JP2011060309A - Node device, storage control program, and information storage method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a node device and the like for acquiring the latest link information in participating in a system without imposing a processing load of a specific node device by storing link information used in participating in this system in a hard disk or the like. <P>SOLUTION: A node device is included in an information communication system in which a plurality of shared information shared by a plurality of node devices is distributed and stored by an overlay network configured of a plurality of node devices, and has a link information acquisition means for acquiring, from the node device at the transmission destination of participation notification, the link information stored by the node device at the transmission destination. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides an information communication system including a plurality of node devices that can communicate with each other via a network, and a plurality of shared information shared by the plurality of node devices is distributed and stored in the plurality of node devices. The present invention relates to the technical field of included node devices and the like.

  In recent years, information communication systems in which various contents such as music and movies are directly exchanged between node devices belonging to a network, for example, each content is distributed among a plurality of node devices and shared by a plurality of node devices. Research and development on P2P type information communication systems is active. This P2P type system is attracting attention as a technique for solving concentration of access to the server and high management costs, which are disadvantages of the conventional client / server type model.

In a peer-to-peer type information communication system, for example, in an overlay network logically constructed using a distributed hash table (hereinafter referred to as DHT (Distributed Hash Table)), each node device participates in the overlay network. It does not recognize link information (for example, destination information) to all the node devices that are present, but to some of the node devices obtained from the contact node device that is accessed first when participating in the overlay network RAM (Random) with only the link information as table information
Access Memory), and when making data inquiries, the CPU directly accesses the RAM and refers to the table information. Patent Documents 1 and 2 disclose techniques relating to DHT.

Further, not only a plurality of contents are distributed and stored in each node device in the system, but also information regarding the location of the content indicating which node device each content is held as cache information. Are distributed and managed.
JP 2003-99337 A JP 2003-216521 A

  When such a node device participating in the overlay network withdraws from the system (turns the power off), all the link information etc. used for communication with other node devices stored in the RAM are all It will be lost.

  When joining the overlay network again, it is necessary to acquire link information from the contact node device again.

  However, immediately after the restoration of a local power failure or the like, access from a large number of node devices to the contact node devices is concentrated, which places an excessive processing burden on the contact node devices. In addition, the processing load becomes more serious as the number of node devices participating in the system increases, and there is a possibility that not only the contact node device but also the entire network may be down.

  The present invention has been made in view of the above points, and the link information used when participating in the system is stored in a hard disk or the like that remains unerased after withdrawal from the system. Thus, when re-joining the system, the processing load of a specific node device is obtained by acquiring link information used at the time of re-joining the system based on the node information included in the link information stored in the hard disk or the like. It is an object of the present invention to provide a node device, a storage control program, and an information storage method that can acquire the latest link information at the time of participation in the system without imposing a service.

  In order to solve the above problem, the invention according to claim 1 includes a plurality of node devices that can communicate with each other via a network, and a plurality of shared information shared by the plurality of node devices includes a plurality of node devices. Link information used when communicating with the node device via the overlay network in the node device included in the information communication system distributed and stored by the overlay network configured by A volatile first storage unit that stores the link information including node information indicating a specific node device; and a node device that includes the first storage unit participates in the information communication system. The link information stored in the first storage means is stored in the nonvolatile second storage means at a predetermined timing. When the node device itself including the first storage control unit and the first storage unit withdraws from the information communication system and then joins the information communication system again, the link information stored in the second storage unit is added to the link information stored in the second storage unit. Link information acquisition means for acquiring the link information to be stored in the first storage means using any of the included node information, and included in the link information stored in the second storage means Based on the read node information, node information reading means for reading the node information, and a participation notification for transmitting a participation notification notifying that the node device related to the node information participates in the information communication system Means for determining whether or not the transmission of the participation notification is successful, and determining whether or not to transmit the participation notification. The link information that acquires the link information stored in the destination node device from the node device that is the transmission destination of the participation notification when it is determined that the participation notification has been successfully transmitted A node device comprising: an acquisition unit; and a second storage control unit that stores the link information acquired by the link information acquisition unit in the first storage unit.

