JP2011008657A - Content distribution system, node device, content distribution method, and node program - Google Patents

Abstract

A distribution system, a node device, a distribution method, and a program capable of shortening the time required for content distribution as a whole without increasing a communication load on a higher-level node device.
Time information indicating a time at which content is acquired from any one of node devices is acquired, a node device storing predetermined content is searched according to the time indicated by the time information, and the searched node A predetermined content is acquired from the device, the acquired content is stored, and when the stored content is retrieved from another node device, the content is transmitted to the other node device, and the content is transmitted. It is determined whether or not a predetermined condition is satisfied, and when it is determined that the predetermined condition is satisfied, the stored content is prohibited from being acquired by another node device.
[Selection] Figure 3

Description

  The present invention relates to a technical field of a peer-to-peer (P2P) type communication system including a plurality of node devices that can communicate with each other via a network.

  In recent years, a peer-to-peer communication system has attracted attention as a new form that replaces the server client system, which is the mainstream form of current content distribution. In this type of peer-to-peer communication system, replica data of a plurality of contents (hereinafter referred to as “replicas”) is distributed and stored (arranged) in a plurality of node devices so that replicas can be used between the node devices. A distributed content storage system is known. This improves fault tolerance and access dispersibility. The location of the replicas thus distributed and stored can be efficiently searched using a distributed hash table (hereinafter referred to as DHT (Distributed Hash Table)) as disclosed in, for example, Patent Document 1.

  In such a distributed content storage system, each node device holds a routing table using DHT. This routing table defines various message transfer destinations on the distributed content storage system. In addition, each node device registers information on the minimum necessary nodes among the nodes participating in the distributed content storage system in the routing table. When a message is sent to a node device whose information is not registered in the routing table, the message is transferred between the node devices and delivered to the target node device.

  Patent Document 1 discloses a technique for efficiently distributing content (as a replica) to each node device using DHT. Specifically, a certain node device transmits content to a plurality of node devices in which information such as a network address is registered in a routing table held by the node device. Similarly, each node device that has received the content transfers the content to a plurality of node devices whose information is registered in the routing table held by itself. In this way, as content is transferred one after another in a push-type manner, the content is distributed evenly to each node device via the distribution route on the tree with the node that first transmitted the content as the apex. . Further, it can be said that this distribution route is determined in advance to some extent by information registered in the routing table of each node device.

JP 2007-53662 A

  In the content distribution described above, as shown in FIG. 9, the content received by each of the node devices N1 to N7 is sequentially transferred from the node device positioned higher in the distribution path to the node device positioned lower than the node device. It is desirable to get it. Here, the node device located at the upper level refers to a node device whose content is acquired relatively early as viewed from the entire node device located on the distribution path. In the example of FIG. 9, the content α received by the node device N2 is acquired by the node device N4. Also, the content β received by the node device N1 is acquired by the node device N2. As shown in FIG. 9, an ideal hierarchical distribution form can be taken by sequentially acquiring the received content to another terminal. However, in the actual peer-to-peer communication system, when viewed from the node N4 in FIG. 9, the server SA, the node device N1, the node device N2, and the node device N3 are acquisition candidates for the content α. In this case, it is desirable to select the node device N2 or the node device N3 as the acquisition destination. However, there is a possibility that the node device N1 is selected as the acquisition destination. When the node device N1 is selected as an acquisition destination, the node device N1 also performs processing for causing the node device N2 and the node device N3 to acquire the received content β. Therefore, in addition to the conventional communication process in which the node device N2 and the node device N3 acquire content, the node device N1 is also responsible for a communication process that causes the node device N4 to acquire content. As a result, the communication load on the node device located at the upper level of the distribution route is increased, and there is a possibility that the time required for completing the distribution of the content is greatly delayed.

  The present invention has been made in view of the above points. An object of the present invention is to provide a distribution system capable of shortening the time required for content distribution as a whole without increasing the communication load on a higher-level node device even when the distribution mode described above is used. It is to provide a node device, a distribution method, and a program.

  In order to solve the above-described problem, the invention according to claim 1 acquires content from one of node devices in a content distribution system capable of transmitting and receiving content between a plurality of node devices that can communicate with each other via a network. An acquisition unit that acquires time information indicating a time to perform, a search unit that searches for a node device that stores predetermined content according to the time indicated by the time information acquired by the acquisition unit, and the search unit A content acquisition unit that acquires the predetermined content from the searched node device, a storage unit that stores the content acquired by the content acquisition unit, and a content stored in the storage unit is another node device. Content searcher that transmits the content to the other node device when searched from And determining means for determining whether or not a predetermined condition is satisfied after the content is transmitted by the content transmitting means; and when the determining means determines that the predetermined condition is satisfied, And a prohibiting unit that prohibits the content stored in the unit from being acquired by another node device.

  According to the present invention, when a predetermined condition is satisfied, the acquired content is prohibited from being acquired by another node device. Therefore, the time required for content distribution as a whole can be shortened without increasing the communication load on the upper node device.

  According to a second aspect of the present invention, in the node device according to the first aspect, the determination unit determines whether the number of transmissions of the content has reached a predetermined number as the predetermined condition, The prohibiting means determines that the content stored in the storage means is acquired by another node device when the determining means determines that the number of transmissions of the content has reached a predetermined number. It is characterized by prohibition.

  According to the present invention, content is not transmitted more than a predetermined number of times, so that content transmission load is not concentrated on a higher-level node device when content is requested from a large number of node devices. be able to. Therefore, the time required for content distribution as a whole can be further shortened.

  According to a third aspect of the present invention, in the node device according to the first aspect, the determination unit determines whether or not a predetermined time has elapsed since the content transmission unit transmitted the content as the predetermined condition. When the determination unit determines that a predetermined time has elapsed since the content was transmitted, the content stored in the storage unit is acquired by the other node device. It is prohibited to do so.

  According to the present invention, since the content is not transmitted after a predetermined time has elapsed, it is possible to reliably prevent an increase in the communication load on the higher-level node device.

  According to a fourth aspect of the present invention, in the node device according to any one of the first to third aspects, a predetermined time elapses after the prohibition unit prohibits acquisition by another node device. A time determination unit that determines whether or not the acquisition has been performed, and a release unit that cancels the prohibition of acquisition by the other node device when the time determination unit determines that a predetermined time has elapsed since the acquisition was prohibited. And further comprising.

  According to the present invention, it is possible to acquire content when a predetermined time elapses after content acquisition is prohibited. Therefore, the node device that has not acquired the content at the time of distributing the content can acquire the content later.

  According to a fifth aspect of the present invention, in the node device according to any one of the first to fourth aspects, a publish message indicating that the content is stored in the storage unit is sent to the content by the storage unit. Based on the location information of the node device searched by the search means, message transmitting means for transmitting the location information including the location information to the node device storing the location information indicating the location of the node device storing Requesting means for requesting transmission of content to the searched node device, wherein the searching means receives the predetermined information from the node device storing the location information of the node device storing the predetermined content. The content transmission means searches for the content requested by the other node device. To the other node device, and when the determination unit determines that the predetermined condition is satisfied by the determination unit, the location information of the node device storing the content by the storage unit An instruction for prohibiting the content that is determined by the determination means to satisfy the predetermined condition from being acquired by another node device is transmitted to the node device that stores the information.

  According to the present invention, since the node device is prohibited from acquiring the content while storing the content, the content can be acquired again when necessary thereafter.

