JP6827012B2 - Content download system, content download method and computer program for content download - Google Patents

Description

The present invention relates to a content download system for selecting a server suitable for downloading a content file and downloading the content file, a content download method, and a computer program for content download.

Content files such as electronic magazines, electronic newspapers, and electronic books, as well as content files containing moving images, are actively distributed via networks. In order to respond to content file download requests (large-scale access) from a large number of users, content distributors preliminarily use multiple servers or server groups (hereinafter, may simply be referred to as "servers") for content files with the same content. We have devised a way to distribute user access to multiple servers and server groups.

Content distribution by a group of servers also includes distribution utilizing a so-called CDN (Content Delivery Network). CDN is a cloud service that holds copies (caches) of content files on a large number of servers. When using a CDN, if there is a content download request from the user and the content file does not exist on the cache server, the cache server acquires the content file from the origin server and is defined. Keep a cache that is a copy of the content file for a period of time. When there is a download request for the same content from another user, the origin server and / or the cache server responds to the download request, so that large-scale access can be distributed. The CDN is disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-507128 (Patent Document 1), Japanese Patent Application Laid-Open No. 2006-502465 (Patent Document 2), and the like.

Conventionally, when multiple servers are used together to download content files, the following two methods have been adopted:
(i) Load balancing model In this model, multiple servers are registered in DNS (Domain Name System) in the same domain, and access is automatically distributed on the DNS side to use multiple servers. It is a thing. In this model, the convenience of some users is impaired if some servers fail or the performance is poor. Also, DNS failures can lead to total cuts:
(ii) Backup model This model automatically switches access to the backup server in the event of a failure of the default server.

These conventional methods are mainly aimed at improving fault tolerance, and have problems in performance (mainly download speed). Therefore, in order to make it possible to use a server that is optimal for each user, that is, has a high download speed, another system as shown in Japanese Patent Application Laid-Open No. 2014-96103 (Patent Document 3) has been developed. ..

In the system described in Patent Document 3, measurement data is prepared in advance for each of a plurality of servers, and measurement data is downloaded from the plurality of servers to reduce the download speed before the start of downloading the content file. Measure and compare the measurement results. Then, the content file is downloaded from the server with the fastest download speed.

Special Table 2004-507128 Special Table 2006-502465 Japanese Unexamined Patent Publication No. 2014-96103

However, the measurement data itself downloaded by the system described in Patent Document 3 is unnecessary data for the user. That is, in the conventional system, there is a problem that it is necessary to download a plurality of data unnecessary for the user in order to measure the download speed. Further, since the download of the content file is not started until the measurement result of the download speed and the comparison result are obtained, there is also a problem that a delay occurs until the download of the content file is started.

An object of the present invention is a content download system, a content download method, and a computer program for content download that can start downloading without delay and accelerate the download of content files without downloading unnecessary data for the user. Is to provide.

The content download system of the present invention selects a server suitable for downloading a content file from a plurality of servers that store the content file of the same content, and downloads the content file. Further, the content file is intended to be a file composed of a part of the content file and a rest file having a larger amount of data than the part of the file.

The content download system includes a content acquisition unit, a speed measurement unit, a speed comparison unit, and a server switching instruction unit. In response to the switching command, the content acquisition unit downloads the remaining files from one server included in the plurality of servers, and downloads some files from the other server included in the plurality of servers. The speed measurement unit measures the download speed of some files. The speed comparison unit compares the download speed of some files measured by the speed measurement unit with the reference speed. If the server switching instruction unit determines that the download speed of some files is faster than the reference speed as a result of comparison by the speed comparison unit, the next time another content file is downloaded, the remaining file of the other content file Outputs a switching command instructing the content acquisition unit to switch the download destination server so that the file is downloaded from another server.

In this way, the content download system of the present invention separates the download destinations of some files and the rest of the files, and when the download speed of some files exceeds the reference speed, the content files are downloaded next. At that time, by switching the download destination so that the remaining files are downloaded from the server that is the download destination of some files, the content file can be downloaded using the server with the faster download speed. The content file is not downloaded from the server with the fastest download speed among many servers, but the content file can be downloaded using the server with the relatively fast download speed. Some files are part of the data that the user wants to download, and do not force the user to download unnecessary data. Moreover, since the download of some files and the rest of the files has started, the download start is not delayed.

The "download speed" is an actually measured value (value expressed in Mbps or MB / s) obtained by dividing the amount of data in the content file by the time required to download the content file.

