 111 measures the number of distribution requests for each predetermined unit time for each content and stores it in the distribution server load DB 131. The load distribution determining unit 112 refers to the distribution server load DB 131 and acquires the number of distribution requests.
In step S82, the load distribution determining unit 112 determines whether or not the rate of temporal change in the number of distribution requests per unit time measured within a predetermined period is greater than a predetermined rate (negative value) (possibility of congestion). Judgment) That is, the load distribution determination unit 112 determines that there is a possibility of congestion when the rate of temporal change in the number of distribution requests per unit time is greater than a predetermined rate (negative value). Here, since the ratio of the temporal change in the number of distribution requests per unit time can take from a positive value to a negative value including 0, the numerical value is large or small in comparison with a predetermined ratio (negative value). Determined. In step S82, when it is determined that the ratio of the temporal change tendency of the number of distribution requests per unit time is larger than a predetermined ratio (negative value) (Yes in step S82), the process proceeds to step S83, and every unit time If it is determined that the ratio of the number of distribution requests to the time change tendency is not greater than a predetermined ratio (negative value) (No in step S82), the process proceeds to step S28 (see FIG. 2).

In step S83, the load distribution determination unit 112 refers to the distribution server load DB 131 and searches for another distribution server 2 that stores the same content. As a result of the search, if one or more other distribution servers 2 are distributing the same content, the process proceeds to step S84.
In step S84, the load distribution determining unit 112 transmits a distribution method instruction to the distribution server 2 having the smallest server load.
In step S85, when receiving a new distribution request, the distribution request receiving unit 115 transmits the connection destination information of the distribution server 2 that has transmitted the distribution method instruction to the terminal 4 to connect to the distribution server 2. Instruct.

  As described above, in the content distribution system 100 of the present embodiment, the distribution control server 1 manages the load status of the distribution server 2 and dynamically controls the load distribution of the distribution server 2, so that load tolerance can be increased. . In addition, since load distribution means (multicast or wide area load distribution) used to reduce the load on the content distribution system 100 is determined based on the characteristics of the content, the service conditions for the content distribution service (whether cueing is necessary or not) )) And load resistance can be increased. Further, since the distribution control server 1 performs the congestion prediction based on the number of new distribution requests at the time of multicast distribution, the load tolerance can be increased.

  In step S82 of FIG. 14, the number of distribution requests within a predetermined period is used for comparison with the threshold value. However, the number of distribution requests within the predetermined period may not be limited. For example, a value obtained by subtracting the number of distribution requests in the predetermined period immediately before from the number of distribution requests in the predetermined period may be used. Alternatively, a weighted average of the number of distribution requests within a plurality of predetermined periods may be used. That is, an index for determining whether the number of distribution requests is increasing or decreasing may be used.

DESCRIPTION OF SYMBOLS 1 Distribution control server 2 Distribution server 3 Connection control server 4 Terminal 5 Network 6 Router 11 and 21 Processing part 12 and 22 Communication part 13 and 23 Storage part 100 Content distribution system 111 Load information collection part 112 Load distribution determination part 113 Load distribution cancellation | release Unit 114 content management unit 115 distribution request receiving unit 131 distribution server load DB
132 Content management DB
133 User registration DB
211 Load measurement unit 212 Load determination unit 213 Load information notification unit 214 Distribution destination change unit 215 Content duplication deletion unit 231 Content DB
232 Number of simultaneous connections DB
233 Load DB
234 Threshold DB

Claims (12)