  The invention according to claim 6 acquires time information indicating a time at which content is acquired from one of node devices in a content distribution system capable of transmitting and receiving content between a plurality of node devices that can communicate with each other via a network. An acquisition step, a search step of searching for a node device storing predetermined content according to a time indicated by the time information acquired in the acquisition step, and the node device searched in the search step, A content acquisition step for acquiring predetermined content, a storage step for storing the content acquired in the content acquisition step, and the content stored in the storage step when the content is retrieved from another node device. To the other node device A content transmission step, a determination step for determining whether or not a predetermined condition has been satisfied since the content was transmitted in the content transmission step, and a determination in the determination step that the predetermined condition has been satisfied And a prohibiting step for prohibiting the content stored in the storing step from being acquired by another node device.

  The invention according to claim 7 acquires time information indicating a time at which content is acquired from one of node devices in a content distribution system capable of transmitting and receiving content between a plurality of node devices that can communicate with each other via a network. An acquisition step, a search step of searching for a node device storing predetermined content according to a time indicated by the time information acquired in the acquisition step, and the node device searched in the search step, A content acquisition step for acquiring predetermined content, a storage step for storing the content acquired in the content acquisition step, and the content stored in the storage step when the content is retrieved from another node device. To the other node device A content transmission step, a determination step for determining whether or not a predetermined condition is satisfied after the content was transmitted in the content transmission step, and when the determination step determines that the predetermined condition is satisfied The computer implements a prohibition step for prohibiting the content transmitted in the content transmission step from being acquired by another node device.

  The invention according to claim 8 acquires time information indicating a time at which content is acquired from one of the node devices in the content distribution system capable of transmitting and receiving content between a plurality of node devices that can communicate with each other via a network. From the acquisition means, the search means for searching for a node device storing predetermined content according to the time indicated by the time information acquired by the acquisition means, and the node device searched by the search means, A content acquisition unit that acquires predetermined content, a storage unit that stores the content acquired by the content acquisition unit, and the content stored in the storage unit when the content is retrieved from another node device. Content transmitting means for transmitting the content to the other node device, and the content transmitter Determining means for determining whether or not a predetermined condition has been satisfied since the content was transmitted by means of, and when the determining means determines that the predetermined condition has been satisfied, the content stored in the storage means Is provided with prohibiting means for prohibiting acquisition by other node devices.

  According to the present invention, when a predetermined condition is satisfied, the acquired content is prohibited from being acquired by another node device. Therefore, the time required for content distribution as a whole can be shortened without increasing the communication load on the upper node device.

It is a figure which shows an example of the connection aspect of each node apparatus in the content distribution storage system S which concerns on 1st Embodiment. It is a figure which shows an example of schematic structure in the content distribution storage system S which concerns on 1st Embodiment. It is a figure which shows the upload state of the center server SA which concerns on 1st Embodiment, and each node Nn, a download state, and a holding state, (a) is a figure in the case of the prohibition method 1, (b) It is a figure in the case of the prohibition method 2. FIG. It is a figure showing an example of outline composition of center server SA concerning a 1st embodiment. It is a figure which shows the example of a schematic structure of the node Nn which concerns on 1st Embodiment. It is a flowchart which shows the process example of the control part 21 in the node Nn which concerns on Example 1 of 1st Embodiment. It is a flowchart which shows the process example of the control part 21 in the node Nn which concerns on Example 2 of 1st Embodiment. It is a flowchart which shows the process example of the node Nn in the content distribution storage system S which concerns on 2nd Embodiment. It is a figure which shows an example of a mode that a content is delivered.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment described below is an embodiment when the present invention is applied to a content distributed storage system.

[1. First Embodiment]
[1.1 Configuration and operation overview of distributed content storage system]
First, with reference to FIG. 1 etc., the structure and the operation | movement outline | summary of the content distributed storage system which concern on 1st Embodiment of this invention are demonstrated.

  FIG. 1 is a diagram showing an example of a connection mode of each node device in the content distributed storage system S according to the present embodiment.

  As shown in the lower frame 101 of FIG. 1, the distributed storage system S is configured by connecting a plurality of node devices Nn via the Internet. Further, as shown in a lower frame 101 of FIG. 1, IX (Internet eXchange) 3, ISP (Internet Service Provider) 4a, 4b, DSL (Digital Subscriber Line) line provider devices 5a, 5b, FTTH (Fiber To A network 8 such as the Internet is constructed by the device 6 of the line provider, the communication line 7 and the like. The network 8 is a real-world communication network. Note that a router for transferring data packets is appropriately inserted in the network 8 in the example of FIG. 1, but is not shown in FIG. 1. For example, a telephone line or an optical cable is used as the communication line 7.

  A plurality of node devices Nn (n = 1, 2, 3,...) Are connected to such a network 8. Hereinafter, the node device is referred to as a “node”. Each node Nn is assigned a unique manufacturing number and an IP (Internet Protocol) address. Then, the content distributed storage system S according to the present embodiment is a peer-to-peer network system formed by connecting any of a plurality of nodes Nn, as shown in the upper frame 100 of FIG. It has become. Each node Nn is a base server distributed and arranged at a plurality of bases in this embodiment.

  The network 9 shown in the upper frame 100 of FIG. 1 is an overlay network 9 that configures a virtual link formed using the existing network 8. The overlay network 9 which is a logical network is realized by a specific algorithm, for example, an algorithm using DHT. Each node Nn connected to the content distributed storage system S is assigned a node ID, which is unique identification information having a predetermined number of digits.

  The node ID is, for example, a value obtained by hashing an IP address or manufacturing number individually assigned to each node Nn using a common hash function. The node IDs are arranged in a distributed manner in the ID space. For example, SHA-1 or the like is used as the hash function. The hashed value has a bit length of 160 bits, for example. The node IDs are distributed in the ID space without being distributed.

  In connection with the content distributed storage system S, a node Nn that is not connected, for example, the node N8 transmits a participation message indicating a request to participate in the content distributed storage system to any connected node Nn. Is done by doing. The participation in the content distributed storage system S means that the node device Nn is connected to the distributed storage system S and content data can be acquired from the distributed storage system S. The arbitrary node Nn is, for example, a contact node that is always connected to the system S.

  Each node Nn holds a routing table using DHT. This routing table defines the transfer destinations of various messages on the content distributed storage system S. Specifically, a plurality of pieces of node information including node IDs, IP addresses, and port numbers of nodes Nn that are moderately separated in the ID space are registered in this routing table. The node information is an example of location information in the present invention.

  One node connected to the content distributed storage system S stores the minimum necessary node information of the node Nn as a routing table. By transferring various messages between the nodes Nn, node information about the node Nn that does not store node information is acquired.

  Such a routing table using DHT is well known in Japanese Patent Application Laid-Open No. 2006-197400 and the like, and will not be described in detail.

  The content distributed storage system S stores various content data replicas having different contents in a predetermined file format in a distributed manner in a plurality of nodes Nn. Hereinafter, the content data is referred to as “content”. A replica can be used between the nodes Nn. The original of each content is stored in the center server SA. For example, a replica of the content of a movie with the title XXX is stored in the node N5. On the other hand, a replica of the movie content whose title is YYY is stored in the node N3. In this way, it is distributed and stored in a plurality of nodes Nn. Hereinafter, the node N in which the content replica is stored is referred to as a “content holding node”.

  Information such as a content name and content ID, which is unique identification information for each content, is added to each content replica described above. This content ID is generated, for example, by hashing the content name + an arbitrary numerical value with a hash function common to the case of obtaining the node ID. Alternatively, the system administrator may give a unique ID value for each content.