  In order to solve the above-mentioned problem, according to a second aspect of the present invention, in the node device according to the first aspect, the first storage means uses the information communication system as the link information via the overlay network. Table information including a plurality of the node information used for communication with the other node devices included in the first node, and the first storage control unit stores the table information stored in the first storage unit as the predetermined information. The node information reading means reads the node information included in the table information stored in the second storage means, and the previous participation notifying means reads the node information. Based on the node information read from the table information by the means, the node device related to the node information The link information acquisition means transmits the participation notification from the node device that is the transmission destination of the participation notification when the participation notification transmission availability determination means determines that the participation notification is successfully transmitted. The table information stored in the destination node device is acquired. The second storage control means stores the table information acquired by the link information acquisition means in the first storage means. Device.

  In order to solve the above-mentioned problem, the invention according to claim 3 is the node device according to claim 1 or 2, wherein the first storage means includes the node device itself among the plurality of shared information. Storing location information indicating the location of the node device that stores the shared information to be managed, and shared information related information relating to the plurality of shared information shared by the plurality of node devices, the first storage The control means stores the location information and the shared information related information stored in the first storage means in the second storage means at the predetermined timing, and the second storage control means After leaving the information communication system, when rejoining the information communication system, the location information and the shared information related information stored in the second storage means are stored in the first storage again. A node apparatus, characterized in that to be stored in the stage.

  According to this, each node device participating in the information communication system stores the acquired cache information and catalog information from the first storage unit such as the RAM to the second storage unit while participating in the system. When leaving the system and joining the system again, the cache information and catalog information stored in the second storage means can be stored in the first storage means and used. You can participate in the system more smoothly.

  In order to solve the above-mentioned problem, according to a fourth aspect of the present invention, in the node device according to any one of the first to third aspects, the predetermined timing is set every time a predetermined time elapses or the information. Each time the link information, the location information, or the shared information related information stored in the first storage means is updated due to the exchange of information with the other node devices included in the communication system, or When the power of the node device itself is turned off, it is at least one of the node devices.

  According to this, when participating in the system, link information and the like can be reliably stored in the second storage means.

  In order to solve the above problem, the invention according to claim 5 is the node device according to any one of claims 1 to 4, wherein the information communication system is configured such that the node devices are connected by an overlay network. The node information included in the link information includes a node ID for uniquely identifying the node device related to the node information in the identification information space of the overlay network, and destination information of the node device. Is a node device characterized by

  According to this, since the node information including the node ID and destination information of the other node device essential for communication with the other node device is stored, it is possible to smoothly rejoin the peer-to-peer information communication system. .

  In order to solve the above problem, the invention according to claim 6 is the node device according to any one of claims 1 to 5, wherein the second storage means is a hard disk, a flash memory, an EEPROM, or A node device characterized by being a semiconductor memory with a backup power source.

  According to this, when the second storage means is any one of a hard disk, a flash memory, an EEPROM, or a semiconductor memory with a backup power source, when communicating with each other node device while participating in the system. Can be stored in the second storage means from the first storage means such as RAM, and when joining the system again, based on the link information stored in the second storage means The latest link information can be acquired.