It is preferable that the switching command includes the content of a command for instructing the content acquisition unit to switch the download destination server so that a part of the other content file is downloaded from a server other than the other server. .. In this way, it is possible to measure and compare the download speed even when downloading other content files.

The method of determining the reference speed is arbitrary. For example, a preset threshold value may be used. Further, in the previous download, the download speed measured by the speed measuring unit when a part of the other content files is downloaded from one server may be used. In this way, for example, when downloading a content file for the first time, the download speed of one server is measured, and then when downloading another content file, the reference speed (download speed of one server) and You can compare the download speed of one other server and compare the download speed of one server with the other one, and the download speed of the server that downloads some files and the download speed of the server that downloads the rest of the files. You will be able to compare with the download speed.

When the speed comparison unit determines that the download speed of some files is faster than the reference speed, the speed comparison unit may store the download speed as the reference speed. In this way, the next download speed can be compared based on the download speed of the server judged to be fast.

The content of the content file is arbitrary, but may be, for example, an electronic publication such as an electronic magazine, an electronic newspaper, or an electronic book, or a moving image. In the case of electronic publications, many electronic publications include thumbnail images obtained by reducing the images of each page in order to improve the visibility of the contents of each page. Therefore, this thumbnail image can be used as a part of the file and the rest as the rest of the file. Generally, a thumbnail image is about several MB, so it is a file size suitable for measuring the download speed of a server.

The present invention can also be grasped (or expressed) as a content download method. In the content download method in which a computer is used to select a server suitable for downloading a content file from a plurality of servers that store the content file of the same content and the content file is downloaded, the content file constitutes the content file. It is composed of some files and the remaining files that have a larger amount of data than some files. In response to the switching command, the remaining files are downloaded from one server included in multiple servers, and some files are downloaded. Download step to download from another server included in multiple servers, speed measurement step to measure the download speed of some files, download speed of some files measured in the speed measurement step, and reference speed If the download speed of some files is faster than the reference speed as a result of the comparison between the speed comparison step and the speed comparison step, the remaining files of the other content files will be downloaded the next time another content file is downloaded. The computer executes a server switching instruction step that outputs a switching command instructing the switching of the download destination server so as to download from the other one server.

The present invention can also be grasped (or expressed) as a computer program for content download. From multiple servers that store content files with the same content, select a server suitable for downloading the content file, and in the content download computer program that is installed and executed on the computer to download the content file, the content file Is composed of some files that make up the content file and the remaining files that have a larger amount of data than some files, and the remaining files are downloaded from one server included in multiple servers in response to a switching command. In addition, a content acquisition unit that downloads some files from another server included in multiple servers, a speed measurement unit that measures the download speed of some files, and some files measured by the speed measurement unit. If it is determined that the download speed of some files is faster than the reference speed as a result of comparison between the speed comparison unit that compares the download speed of the computer with the reference speed and the speed comparison unit, then another content file is downloaded. At that time, a server switching instruction unit that outputs a switching command for instructing the content acquisition unit to switch the download destination server so that the remaining files of other content files are downloaded from another server is realized in the computer. It is configured as follows. Of course, this program may be recorded on a computer-readable recording medium.

It is a block diagram which shows the structure of embodiment of the content download system of this invention. This is an example of the algorithm of the computer program for content download when the optimization setting is off. This is an example of the algorithm of the computer program for content download when the optimization setting is on. It is a matrix table showing the CDN of the download destination of the key file KF and the main body file MF at the time of the first download. From the second time onward, it is a matrix table showing the key file KF at the time of download before switching the CDN and the CDN of the download destination of the main file MF. It is a matrix table showing the key file KF at the time of download after the first CDN switching and the CDN of the download destination of the main file MF. It is a matrix table showing the CDN of the download destination of the key file KF and the main body file MF at the time of download after the second CDN switching.

Hereinafter, embodiments of the content download system of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an embodiment of the content download system of the present invention, and FIGS. 2 and 3 show a case where the content download system of the present invention is realized by using a computer. It is a flowchart which shows an example of the algorithm of the program to be used.