  The location of the content replicas that are distributed and stored is stored as index information by the node Nn or the like that manages (stores) the location of the content replicas. Hereinafter, the node Nn that manages (stores) the location of the replica is referred to as a “root node”. The index information includes a set of node information of the node Nn that stores the replica, a content ID of the content, and the like. Such a root node is determined to be a node Nn having a node ID closest to the content ID, for example. The node ID closest to the content ID is, for example, the node ID with the highest number of upper digits that match.

  For example, index information about a replica of a movie content whose title is XXX is managed by the node N4 which is the root node of the content. Further, for example, index information about a content replica of a movie whose title is YYY is managed by the node N7 which is the root node of the content. Further, such a root node is determined to be a node Nn having a node ID closest to the content ID, for example. The node ID closest to the content ID is, for example, a node ID that matches the content ID more frequently with the upper digits.

  When a user of a certain node Nn wants to obtain a replica of the desired content, the node Nn that desires to obtain this replica generates a message. Hereinafter, the node Nn that the user desires to acquire a replica is referred to as a “user node”. This message is a content location inquiry message including the content ID of the content desired to be acquired and the IP address of the user node. The content location inquiry message is also a message for searching for a content holding node. The above-described content location inquiry message is sent to another node Nn according to the DHT routing table acquired by the user node. That is, the user node sends a content location inquiry message toward the root node. As a result, the content location inquiry message finally arrives at the root node by DHT routing using the content ID as a key.

  In each node Nn, attribute information such as content name and content ID of the content is described in the content catalog information. This content catalog information is distributed, for example, from the center server SA to all the nodes Nn.

  The content ID included in the content location inquiry message may be generated by the user node by hashing the content name with the common hash function. The DHT routing is known in Japanese Patent Application Laid-Open No. 2006-197400 and the like, and thus detailed description thereof is omitted.

  The root node that has received the content location inquiry message obtains index information corresponding to the content ID included therein from the index information cache. The acquired index information is returned to the user node that is the transmission source of the content location inquiry message. The user node that has acquired the index information in this way can download (acquire) a replica of the content based on the index information. The user node accesses the content holding node based on the IP address of the content holding node included in the index information. A content replica can be downloaded from the accessed content holding node. Note that the index information may include, for example, node information of a plurality of content holding nodes. In this case, the user node selects one content holding node from among the plurality of content holding nodes. The user node can then connect to the selected content holding node and download a replica of the content.

  The root node transmits a content transmission request message to the content holding node indicated by the IP address or the like included in the index information, whereby the user node downloads the replica from the content holding node. You can also. In addition, the user node can obtain the index information from a cache node that caches the same index information as the root node until the content location inquiry message reaches the root node.

  When the user node acquires and stores a content replica from the content holding node, the stored user node generates a publish message. The publish message is a message for informing the root node that the replica has been saved. The publish message includes the content ID of the replica and the node information of the node device that stores the replica. The publish message is sent toward the root node. As a result, the publish message arrives at the root node by DHT routing using the content ID as a key, like the content location inquiry message. Then, the root node receives the publish message. The root node stores index information including a set of node information and content ID included in the publish message in the index information cache area. In this way, the user node becomes a new content holding node that holds a replica of the content.

[1.2 Content distribution to each node Nn]
[1.2.1 Overview of content distribution]
Next, content distribution to each node Nn will be described with reference to FIGS. In the following description, the replica stored in each node Nn is also referred to as content.

  FIG. 2 is a diagram showing an example of a schematic configuration in the content distributed storage system S according to the present embodiment.

  As shown in FIG. 2, in the content distributed storage system S, nodes Nn as base servers are distributed and installed at each base. The nodes Nn are connected to each other by an overlay network 9 using DHT as a grid technology. Each base is provided with a distribution server Pn (n = 1, 2, 3,...). Further, a plurality of user terminals Um (any of m = 1, 2, 3,...) Are installed at each base.

  At each base, for example, a network such as a LAN (Local Area Network) is constructed. The node Nn and the distribution server Pn at each base are connected so as to be able to communicate with each other by a network such as a LAN. In addition, the distribution server Pn and the plurality of user terminals Um at each site are connected to be communicable with each other.

  The content downloaded by the node Nn via the overlay network 9 is transferred to the distribution server Pn at the base where the node Nn is installed. The transferred content is stored by the distribution server Pn. The user at the base operates the user terminal Um when he wants to use desired content. By this operation, content is requested from the user terminal Um to the distribution server Pn at the site where the user terminal Um is installed. When the requested distribution server Pn stores the requested content, the distribution server Pn transmits the stored content to the user terminal Um. On the other hand, if the distribution server Pn does not store the requested content, the distribution server Pn requests the content from the node Nn at the site where the distribution server Pn is installed. The node Nn that has requested the content downloads the content from another node Nn that stores the content. Then, the node Nn transfers the downloaded content to the distribution server Pn.

  In some cases, specific content may be distributed and stored in advance to all nodes Nn or a plurality of specific nodes Nn. In this case, in the content distributed storage system S, a plurality of nodes Nn form a tree-like distribution route, and the content is sequentially transferred. The specific content to be distributed is further divided into a plurality of contents (for example, content 1, content 2, content 3...). Each content created by the division is assigned a content ID and stored in the center server SA. Each node Nn sequentially transfers content 1, content 2, content 3,... For example, when the node Nn downloads the content 1, the node Nn next uploads the content 1 to another node Nn while downloading the content 2. Next, the node Nn uploads the content 2 to another node Nn while downloading the content 3. As a result, the processing capability and communication line of the node Nn can be used efficiently, and the time required for content distribution as a whole is reduced.

  Each node Nn is assigned an order in which content is requested in content distribution. Hereinafter, the order of requesting content is referred to as “content request order”. The content request order is synonymous with the content acquisition order. As the allocation method of the content request order, for example, as in the example shown in FIG. 9, No. 1 for the node N1, No. 2 for the nodes N2 and N3, No. 3 for the nodes N4 to N7,. Is assigned. In this case, the node N1 downloads content from the center server SA. Nodes N2 and N3 download contents from node N1, respectively. The nodes N4 to N7 download contents from the node N2 or N3, respectively. In this case, one node Nn uploads content to two nodes Nn. The number of contents downloaded by one node Nn is referred to as “number of uploads”. The number of uploads is not limited to two.

  The node Nn whose content request order is Xth (X = 1, 2, 3...) Starts acquiring the content, and the node Nn whose content request order is X + 1 acquires content after a predetermined time delay. To start. Hereinafter, this predetermined time is referred to as “delay time”. For example, the delay time is set to be longer than the time required for the node Nn to download one content. The time at which content acquisition is started is the time at which the first content, that is, content 1 is requested from among the divided content. The time at which the node Nn having the first content request order starts acquiring content is the content distribution start time. Each node Nn requests content Y + 1 when a delay time elapses after requesting content Y (Y = 1, 2, 3,...).

[1.2.2 Specific examples of content distribution and prohibition of content upload]
Based on the above, the manner in which content is distributed will be specifically described. First, at time T0, which is the content distribution start time, for example, the node N1 whose content request order is No. 1 transmits a content location inquiry message. By transmitting the content location inquiry message, the node N1 searches for the location of the content 1. However, at this time, the node Nn storing the content 1 does not exist. Therefore, in this case, the node N1 downloads the content from the center server SA that stores the content 1 in advance. The node N1 that has downloaded the content 1 stores the content 1 and transmits a publish message. Thereby, the node information of the node N1 is registered in the index information held by the root node of the content 1.

