JP6015338B2 - Data transmission apparatus, data transmission system, data transmission method, and program - Google Patents

Description

The present invention relates to a data transmission device, a data transmission system, a data transmission method, and a program.

  For example, some video content distribution systems include a center server that centrally manages all content, and an edge server that is distributed and arranged near the viewing terminal.

  The edge server is directly accessed from the viewing terminal, acquires content to be viewed from the center server, and distributes the content to the viewing terminal. The edge server also has a function of caching viewed content. Therefore, when the content to be viewed is cached, the edge server distributes the cached content. By doing so, it is possible to improve the responsiveness to the viewing terminal, reduce the network load between the center server and the edge server, and the like.

JP 2001-313919 A JP 2007-6145 A

  However, since the cache capacity of the edge server is limited, the edge server cannot generally cache all contents. Therefore, the cached data is deleted by a predetermined algorithm. Therefore, a cache miss hit occurs in the edge server.

  The cache hit rate in the edge server greatly affects the network load between the center server and the edge server. When mis-hits occur at a plurality of edge servers almost simultaneously, access from the edge server to the center server is concentrated, and there is a possibility that the network between the center server and the edge server becomes insufficient in bandwidth.

  Therefore, an object of one aspect is to level the network load in data transmission.

  In one proposal, the data transmission device receives the first transmission request for data received via the network, acquires the data via the network, and acquires the acquired data as the first data. A transmission unit that transmits to one transmission request source, a storage unit that stores the acquired data, and a deletion unit that deletes a part of the data from the middle of the storage unit, the acquisition unit, In response to a second transmission request for data, the part is acquired via the network at a slower rate than when acquiring all of the data, and the transmission unit responds to the second transmission request and the data Next to the remaining part excluding the part, the part acquired by the acquisition unit is transmitted to the second transmission request source.

  According to one aspect, the network load in data transmission can be leveled.

It is a figure which shows the structural example of the delivery system in this Embodiment. It is a figure which shows the hardware structural example of the edge server in this Embodiment. It is a figure which shows the function structural example of the edge server in this Embodiment. It is a figure which shows the function structural example of the center server in this Embodiment. It is a flowchart for demonstrating an example of the process sequence which an edge server performs. It is a figure which shows the structural example of a cache management information storage part. It is a flowchart for demonstrating an example of the process sequence of a cache data deletion process. It is a flowchart for demonstrating an example of the process sequence which a center server performs. It is a figure which shows the 2nd function structural example of the edge server in this Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration example of a distribution system according to the present embodiment. In FIG. 1, the distribution system 1 includes a center server 20 and a plurality of edge servers 10. The center server 20 and each edge server 10 can communicate with each other via a network N1 such as the Internet.

  The center server 20 is a computer that centrally manages all contents to be distributed.

  The edge server 10 is a computer arranged to distribute the load on the center server 20. The edge server 10 is connected to a terminal 30 used for viewing content via a network N2 such as the Internet, and relays the distribution of content to the terminal 30. The edge server 10 caches the relayed content. When the content related to the distribution request from the terminal 30 is cached, the edge server 10 distributes the cached content to the terminal 30.

  The edge server 10 deletes the cached content based on a predetermined algorithm. That is, the contents to be cached are replaced. As the predetermined algorithm, a known algorithm such as an LRU (Least Recently Used) method may be used.

  However, the edge server 10 deletes a part from the end of the content without deleting all of the content to be deleted. Hereinafter, the deleted part is referred to as “missing part”, and the remaining part is referred to as “remaining part”. When the terminal 30 requests distribution of the content that has been partially deleted, the edge server 10 acquires a missing portion (receives distribution) from the content server in parallel with the distribution of the remaining portion of the content. At this time, the edge server 10 determines the acquisition speed of the missing part from the acquisition speed when acquiring all of the content or the transmission speed of the residual part to the terminal 30 within a range in which there is no delay with respect to the distribution of the residual part. The missing part is acquired from the center server 20 by reducing the value. By doing so, it is possible to level the load on the network N1 between the edge server 10 and the center server 20 while keeping the transmission speed (bandwidth) of content to the terminal 30 constant. In addition, the state where “there is no delay with respect to the delivery of the remaining part” refers to a state where the missing part is delivered after the remaining part in a state where there is no separation between the remaining part. That is, it means a state in which the remaining part and the missing part can be distributed at the transmission speed in a state where all of the contents exist in the edge server 10 when the distribution request is received.