<Content download system>
As shown in FIG. 1, the main part of the content download system 1 of the present embodiment is configured in the terminal device 3 that executes the content download computer program. The terminal device 3 may be a mobile terminal such as a smartphone, a tablet PC, or a notebook PC, or may be a stationary PC or the like. The terminal device 3 is configured to be able to communicate with the origin server 5 via the communication line NW. In the present embodiment, the origin server 5 uses three CDNs (Content Delivery Networks) (CDN1, CDN2, CDN3) to respond to content download requests from a large number of users. Each CDN is composed of a group of servers composed of a plurality of servers, but from a macroscopic point of view, each CDN can be equated with one server. Therefore, in this specification, each CDN is referred to as a CDN1. , CDN2, CDN3. The access priority of the CDN is set in advance in the order of CDN1, CDN2, and CDN3. Further, for convenience of explanation, it is assumed that each of CDN1, CDN2, and CDN3 already holds a cache of content files having the same contents.

The content file to be downloaded by the content download system 1 of the present embodiment is an electronic publication such as an electronic magazine, an electronic newspaper, or an electronic book. Further, the electronic publication targeted by the present embodiment is not composed of a single file, but is composed of a plurality of file groups. In the present specification, among the files constituting the electronic publication, the files of the thumbnail image of each page are defined as the key file KF (partial file), and the other files excluding the key file KF are the main files. Defined as MF (remaining file). Although it depends on the contents of the electronic publication, the key file KF is about several MB, and the main file MF is about several tens to several hundred MB.

The origin server 5 is a management server that stores the original file of the content file. The origin server 5 can turn on / off the optimization setting. Normally, the optimization setting is turned on, and the optimization setting can be turned off at the discretion of the administrator of the origin server 5 when a failure occurs in a plurality of CDNs.

In the present specification, "optimization" means to enable the main body file MF, which is a remaining file having a large amount of data, to be downloaded from a server having a high download speed according to the user's environment. More specifically, the download process is performed based on the flowchart shown in FIG. 3 described later.

A computer program for content download is installed in the terminal device 3, and is composed of an input unit 7 operated by a user, a control unit 9, a communication unit 11, a data storage unit 13, and a display screen 15. ing.

The input unit 7 may be one according to the type of the terminal device 3. For example, in the case of a smartphone, if the display screen 15 is a touch panel type liquid crystal screen, the display screen 15 also serves as the input unit 7.

The control unit 9 includes a content acquisition unit 9A, a speed measurement unit 9B, a speed comparison unit 9C, a server switching instruction unit 9D, and a display screen control unit 9E.

The content acquisition unit 9A accesses the origin server 5 via the communication unit 11 and confirms the state of the optimization setting and the location of the content file. The content acquisition unit 9A performs a content file download process according to the state of the optimization setting (details will be described later).

The speed measurement unit 9B, the speed comparison unit 9C, and the server switching instruction unit 9D function when the optimization setting of the origin server 5 is on. The speed measurement unit 9B measures the download speed of the key file KF when the optimization setting is on. The speed comparison unit 9C compares the download speed of the key file KF measured by the speed measurement unit 9B with the reference speed. When the server switching instruction unit 9D determines that the download speed of the key file KF is faster than the reference speed as a result of comparison by the speed comparison unit 9C, the next time another content file is downloaded, the main body of the content file is used. Instruct the switching content acquisition unit 9A of the download destination CDN to download the file MF from another CDN. The display screen control unit 9E outputs an image display signal, and the image is displayed on the display screen 15.

The data storage unit 13 stores the downloaded content file and the reference speed (evaluation data) to be compared by the speed comparison unit 9C.

<Download process>
When the user selects the content file (electronic publication) to be downloaded using the input unit 7 and requests the download, the content acquisition unit 9A accesses the origin server 5 via the communication unit 11 and is in the state of the optimization setting. According to the following, the download process is performed.

[When the optimization setting is off]
When the optimization setting of the origin server 5 is off, the download is performed according to the flowchart of FIG. FIG. 2 is an example of an algorithm of a computer program for content download when the optimization setting is off.

In this case, the content download system 1 operates in the same manner as the conventional backup model. The content acquisition unit 9A accesses the CDN having a high priority and starts downloading (step ST1). In the present embodiment, since "CDN1" is set as the default CDN, the download from the CDN1 is started. If the download is successful in step ST2, the user obtains the desired electronic publication and ends. If the download fails in step ST2 due to an error in the accessed CDN or the like, the download is tried a predetermined number of retries (step ST3). When the upper limit of the number of retries is exceeded, it is confirmed whether the terminal device 3 is not connected to the communication line NW and is in the offline state (step ST4), and if it is offline, an error is displayed on the display screen 15. I do. If the download fails even though you are not offline, switch the download destination CDN (step ST5) and try the download again.