  In order to solve the above problem, an invention according to claim 7 includes a plurality of node devices that can communicate with each other via a network, and a plurality of pieces of shared information shared by the plurality of node devices includes a plurality of node devices. Link information used when communicating with the node device via the overlay network to a computer of the node device in an information communication system distributed and stored by an overlay network configured by Storing the link information including the node information indicating the specific node device in the volatile first storage means, and the node device itself including the first storage means participating in the information communication system The link information stored in the first storage means is stored in a nonvolatile second storage at a predetermined timing. The first storage control step to be stored in the stage and the node device itself provided with the first storage means are stored in the second storage means when rejoining the information communication system after leaving the information communication system. A link information acquisition step for acquiring the link information to be stored in the first storage means using any of the node information included in the link information, wherein the link information is stored in the second storage means A step of reading the node information included in the link information, and transmitting a participation notification notifying the node device related to the node information that the node information is to be joined based on the read node information. A participation notification step; and a participation notification transmission permission determination step for determining whether or not the transmission of the participation notification is successful. When it is determined in the notification transmission permission determination step that the participation notification is successfully transmitted, the link information stored in the transmission destination node device is acquired from the node device that is the transmission destination of the participation notification. A storage control program that executes the link information acquisition step and the second storage control step of storing the acquired link information in the first storage means.

  In order to solve the above-described problem, an invention according to claim 8 is provided with a plurality of node devices that can communicate with each other via a network, and a plurality of shared information shared by the plurality of node devices is a plurality of node devices. In an information storage method in an information communication system distributed and stored by an overlay network configured by the link network, link information used when communicating with the node device via the overlay network, and a plurality of identification information Storing the link information including the node information indicating the node device in the volatile first storage unit, and the node device itself including the first storage unit participating in the information communication system, The link information stored in the first storage means is stored in the nonvolatile second storage means at a predetermined timing. The link information stored in the second storage means when the node device itself comprising the first storage control step and the first storage means leaves the information communication system and then joins the information communication system again. In the link information acquisition step of acquiring the link information to be stored in the first storage means using the node information included in the node, the node included in the link information stored in the second storage means A step of reading any of the information, a step of transmitting a participation notification notifying that the node device related to the node information participates in the information communication system based on the read node information, A participation notification transmission availability determination step for determining whether or not the participation notification transmission is successful, and the participation notification transmission availability determination step includes The link information acquisition step of acquiring the link information stored in the node device of the transmission destination from the node device of the transmission destination of the participation notification when it is determined that the communication is successful. And a second storage control step of storing the link information in the first storage means.

  According to the present invention, each node device participating in the information communication system stores link information such as table information including node information used when communicating with each other node device in a first storage such as a RAM. From the means, when storing in the second storage means, and withdrawing from the system, and joining the system again, using the node information included in the link information stored in the second storage means, Since the link information to be stored in the first storage means is acquired from other node devices participating in the system, only a specific node device participates in the system without receiving an excessive processing burden. In addition, the latest link information can be acquired.

It is a figure which shows an example of the connection aspect of each node apparatus in the content delivery system which concerns on this embodiment. 2 is a block diagram illustrating a schematic configuration example of a node device 1. FIG. It is a figure which shows an example of a mode that a routing table is produced by DHT. (A) An example of a level 1 table. (B) An example of a level 2 table. (C) An example of a level 3 table. (D) An example of a completed routing table. (A) (D) It is the figure which showed the mode at the time of the node apparatus 1 participating in the content delivery system S in ID space of DHT. (B) (C) It is the figure which showed the mode of the node apparatus 1 participating in the content delivery system S in ID space of DHT. It is a figure which shows an example of content ID and node ID in ID space of DHT. It is the figure which showed the mode at the time of a content being released, and the mode at the time of a content being searched in ID space of DHT. 4 is a flowchart illustrating an example of main processing in the node device 1. 4 is a flowchart illustrating an example of “table information reading process” in the node device 1. 5A is a flowchart showing an example of “cache information read processing” in the node device 1. FIG. 5B is a flowchart illustrating an example of “catalog information reading process” in the node device 1. FIG. 4 is a flowchart illustrating an example of “a process of saving table information, cache information, and catalog information stored in a RAM to a hard disk storage unit 22” in the node device 1. 4 is a flowchart illustrating an example of “a process of saving table information, cache information, and catalog information stored in a RAM to a hard disk storage unit 22” in the node device 1.