  The “speed” such as the acquisition speed and the transmission speed refers to the amount of data transferred per unit time. That is, the speed is synonymous with a bit rate or a band related to data transmission.

  The terminal 30 is not limited to a predetermined device as long as it can reproduce content. For example, a PC (Personal Computer), a mobile phone, a smartphone, a tablet terminal, or the like may be used as the terminal 30.

  Note that the content to be distributed in the present embodiment is preferably data reproduced at a predetermined bit rate (reproduction size per unit time) such as video (moving image) data or audio data. Further, the distribution format is preferably a streaming format. In the case of the streaming format, the content may be distributed at a speed according to the bit rate of the content itself. However, the present embodiment may be applied to the case where still image data and other types of data are distributed in a general download format.

  In this embodiment, the term “speed” is used for the latter in order to avoid confusion between the bit rate related to content reproduction and the bit rate related to content transmission.

  FIG. 2 is a diagram illustrating a hardware configuration example of the edge server in the present embodiment. The edge server 10 in FIG. 2 includes a drive device 100, an auxiliary storage device 102, a memory device 103, a CPU 104, an interface device 105, and the like that are mutually connected by a bus B.

  A program for realizing processing in the edge server 10 is provided by the recording medium 101. When the recording medium 101 on which the program is recorded is set in the drive device 100, the program is installed from the recording medium 101 to the auxiliary storage device 102 via the drive device 100. However, the program need not be installed from the recording medium 101 and may be downloaded from another computer via a network. The auxiliary storage device 102 stores the installed program and also stores necessary files and data.

  The memory device 103 reads the program from the auxiliary storage device 102 and stores it when there is an instruction to start the program. The CPU 104 executes a function related to the edge server 10 according to a program stored in the memory device 103. The interface device 105 is used as an interface for connecting to a network.

  An example of the recording medium 101 is a portable recording medium such as a CD-ROM, a DVD disk, or a USB memory. An example of the auxiliary storage device 102 is an HDD (Hard Disk Drive) or a flash memory. Both the recording medium 101 and the auxiliary storage device 102 correspond to computer-readable recording media.

  The center server 20 may also have the hardware shown in FIG.

  FIG. 3 is a diagram illustrating a functional configuration example of the edge server according to the present embodiment. In FIG. 3, the edge server 10 includes a terminal side communication unit 11, a center side communication unit 12, a cache unit 13, a cache management unit 14, a bit rate determination unit 15, a transmission rate calculation unit 16, a missing rate calculation unit 17, and the like. Have. Each of these units is realized by processing executed by the CPU 104 by a program installed in the edge server 10. The edge server 10 also has a cache management information storage unit 18. The cache management information storage unit 18 and the cache storage unit 133 in the cache unit 13 can be realized using the auxiliary storage device 102 or the like, for example.

  The terminal side communication unit 11 controls communication with the terminal 30. The terminal-side communication unit 11 includes a request reception unit 111, a data transmission unit 112, a bandwidth control unit 113, and the like. The request receiving unit 111 receives a content distribution request from the terminal 30. The data transmission unit 112 transmits the content related to the distribution request to the terminal 30. The bandwidth control unit 113 controls the transmission speed (distribution bandwidth) of the content so that the content is appropriately played back.

  The center side communication unit 12 includes a request transmission unit 121, a data reception unit 122, and the like. The request transmission unit 121 transmits a content acquisition request to the center server 20. For content in which a part from the end is deleted, acquisition of the part is requested. The data receiving unit 122 receives the content returned from the center server 20 in response to the content acquisition request.

  The cache unit 13 caches content received from the center server 20 (that is, content previously delivered to the terminal 30). The cache unit 13 includes a reading unit 131, a writing unit 132, a cache storage unit 133, and the like. The cache storage unit 133 stores content to be cached. The reading unit 131 reads content from the cache storage unit 133. The writing unit 132 writes content in the cache storage unit 133.

  The cache management unit 14 manages cached content. The cache management unit 14 includes a deletion target selection unit 141, a deletion unit 142, and the like. The deletion target selection unit 141 selects content to be deleted based on the access status (usage status) of the content stored in the cache storage unit 133. The deletion unit 142 deletes a part from the end of the remaining part of the content selected by the deletion target selection unit 141 (hereinafter referred to as “current end”). If the content has not been deleted, all of the content remains. The entire end of the content is hereinafter referred to as “original end”.

  The cache management information storage unit 18 stores attribute information of each content stored in the cache storage unit 133. The attribute information includes information indicating the access status.

