JP5798523B2 - Communication control system, aggregation server, and communication control method - Google Patents

Description

  The present invention relates to a communication control system, an aggregation server, and a communication control technique for caching content on the Internet.

  Conventionally, when a plurality of user terminals request acquisition of the same content, there is a technology for distributing content from a device (cache server) physically located near the user terminal using a cache technology. With this technology, it is considered possible to suppress traffic in the network and speed up response to requests. Here, when it is necessary to store a large amount of content and process a request (content acquisition request) in a large-scale network that accommodates a very large number of user terminals, usually a plurality of cache servers in the network Are distributed in a distributed manner.

  In a system in which a plurality of cache servers are distributed in this way, a control server connected to a gateway device with another network discriminates content with a high data request frequency, and the data request frequency is distributed to the distributed cache servers. There is a technology that distributes high content in advance (Patent Document 1). According to such a technique, the user terminal is more likely to browse the content stored in the cache server. Therefore, traffic in the network can be suppressed and the response to the request can be further speeded up.

JP 2005-10970 A

  However, in the prior art, the content distributed to the cache server is only the content determined as having a high data request frequency by the control server, and may not actually be viewed from the user terminal. For this reason, there is a possibility that the resources (data storage capacity and CPU (Central Processing Unit) usage rate) of the cache server may be tight for storing content that is not actually browsed by the user terminal. Moreover, there is a possibility that useless traffic may occur in the network due to the distribution of content that is not browsed.

  Therefore, the present invention solves the above-described problem, effectively utilizes resources of a plurality of cache servers distributed and deployed in the network, and can suppress the occurrence of useless traffic in the network. It is another object of the present invention to provide a communication control method.

  In order to solve the above-described problems, a communication control system of the present invention includes an aggregation server that analyzes an access frequency for each content, an edge device connected to a user terminal, and a content cache server connected to the edge device. Prepare. The aggregation server of this communication control system acquires a content acquisition request from the user terminal to the content server via the network, and analyzes the access frequency for each content based on the acquisition request for each predetermined period. And an aggregation unit that transmits the content identifier of the content whose access frequency is equal to or higher than a predetermined value to the edge device. The edge device also has a storage unit for storing the content identifier transmitted from the aggregation server, and a cache connected to the edge device when the acquisition request for the content including the content identifier is received from the user terminal. And a DPI (Deep Packet Inspection) processing unit for redirecting to the server. Furthermore, when the cache server receives the redirected acquisition request and the storage unit that stores the content, the cache server distributes the content to the user terminal and the acquisition request target when the acquisition request target content is in the storage unit. When the content is not in the storage unit, the content is acquired from the content server, stored in the storage unit, and delivered to the user terminal. Among the content stored in the storage unit, A cache processing unit for erasing content that has passed a predetermined time from distribution.

  As described above, the aggregation server transmits the content identifier of the frequently accessed content (popular content) to the edge device so that the user terminal goes through the cache server when accessing the popular content. If the access target (acquisition request target) content is already stored in the cache server, the content stored in itself is distributed. On the other hand, if the access target content is not stored in the cache server, the content is acquired from the content server, stored, and then distributed. As a result, the cache server performs storage and distribution of popular content, so that it is possible to prevent unnecessary traffic from occurring in the network. In addition, since popular contents are stored in the cache server, the resources of the cache server are efficiently used.

  In addition, the aggregation unit in the aggregation server of the communication control system of the present invention further transmits a content identifier of content whose analyzed access frequency increase rate is a predetermined value or more to the edge device.

  In this way, the cache server can store and distribute content that may increase in access frequency in the future.

  The aggregation unit in the aggregation server of the communication control system of the present invention further selects content whose access frequency increases every predetermined period as the non-erasable content in the cache server, and the content identifier of the selected non-erasable content Is sent to the cache server. Further, the cache processing unit in the cache server further erases content other than the content indicated by the content identifier of the non-erasable content among the content stored in the storage unit.

  By doing so, the cache server selects content whose access frequency increases every predetermined period and stores it in the storage unit, so that the storage capacity of the storage unit can be used effectively.

  In addition, the cache server of the communication control system of the present invention further includes a cache access frequency counting unit that counts the access frequency from the user terminal for each content of its own cache server, and the communication processing unit calculates the total access frequency. Send to the aggregation server. Further, the aggregation unit of the aggregation server transmits the content identifier of the content whose access frequency is a predetermined value or more to the edge device based on the access frequency analyzed by the analysis unit and the access frequency received from the cache server.