<1. Content distribution system configuration>
First, with reference to FIG. 1, a schematic configuration and the like of a content distribution system as an information communication system in which information is shared by a plurality of node devices will be described.

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

As shown in the lower frame 501 of FIG. 1, IX (Internet eXchange) 3 as an relay device, ISP (Internet Service Provider) 4, DSL (Digital Subscriber Line) device 5 and FTTH (Fiber To Me). ) A network (real-world network) 8 such as the Internet is constructed by the line provider device 6 and a communication line (for example, a telephone line or an optical cable) 7.

  The node devices 1a, 1b, 1c,... 1x, 1y, 1z,... Connected to each other via the network 8 have destination information of IP (Internet Protocol) address and port number, Each node device is specified, and a node ID (IDentifier) as a unique value for uniquely identifying one node device is assigned as node information. These node IDs do not overlap among a plurality of node devices. In the following description, when any one of the node devices 1a, 1b, 1c... 1x, 1y, 1z.

  Further, in the content distribution system S, when the node device 1 accesses information held by another node device 1, it is necessary to know destination information such as an IP address of the node device 1 having the information.

  As an example of such a system, an overlay network 9 as shown in the upper frame 500 of FIG. 1 is constructed by an algorithm using DHT. That is, the overlay network 9 means a network that forms a virtual link formed using the existing network 8, and the content distribution system S of the present embodiment has a plurality of nodes participating in the overlay network 9. The apparatus 1 is constituted.

  The node ID only needs to be able to uniquely identify each node device. For example, the node ID is obtained by hashing a production number or a machine name allocated in advance at the time of factory shipment using a common hash function (hash algorithm). It is possible to use the hash value as a GUID (Global Unique IDentifier) and use it as a node ID for each node device 1.

Also, the node ID needs to have a number of bits that can accommodate the maximum number of node devices in the content distribution system S. For example, if the number is 128 bits, 2 ^ 128≈340 * 10 ^ 36 node devices can be operated. Actually, SHA-1 (Secure Hash Algorithm 1) (number of generated digits 160 bits) or MD5 (Message Digest 5) (known hash functions)
It is assumed that the number of generated digits (120 bits) is used. Thus, the node ID obtained by the common hash function has a very low probability of having the same value if the serial number or the machine name is different. Since the hash function is publicly known, detailed description thereof is omitted.

<1-2. Configuration and function of node device>
Next, the configuration and function of the node device 1 will be described. FIG. 2 is a block diagram illustrating a schematic configuration example of the node device 1. As shown in the figure, the node device 1 according to the embodiment includes a CPU having an arithmetic function, table information (an example of link information), cache information (an example of location information), catalog information (an example of shared information related information). ) Etc. As a computer comprising a work RAM (Random Access Memory) (an example of the first storage means) and a ROM etc. for storing various data and programs (including the storage control program of the present invention) Control unit 11, a storage unit 12 configured by an HDD or the like for storing and storing (storing) programs and the like (content data may be stored in the node device 1), and temporarily storing received content data Buffer memory 13 for encoding, encoded video data (video information) included in the content data, and A decoder unit 14 that decodes (decompresses and decodes) audio data (audio information) and the like, a video processing unit 15 that performs a predetermined drawing process on the decoded video data and outputs the video signal, and A display unit 16 such as a CRT or a liquid crystal display for displaying video based on the video signal output from the video processing unit 15, and the decoded audio data after D (Digital) / A (Analog) conversion into an analog audio signal Communication control of information between the audio processing unit 17 that amplifies the signal by an amplifier, the speaker 18 that outputs the audio signal output from the audio processing unit 17 as a sound wave, and the other node device 1 through the network 8 And a communication unit 20 for receiving an instruction from a user and receiving instructions from the user An input unit (for example, a keyboard, a mouse, or an operation panel) 21 serving as an input means for giving an indication signal to the control unit 11 and rewritable storage for storing content data, table information, cache information, catalog information, and the like A hard disk storage unit 22 (an example of a second storage unit) that is a non-volatile storage unit, and includes a control unit 11, a storage unit 12, a buffer memory 13, a decoder unit 14, a communication unit 20, and a hard disk storage unit. 22 are connected to each other via a bus 23.