[When optimization setting is on]
When the optimization setting of the origin server 5 is on, the download is performed according to the flowchart of FIG. FIG. 3 is an example of an algorithm of a computer program for content download when the optimization setting is on.

4 to 7 are matrix tables showing the transition of the CDN of the download destination of the key file KF and the main file MF when the optimization setting is on. In the matrix table, the row shows the CDN (repeated twice) and the column shows the file group to be downloaded. For example, if the CDN "1" and the "body" are crossed by "○", the CDN1 It indicates that the main file MF is downloaded from. FIG. 4 is a matrix table at the time of the first download, FIG. 5 is a matrix table at the time of downloading after the second and subsequent CDN switching, and FIG. 6 is a matrix table at the time of downloading after the first CDN switching. Yes, FIG. 7 is a matrix table at the time of download after the second CDN switching.

When the optimization setting is on, the content acquisition unit 9A separates the key file KF and the main body file MF and performs the download process.

(At the time of initial download: Fig. 4)
The evaluation data (reference speed) is empty at the time of the first download, and the content acquisition unit 9A determines the CDN to download the key file KF and the main body file MF as follows;
-Key file KF: Step ST10-> Step ST12-> Step ST13-> CDN-Level
-Main file MF: Step ST10-> Step ST11-> CDN-Level.

Since "CDN1" is set as the default CDN in the CDN-Level, as shown in FIG. 4, both the key file KF and the main file MF are downloaded from the CDN1 at the time of the first download. For the key file KF, the speed measuring unit 9B measures the download speed at the time of downloading (step ST15).

If the download is successful (step ST16), the processing of the main file MF ends, but for the key file KF, the download speed measured by the speed measurement unit 9B is recorded as evaluation data (reference speed) (step ST17 → step). ST18 → step ST19).

Since the processes of steps ST23 to ST25 are backup models like the processes of steps ST3 to ST5 of FIG. 2, the description thereof will be omitted.

(From the second time onward, when downloading before switching the CDN: Fig. 5)
At the time of the second download (when downloading a content file different from the first time), the content acquisition unit 9A determines the CDN to download the key file KF and the main body file MF as follows;
-Key file KF: Step ST10-> Step ST12-> Step ST14-> CDN-Level + 1
-Main file MF: Step ST10-> Step ST11-> CDN-Level.

Since "CDN1" is set in the CDN-Level, the key file KF is downloaded from CDN2 and the main file MF is downloaded from CDN1 at the time of the second download, as shown in FIG. For the key file KF, the speed measuring unit 9B measures the download speed at the time of downloading (step ST15).

If the download is successful (step ST16), the processing of the main file MF ends. For the key file KF, the speed comparison unit 9C compares the download speed measured by the speed measurement unit 9B with the evaluation data (reference speed) (step ST17 → step ST18 → step ST20). This makes it possible to compare the download speed of CDN1 with the download speed of CDN2. As a result of the comparison, if the download speed measured by the speed measurement unit 9B is slower, the process ends, and the next download will be performed with the combination of CDNs shown in FIG.

As a result of the comparison, if the download speed measured by the speed measurement unit 9B is faster, the speed comparison unit 9C updates the evaluation data (reference speed) (stores the download speed of CDN2) (step ST21). Then, the server switching instruction unit 9D outputs a switching command so as to switch the CDN of the download destination of the key file KF and the main body file MF in preparation for the next download (step ST22). That is, the CDN-Level is switched from "CDN1" to "CDN2".

(At the time of download after the first CDN switching: Fig. 6)
When downloading another content file after the download destination CDN is switched by the switching command, the content acquisition unit 9A determines the CDN to download the key file KF and the main body file MF as follows;
-Key file KF: Step ST10-> Step ST12-> Step ST14-> CDN-Level + 1
-Main file MF: Step ST10-> Step ST11-> CDN-Level.

Since "CDN2" is set in the CDN-Level, at the time of this download, the key file KF is downloaded from CDN3 and the main file MF is downloaded from CDN2, as shown in FIG. For the key file KF, the speed measuring unit 9B measures the download speed at the time of downloading (step ST15).