  At time T1 when a set delay time has elapsed from time T0, the node Nn downloads the content 2 from the center server SA in the same manner as described above. Further, for example, the nodes N2 and N3 having the second content request order search for the location of the content 1, respectively. Then, since it becomes clear that the node N1 is a content holding node, the nodes N2 and N3 download the content 1 from the node N1, respectively.

  At time T2 when the delay time has elapsed from time T1, the node N1 downloads the content 3 from the center server SA. Also, the nodes N2 and N3 download the content 2 from the node N1, respectively.

  Further, at time T2, for example, the nodes N4 to N7 whose content request order is No. 3 search for the location of the content 1, respectively. At this time, the content holding nodes corresponding to the content 1 are originally nodes N1 to N3. Then, the nodes N4 to N7 download the content 1 from any one of the nodes N1 to N3. However, at time T2, the node N1 uploads the content 2. Therefore, when the node N1 uploads the content 1 in addition to the content 2, the processing load and the network load on the node N1 increase, and content distribution delay occurs.

  Therefore, the node N1 prohibits the content N1 from being downloaded by another node Nn, that is, the node N1 from uploading the content 1 when a predetermined condition is satisfied. Details of the conditions for prohibiting the download of contents and the prohibition method will be described later. By prohibiting the upload of the content 1 from the node N1, the nodes N4 to N7 download the content 1 from the node N2 or N3, respectively.

  At time T3 when the delay time has elapsed from time T2, the node N1 downloads the content 4 from the center server SA. Further, the nodes N2 and N3 download the content 3 from the node N1, respectively. Further, the nodes N4 to N7 download the content 2 from the node N2 or N3, respectively. Also in this case, uploading of the content 2 from the node N1 is prohibited. Further, for example, the nodes N8 to N15 whose content request order is No. 4 search the location of the content 1 respectively. At this time, the content holding nodes corresponding to the content 1 are originally nodes N1 to N7. Upload of content 1 from node N1 is already prohibited. Here, uploading of content 1 from nodes N2 and N3 is also prohibited. Accordingly, the nodes N8 to N15 download the content 1 from any one of the nodes N4 to N7.

  Content 5 and subsequent content are transferred in the same manner as described above, and when all the content is transferred to each node Nn, the content distribution is completed.

[1.2.3 Conditions for prohibiting content upload]
The condition for prohibiting the uploading of content is that the node Nn whose content request order is Xth and the content request order can be uploaded to the node Nn whose content request order is X + 1, but the content request order is X + 2nd node Nn is defined so that content cannot be uploaded.

For example, conditions for prohibiting upload include the following conditions. Hereinafter, the condition for prohibiting uploading of content is referred to as “upload prohibition condition”. The upload prohibition conditions are not limited to the following three conditions.
Condition 1: Limit the number of times that upload is possible Condition 2: Limit the time that can be uploaded Condition 3: Instruction from the outside

In the upload prohibition condition 1, the number of times each node Nn can upload to each other node Nn for each content (content 1, content 2, content 3...) Is limited. Hereinafter, the number of times uploading is possible is referred to as “uploadable number”. here,
Number of possible uploads at Xth = X + 1 number of nodes Nn / number of Xth nodes Nn. In other words, the number of uploadable times is the same as the number of uploads. When all the nodes Nn whose content request order is X upload the content Y by the number of uploads, the contents Y are distributed to all the nodes Nn whose content request order is X + 1. After the content Y reaches all the nodes Nn whose content request order is X + 1, the content Y cannot be downloaded from all the nodes Nn whose content request order is Xth.

  Note that the number of times that upload is possible may be actually calculated using the above formula at the node Nn, for example. In addition, the uploadable number of times may be actually calculated using the above formula in the server SA, and distributed to each node Nn by being included in a setting file to be described later. In addition to the actual upload count, for example, a setting value set in advance as the upload count may be distributed from the server SA to each node Nn.

  In the upload prohibition condition 2, for example, content upload is permitted until a predetermined time elapses after the content is released, and content upload is prohibited after the predetermined time elapses. Hereinafter, the time during which content upload is permitted is referred to as “publication time”. Here, publishing the content means that the node Nn that has downloaded the content transmits a publish message so that it can be searched from another node Nn as a content holding node that holds the downloaded content. To make it possible.

  The release time is determined as follows, for example. First, the publication time is the time required for the X + 1th node Nn to start downloading the content after the Xth node Nn in the content request order transmits the publish message, that is, the transmission from the X + 1th node Nn. More than the time required for receiving the received content transmission request message. Furthermore, the publication time is set to be less than the time required for receiving the content transmission request message transmitted from the (X + 2) th node Nn after the Xth node Nn in the content request order transmits the publish message. Thereby, the node Nn whose content request order is X + 1 can download the content Y from the Xth node Nn, but the node Nn whose content request order is X + 2 is to download the content Y from the Xth node Nn. It cannot be downloaded.

  It should be noted that the start point of the disclosure time may be, for example, any time when the content is downloaded, when the downloaded content is stored, or when a publish message is transmitted. Also, the counting of the publication time may be started, for example, from the time when the published content is first uploaded to the user node.

  In the upload prohibition condition 3, for example, the center server SA transmits a disclosure stop instruction message to each node Nn. The disclosure stop instruction message includes, for example, a content ID of content prohibited from uploading. For example, the center server SA instructs the X-th node Nn to prohibit uploading of the content Y immediately before the time when the content Y is acquired by the X + second node Nn in the content request order. Send a message. The node Nn that has received the publication stop instruction message prohibits uploading of the content corresponding to the content ID included in the publication stop instruction message.

[1.2.4 Prohibiting content upload]
Examples of a method for prohibiting content upload include the following methods. Note that the method of prohibiting uploading is not limited to the following three methods.
Prohibition method 1: Make content private Prohibition method 2: Delete content Prohibition method 3: Introduce another node Nn when content is requested

  In the prohibition method 1, the content holding node holds the downloaded content, but prevents it from being searched by other nodes Nn as the content holding node of the content. This is called non-disclosure of content. For example, the content holding node transmits a content deletion message when a condition for prohibiting content upload is satisfied. The content deletion message includes the content ID of the content to be made private and the node information of the content holding node that stores the content to be made private. The content deletion message arrives at the root node by DHT routing using the content ID included in the content deletion message as a key. The root node that has received the content deletion message deletes the node information of the content holding node indicated by the node ID included in the content deletion message from the index information corresponding to the content ID included in the content deletion message. As a result, the content is not disclosed to the content holding node that has transmitted the content deletion message.

  FIG. 3A is a diagram illustrating the content upload state, download state, and holding state of the center server SA and each node Nn in the prohibition method 1. Specifically, in FIG. 3A, at each time from the time T0 to the time T4, which is the content distribution start time, the center server SA and the first, second, and third nodes Nn in the content request order. The state of is shown. In each column, the content to be uploaded, the content to be downloaded, and the held content are shown. In addition, the held contents are shown separately for published contents and unpublished contents.

  As shown in FIG. 3A, the center server SA holds contents 1-5. At time T0, the node N1 with the first content request order downloads the content 1 from the center server SA.

  At time T1, the node N1 holds the downloaded content 1. Further, the node N1 downloads the content 2 from the center server SA. The nodes N2 and N3 having the second content request order download the content 1 from the node N1.