  Then, the CPU in the control unit 11 executes various programs recorded in the storage unit 12 or the like, so that the control unit 11 performs overall control of the overall operation as the node device 1 according to the embodiment. In cooperation, first storage means, second storage means, first storage control means, second storage control means, third storage control means, link information acquisition means, node information reading means, participation notification means, participation notification transmission Availability determination means, link information reception means, node information presence / absence determination means, node information selection means, deletion means, shared information storage means, disclosure notification means, first storage time determination means, second storage time determination means, and disclosure notification transmission It functions as a determination unit.

  The contact node device 1CC that is first accessed by the node device that first participates in the content distribution system S is an example of the participation management node device of the present invention, and the node device that has not participated in the system while participating in the system. When the participation message is received from 1, the table information stored by itself is transmitted to the node device 1.

  Hereinafter, an algorithm using a distributed hash table (hereinafter referred to as DHT (Distributed Hash Table)) according to the present embodiment and a specific mechanism of content distribution will be described as an example of the first storage unit of the present invention. The table information and the like stored in the RAM of the control unit 11 and the hard disk storage unit 22 which is an example of the second storage unit will be described in detail.

<1-3. Overview of DHT>
Hereinafter, an algorithm using a distributed hash table (hereinafter referred to as DHT (Distributed Hash Table)) according to the present embodiment will be described.

  This embodiment is based on an overlay network 9 constructed by an algorithm using DHT, and a node device 1 arranged in the overlay network 9 (in the upper frame 500 of FIG. 1) participates in the overlay network 9. A node device 1 that is participating in the content distribution system S.

  Participation in such a content distribution system S is table information (an example of link information) that is used by a non-participating node device 1 for communication with other node devices. It is necessary to acquire the latest table information of the node devices (including the contact node device 1CC), but the present invention stores the information in the RAM of the control unit 11 when participating in the content distribution system S. When the table information that has been used is stored in the hard disk storage unit 22 and rejoins the system, the latest table is based on the node information included in the table information stored in the hard disk storage unit 22. Configure to obtain information. Specifically, the configuration is made by requesting the node apparatus 1 related to the node information included in the table information stored in the hard disk storage unit 22 to participate in the system and copying the table information. The latest table information can be acquired without imposing a processing burden on the contact node device 1CC.

  Next, an example of a table information creation method will be described with reference to FIGS. 3 and 4. The table information is also created (updated) while being transferred between a plurality of node devices, and is also called a routing table.

  FIG. 3 is a diagram illustrating an example of how a routing table (table information) is created, and FIG. 4 is a diagram illustrating an example of a routing table (table information).

  First, as shown in FIG. 4A, the ID space is divided into several areas. In this area, the ID space is divided in order to create a routing table. Actually, about 16 divisions are often used. However, for the sake of simplicity of explanation, the area is assumed to be four divisions, and the ID is a bit. It was expressed as a long 16-bit quaternary number. An example in which the node ID of the node device 1N is “10230210” and the routing table of the node device 1N is created will be described.

(Level 1 routing)
First, if the ID space is divided into four areas, each area is represented by four areas “0XXXXXXX”, “1XXXXXXX”, “2XXXXXXX”, “3XXXXXXX” (X is a natural number of 0 to 3, below) The same). Since a node ID of the node device 1N itself is “10230210”, a certain node device (hereinafter referred to as the node device 1N) exists in the area “1XXXXXXX” in the lower left in the drawing. Then, the node device 1N appropriately selects the node device 1 existing in an area other than the area where the node device 1 exists (that is, the area of “1XXXXXXX”), and sets the destination information such as the IP address of the node ID as Level 1 Store in the table. FIG. 4A shows an example of a level 1 table. Since the second column indicates the node device 1N itself, it is not necessary to store destination information such as an IP address.