If the download is successful (step ST16), the processing of the main file MF ends. For the key file KF, the speed comparison unit 9C compares the download speed measured by the speed measurement unit 9B with the evaluation data (reference speed) (step ST17 → step ST18 → step ST20). This makes it possible to compare the download speed of CDN2 with the download speed of CDN3. As a result of the comparison, if the download speed measured by the speed measurement unit 9B is slower, the process ends, and the next download will be performed with the combination of CDNs shown in FIG.

As a result of the comparison, if the download speed measured by the speed measurement unit 9B is faster, the speed comparison unit 9C updates the evaluation data (reference speed) (stores the download speed of CDN3) (step ST21). Then, the server switching instruction unit 9D outputs a switching command so as to switch the CDN of the download destination of the key file KF and the main body file MF in preparation for the next download (step ST22). That is, the setting of CDN-Level is switched from "CDN2" to "CDN3".

(During download after the second CDN switch: Fig. 7)
When another content file is downloaded after the download destination CDN is switched by the switching command, the content acquisition unit 9A determines the CDN to download the key file KF and the main body file MF as follows;
-Key file KF: Step ST10-> Step ST12-> Step ST14-> CDN-Level + 1
-Main file MF: Step ST10-> Step ST11-> CDN-Level.

Since "CDN3" is set in the CDN-Level, at the time of this download, the key file KF is downloaded from CDN1 and the main file MF is downloaded from CDN3, as shown in FIG. 7. For the key file KF, the speed measuring unit 9B measures the download speed at the time of downloading (step ST15).

If the download is successful (step ST16), the processing of the main file MF ends. For the key file KF, the speed comparison unit 9C compares the download speed measured by the speed measurement unit 9B with the evaluation data (reference speed) (step ST17 → step ST18 → step ST20). This makes it possible to compare the download speed of CDN3 with the download speed of CDN1. As a result of the comparison, if the download speed measured by the speed measurement unit 9B is slower, the process ends, and the next download will be performed with the combination of CDNs shown in FIG. 7.

As a result of the comparison, if the download speed measured by the speed measurement unit 9B is faster, the speed comparison unit 9C updates the evaluation data (reference speed) (stores the download speed of CDN1) (step ST21). Then, the server switching instruction unit 9D outputs a switching command so as to switch the CDN of the download destination of the key file KF and the main body file MF in preparation for the next download (step ST22). That is, the setting of the CDN-Level is switched from "CDN3" to "CDN1".

After that, the flowchart of FIG. 3 is repeated for each download.

Initialize the reference speed and / or CDN-Level settings (ie, set the reference speed to "empty" and / or set the CDN-Level to "CDN1") at any time (eg, once every few days). You may do so. If you initialize the reference speed, if the downloaded key file KF is a small file that is not suitable for measuring the download speed, and the download speed faster than usual is recorded as the reference speed again, You will be able to re-record the reference speed. Further, if the CDN-Level setting is initialized, the optimization can be executed again from the CDN that originally has the fastest download speed.

The above-described embodiment is described as an example, and the present invention is not limited to the present embodiment as long as it does not deviate from the gist thereof. For example, in the above embodiment, the reference speed (evaluation data) is empty at the time of the first download, but the ideal download speed may be recorded in advance as the reference speed. In this case, the content file download process is performed in the state shown in FIG. 5 from the first download.

Further, in the above embodiment, the download destination server is set to three CDNs, but the number of servers is not limited to this, and the number of servers may be two or four or more. In that case, the matrix table shown in FIGS. 4 to 7 may have more or less rows to match the number.

Of course, the download destination server may be a server other than the CDN, such as a mirror server that records the content file of the same content.

In the above embodiment, the thumbnail image of the electronic publication which is the content file is used as the key file KF, but it goes without saying that other files may be used as the key file KF.

Furthermore, the content file is not limited to electronic publications, and of course, it may be another content file such as a moving image. In the case of a moving image, for example, a part of the moving image may be a partial file and the other part may be a remaining file.

According to the present invention, a content download system, a content download method, and a content download computer capable of starting a download without delay and accelerating the download of a content file without downloading unnecessary data for the user. A program can be provided.