A distribution server that distributes content and a distribution method for determining the distribution method and transmitting the determined distribution method to the distribution server, and a distribution server that distributes content based on the received distribution method A content distribution system,
The distribution server
Means for measuring a load parameter as a load parameter, a parameter indicating its own server load, and a parameter indicating the number of simultaneous connections indicating the number of content simultaneously distributed by unicast for each content;
Means for generating load information including at least a measurement value of the load parameter and transmitting the load information to the distribution control server;
Means for distributing content based on the distribution method received from the distribution control server;
With
The distribution control server
Storage means storing distribution server load information storing the load information received from the distribution server for each distribution server and content;
Means for determining a distribution server and a distribution method for distributing the content according to the magnitude of the measured value of the load parameter stored in the distribution server load information, and transmitting the determined distribution method to the distribution server; ,
A content distribution system comprising: The distribution server
Means for comparing the measured value of the load parameter with a first threshold stored in advance;
Based on the comparison result, when the measured value is equal to or greater than the first threshold, it is determined that the load is high, high load identification information for identifying the high load is attached to the parameter of the measured value, and the measured value Means for including the high load identification information in the load information and transmitting to the distribution control server;
With
The distribution control server
The distribution server load information storing the load information including the high load identification information is associated with the type of load distribution means for eliminating the high load of the parameter to which the high load identification information is attached for each content. The storage means for storing the content management information that is attached and stored;
For the distribution server that has transmitted the load information, when the high load identification information exists in the distribution server load information and the parameter to which the high load identification information is attached is a server load parameter, the distribution server load Means for referring to the information, specifying the content having the largest number of simultaneous connections in the distribution server, referring to the content management information, and determining a load distribution means associated with the content as a distribution method; ,
For the distribution server that has transmitted the load information, if the high load identification information exists in the distribution server load information and the parameter to which the high load identification information is attached is a parameter indicating the number of simultaneous connections, Means for identifying content having a parameter value to which load identification information is attached, referring to the content management information, and determining a load distribution means associated with the content as a distribution method;
The content distribution system according to claim 1, further comprising: One of the types of load balancing means is multicast,
The content according to claim 1 or 2, wherein the other of the types of the load distribution means is wide area load distribution for distributing content from a distribution server different from the distribution server determined to be high load. Distribution system. The distribution control server
If multicast distribution is being performed on a distribution server that has not been determined to be highly loaded,
Means for measuring the number of distribution requests of content distributed by the multicast every predetermined unit time;
Means for determining whether a rate of temporal change in the number of distribution requests per unit time measured within a predetermined period is greater than a predetermined rate;
When it is determined that the rate of temporal change in the number of distribution requests per unit time is not greater than a predetermined rate, the content management information is referenced to store the same content as the content for which multicast distribution is being performed Means for searching for another delivery server;
Means for determining a delivery method indicating delivery of content from the other delivery server when the other delivery server exists based on a search result;
With
The distribution server
4. The content distribution system according to claim 3, further comprising means for receiving a distribution method determined by the distribution control server and distributing content based on the distribution method. The distribution control server
If multicast distribution is being performed on a distribution server that has not been determined to be highly loaded,
Means for measuring the number of distribution requests of content distributed by the multicast every predetermined unit time;
The number of distribution requests per unit time measured within a predetermined period, the time series individual values of the measured values of the load parameters stored in the distribution server load information, and the respective values stored in advance Means for comparing with a corresponding second threshold;
Based on the comparison result, when all the number of distribution requests per unit time within the predetermined period and the measured value of the load parameter are less than or equal to the second threshold, instruction information for canceling the multicast distribution is given to the distribution server. Means for sending to
With
The distribution server
4. The content according to claim 3, further comprising means for receiving instruction information for canceling the multicast distribution, stopping the multicast distribution instructed to be canceled by the instruction information, and changing the multicast distribution to unicast distribution. Distribution system. The distribution control server
When a wide-area load distribution distribution is being performed on a distribution server that has not been determined to have a high load,
Means for comparing each time-series value of the measured values of the load parameter within a predetermined period read from the distribution server load information with a second threshold value corresponding to each value stored in advance;
Based on the comparison result, when all the measured values of the load parameter within the predetermined period are less than or equal to the second threshold value, means for transmitting instruction information for canceling the wide area load distribution distribution to the distribution server;
With
The distribution server