  At time T2, the node N1 holds the contents 1 and 2. However, the content 1 is not disclosed before the time T2 elapses. Further, the node N1 downloads the content 3 from the center server SA. Nodes N2 and N3 download content 2 from node N1. Also, the nodes N4 to N7 download from the node N2 or N3 that publishes the content 1 among the nodes that hold the content 1.

  At time T3, content 2 is newly undisclosed at node N1, and content 1 is undisclosed at nodes N2 and N3. Then, the node N1 downloads the content 4 from the center server SA. Further, the nodes N2 and N3 download the content 3 from the node N1. Further, the nodes N4 to N7 download the content 2 from the node N2 or N3.

  At time T4, content 3 is newly undisclosed at node N1, content 2 is newly undisclosed at nodes N2 and N3, and content 1 is undisclosed at nodes N4 to N7. Then, the node N1 downloads the content 5 from the center server SA. In addition, the nodes N2 and N3 download the content 4 from the node N1. The nodes N4 to N7 download the content 1 from the node N2 or N3.

  In the prohibition method 2, when the content holding node satisfies a condition for prohibiting uploading of content, the content holding node deletes the corresponding content from the cache of the content holding node itself. In this case, the content holding node may or may not transmit a content deletion message.

  If the distribution server Pn does not exist and the node Nn deletes the downloaded content, the user terminal Um cannot download the content from the node Nn. Therefore, in this embodiment, in addition to the node Nn as a base server, a distribution server Pn is also installed at each base. Then, when the node Nn downloads the content, the node Nn transfers the content to the distribution server Pn. The user terminal Um can download the content from the distribution server Pn even if the content is deleted from the node Nn. In the prohibition methods 1 and 3, the distribution server Pn may not be installed. This is because the node Nn itself can distribute the content to the user terminal Um.

  FIG. 3B is a diagram illustrating the content upload state, download state, and holding state of the center server SA and each node Nn in the prohibition method 2. As shown in FIG. 3B, the timing at which content uploading is prohibited in each node Nn is the same as in FIG. In the node N1, the content 1 is deleted at the time T2, the content 2 is deleted at the time T3, and the content 3 is deleted at the time T4. In nodes N2 and N3, content 1 is deleted at time T3 and content 2 is deleted at time T4. In the nodes N4 to N7, the content 1 is deleted at the time T4.

  In the prohibition method 3, when a content transmission request message is transmitted from a user node to a content holding node that satisfies a condition for prohibiting uploading of content, another content holding node is introduced to the user node. For example, a content holding node that satisfies a condition for prohibiting uploading of content transmits a content transmission impossible message to the user node. The content transmission impossible message is a message indicating that content cannot be transmitted. The user node that has received the content transmission impossible message transmits the content location inquiry message again and acquires index information from the root node. Then, the user node selects another content holding node from the acquired index information and transmits the content transmission request message again. Alternatively, when the user node has acquired index information including node information of a plurality of content holding nodes from the root node, the user node selects another content holding node based on the acquired index information. You may do it.

[1.2.5 Conditions for re-enabling content upload]
After the content upload is prohibited, the content upload may be permitted again. For example, after content distribution to each node Nn is completed, a new node Nn may participate in the content distributed storage system S due to an increase in the number of locations. Further, there may be a node Nn in which content cannot be acquired at the time of content distribution because the power is turned off. In this case, it may be necessary for the node Nn to acquire content that has been distributed. In preparation for such a situation, uploading of content is permitted again.

Examples of the condition for permitting content upload again include the following conditions. Hereinafter, a condition for permitting content upload again is referred to as an “upload re-permission condition”. The upload re-permission condition is not limited to the following three conditions.
Condition 1: After a certain period of time
Condition 2: Not permitted Condition 3: Instruction from outside

  In the upload re-permission condition 1, for example, after a predetermined time elapses after the content upload is prohibited, the content upload is permitted again. Hereinafter, the time required for content uploading to be permitted again after being prohibited is referred to as “private time”.

  In the upload re-permission condition 2, content uploading is not permitted again in principle.

  In the upload re-permission condition 3, for example, the center server SA transmits a public resumption instruction message to each node Nn. The public resumption instruction message includes, for example, the content ID of the content for which uploading is permitted again. For example, the center server SA may transmit a public resumption instruction message to all the nodes Nn at a predetermined time. The node Nn that has received the public resumption instruction message again permits uploading of the content corresponding to the content ID included in the public resumption instruction message.

  The method of permitting content upload again depends on the method of prohibiting content upload. For example, in the case of the prohibition method 1, the content holding node transmits a publish message for the content whose upload is permitted again. That is, the content holding node republishes the content. In the case of the prohibition method 3, the content holding node ends the prohibition of content uploading by the method 3. That is, the content holding node may upload the requested content as it is to the user node.

  Which condition and method to use for the upload prohibition condition, prohibition method, and upload re-permission condition described above are determined in advance in the content distributed storage system S, for example.

[1.3 Configuration and functions of center server SA]
Next, the configuration and functions of the center server SA will be described with reference to FIG.

  FIG. 4 is a diagram illustrating a schematic configuration example of the center server SA.

  As shown in FIG. 4, the center server SA includes a control unit 11 as a computer including a CPU having a calculation function, a working RAM, a ROM that stores various data and programs, and the like. Further, the center server SA includes a storage unit 12 composed of an HD or the like for storing and storing various data and various programs. Furthermore, the center server SA includes a communication unit 13 for controlling communication of information with the node Nn through the network 8 or the like. Furthermore, the center server SA includes a display unit 14 such as a CRT or a liquid crystal display that displays various types of information. Furthermore, the center server SA includes an input unit (for example, a keyboard, a mouse, etc.) 15 that receives an instruction from the operator and gives an instruction signal corresponding to the instruction to the control unit 11. The control unit 11, the storage unit 12, the communication unit 13, the display unit 14, and the input unit 15 are connected to each other via a bus 16.

  The storage unit 12 stores the node ID, IP address, port number, and the like of each node Nn. The storage unit 12 stores content to be distributed.

  Furthermore, the storage unit 12 stores a setting file used for content distribution. The setting file is an example of time information in the present invention. In the setting file, for example, content distribution start time, delay time, node ID of each node Nn to which the content is distributed, and content request order of each node Nn are described. Alternatively, instead of the content distribution start time and the delay time, the time for requesting each content may be described for each content request order. In the setting file, for example, the content IDs of a plurality of contents to be distributed and the distribution order of the contents are described.

  Further, when the upload prohibition condition is the upload prohibition condition 1 described above, that is, when the number of uploadable times is limited, the number of uploadable times is described in the setting file. When the upload prohibition condition is the upload prohibition condition 2, that is, when the uploadable time is limited, the disclosure time is described in the setting file. In addition, when the upload re-permission condition is the above-described upload re-permission condition 1, that is, after a predetermined time has elapsed, the non-disclosure time is described in the setting file. Further, when the upload re-permission condition is the above-described upload re-permission condition 3, that is, an instruction from the outside, the setting file describes the time at which the center server SA transmits the disclosure resumption instruction message. .

  The setting file having such contents may be created by an operator, for example, or may be automatically created by the center server SA.

  The control unit 11 performs overall control of the entire center server SA when the CPU reads and executes a program stored in the storage unit 12 or the like.

  For example, the control unit 11 distributes the setting file stored in the storage unit 12 to each node Nn. The distribution of the setting file may be performed for all nodes Nn participating in the content distributed storage system S by, for example, DHT multicast (multicast message transfer processing) disclosed in Japanese Patent Application Laid-Open No. 2007-053662. good.