1 Content download system 3 Terminal device 5 Origin server 7 Input unit 9 Control unit 9A Content acquisition unit 9B Speed measurement unit 9C Speed comparison unit 9D Server switching instruction unit 9E Display screen Control unit 11 Communication unit 13 Data storage unit 15 Display screen KF key file MF main body file CDN1,2,3 CDN

Claims (8)

A content download system that selects the server suitable for downloading the content file from a plurality of servers that store the content file of the same content and downloads the content file.
The content file is composed of a partial file constituting the content file and a remaining file having a larger amount of data than the partial file.
A content acquisition unit that downloads the remaining files from one server included in the plurality of servers in response to a switching command, and downloads some of the files from another server included in the plurality of servers. ,
A speed measuring unit that measures the download speed of some of the files,
A speed comparison unit that compares the download speed of the partial file measured by the speed measurement unit with the reference speed.
As a result of the comparison by the speed comparison unit, when it is determined that the download speed of the partial file is faster than the reference speed, the remaining file of the other content file is downloaded the next time another content file is downloaded. It is provided with a server switching instruction unit that outputs the switching command that instructs the content acquisition unit to switch the download destination server so as to download from another one server.
In the switching command output by the server switching instruction unit, the content acquisition unit is switched to the download destination server so that a part of the other content file is downloaded from a server other than the other one server. Contains the content of the instruction to instruct
The reference speed is the download speed measured by the speed measuring unit when a part of the other content files is downloaded from the one server in the previous download.
When the speed comparison unit determines that the download speed of the partial file is faster than the reference speed, the speed comparison unit stores the download speed as the reference speed.
The content file is an electronic publication and
The partial file is a content download system that is a thumbnail image of each page of the electronic publication. A content download system that selects the server suitable for downloading the content file from a plurality of servers that store the content file of the same content and downloads the content file.
The content file is composed of a partial file constituting the content file and a remaining file having a larger amount of data than the partial file.
A content acquisition unit that downloads the remaining files from one server included in the plurality of servers in response to a switching command, and downloads some of the files from another server included in the plurality of servers. ,
A speed measuring unit that measures the download speed of some of the files,
A speed comparison unit that compares the download speed of the partial file measured by the speed measurement unit with the reference speed.
As a result of the comparison by the speed comparison unit, when it is determined that the download speed of the partial file is faster than the reference speed, the remaining file of the other content file is downloaded the next time another content file is downloaded. A content download system including a server switching instruction unit that outputs the switching command for instructing the content acquisition unit to switch the download destination server so as to download from another one server. In the switching command output by the server switching instruction unit, the content acquisition unit is switched to the download destination server so that a part of the other content file is downloaded from a server other than the other one server. The content download system according to claim 2 , which includes the content of the instruction to be instructed. The content download according to claim 2 , wherein the reference speed is a download speed measured by the speed measuring unit when a part of another content file is downloaded from the one server in the previous download. system. The content download system according to claim 2, wherein when the speed comparison unit determines that the download speed of the partial file is faster than the reference speed, the speed comparison unit stores the download speed as the reference speed. The content file is an electronic publication and
The content download system according to claim 2 , wherein the partial file is a thumbnail image of each page of the electronic publication. A content download method in which a computer is used to select a server suitable for downloading a content file from a plurality of servers that store the content file having the same content, and the content file is downloaded.
The content file is composed of a partial file constituting the content file and a remaining file having a larger amount of data than the partial file.
A download step of downloading the remaining file from one server included in the plurality of servers and downloading the part of the file from another server included in the plurality of servers in response to the switching command.
A speed measurement step that measures the download speed of some of the files,
A speed comparison step for comparing the download speed of the partial file measured in the speed measurement step with a reference speed,
As a result of the comparison by the speed comparison step, when the download speed of the partial file is faster than the reference speed, the remaining file of the other content file is selected as the other 1 when the other content file is downloaded next time. A content download method, characterized in that the computer executes a server switching instruction step that outputs a switching command that instructs switching of a download destination server so as to download from one server. A content download computer program that selects the server suitable for downloading the content file from a plurality of servers that store the content file of the same content, and is installed and executed on the computer to download the content file. There,
The content file is composed of a partial file constituting the content file and a remaining file having a larger amount of data than the partial file.
A content acquisition unit that downloads the remaining files from one server included in the plurality of servers in response to a switching command, and downloads some of the files from another server included in the plurality of servers. ,
A speed measuring unit that measures the download speed of some of the files,
A speed comparison unit that compares the download speed of the partial file measured by the speed measurement unit with the reference speed.
As a result of comparison by the speed comparison unit, when it is determined that the download speed of the partial file is faster than the reference speed, the remaining file of the other content file is used as the remaining file when the other content file is downloaded next time. A content configured to realize in the computer a server switching instruction unit that outputs the switching command instructing the content acquisition unit to switch the download destination server so as to download from another one server. Computer program for download.

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