  The bit rate determining unit 15 determines the bit rate (reproduction data amount per unit time) of the content related to the distribution request from the terminal 30. For example, the bit rate may be determined based on information recorded in the content.

  The transmission speed calculation unit 16 calculates the transmission speed of content for the terminal 30. For example, the bit rate of the content may be the transmission speed of the content. Or, in order to avoid a delay in reproducing the content in accordance with the change in the bandwidth of the network N2, even if a value obtained by multiplying the bit rate of the content by a coefficient exceeding 1.0 is set as the transmission speed of the content Good.

  The missing rate calculation unit 17 calculates the ratio of the missing portion to the entire content (hereinafter referred to as “missing rate”) for the content related to the distribution request. The missing rate is specified in the content acquisition request from the request transmission unit 121 to the center server 20. However, the missing rate is not specified for uncached content. Alternatively, 1.0 (100%) may be designated as a missing rate for content that is not cached.

  FIG. 4 is a diagram illustrating a functional configuration example of the center server according to the present embodiment. 4, the center server 20 includes a communication processing unit 21, a reading unit 22, a missing rate determination unit 23, a bit rate determination unit 24, a transmission speed calculation unit 25, and the like. Each of these units is realized by processing that a program installed in the center server 20 causes the CPU of the center server 20 to execute. The center server 20 also has a content storage unit 26. The content storage unit 26 can be realized using, for example, an auxiliary storage device included in the center server 20.

  The communication processing unit 21 controls communication with the edge server 10. The communication processing unit 21 includes a request reception unit 211, a data transmission unit 212, a bandwidth control unit 213, and the like. The request reception unit 211 receives a content acquisition request from the edge server 10. The data transmission unit 212 transmits the requested content to the edge server 10. The bandwidth control unit 213 controls the transmission speed of content by the data transmission unit 212.

  The reading unit 22 reads content transmitted from the data transmission unit 212 to the edge server 10 from the content storage unit 26. The content storage unit 26 stores each content.

  The bit rate determination unit 24 determines the bit rate of the content related to the acquisition request from the edge server 10.

  The transmission speed calculation unit 25 calculates the transmission speed of content to the edge server 10. Specifically, the transmission speed calculation unit 25 sets a value obtained by multiplying the transmission speed in the case of transmitting all of the content to the edge server 10 by the missing rate of the content as the content transmission speed for the edge server 10. . In the present embodiment, the transmission speed when transmitting all of the content to the edge server 10 is based on the bit rate determined by the bit rate determination unit 24 for the content. For example, the result of multiplying the bit rate by a predetermined coefficient of 1.0 or more may be the transmission speed when the entire content is transmitted to the edge server 10.

  Hereinafter, processing procedures executed by each of the edge server 10 and the center server 20 will be described. FIG. 5 is a flowchart for explaining an example of a processing procedure executed by the edge server.

  In step S <b> 101, the request reception unit 111 receives a content distribution request from the terminal 30. A content name is specified in the content distribution request. In response to the reception of the content distribution request, the reading unit 131 refers to the cache storage unit 133 to determine whether or not there is cache data of the content related to the content name specified in the distribution request (hereinafter referred to as “target content”). Is determined (S102). The presence or absence of cache data refers to whether or not at least a part of the target content is stored in the cache storage unit 133.

  When there is no cache data (No in S102), the request transmission unit 121 transmits an acquisition request for the target content to the center server 20 without specifying the missing rate (S103). The content name of the target content is specified in the acquisition request.

  When a part of the data of the target content returned from the center server 20 in response to the acquisition request is received by the data receiving unit 122 (S104), the cache management unit 14 executes a cache data deletion process (S105). . Although details of the cache data deletion process will be described later, the cache data deletion process deletes the cache data as necessary and secures a free capacity in the cache storage unit 133.

  Subsequently, the writing unit 132 writes the received data in the cache storage unit 133 (S106). Specifically, for example, a file of the target content is generated in the cache storage unit 133, and the received data is written in the file.

  Subsequently, the data transmission unit 112 transmits the received data to the terminal 30 (S107). At this time, the bit rate determination unit 15 determines the bit rate of the target content. The transmission speed calculation unit 16 calculates, as the transmission speed, a value obtained by multiplying the bit rate determined by the bit rate determination unit 15 by a predetermined coefficient of 1.0 or more. The bandwidth control unit 113 controls the data transmission rate of the data transmission unit 112 so as to be maintained at the calculated transmission rate. As a method for controlling the transmission rate by the band control unit 113, a known method such as a method described in Japanese Patent Application Laid-Open No. 2010-232728 may be used.