  In this way, the aggregation server analyzes the content access frequency in consideration of the content access frequency (cache usage frequency) in each cache server, so the content identifier transmitted by the aggregation server to each edge device The content identifier having a high distribution frequency from each cache server can be included. As a result, the cache hit rate of each cache server (the rate of delivering the content to the user terminal among the content stored in its own cache server) can be improved, so the resources of the cache server are more efficient. Can be used. In addition, it is possible to further suppress the occurrence of useless traffic in the network.

  According to the present invention, it is possible to effectively use resources of a plurality of cache servers distributed and deployed in a network, and to suppress the generation of useless traffic in the network.

It is the figure explaining the structure and the outline | summary of the communication control system of this Embodiment. It is the figure explaining the structure of the communication control system of this Embodiment in detail. It is the figure which illustrated the content access frequency information of FIG. It is a figure explaining the cache server of FIG. It is a figure explaining the operation | movement at the time of totaling of the access frequency in the system of this Embodiment. It is a figure explaining the operation | movement at the time of the content preservation | save in the system of this Embodiment.

<Overview>
Embodiments of the present invention will be described with reference to the drawings. First, the configuration and outline of a communication control system (hereinafter abbreviated as a system) according to an embodiment will be described with reference to FIG. The system includes a user terminal 10, a copy device 20 that copies packets, an aggregation server 30 that analyzes the access frequency for each content identifier, an IP (Internet Protocol) network 40 using a communication carrier, and another network 50 that is a network outside the IP network 40. The gateway device 60 installed between the IP network 40 and the other network 50, the content server 70 for distributing content, the edge device 80 (80A, 80B) installed in the IP network 40 and accommodating the user terminal 10 and the cache Server 90 (90A, 90B) is provided. The number of servers and devices is not limited to the number shown in FIG. In the following description, the content identifier is, for example, a content URL (Uniform Resource Locator), an IP address, or the like.

  The user terminal 10 is connected to the IP network 40 via each edge device 80, and passes through the edge device 80, the IP network 40, and the gateway device 60, and various servers (for example, the content server 70) arranged in the other network 50. Etc.). For example, the user terminal 10 transmits a content acquisition request to the content server 70 to acquire the content.

  Here, the copy device 20 copies the packet from the IP network 40 to the other network 50. Then, the aggregation server 30 extracts an acquisition request for a predetermined content server 70 from the packet copied by the copy device 20. The aggregation server 30 totals the access frequency of each content every predetermined period, and identifies URLs and the like of popular content with high access frequency. Thereafter, the aggregation server 30 instructs the DPI (Deep Packet Inspection) processing unit 811 of the edge device 80 to redirect the communication related to the acquisition of the identified popular content to the cache server 90. As a result, the edge device 80 identifies a popular content acquisition request and redirects the identified acquisition request to the cache server 90. If there is no acquisition target content indicated in the redirected acquisition request, the cache server 90 acquires and stores it from the content server 70 and distributes it to the user terminal 10. If there is already the acquisition target content, the content is stored in the user terminal 10. Deliver to (save and distribute content). By doing so, the aggregation server 30 can cause the cache server 90 to store popular content and thereafter distribute the popular content from the cache server 90 to the user terminal 10.

  Next, each component of the system will be described in detail with reference to FIG.

<Copy device>
The copy device 20 is disposed between the gateway device 60 and the IP network 40, copies a packet from the IP network 40 to the other network 50, and transmits the packet to the aggregation server 30. As a copy method, a method of physically copying using optical TAP and identifying and specifying a packet based on 5 tuples (a combination of a source IP address, a destination IP address, a source port, a destination port and a protocol) And a method of copying the packet. Further, the copy device 20 may pull the packet into the aggregation server 30 by redirecting the packet to the aggregation server 30.

<Aggregation server>
The aggregation server 30 acquires a content acquisition request from the user terminal 10 by the copy device 20, and analyzes the access frequency for each content every predetermined period. Then, the aggregation server 30 transmits a content identifier having a high access frequency (for example, the access frequency is a predetermined value or more) to the edge device 80. After that, the edge device 80 that has received the content identifier redirects the acquisition request for the content with the content identifier in the packet from the user terminal 10 to the cache server 90. In other words, the aggregation server 30 instructs the edge device 80 to redirect the acquisition request for the frequently accessed content from the user terminal 10 to the cache server 90.