(Level 2 routing)
Next, as shown in FIG. 3B, among the areas divided into four by the above routing, the area where the user exists is further divided into four, and further four areas “10XXXXXXX” “11XXXXXXX”, “12XXXXXXX”, “13XXXXXXX” ". Then, similarly to the above, the node device 1 existing in an area other than the area in which it exists is appropriately selected, and destination information such as the IP address of the node ID is stored in the level 2 table. FIG. 4B is an example of a level 2 table. Since the first column indicates the node device 1N itself, it is not necessary to store the destination information.

(Level 3 routing)
Further, as shown in FIG. 3C, among the areas divided into four by the above routing, the area where the user exists is further divided into four, and further four areas “100XXXX”, “101XXXX”, “102XXXX”, “103XXXX” And divide. Then, similarly to the above, the node device 1 existing in an area other than the area in which it exists is appropriately selected, and the destination information such as the IP address of the node ID is stored in the level 1 table. FIG. 4C is an example of a level 3 table. Since the third column indicates the node device 1N itself, it is not necessary to store destination information such as an IP address, and the second column and the fourth column are blank because there is no node device in the area.

  In this way, all the 16-bit IDs can be covered by creating a routing table as shown in FIG. As the level goes up, white space becomes more noticeable in the table.

  As described above, each node device 1 stores destination information such as an IP address of another node device 1 in association with an area of the node ID space, that is, each level and each column of DHT. That is, each node device 1 defines destination information such as an IP address of one node belonging to each of the divided areas as one stage (level) in association with each area, and further belongs to itself. A routing table in which areas are divided into a plurality of areas, and destination information such as an IP address of one node device 1 belonging to each of the divided areas is defined as the next stage (level) in association with each area. (Hereinafter referred to as table information) is stored in the RAM of the control unit 11.

  Actually, in order for the node device 1 that has not participated in the content distribution system S to participate in the content distribution system S and acquire the table information as described above, first, it has not participated in the system in the past. When participating in the system (new participation), a “participation message” (an example of a participation notification) is transmitted to the contact node device 1CC to obtain table information from the contact node device 1CC (FIG. 5 ( A)).

  Then, the node device 1 stores the table information acquired from the contact node device 1CC in the RAM of the control unit 11 while participating in the system, and is performed when searching for content or publishing content. It is used during message transfer and dynamically rewritten with the latest information (see FIG. 5B). Specifically, at the time of knowing the existence of another node device 1 at the time of message transfer, content distribution, etc., it is determined which cell in the table the node ID of that device matches, and each table We will add (update) the contents of. At the timing when it is known that another node device has left, the node ID of the device is deleted from the table.

  The node device 1 stores the table information from the RAM of the control unit 11 in the hard disk storage unit 22 while participating in the content distribution system S (see FIG. 5C). Then, when the node device 1 leaves the system and rejoins the system, the node device 1 does not use the contact node device 1CC but the node information described in the table information stored in the hard disk storage unit 22 as “ Select node information to send "join message". Specifically, the table information stored in the hard disk storage unit 22 is temporarily transferred (stored) to the RAM of the control unit 11 for work (see the arrow in FIG. 5D), and the node device is selected from the table information. Select and send a “participation message” (including its own node information and the node ID of the selected node information) to the selected node device 1 according to the routing using the node ID of the selected node information as a key. Then, the table information is received (see FIG. 5D). The received table information is stored in the RAM of the control unit 11 and used for information transfer with other node devices.

  In this way, the table information is always dynamically rewritten by exchanging information such as message and content distribution. Therefore, the table information is withdrawn from the system by obtaining the table information from the node device 1 currently participating in the system. It is possible to obtain the latest table information in which the node information of the node devices is relatively small and the node information of the node devices participating in the system is relatively large. In particular, in the case of rejoining the system, a processing load is not imposed on the contact node device 1CC, so that a more useful system can be provided.