4. The content distribution system according to claim 3, further comprising means for receiving instruction information for canceling the wide area load distribution distribution and stopping the wide area load distribution distribution instructed to be released by the instruction information. A distribution server that distributes content and a distribution method for determining the distribution method and transmitting the determined distribution method to the distribution server, and a distribution server that distributes content based on the received distribution method A content distribution method used in a content distribution system,
The distribution server
A parameter indicating its own server load and a parameter indicating the number of simultaneous connections indicating the number of contents simultaneously delivered by unicast for each content as a load parameter, and measuring the value of the load parameter at a predetermined period;
Generating load information including at least a measurement value of the load parameter and transmitting the load information to the distribution control server;
Delivering content based on the delivery method received from the delivery control server;
Run
The distribution control server
For each distribution server and content, comprising storage means for storing distribution server load information storing the load information received from the distribution server,
Determining a distribution server and a distribution method for distributing content according to the magnitude of the measured value of the load parameter stored in the distribution server load information, and transmitting the determined distribution method to the distribution server; Run,
The distribution server
A content distribution method comprising: executing a step of distributing content based on the distribution method received from the distribution control server. The distribution server
Comparing the measured value of the load parameter with a first threshold stored in advance;
Based on the comparison result, when the measured value is equal to or greater than the first threshold, it is determined that the load is high, high load identification information for identifying the high load is attached to the parameter of the measured value, and the measured value Including the high load identification information in the load information and transmitting to the distribution control server;
Run
The distribution control server
The distribution server load information storing the load information including the high load identification information is associated with the type of load distribution means for eliminating the high load of the parameter to which the high load identification information is attached for each content. And storing the content management information stored with the storage means,
For the distribution server that has transmitted the load information, when the high load identification information exists in the distribution server load information and the parameter to which the high load identification information is attached is a server load parameter, the distribution server load Referring to the information, identifying the content having the largest number of simultaneous connections in the distribution server, referring to the content management information, and determining a load distribution means associated with the content as a distribution method; ,
For the distribution server that has transmitted the load information, if the high load identification information exists in the distribution server load information and the parameter to which the high load identification information is attached is a parameter indicating the number of simultaneous connections, Identifying a content having a parameter value to which load identification information is attached, referring to the content management information, and determining a load distribution means associated with the content as a distribution method;
The content distribution method according to claim 7, wherein: One of the types of load balancing means is multicast,
9. The content according to claim 7, wherein the other of the types of load distribution means is wide area load distribution for distributing content from a distribution server different from the distribution server determined to be high load. Delivery method. The distribution control server
If multicast distribution is being performed on a distribution server that has not been determined to be highly loaded,
Measuring the number of distribution requests for content distributed by the multicast every predetermined unit time; and
Determining whether a rate of temporal change in the number of distribution requests per unit time measured within a predetermined period is greater than a predetermined rate;
When it is determined that the rate of temporal change in the number of distribution requests per unit time is not greater than a predetermined rate, the content management information is referenced to store the same content as the content for which multicast distribution is being performed Searching for another delivery server;
Determining a delivery method indicating delivery of content from the other delivery server when the other delivery server exists based on a search result;
Run
The distribution server
9. The content distribution method according to claim 8, wherein the distribution method determined by the distribution control server is received, and the step of distributing content based on the distribution method is executed. The distribution control server
If multicast distribution is being performed on a distribution server that has not been determined to be highly loaded,
Measuring the number of distribution requests for content distributed by the multicast every predetermined unit time; and
The number of distribution requests per unit time measured within a predetermined period, the time series individual values of the measured values of the load parameters stored in the distribution server load information, and the respective values stored in advance Comparing a corresponding second threshold;
Based on the comparison result, when all the number of distribution requests per unit time within the predetermined period and the measured value of the load parameter are less than or equal to the second threshold, instruction information for canceling the multicast distribution is given to the distribution server. Sending to
Run
The distribution server
9. The step of receiving the instruction information for canceling the multicast distribution, and executing the step of stopping the multicast distribution instructed to be canceled by the instruction information and changing to the unicast distribution. Content distribution method. The distribution control server
When a wide-area load distribution distribution is being performed on a distribution server that has not been determined to have a high load,
Comparing each time-series value of the measured value of the load parameter within a predetermined period read from the distribution server load information with a second threshold value corresponding to each prestored value;
Based on the comparison result, if all the measured values of the load parameter within the predetermined period are less than or equal to the second threshold, transmitting instruction information for canceling the wide area load distribution distribution to the distribution server;
Run
The distribution server
9. The content distribution method according to claim 8, wherein the instruction information for canceling the wide area load distribution distribution is received, and the step of stopping the wide area load distribution distribution instructed to be released by the instruction information is executed. .

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