  The aggregation server 30 includes a distribution unit 31, a plurality of analysis units 32, an aggregation unit 33, and an access frequency storage unit 34.

  The distribution unit 31 transmits the packet received from the copy device 20 to any of the analysis units 32.

  The analysis unit 32 selects a content request (content acquisition request) packet for a predetermined site from the packets received from the distribution unit 31. The analysis unit 32 acquires a content identifier such as an IP address or URL from the selected content request packet, and records the number of accesses for each content identifier. Then, the analysis unit 32 notifies the aggregation unit 33 of the number of accesses (access frequency) for each content identifier every predetermined period. Here, the analysis unit 32 preferably deletes the access frequency held in the memory or the like after the notification of the access frequency. By doing so, the storage capacity of the memory used by the analysis unit 32 can be effectively utilized. Here, in the IP network 40 in which many user terminals 10 are accommodated, it is assumed that a very large number of packets are distributed between the gateway device 60 and the IP network 40. For this reason, it is preferable to arrange a plurality of analysis units 32 in the aggregation server 30 and perform distributed processing using the distribution unit 31. In this case, the distribution unit 31 distributes the packet to one of the analysis units 32 by, for example, hash calculation based on the destination IP address of the packet.

  The aggregation unit 33 aggregates the access frequencies notified from the analysis unit 32 and creates content access frequency information (access frequency information) indicating the access frequency for each content identifier. This content access frequency information is stored in the access frequency information storage unit 34. Further, the aggregating unit 33 selects a content identifier having a high access frequency based on the created access frequency information, and transmits the selected content identifier to the edge device 80.

  The aggregation unit 33 includes a content access frequency aggregation unit 331 and a content selection unit 332. The content access frequency totaling unit 331 creates access frequency information indicating the access frequency for each content identifier notified from the analysis unit 32. This access frequency information is, for example, information indicating the access frequency of each content at each date and time, as shown in FIG.

  The content selection unit 332 selects content to be stored and distributed in each cache server 90 based on the access frequency information for each predetermined period. For example, the content selection unit 332 selects content with a high access frequency every predetermined period such as one day or one hour based on the access frequency information. Then, the content selection unit 332 transmits the content identifier of the selected content to the edge device 80. Here, as a selection method, a method of selecting an access frequency of a predetermined value or more, a method of selecting a predetermined number in order from the most recent access frequency, or a method of increasing the access frequency is selected. For example, a method for predicting and selecting contents that will be frequently accessed in the future, or a method for comprehensively selecting contents that take these into consideration, and the like. According to such a selection method, the content selection unit 332 selects content that is assumed to have a high effect on the traffic suppression and the improvement of the user's experience quality due to the recent access frequency being high and storage in the cache server 90. Can do. The method of selecting the content with the most recent access frequency in this way is considered to be particularly effective for content on the Internet where the variation of popular content is large and the life cycle is short.

  Such an aggregation server 30 is realized by a computer including a CPU, a communication interface, and a storage medium. The distribution unit 31, the analysis unit 32, and the aggregation unit 33 are implemented by a communication interface and a program execution process by the CPU, a dedicated circuit, and the like. Furthermore, the access frequency storage unit 34 includes a storage medium such as a random access memory (RAM), a read only memory (ROM), a hard disk drive (HDD), and a flash memory.

<Edge device>
The edge device 80 (80A, 80B) identifies the communication related to the acquisition of the content with the content identifier notified from the aggregation unit 33 of the aggregation server 30, and redirects the communication to the cache server 90. The edge device 80 is realized by a computer including a CPU, a communication interface, and a storage medium. The function of the edge device 80 is roughly divided into a communication processing unit 81 and a storage unit 82. The communication processing unit 81 performs route control and the like when the user terminal 10 performs communication via the IP network 40. The communication processing unit 81 includes a DPI processing unit 811.

  The DPI processing unit 811 stores the content identifier transmitted from the aggregation server 30 in the storage unit 82, and when the content acquisition request for the content identifier stored in the storage unit 82 is received from the user terminal 10, the acquisition is performed. The request is redirected to the cache server 90. The DPI processing unit 811 receives a content identifier from the aggregation server 30 every predetermined period, and uses the latest content identifier for redirection.