  Further, when selecting the node device 1 that is currently participating in the system based on the table information (table information stored in the hard disk storage unit 22) that has been used in the past when participating in the system, If it is configured to select the node device 1 related to the node ID relatively far from its own node ID, a “participation message” including its own node information can be transferred between a relatively large number of node devices 1, A relatively large number of node devices can be notified of their existence.

<1-4. Content storage and distribution>
Next, storage of content shared by each node device 1 and distribution of the content will be described. Content data (for example, movies and music) as shared information distributed from one node device 1 to another node device 1 is distributed to a plurality of node devices 1 participating in the content distribution system S. Although stored (stored), a unique (unique) content ID is assigned to each content. This content ID has the same length as the node ID (for example, 128 bits), is determined by the server 100 that inputs the content into the content distribution system S and registers with the node device 1, and is assigned to each content. .

  In FIG. 6, a node ID and a content ID are assigned in 32 bits and are illustrated on the ID space. In the figure, a black dot indicates a node ID, a black diamond indicates a content ID, and the ID increases counterclockwise.

  In the ID space as shown in FIG. 6, which content is managed by which node device 1 is determined by whether or not the content ID and the node ID are in a “predetermined relationship”. Here, the “predetermined relationship” is determined under a certain rule. In the present embodiment, “a node device that manages content having a certain content ID is the node closest to the content ID. The rule is “the node device 1 has an ID”. That is, the node device 1 having a node ID that is closest to the content ID (for example, the higher-order digit matches more) and has a node ID that is equal to or less than the value of the content ID, The location information of the node device 1 to be stored is managed.

  For example, the “predetermined relationship” is defined as one that does not exceed the content ID and has the smallest difference between the content ID and the node ID. In the example shown in the figure, based on this definition, the content IDa is managed by the node device having the node IDa, and the content IDb is managed by the node device having the node IDb. In addition, any definition may be used as long as it is consistent when the management of each content is allocated to each node device 1.

  In addition, a certain node device may manage a plurality of different content data so that the content IDc and IDd are managed by the node device 1 having the node IDc. Here, “management” does not mean that content is stored / held, but “knows which node device 1 stores content data (content data)”. That is, it means that destination information such as the IP address of the node device holding the content is stored (cached) as the location information of the content.

Table 1 shows an example of cache information that each node device 1 stores in the RAM of the control unit 11.

  The node apparatus 1 is included in a “public message” (an example of a public notice) that is transmitted when a node apparatus that holds content publishes new content so that it can be seen by other node apparatuses participating in the content distribution system S. Destination information (content location information) such as an IP address is received and acquired, and is written in cache information (Table 1) stored in the RAM of the control unit 11. In the present embodiment, not only the node device 1 related to the node ID having a predetermined relationship with the content ID, but also the node device 1 on the path when the “public message” is transferred between the node devices. The content location information is configured to be stored as cache information in the RAM of the control unit 11.

  Hereinafter, the process of publishing contents and storing cache information in the RAM of the control unit 11 of the node device will be described in detail.

<1-5. Publication of content and storage of content location information>
FIG. 7 is a diagram illustrating an example of how new content is released by DHT.

  The node device that holds the content obtains the content ID from the content title or the like and is directed to the node device having the same node ID as the content ID (whether or not this node device actually exists is unknown at this time). Send "public message".

  Here, a procedure when the node device 1a having the node ID “12003030” publishes the content having the content ID “31330012” held by itself will be described.

  First, the node device 1a refers to the level 1 table of the table information (see FIG. 4D) stored in the RAM of the control unit 11 and refers to the node ID of the same area as the content ID “31330012”. A “public message” is transmitted to the node device having That is, since the content ID “31330012” is an area of “3XXXXXXX”, the node device 1 belonging to the area of “3XXXXXXX” knows destination information such as an IP address (that is, an IP address or the like in the table information). The “public message” is transmitted to the node device 1b in which the destination information is stored.