  Note that the bit rate of the target content may be determined based on information recorded in the header portion or the like of the target content.

  The above steps S104 to S107 are repeated until the entire target content is transmitted to the terminal 30 (S108). That is, reception of the target content from the center server 20 and transmission of the target content to the terminal 30 are performed in parallel. When all of the target content is transmitted to the terminal 30, the writing unit 132 registers cache management information related to the newly cached content in the cache management information storage unit 18 (S109).

  FIG. 6 is a diagram illustrating a configuration example of the cache management information storage unit. In FIG. 6, the cache management information storage unit 18 stores a content name, last access date / time, size, missing amount, content scale, and the like for each content stored in the cache storage unit 133.

  The content name is a content identification name. For example, the file name of the file storing the content may be the content name. The last access date and time is the date and time when the content was last accessed. The size is the total data size of the content. The missing amount is the data size of the missing portion of the content. The content scale is the total playback time of the content.

  In step S109, the current date is stored as the last access date. 0 is stored in the missing amount. Note that the content name, size, and content scale may be acquired from the content itself, or may be acquired from the center server 20 as content attribute information together with the content.

  On the other hand, when there is cache data (Yes in S102), the process of distributing the cache data to the terminal 30 (S110) and the process of acquiring the missing part from the center server 20 (S120) are executed in parallel.

  In the process of distributing cache data to the terminal 30 (S110), the following process is executed. In step S111, the reading unit 131 updates the last access date and time stored in the cache management information storage unit 18 in association with the content name of the target content to the current date and time (S111). Subsequently, the reading unit 131 reads a part of the target content from the data cache storage unit 133 to the memory device 103 (S112). The data transmission unit 112 transmits the data read into the memory device 103 to the terminal 30 (S113). Steps S112 and S113 are repeated until the original end of the target content is transmitted (S114). In step S113, the bit rate determination unit 15 determines the bit rate of the target content. The transmission speed calculation unit 16 calculates, as the transmission speed, a value obtained by multiplying the bit rate determined by the bit rate determination unit 15 by a predetermined coefficient of 1.0 or more. The bandwidth control unit 113 controls the data transmission rate of the data transmission unit 112 so as to be maintained at the calculated transmission rate.

  In the missing part acquisition process (S120) from the center server 20, the following process is executed. First, the missing rate calculation unit 17 determines the presence or absence of a missing part for the target content (S121). The presence or absence of a missing part can be determined by referring to the missing amount stored in the cache management information storage unit 18 in association with the content name of the target content. That is, if the missing amount exceeds 0, it is determined that there is a missing portion.

  When there is no missing part (No in S121), the missing part acquisition process (S120) from the center server 20 ends. When there is a missing part (Yes in S121), the missing rate calculation unit 17 calculates the missing rate of the target content (S122). The missing rate can be calculated based on the size and the missing amount stored in the cache management information storage unit 18 in association with the content name of the target content. That is, the missing rate can be calculated by dividing the missing amount by the size.

  Subsequently, the request transmission unit 121 specifies the content name of the target content and the calculated missing rate, and transmits a target content acquisition request to the center server 20 (S123). When a part of the data of the target content returned from the center server 20 in response to the acquisition request is received by the data receiving unit 122 (S124), the cache management unit 14 executes a cache data deletion process (S125). . Subsequently, the writing unit 132 writes the received data in the cache storage unit 133 (S126). For example, the received data is additionally written at the end of the target content file stored in the cache storage unit 133.

  Steps S124 to S126 are repeated until all of the missing parts of the target content are written in the cache storage unit 133 (S127). The missing part of the target content acquired from the center server 20 and written in the cache storage unit 133 is the terminal 30 following the remaining part of the target content in the distribution process of cache data to the terminal 30 (S110). Sent to. In other words, if the acquisition of the missing part is performed without delay with respect to the transmission of the remaining part, the presence of the missing part is not recognized in the cache data distribution process (S110) to the terminal 30, On the other hand, the remaining part and missing part of the target content are transmitted.

  Subsequently, the writing unit 132 updates the missing amount stored in the cache management information storage unit 18 in association with the content name of the target content to 0 (S128).

  Next, details of steps S105 and S125 will be described. FIG. 7 is a flowchart for explaining an example of the processing procedure of the cache data deletion processing.

  In step S131, the deletion target selection unit 141 determines whether or not the cache storage unit 133 has a predetermined amount of free space. For example, the predetermined amount may be a fixed value set in advance, or may be a value equal to or larger than the size of the data received in step S104 or S124 in FIG.