  Further, when receiving the content transmission request message from the node Nn, the control unit 11 transmits the content corresponding to the content transmission request message to the requesting node Nn.

  The above program may be downloaded from a predetermined server on the network 8, for example. The program may be recorded on a recording medium such as a CD-ROM and read via a drive of the recording medium.

[1.4 Node Nn configuration and functions]
Next, the configuration and function of the node Nn will be described with reference to FIG.

  FIG. 5 is a diagram illustrating a schematic configuration example of the node Nn.

  As shown in FIG. 5, each node Nn includes a control unit 21 as a computer including a CPU having a calculation function, a working RAM, a ROM that stores various data and programs, and the like. Each node Nn includes a storage unit 22 composed of an HD (hard disk) or the like for storing and storing various data and various programs, and a buffer memory 23 for temporarily storing a replica of the received content. ing. The storage unit 22 is an example of a storage unit in the present invention. Further, each node Nn includes a decoder unit 24 that decodes encoded video data (video information), audio data (audio information), and the like included in the content replica. Further, each node Nn performs a predetermined drawing process on the decoded video data and the like, and outputs it as a video signal, and displays a video based on the video signal output from the video processor 25. And a display unit 26 such as a CRT or a liquid crystal display. Further, each node Nn converts the decoded audio data into an analog audio signal by D (Digital) / A (Analog) conversion, and then amplifies this by an amplifier and outputs the audio processing unit 27, and this audio processing unit And a speaker 28 that outputs the audio signal output from the sound wave 27 as a sound wave. Furthermore, each node Nn includes a communication unit 29 for controlling communication of information between other nodes Nn and the like through the network 8. Furthermore, each node Nn includes an input unit (for example, a keyboard, a mouse, a remote controller, an operation panel, or the like) 30 that receives an instruction from the user and gives an instruction signal corresponding to the instruction to the control unit 21. Yes. The control unit 21, the storage unit 22, the buffer memory 23, the decoder unit 24, the communication unit 29, and the input unit 30 are connected to each other via a bus 31. As the node Nn, a personal computer, an STB (Set Top Box), or the like can be applied in addition to a dedicated server device.

  The storage unit 22 includes a routing table using DHT, an index, an IP address and a port number of a contact node that is an access destination when participating in the content distributed storage system S, and an IP address and a port number of the center server SA. Etc. are stored. The storage unit 22 stores file information distributed from the center server SA. Further, the downloaded content is stored in the storage unit 22.

  The control unit 21 reads and executes a program (including the node program of the present invention) stored in the storage unit 22 or the like by the CPU, whereby an acquisition unit, a search unit, a content acquisition unit, a content transmission unit, It functions as a determination unit, a prohibition unit, a time determination unit, and a release unit.

  The node program may be downloaded from a predetermined server on the network 8, for example, or recorded on a recording medium such as a CD-ROM and read via a drive of the recording medium. You may do it.

[1.5 Operation of Content Distributed Storage System S]
Next, with reference to FIGS. 6 and 7, the operation of the distributed content storage system S according to the present embodiment will be described for each example.

  In the first embodiment, the condition 1 is applied as the upload prohibition condition, the method 1 is used as the prohibition method, and the condition 1 is applied as the upload re-permission condition.

  FIG. 6 is a flowchart illustrating a processing example of the control unit 21 in the node Nn according to the first example of the present embodiment.

  The process illustrated in FIG. 6 is started, for example, when the node Nn is powered on. First, the control unit 21 determines whether or not the power supply of the node Nn is turned off (step S1). At this time, when the power of the node Nn is not turned off (step S1: NO), the control unit 21 determines whether a setting file has been received from the center server SA as an acquisition unit (step S2). . At this time, when the setting file is received (step S2: YES), the control unit 21 overwrites and stores the received setting file in the storage unit 22 (step S3).

  When the setting file is not received in step S2 or when the process of step S3 is finished, the control unit 21 determines whether or not content is requested from another node Nn (step S4). That is, the control unit 21 determines whether or not a content transmission request message has been received.

  At this time, when the content is requested (step S4: YES), the control unit 21 uploads the content corresponding to the content ID included in the content transmission request message to the requesting user node as the content transmission means. (Step S5). Next, the control unit 21 increases the upload count of the uploaded content by 1 (step S6). Next, the control unit 21 determines, as determination means, whether the upload prohibition condition is satisfied based on the setting file (step S7). Specifically, the control unit 21 determines whether or not the number of uploads has reached the number of uploadable times described in the setting file. At this time, when the number of uploads does not reach the number of uploadable times (step S7: NO), the control unit 21 proceeds to step S1.

  On the other hand, when the number of uploads reaches the number of uploadable times (step S7: YES), the control unit 21 prohibits uploading of the corresponding content as a prohibiting unit (step S8). Specifically, the control unit 21 transmits a content deletion message toward the root node. At this time, the control unit 21 sets the content ID of the content whose upload count reaches the uploadable count in this content deletion message. Next, the control unit 21 stores the content deletion message transmission time in the storage unit 22 (step S9). At this time, the control unit 21 stores the content deletion message transmission time in association with the content ID of the content whose number of uploads has reached the number of uploadable times. The current time at that time is applied to the content deletion message transmission time. After completing the process of step S9, the control unit 21 proceeds to step S1.

  In step S4, when the content is not requested from another node Nn (step S4: NO), the control unit 21 determines whether or not the content that has been made secret is present (step S10). Whether or not there is a non-public content can be determined, for example, based on whether or not the content deletion message transmission time is stored in the storage unit 22. Then, when there is a content that has been made private (step S10: YES), the control unit 21 serves as a time determination unit, and the private time described in the setting file has elapsed since it was made private. It is determined whether or not (step S11). For example, the control unit 21 determines whether or not the non-disclosure time has elapsed with the content deletion message transmission time stored in the storage unit 22 as the content non-disclosure start time. When the non-disclosure time has elapsed since the content was made private (step S11: YES), the control unit 21 cancels the prohibition of content uploading as a release unit (step S12). Specifically, the control unit 21 transmits a publish message toward the root node. At this time, the control unit 21 sets the content ID of the content whose non-disclosure time has elapsed in the publish message. In addition, the control unit 21 deletes the content deletion message transmission time corresponding to the content ID of the content whose non-disclosure time has elapsed from the storage unit 22. When the non-disclosure time has not elapsed since the content was made private in step S11, or when the process of step S12 is completed, the control unit 21 proceeds to step S1.

In step S10, when there is no non-disclosure content (step S10: NO), the control unit 21 determines whether the time for requesting the content has arrived based on the description content of the setting file. (Step S13). For example, when the time at which content is requested is described in the setting file, it may be determined whether or not the described time has arrived. Alternatively, when the content distribution start time and the delay time are described in the setting file, the time T (X, Y) at which the node Nn whose content request order is X requests the content Y is obtained by the following equation. Can do.
T (X, Y) = content distribution start time + (X−1) × delay time + (Y−1) × delay time

  If it is determined in step S13 that the time for requesting content has arrived (step S13: YES), the control unit 21 transmits a content location inquiry message to the root node as a search unit (step S14). In this content location inquiry message, the content ID of the content whose requested time has arrived is set based on the setting file. Thereafter, the control unit 21 acquires index information transmitted from the root node. As a result, the content holding node is searched. And the control part 21 transmits a content transmission request message to a content holding node based on the node information contained in index information as a content acquisition means. After finishing the process of step S14, the control part 21 transfers to step S1.