  As a result, the edge device 80 allows the communication related to the acquisition of the frequently accessed content from the user terminal 10 to pass through the cache server 90, and the communication related to the acquisition of the other content with the low access frequency does not pass through the cache server 90. The action can be performed. Further, it is possible to prevent the infrequently accessed content from being stored in the cache server 90, so that the resources of the cache server 90 can be used effectively.

<Cache server>
The cache server 90 stores and distributes content based on the content acquisition request from the user terminal 10 redirected from the edge device 80. As shown in FIG. 4, the cache server 90 includes a communication processing unit 91, a cache processing unit 92, and a storage unit 93. Note that the cache access frequency information, the cache access frequency totaling unit 93, and the cache access frequency information transmitting unit 94 indicated by broken lines may or may not be equipped, and the case of being equipped will be described later.

The communication processing unit 91 stores content in the storage unit 93 and performs user terminal 10 (see FIG. 2) and distribution. That is, when receiving a content acquisition request from the user terminal 10, the communication processing unit 91 transmits this content to the user terminal 10 when the content to be acquired is in the storage unit 93. On the other hand, the communication processing unit 91, when the subject content acquisition request is not in the storage unit 93, acquires the content from the content server 70, stored in the storage unit 93. Then, the stored content is transmitted to the user terminal 10.

  When the total amount of content stored in the storage unit 93 is close to the data storage capacity, the cache processing unit 92 starts from the previous transmission to the user terminal 10 among the content stored in the storage unit 93 (that is, browsing the previous content). ) Delete the content after a predetermined time. Thereby, the limited storage capacity of the storage unit 93 can be effectively used.

<Operation procedure>
Next, the operation procedure of the system shown in FIG. 2 will be described with reference to FIGS. Here, a case where the user terminal 10 acquires the content A stored in the content server 70 via the gateway device 60 will be described as an example.

<Access frequency count>
First, with reference to FIG. 5, the aggregation processing of the content access frequency by the aggregation server 30 will be described. The user terminal 10 under the edge device 80A acquires the content A (“A” in FIG. 5) stored in the content server 70 of the other network 50 via the gateway device 60 (S11). That is, the user terminal 10 transmits a packet for acquiring the content A. At this time, the packet is copied by the copy device 20 provided between the gateway device 60 and the IP network 40 and transmitted to the aggregation server 30 (S12). The aggregation server 30 receives the packet, and then distributes the packet to the analysis unit 32 by the distribution unit 31 in the aggregation server 30 (S13). For example, the distribution unit 31 selects one analysis unit 32 from the plurality of analysis units 32 based on the IP address of the packet, and transmits the packet to the selected analysis unit 32.

  The analysis unit 32 extracts a content identifier from the received packet (S14). That is, when the analysis unit 32 determines that the packet received from the distribution unit 31 is a content request packet to a predetermined website or server, the content identifier (IP address, URL, etc.) of the content requested by the packet ). Then, the analysis unit 32 records the number of accesses for each content identifier. The analysis unit 32 notifies the aggregation unit 33 of the access frequency for each content identifier every predetermined period, and deletes the access frequency held by the analysis unit 32.

  The aggregation unit 33 creates access frequency information (see FIG. 3) based on the access count for each content identifier notified from the analysis unit 32 by the content access frequency aggregation unit 331 (see FIG. 2) (S15). That is, the content access frequency totaling unit 331 creates access frequency information in which the number of accesses for each predetermined period (for example, every day or every hour) is recorded for each content identifier.

<Storage and distribution of content>
Next, content storage and distribution by the cache server 90 will be described with reference to FIG. After S15 in FIG. 5, the content selection unit 332 (see FIG. 2) of the aggregation unit 33 of the aggregation server 30 selects a predetermined number of contents stored in the cache server 90 for each predetermined period, and the DPI of each edge device 80 is selected. The processing unit 811 is notified (S16). That is, the content selection unit 332 of the aggregation unit 33 refers to the access frequency information, selects a predetermined number of content identifiers of the requested content of the packet to be redirected to the cache server 90, and transmits it to the DPI processing unit 811 of the edge device 80. To do. S17 indicated by a broken line will be described later in the section of other embodiments.