  When there is no predetermined amount of space (No in S131), the deletion target selection unit 141 deletes the content related to the content name associated with the last access date and time indicating the oldest date and time in the cache management information storage unit 18. (S132). Subsequently, the deletion unit 142 deletes a part from the end of the remaining part of the cache data of the selected content (S133). For example, the partial data size may be a predetermined ratio with respect to the size of the content, or may be a fixed value common to all the content.

  Subsequently, the deletion unit 142 updates the last access date and missing amount stored in the cache management information storage unit 18 for the selected content (S134). The last access date / time is updated to the current date / time. The missing amount is updated to a value obtained by adding a part of the data size deleted in step S133 to the missing amount before update.

  Steps S132 to S134 are repeated until a predetermined amount of free space is secured in the cache storage unit 133 (S131).

  As described above, in this embodiment, in order to secure the capacity of the cache storage unit 133, not all of the content selected as the deletion target is deleted, but a part of the content selected as the deletion target is stored. Deleted. Therefore, the number of contents to be deleted is increased, but the number of contents to be deleted can be reduced compared to the case where all the contents selected as the deletion target are deleted. As a result, the number of contents that are at least partially cached can be increased, and the apparent hit rate of the cache can be increased.

  Note that there may be content in which all of the remaining part is finally deleted by repeatedly deleting the part. Alternatively, content whose remaining portion is equal to or less than a predetermined amount may be excluded from the deletion target. In this case, if a predetermined amount of free space cannot be secured in the cache storage unit 133 even though the remaining portion of all cached content is less than or equal to a predetermined amount, the content whose remaining portion is less than or equal to the predetermined amount Rules such as exclusion from the deletion target may be ignored.

  In this embodiment, an example in which a deletion target is selected by a so-called LRU method has been described, but the deletion target may be selected by an algorithm other than the LRU method. For example, the content with the largest data size or ratio of the remaining part may be selected as the deletion target.

  In the present embodiment, an example is shown in which the cache data deletion process is executed in response to the reception of a content distribution request from the terminal 30 (S101). May be performed asynchronously. For example, cache data deletion processing may be executed periodically.

  Subsequently, a processing procedure executed by the center server 20 will be described. FIG. 8 is a flowchart for explaining an example of a processing procedure executed by the center server.

  In step S <b> 201, the request reception unit 211 receives a content acquisition request from the edge server 10. For example, the acquisition request is transmitted from the edge server 10 in step S103 or step S123 of FIG.

  Subsequently, the bit rate determination unit 24 determines the bit rate of the content related to the acquisition request (hereinafter referred to as “target content”) (S202). Subsequently, the transmission speed calculation unit 25 calculates the transmission speed of the target content (S203). For example, a result obtained by multiplying the bit rate by a predetermined coefficient of 1.0 or more is calculated as the transmission speed.

  Subsequently, the missing rate determination unit 23 determines whether or not the missing rate is specified in the target content acquisition request received in step S201 (S204). When the missing rate is specified (Yes in S204), the transmission rate calculation unit 25 multiplies the transmission rate calculated in Step S203 (hereinafter referred to as “basic transmission rate”) by the missing rate. The transmission speed is set (S205). Therefore, for example, when the predetermined coefficient is 1.0, if the bit rate of the content is 6 Mbps and the missing rate is 50%, the transmission speed is 6.0 × 0.5 = 3 Mbps. .

  The transmission speed can be calculated on the edge server 10 side. Therefore, for example, the missing rate calculation unit 17 of the edge server 10 may calculate the transmission speed based on the missing rate. In this case, the transmission speed may be specified in the target content acquisition request to the center server 20. The transmission speed calculation unit 25 of the center server 20 may use the designated transmission speed as the transmission speed of the target content.

  Note that a speed exceeding the value obtained by multiplying the basic transmission speed by the missing rate may be set as the transmission speed. If the missing part is transmitted to the edge server 10 at a speed exceeding the value obtained by multiplying the basic transmission speed by the missing rate, there is a possibility that the missing part will be delayed with respect to the remaining part in the distribution of content to the terminal 30. This is because it can be lowered. However, from the viewpoint of leveling the load on the network N1, it is desirable that the transmission speed calculated in step S205 is slower than the transmission speed (that is, the basic transmission speed) when transmitting all of the target content. If the transmission speed is slow, the bandwidth used for the network N1 for one content can be reduced, and even if content acquisition requests concentrate on the center server 20, the network N1 may run out of bandwidth. This is because it can be reduced.