  In step S13, when the time for requesting the content has not arrived (step S13: NO), the control unit 21 determines whether the content is received from the content holding node as the content acquisition unit (step S15). ). At this time, when the content is received (step S15: YES), the control unit 21 stores the received content in the storage unit 22 (step S16). Next, the control unit 21 transmits a publish message toward the root node (step S17). At this time, the control unit 21 sets the content ID of the stored content in the publish message. After completing the process of step S17, the control unit 21 proceeds to step S1.

  In step S1, when the power of the node Nn is turned off (step S1: YES), the control unit 21 ends the process shown in FIG.

  In the second embodiment, the condition 2 is applied as the upload prohibition condition, the method 2 is used as the prohibition method, and the condition 2 is applied as the upload re-permission condition.

  FIG. 7 is a flowchart illustrating a processing example of the control unit 21 in the node Nn according to the second example of the present embodiment. In FIG. 7, elements similar to those in FIG.

  The processing in steps S1 to S5 is the same as the processing in the first embodiment. When the content is uploaded in step S5, the control unit 21 proceeds to step S1.

  In step S4, when no content is requested from another node Nn (step S4: NO), the control unit 21 determines whether there is a published content (step S51). Whether there is a published content can be determined, for example, based on whether the publish message transmission time is stored in the storage unit 22. When there is a published content (step S51: YES), the control unit 21 determines whether the publication time described in the setting file has elapsed since the content was published as a determination unit. Is determined (step S52). For example, the control unit 21 determines whether or not the publishing time has elapsed with the publish message transmission time stored in the storage unit 22 as the content publishing start time. Then, when the publication time has elapsed since the content was published (step S52: YES), the control unit 21 transmits a content deletion message toward the root node (step S53). At this time, the control unit 21 sets the content ID of the content whose publication time has elapsed in the content deletion message. Next, the control unit 21 deletes the content whose publication time has elapsed as a prohibition unit from the storage unit 22 (step S54). In addition, the control unit 21 deletes the publish message transmission time corresponding to the content ID of the content whose publication time has elapsed from the storage unit 22. In step S52, the control unit 21 proceeds to step S1 when the publication time has not elapsed since the content was published or when the process of step S54 is completed.

  In step S51, when there is no published content (step S51: NO), the control unit 21 performs the determination in step S13. The processes in steps S13 to S17 are the same as those in the first embodiment. When transmitting the publish message in step S17, the control unit 21 stores the publish message transmission time in the storage unit 22 (step S55). At this time, the control unit 21 stores the publish message transmission time in association with the content ID of the content stored in step S16. The current time at that time is applied as the publish message transmission time. When the control section 21 finishes the process of step S55, the control section 21 proceeds to step S1.

  In the third embodiment, the condition 3 is applied as the upload prohibition condition, the method 1 is applied as the prohibition method, and the condition 3 is applied as the upload re-permission condition.

  The control unit 21 of the node Nn determines whether or not the time for requesting the content has arrived based on the setting file stored in the storage unit 22. Then, when the time for requesting content has arrived, the control unit 21 transmits a content location inquiry message. Thus, the control unit 21 receives the content transmitted from the content holding node and stores it in the storage unit 22.

  Thereafter, when receiving a disclosure stop instruction message from the center server SA for the stored content, the control unit 21 transmits a content deletion message toward the root node. At this time, the control unit 21 sets the content ID included in the disclosure stop instruction message in the content deletion message. Note that the control unit 21 does not delete the corresponding content from the storage unit 22.

  After that, when receiving a disclosure resumption instruction message from the center server SA for the content for which the content deletion message has been transmitted, the control unit 21 transmits a publish message to the root node. At this time, the control unit 21 sets the content ID included in the public resumption instruction message in the publish message.

  As described above, according to the present embodiment, the control unit 21 of the node Nn receives the setting file transmitted from the center server SA. In addition, when the time when the control unit 21 requests the content described in the received setting file or the time when the content requested based on the information described in the setting file has arrived, the setting file The content holding node of the content corresponding to the content ID described in is searched. In addition, the control unit 21 downloads content from the searched content holding node. In addition, the control unit 21 stores the downloaded content in the storage unit 22. Further, the control unit 21 determines whether or not the upload prohibition condition is satisfied after the content is stored in the storage unit 22 and released. Further, when it is determined that the upload prohibition condition is satisfied, the control unit 21 prohibits uploading of the content stored in the storage unit 22 to another node Nn.

  Therefore, when the upload prohibition condition is satisfied, the downloaded content is prohibited from being downloaded by another node Nn. Therefore, the time required for content distribution as a whole can be shortened without increasing the communication load on the node Nn whose content request order is relatively fast when viewed from the entire node Nn to which the content is distributed.

  Further, when the control unit 21 determines that the number of uploads has reached the number of uploadable times described in the setting file as the upload prohibition condition, the uploading of the content stored in the storage unit 22 is prohibited.

  Further, when the control unit 21 determines that the publication time described in the setting file has elapsed since the content was published as the upload prohibition condition, the uploading of the content stored in the storage unit 22 is prohibited. .

  Therefore, since the content is not uploaded after the publishing time has elapsed, it is possible to reliably prevent an increase in the communication load on the node device having the relatively fast content request order.

  Further, when the control unit 21 determines that the disclosure stop instruction message transmitted from the center server SA is received as the upload prohibition condition, the upload of the content stored in the storage unit 22 is prohibited.

  Therefore, it is not necessary for the node Nn itself to manage a schedule for prohibiting content upload.

  When the control unit 21 prohibits uploading the content stored in the storage unit 22 to another node Nn, and determines that the non-disclosure time described in the setting file has elapsed. The prohibition of uploading of the content stored in the storage unit 22 is lifted.

  Therefore, the node Nn that has not downloaded the content at the time of content distribution can download the content later.

  When the control unit 21 stores the content in the storage unit 22, the control unit 21 transmits a publish message including the node information of the node Nn of the control unit 21 itself to the root node. The control unit 21 transmits a content inquiry message to the root node and receives index information from the root node to search for a content holding node. Further, the control unit 21 transmits a content transmission request message to the searched content holding node based on the node information included in the received index information. When the control unit 21 determines that the upload prohibition condition is satisfied, the control unit 21 transmits a content deletion message including the node information of the node Nn of the control unit 21 itself to the root node.

  Accordingly, since the node Nn stores the content and uploading of the content is prohibited, the content can be uploaded again when necessary thereafter.

[2. Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG. In the first embodiment described above, the content holding node performs control to prohibit uploading of content. On the other hand, in the second embodiment described below, the root node controls to prohibit uploading of content. In the present embodiment, for example, Condition 1 is applied as the upload prohibition condition.

  The configuration and operation outline of the content distributed storage system S, the content distribution method, the configuration of the center server SA, and the configuration of the node Nn are the same as those in the first embodiment. Therefore, these descriptions are omitted.

  The root node storage unit 22 stores index information as described above. In this embodiment, the index information stored in the root node includes the content ID of the content managed by the root node, the node information of the content holding node that stores the content, and the content holding node that stores the content. A pair with the number of uploads uploaded is included. When the root node receives a publish message from the content holding node, the root node registers the node information of the content holding node in the index information stored in the storage unit 22. At this time, the root node sets 0 as the upload count in association with the node information of the content holding node.

  FIG. 8 is a flowchart showing a processing example of the node Nn in the content distributed storage system S according to the present embodiment.