  The DPI processing unit 811 of the edge device 80 stores the content identifier notified from the aggregation server 30 in the storage unit 82 and redirects communication related to content acquisition of the notified content identifier so as to pass through the cache server 90. (S18).

  Here, in the discrimination of communication by the DPI processing unit 811, for example, the following method can be considered. That is, the DPI processing unit 811 first identifies the IP address or the like described in a fixed-length specific field in the header of the received IP packet, and then uses the information that changes the description position in the IP packet such as a URL. A secondary identification method is mentioned. As described above, when the DPI processing unit 811 performs primary identification based on an IP address or the like, information identification of a higher layer such as a URL becomes only part of communication. Therefore, the time required for the redirect determination in the DPI processing unit 811 can be reduced as compared with the case where communication is identified based on information that is not described in a fixed-length header of a packet such as a URL.

  The communication processing unit 91 (see FIG. 4) of the cache server 90 acquires the requested content from the content server 70 in the case of a request for unsaved content to the server for the communication redirected from the edge device 80, It preserve | saves at the memory | storage part 93 and delivers to the user terminal 10 (S19). On the other hand, when the redirected communication is a request for stored content of the own server, the requested content is distributed to the user terminal 10 (S20). S21 indicated by a broken line will be described later in the section of other embodiments.

  According to such a system, content with high access frequency is stored in the cache server 90, so that the resources of the cache server 90 are efficiently used. In addition, since the cache server 90 performs distribution of contents with high access frequency, it is possible to suppress the occurrence of useless traffic in the network.

<Other embodiments>
In the system described above, the aggregation server 30 may instruct the cache server 90 of the content to be deleted from the cache server 90.

  For example, the content selection unit 332 of the aggregation server 30 selects content whose access frequency increases at a predetermined interval (for example, access frequency increases during the daytime), and sets the content identifier of the selected content as a non-erasing target The content identifier is notified to the cache server 90 (S17 in FIG. 6). When the total amount of stored contents in the storage unit 93 of the cache server 90 is close to the data storage capacity, the cache processing unit 92 selects and deletes content other than the non-erased content notified from the aggregation server 30. (S21 in FIG. 6).

  As a result, it is possible to leave on the cache server 90 content whose access frequency is periodically higher than when the cache server 90 selects the content to be deleted based on the frequency of access to its own server. Therefore, it is possible to prevent useless traffic communication while the content erased from the cache server 90 is cached again.

  Further, the content selection unit 332 of the aggregation server 30 may select the content to be stored and distributed in each cache server 90 in consideration of the content access frequency in each cache server 90. In this case, the cache server 90 further includes a cache access frequency totaling unit 94 and a cache access frequency information transmitting unit 95 indicated by broken lines in FIG. The storage unit 93 stores cache access frequency information created by the cache access frequency totaling unit 94. The cache access frequency counting unit 94 records the number of distributions from the cache server 90 to the user terminal 10 for each content in the storage unit 93. Then, the cache access frequency totaling unit 94 creates cache access frequency information indicating the content identifier accessed and the number of accesses every predetermined period (for example, 1 day or 1 hour to 12 hours), and accesses the cache. The frequency information transmission unit 95 transmits this cache access frequency information to the aggregation server 30. Then, the content access frequency totaling unit 331 of the aggregation server 30 selects content to be stored and distributed in the cache server 90 based on the cache access frequency information transmitted from each cache server 90 and the content access frequency information. That is, the content selection unit 332 of the aggregation server 30 can also select content that is frequently distributed in each cache server 90 as content to be stored and distributed in each cache server 90. Thereby, the cache hit rate in each cache server 90 can be improved.

  Further, when the content access frequency totaling unit 331 (see FIG. 2) of the aggregation server 30 creates the access frequency information (see FIG. 3), the latest access records are recorded in detail, and the old records are aggregated. Further, the information before the predetermined period may be deleted to prevent the size from increasing. For example, as in the access frequency information shown in FIG. 3, the access frequency is recorded every hour, and the records before 6 hours are the early morning from 0:00 to 5:00, the daytime from 6:00 to 17:00, and 18:00 The records may be aggregated according to the time zone such as the night time zone from 23:00 to 3 days before. In addition, the content access frequency totaling unit 331, in creating the access frequency information (see FIG. 3), based on the user identifier such as the IP address and the accommodation location information of the user terminal 10 Regionality may be taken into consideration, such as weighting access from large cities such as or creating access frequency information for each region. By doing so, the cache hit rate of the cache server 90 can be improved.