  Subsequently, the reading unit 22 reads, from the content storage unit 26, partial data of the target content related to the content name specified in the target content acquisition request (S206). Subsequently, the data transmission unit 212 transmits the read data to the edge server 10 (S207). The bandwidth control unit 213 controls the data transmission rate of the data transmission unit 212 to be maintained at the transmission rate calculated for the target content. Note that the transmission rate control method by the bandwidth control unit 213 may be the same as the transmission rate control method by the bandwidth control unit 113.

  Steps S206 and S207 are repeated until the entire target content is transmitted. However, when the missing rate is specified in the content acquisition request, the data to be processed in steps S206 and S207 is the data of the missing portion of the target content. Therefore, when the missing rate is specified, steps S206 and S207 are executed in order from the beginning of the data of the missing part of the target content. The data size of the data of the missing portion of the target content can be obtained by multiplying the data size of the target content by the missing rate specified in the target content transmission request. Alternatively, the start position of the missing portion data may be specified in the transmission request for the target content.

  As described above, according to the present embodiment, the content cached in the edge server 10 is deleted part by part, so that the apparent hit rate of the cache can be increased. Therefore, it is possible to reduce the risk of occurrence of insufficient bandwidth of the network N1 due to frequent occurrence of cache misses at the same time.

  Further, when transmitting the missing content portion from the center server 20 to the edge server 10, there is a margin for the time required for transmission from the edge server 10 of the remaining content portion to the terminal 30. Therefore, the transmission speed can be reduced by the margin for the transmission of the missing portion of the content from the center server 20 to the edge server 10 as compared to the case where the entire content is to be transmitted. As a result, the load on the network N1 between the center server 20 and the edge server 10 can be leveled.

  Further, when the transmission rate of the missing part is set to (basic transmission rate × missing rate) or more, there is a possibility that a delay will occur with respect to the cached remaining part in the delivery to the missing part to the terminal 30. Can be reduced. Therefore, it is possible to increase the possibility that the content will be distributed without giving a sense of incongruity to the viewer of the content (for example, without degrading the quality of the distributed video).

  The missing part may not be a part from the end of the content. For example, the deletion unit 142 may delete an intermediate part of the content. The intermediate part refers to a part excluding the top and end of the content. That is, the deletion target by the missing part may be a part from the middle of the content, and the end of the part may not necessarily match the original end of the content. In addition, the deletion unit 142 may delete the content so that a plurality of missing portions are formed in a missing shape for one content.

  When the middle part is a missing part, the transmission rate of the missing part is the ratio of the data size of the missing part to the total data size of the remaining part immediately before the missing part and the missing part. A value obtained by multiplying by may be used as the transmission speed from the center server 20 to the edge server 10 for the missing portion.

  The edge server 10 may not include the bandwidth control unit 113, the bit rate determination unit 15, and the transmission speed calculation unit 16. FIG. 9 is a diagram illustrating a second functional configuration example of the edge server in the present embodiment. 9, parts that are the same as those shown in FIG. 3 are given the same reference numerals, and explanation thereof is omitted.

  In FIG. 9, the edge server 10 does not have the bandwidth control unit 113, the bit rate determination unit 15, and the transmission speed calculation unit 16. In this case, the content transmission speed to the terminal 30 is controlled by the initiative of the terminal 30. For example, in communication with the terminal 30, content may be transmitted to the terminal 30 by the data size notified from the terminal 30. An example of such a form is flow control by notification of window size in TCP.

  In the present embodiment, the center side communication unit 12 is an example of an acquisition unit. The data transmission unit 112 is an example of a transmission unit. The cache storage unit 133 is an example of a storage unit.

  As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to such specific embodiment, In the range of the summary of this invention described in the claim, various deformation | transformation・ Change is possible.