  The process illustrated in FIG. 8 is started when the user node determines that the time for requesting content has arrived based on the description content of the setting file. First, the user node transmits a content location inquiry message to the root node (step S101).

  When receiving the content location inquiry message (step S102), the root node transmits a content holding node to the user node (step S103). At this time, the root node selects, for example, one content holding node from among the content holding nodes whose number of uploads of content requested by the user node is less than the number of uploadable times. Then, the root node transmits index information including the node information of the selected content holding node to the user node. That is, in this case, the root node as the determination unit determines whether the number of uploads has reached the number of uploadable times for each content holding node based on the index information. Then, the root node as the prohibition unit controls the content holding node whose number of uploads has reached the number of uploadable times so that it is not searched by the user node. By this control, the content holding node that satisfies the upload prohibition condition for the specific content is prohibited from uploading the specific content.

  Further, the root node increases the number of uploads of the content holding node that transmitted the node information to the user node by one. That is, the number of times notified to the user node as the content holding node is regarded as the number of uploads.

  The user node that has received the index information transmits a content transmission request message to the content holding node based on the node information included in the received index information (step S104). Then, the user node receives the content transmitted from the content holding node (step S105).

  As described above, a content holding node whose number of uploads reaches the number of uploadable times for the content requested from the user node is not searched for by the user node. Therefore, the content holding node that satisfies the upload prohibition condition for the requested content is prohibited from uploading the requested content. Therefore, it is possible to shorten the time required for content distribution as a whole without increasing the communication load on the node Nn whose content request order is relatively fast when viewed as a whole.

  In each of the above embodiments, each node Nn determines whether or not the content request time has arrived based on the setting file. However, the present invention is not limited to this. For example, each node Nn may request a content when receiving a message indicating an instruction to request the content from the center server SA.

  In each of the above embodiments, the root node manages the location of the content. However, the present invention is not limited to this. For example, a predetermined server device other than the node Nn may manage the location of the content. In this case, each node Nn searches for a content holding node by making a request to a predetermined server device.

  In each of the above embodiments, the content distribution system is applied to a content distributed storage system using DHT. However, the present invention is not limited to this. For example, the content distribution system may be applied to other peer-to-peer systems.

3 IX
4a, 4b ISP
5a, 5b DSL line dealer apparatus 6 FTTH line dealer apparatus 7 communication line 8 network 9 overlay network 11 control section 12 storage section 13 communication section 14 display section 15 input section 16 bus 21 control section 22 storage section 23 buffer memory 24 decoder Unit 25 Video processing unit 26 Display unit 27 Audio processing unit 28 Speaker 29 Communication unit 30 Input unit 31 Bus Nn node (base server)
Pn distribution server SA center server Um User terminal S Content distributed storage system

Claims (8)

An acquisition means for acquiring time information indicating a time for acquiring content from any of the node devices in the content distribution system capable of transmitting and receiving content between a plurality of node devices that can communicate with each other via a network;
Search means for searching for a node device storing predetermined content according to the time indicated by the time information acquired by the acquisition means;
Content acquisition means for acquiring the predetermined content from the node device searched by the search means;
Storage means for storing the content acquired by the content acquisition means;
Content transmitting means for transmitting the content to the other node device when the content stored in the storage means is retrieved from the other node device;
Determination means for determining whether or not a predetermined condition is satisfied after the content is transmitted by the content transmission means;
A prohibiting unit that prohibits the content stored in the storage unit from being acquired by another node device when the determination unit determines that the predetermined condition is satisfied;
A node device comprising: The determination means determines whether the number of transmissions of the content has reached a predetermined number as the predetermined condition,
The prohibiting means determines that the content stored in the storage means is acquired by another node device when the determining means determines that the number of transmissions of the content has reached a predetermined number. The node device according to claim 1, wherein the node device is prohibited. The determination means determines, as the predetermined condition, whether or not a predetermined time has passed since the content was transmitted by the content transmission means,
The prohibition unit prohibits the content stored in the storage unit from being acquired by another node device when the determination unit determines that a predetermined time has elapsed since the content was transmitted. The node device according to claim 1, wherein: Time determination means for determining whether a predetermined time has elapsed since the prohibition means has prohibited the acquisition by the other node device; and
Release means for canceling the prohibition of acquisition by the other node device when it is determined by the time determination means that a predetermined time has passed since the acquisition was prohibited;
The node device according to any one of claims 1 to 3, further comprising: A publish message indicating that the content is stored in the storage means is transmitted to the node device storing the location information indicating the location of the node device storing the content by the storage means, including the location information. Message sending means;
Requesting means for requesting transmission of content to the searched node device based on the location information of the node device searched by the searching means;
The search means searches for a node device storing the predetermined content from a node device storing the location information of the node device storing the predetermined content,
The content transmission means transmits the content requested from the other node device to the other node device,
When the determination unit determines that the predetermined condition is satisfied by the determination unit, the prohibition unit transfers the location information of the node device storing the content by the storage unit to the determination unit. 5. The command according to claim 1, further comprising: transmitting a command that prohibits the content determined to satisfy the predetermined condition from being acquired by another node device. 6. Node equipment. An acquisition step of acquiring time information indicating a time to acquire content from any of the node devices in the content distribution system capable of transmitting and receiving content between a plurality of node devices that can communicate with each other via a network;
A search step of searching for a node device storing predetermined content according to the time indicated by the time information acquired in the acquisition step;
A content acquisition step of acquiring the predetermined content from the node device searched in the search step;
A storage step of storing the content acquired in the content acquisition step;
A content transmission step of transmitting the content to the other node device when the content stored in the storage step is retrieved from the other node device;
A determination step of determining whether or not a predetermined condition has been satisfied since the content was transmitted in the content transmission step;
In the determination step, when it is determined that the predetermined condition is satisfied, a prohibition step for prohibiting the content stored in the storage step from being acquired by another node device;
A content distribution method comprising: An acquisition step of acquiring time information indicating a time to acquire content from any of the node devices in the content distribution system capable of transmitting and receiving content between a plurality of node devices that can communicate with each other via a network;
A search step of searching for a node device storing predetermined content according to the time indicated by the time information acquired in the acquisition step;
A content acquisition step of acquiring the predetermined content from the node device searched in the search step;
A storage step of storing the content acquired in the content acquisition step;
A content transmission step of transmitting the content to the other node device when the content stored in the storage step is retrieved from the other node device;
A determination step of determining whether or not a predetermined condition has been satisfied since the content was transmitted in the content transmission step;
When the determination step determines that the predetermined condition is satisfied, a prohibition step for prohibiting the content transmitted in the content transmission step from being acquired by another node device;
A node program that enables a computer to realize An acquisition means for acquiring time information indicating a time for acquiring content from any of the node devices in the content distribution system capable of transmitting and receiving content between a plurality of node devices that can communicate with each other via a network;
Search means for searching for a node device storing predetermined content according to the time indicated by the time information acquired by the acquisition means;
Content acquisition means for acquiring the predetermined content from the node device searched by the search means;
Storage means for storing the content acquired by the content acquisition means;
Content transmitting means for transmitting the content to the other node device when the content stored in the storage means is retrieved from the other node device;
Determination means for determining whether or not a predetermined condition is satisfied after the content is transmitted by the content transmission means;
A prohibiting unit that prohibits the content stored in the storage unit from being acquired by another node device when the determination unit determines that the predetermined condition is satisfied;
A content distribution system comprising:

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