DESCRIPTION OF SYMBOLS 10 User terminal 20 Copy apparatus 30 Aggregation server 31 Distribution part 32 Analysis part 33 Aggregation part 34 Access frequency memory | storage part 40 IP network 50 Other network 60 Gateway apparatus 70 Content server 80 (80A, 80B) Edge apparatus 81, 91 Communication processing part 82, 93 Storage unit 90 Cache server 92 Cache processing unit 94 Cache access frequency totaling unit 95 Cache access frequency information transmitting unit 331 Content access frequency totaling unit 332 Content selection unit 811 DPI processing unit

Claims (6)

An aggregation server for analyzing the access frequency for each content, an edge device connected to a user terminal, and a cache server for the content connected to the edge device;
The aggregation server is
An acquisition unit that acquires a content acquisition request from the user terminal to the content server via the network and analyzes the access frequency for each content based on the acquisition request for each predetermined period; and the analyzed access frequency is predetermined An aggregation unit that transmits a content identifier of content that is greater than or equal to a value to the edge device;
The edge device is
The storage unit that stores the content identifier transmitted from the aggregation server, and the cache that is connected to its edge device when the acquisition request for the content including the content identifier is received from the user terminal A DPI (Deep Packet Inspection) processing unit that redirects to the server,
The cache server is
In the case where the storage unit that stores the content and the redirected acquisition request is received, when the content targeted for the acquisition request is in the storage unit, the content is delivered to the user terminal, and the acquisition request When the target content is not in the storage unit, the content is acquired from the content server, stored in the storage unit, and delivered to the user terminal; among the content stored in the storage unit A cache processing unit for erasing content that has passed a predetermined time since the previous delivery to the user terminal;
A communication control system comprising: The aggregation unit is
The communication control system according to claim 1, further comprising: transmitting to the edge device a content identifier of a content whose analyzed access frequency increase rate is a predetermined value or more. The aggregation unit is
A content selection unit that selects content whose access frequency increases every predetermined period as non-erasable content in the cache server and transmits a content identifier of the selected non-erasable content to the cache server,
The cache processing unit
The communication control system according to claim 1 or 2, wherein content other than the content indicated by a content identifier of the non-erasable content is erased from the content stored in the storage unit. The cache server is
For each content of its own cache server, it further comprises a cache access frequency counting unit that counts the access frequency from the user terminal,
The communication processing unit
Sending the aggregated access frequency to the aggregation server;
The aggregation unit is
The content identifier of the content whose access frequency is a predetermined value or more is transmitted to the edge device based on the access frequency analyzed by the analysis unit and the access frequency received from the cache server. The communication control system according to any one of claims 1 to 3. When receiving an acquisition request including the content identifier from the user terminal, the access frequency to the content server identifies the acquisition request including the content identifier of the content of the predetermined value or more, the identification and acquisition request, storing the content An aggregation server used in a communication control system including an edge device that redirects to a cache server,
Get the acquisition request of content from the user terminal via the network to the content server for each predetermined time period, an analysis unit for analyzing the access frequency of each of the contents based on the obtained acquisition request, the analyzed access aggregation server that frequency content identifier of the content is the predetermined value or more, characterized in that it comprises a collection portion to be transmitted to the edge device. A communication control system comprising an aggregation server that acquires a content acquisition request from a user terminal to a content server via a network, an edge device connected to the user terminal, and a cache server for the content connected to the edge device A communication control method in
The aggregation server is
Analyzing the access frequency for each content based on the acquisition request for each predetermined period;
Transmitting the content identifier of the content whose analyzed access frequency is a predetermined value or more to an edge device connected to the user terminal,
The edge device is
When receiving an acquisition request for content including the content identifier from the user terminal, the step of redirecting the acquisition request to the cache server connected to its edge device,
The cache server is
In the case of receiving the redirected acquisition request,
When the content of the acquisition request target is in a storage unit, the step of delivering the content to the user terminal is executed,
When the content subject of the acquisition request is not in the storage unit, it acquires the content from the content server, stored in the storage unit, executes the steps to be distributed to the user terminal,
The communication control method characterized by performing the step which deletes the content which predetermined time passed from the delivery to the said user terminal last time among the contents memorize | stored in the said memory | storage part.

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