Regarding the above description, the following items are further disclosed.
(Appendix 1)
An acquisition unit for acquiring the data via the network in response to reception of the first transmission request for the data received via the network;
A transmission unit for transmitting the acquired data to the first transmission request source;
A storage unit for storing the acquired data;
A deletion unit that deletes a portion from the middle of the data from the storage unit,
The acquisition unit acquires the part via the network at a slower rate than when acquiring all of the data in response to a second transmission request for the data,
In response to the second transmission request, the transmission unit transmits the part acquired by the acquisition unit to the second transmission request source following the remaining part excluding the part of the data. apparatus.
(Appendix 2)
In response to the second transmission request, the acquisition unit sets the portion to the second transmission request source so that transmission of the portion to the second transmission request source is not delayed with respect to transmission of the remaining portion. The data transmission device according to appendix 1, which is acquired through a network.
(Appendix 3)
In response to the second transmission request, the obtaining unit multiplies the part at a speed equal to or higher than a value obtained by multiplying a speed when obtaining all the data by a ratio of the part to the whole data. The data transmission device according to appendix 2, which is acquired via the network.
(Appendix 4)
In response to the second transmission request, the acquisition unit transfers the part to the network at a speed equal to or higher than a value obtained by multiplying a bit rate at the time of reproducing the data by a ratio of the part to the whole of the data. The data transmitting apparatus according to supplementary note 2, which is acquired via
(Appendix 5)
A data transmission system comprising a data storage device for storing data and a data transmission device connected to the data storage device via a network,
The data transmission device includes:
An acquisition unit for acquiring the data from the data storage device in response to reception of a first transmission request for data received via a network;
A transmission unit for transmitting the acquired data to the first transmission request source;
A storage unit for storing the acquired data;
A deletion unit that deletes a portion from the middle of the data from the storage unit,
The acquisition unit acquires the part from the data storage device in response to a second transmission request for the data at a slower rate than when acquiring all of the data,
In response to the second transmission request, the transmission unit transmits the part acquired by the acquisition unit to the second transmission request source following the remaining part excluding the part of the data. system.
(Appendix 6)
In response to receiving a first transmission request for data received via the network, the data is obtained via the network;
Send the acquired data to the first transmission request source,
Store the acquired data in the storage unit,
A part of the data from the middle is deleted from the storage unit,
In response to a second transmission request for the data, the portion is acquired via the network at a slower rate than when all of the data is acquired;
In response to the second transmission request for the data, the computer transmits the part acquired by the acquisition unit to the second transmission request source following the remaining part of the data excluding the part. Data transmission method to be executed.
(Appendix 7)
In response to the second transmission request, the part is acquired via the network so that the transmission of the part to the second transmission request source by the transmission unit is not delayed with respect to the transmission of the remaining part. The data transmission method according to appendix 6.
(Appendix 8)
In response to the second transmission request, the part is transmitted via the network at a speed equal to or higher than a value obtained by multiplying the speed for obtaining all the data by the ratio of the part to the whole data. The data transmission method according to appendix 7, which is acquired.
(Appendix 9)
In response to the second transmission request, the part is acquired via the network at a speed equal to or higher than a value obtained by multiplying the bit rate at the time of reproduction of the data by the ratio of the part to the whole of the data. The data transmission method according to appendix 7.
(Appendix 10)
In response to receiving a first transmission request for data received via the network, the data is obtained via the network;
Send the acquired data to the first transmission request source,
Store the acquired data in the storage unit,
A part of the data from the middle is deleted from the storage unit,
In response to a second transmission request for the data, the portion is acquired via the network at a slower rate than when all of the data is acquired;
In response to the second transmission request for the data, a process of transmitting the part acquired by the acquisition unit to the second transmission request source subsequent to the remaining part of the data excluding the part. The program to be executed.
(Appendix 11)
In response to the second transmission request, the part is acquired via the network so that the transmission of the part to the second transmission request source by the transmission unit is not delayed with respect to the transmission of the remaining part. The program according to appendix 10.
(Appendix 12)
In response to the second transmission request, the part is transmitted via the network at a speed equal to or higher than a value obtained by multiplying the speed for obtaining all the data by the ratio of the part to the whole data. The program according to attachment 11 to be acquired.
(Appendix 13)
In response to the second transmission request, the part is acquired via the network at a speed equal to or higher than a value obtained by multiplying the bit rate at the time of reproduction of the data by the ratio of the part to the whole of the data. The program according to appendix 11.

DESCRIPTION OF SYMBOLS 1 Distribution system 10 Edge server 11 Terminal side communication part 12 Center side communication part 13 Cache part 14 Cache management part 15 Bit rate determination part 16 Transmission rate calculation part 17 Missing rate calculation part 18 Cache management information storage part 20 Center server 21 Communication processing Unit 22 Reading unit 23 Missing rate determination unit 24 Bit rate determination unit 25 Transmission speed calculation unit 26 Content storage unit 30 Terminal 100 Drive device 101 Recording medium 102 Auxiliary storage device 103 Memory device 104 CPU
105 interface device 111 request receiving unit 112 data transmitting unit 113 bandwidth control unit 121 request transmitting unit 122 data receiving unit 131 reading unit 132 writing unit 133 cache storage unit 141 deletion target selecting unit 142 deleting unit 211 request receiving unit 212 data transmitting unit 213 Band control part B bus

Claims (7)

An acquisition unit for acquiring the data via the network in response to reception of the first transmission request for the data received via the network;
A transmission unit for transmitting the acquired data to the first transmission request source;
A storage unit for storing the acquired data;
When data different from the data stored in the storage unit is acquired by the acquisition unit, each of the plurality of data stored in the storage unit is stored before the different data is stored in the storage unit. for, and a deleting unit for deleting from the storage unit a part of the middle,
The acquisition unit acquires the part via the network at a slower rate than when acquiring all of the data in response to a second transmission request for the data,
In response to the second transmission request, the transmission unit transmits the portion acquired by the acquisition unit to the second transmission request source following the remaining portion excluding the portion of the data ,
The deletion unit deletes a part of the data that has already been partially deleted when the different data cannot be stored in the storage unit even if a part of the data stored in the storage unit is deleted. ,
Data transmission device.   In response to the second transmission request, the acquisition unit sets the portion to the second transmission request source so that transmission of the portion to the second transmission request source is not delayed with respect to transmission of the remaining portion. The data transmission device according to claim 1, wherein the data transmission device is acquired via a network.   In response to the second transmission request, the obtaining unit multiplies the part at a speed equal to or higher than a value obtained by multiplying a speed when obtaining all the data by a ratio of the part to the whole data. The data transmission device according to claim 2, wherein the data transmission device is acquired via the network.   In response to the second transmission request, the acquisition unit transfers the part to the network at a speed equal to or higher than a value obtained by multiplying a bit rate at the time of reproducing the data by a ratio of the part to the whole of the data. The data transmission device according to claim 2, acquired via A data transmission system comprising a data storage device for storing data and a data transmission device connected to the data storage device via a network,
The data transmission device includes:
An acquisition unit for acquiring the data from the data storage device in response to reception of a first transmission request for data received via a network;
A transmission unit for transmitting the acquired data to the first transmission request source;
A storage unit for storing the acquired data;
When data different from the data stored in the storage unit is acquired by the acquisition unit, each of the plurality of data stored in the storage unit is stored before the different data is stored in the storage unit. for, and a deleting unit for deleting from the storage unit a part of the middle,
The acquisition unit acquires the part from the data storage device in response to a second transmission request for the data at a slower rate than when acquiring all of the data,
In response to the second transmission request, the transmission unit transmits the portion acquired by the acquisition unit to the second transmission request source following the remaining portion excluding the portion of the data ,
The deletion unit deletes a part of the data that has already been partially deleted when the different data cannot be stored in the storage unit even if a part of the data stored in the storage unit is deleted. ,
Data transmission system. In response to receiving a first transmission request for data received via the network, the data is obtained via the network;
Send the acquired data to the first transmission request source,
Store the acquired data in the storage unit,
When data different from the data stored in the storage unit is acquired by the acquisition process, before the different data is stored in the storage unit, a plurality of data stored in the storage unit is stored. For each, a part from the middle is deleted from the storage unit,
In response to a second transmission request for the data, the portion is acquired via the network at a slower rate than when all of the data is acquired;
In response to the second transmission request for the data, following the remaining portion excluding the portion of the data, the portion acquired by the process of acquiring the portion via the network is changed to the second transmission request. The computer executes the process to send to the original ,
In the process of deleting, if the different data cannot be stored in the storage unit even if a part of all the data stored in the storage unit is deleted, a part of the data that has already been deleted is deleted. To
Data transmission method. In response to receiving a first transmission request for data received via the network, the data is obtained via the network;
Send the acquired data to the first transmission request source,
Store the acquired data in the storage unit,
When data different from the data stored in the storage unit is acquired by the acquisition process, before the different data is stored in the storage unit, a plurality of data stored in the storage unit is stored. For each, a part from the middle is deleted from the storage unit,
In response to a second transmission request for the data, the portion is acquired via the network at a slower rate than when all of the data is acquired;
In response to the second transmission request for the data, following the remaining portion excluding the portion of the data, the portion acquired by the process of acquiring the portion via the network is changed to the second transmission request. Let the computer execute the process to send to the original ,
In the process of deleting, if the different data cannot be stored in the storage unit even if a part of all the data stored in the storage unit is deleted, a part of the data that has already been deleted is deleted. To
program.

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