  According to the example shown in FIG. 7, since the destination information such as the IP address of the node device 1b whose node ID is “30100000” is stored in the table information of the node device 1a, the node device 1a has the node ID “ A “public message” is transmitted to the node device 1b which is “30100000”.

  Next, the node device 1b that has received the “public message” refers to the level 2 table of the table information stored in the RAM of the control unit 11 by the node device 1b itself, and belongs to the area “31XXXXXXX”. The “public message” is transferred to the node device 1c (node ID “31012001”) that knows the destination information such as the IP address among the node devices 1.

  In this way, the transfer of the “public message” proceeds in the manner of adapting the digits of the content ID in order from the top, and finally reaches the node device 1d.

  Then, the node device 1d finally arrived has its own control unit using the content ID included in the “public message” and the IP address “IP address 1” of the node device 1a holding the content as the location information of the content. 11 is stored in the cache information stored in the RAM. In the present embodiment, the node devices 1b and 1c that have transferred (relayed) the “public message” from the node device 1a that holds the content according to the table information also hold the content ID and content included in the “public message”. The IP address “IP address 1” of the node device 1a to be stored is stored in the cache information stored in the RAM of its own control unit 11 as the location information of the content.

  When a user wishes to view content, a “search message” that inquires about the location of the content including the content ID passes between the node devices according to the routing using the content ID included in the “search message” as a key. When the node device storing the content cache information in the RAM is transferred, the IP address of the node device holding the content is received as the content location information from the node device and received. The node device accesses the node device holding the content and requests distribution. In the case of the example illustrated in FIG. 7, the “search message” including the content ID “31330012” of the search target content transmitted from the node device 1 e is transmitted between the other node devices with the content ID “31330012”. The node device 1e arrives at the node device 1c having the location information, and acquires “IP address 1” of the node device 1a as the location information of the content corresponding to the content ID “31330012” from the node device 1c. Then, the node device 1e requests content distribution to the node device 1a according to the IP address 1, and receives content distribution from the node device 1a.

  The node device 1e desiring to distribute the content receives the content location information from the node device 1c having the content location information and exchanges the information, thereby knowing the existence of each other. The node information (the destination information such as the IP address and the node ID) of the node device 1c is added to the table information stored in the RAM of the control unit 11, and is stored in the RAM of the control unit 11 in the same manner. If there is no node information of the node device 1e in the table information, the node information of the node device 1e is added.

  Also, the node device 1a that holds the content and the node device 1e that desires to distribute the content know each other by exchanging information called content distribution. In the node device 1a, the control unit If the node information of the node device 1e is not included in the table information stored in the RAM of the node 11, the node information of the node device 1e is additionally written. Similarly, the table stored in the RAM of the control unit 11 is also stored in the node device 1e. If there is no node information of the node device 1a in the information, the node information of the node device 1a is appended.

  In the present embodiment, it is catalog information (an example of shared information related information) that constitutes a catalog list that is desired to be distributed and referred to (browse) when searching, and is used together with other node devices 1 ( The catalog information (shared) is also stored in the RAM of the control unit 11. In the catalog information, content attribute information is described in association with each content ID. Examples of the attribute information include a content name (a movie title when the content is a movie, a song title when the content is a song, a program title when the content is a broadcast program), a genre (an action when the content is a movie, an action, Horror, comedy, love story, etc. If the content is music, rock, jazz, pop, classic, etc. If the content is a broadcast program, drama, sports, news, movie, music, anime, variety, etc.), artist name (content Singer, group, etc.), performers (cast when content is a movie or broadcast program), director name (when content is a movie), and the like. The applicant of the present application has filed a patent application (Japanese Patent Application No. 2006-109158 and Japanese Patent Application No. 2006-109159) regarding catalog information used (shared) with other node devices 1, and therefore catalog information is stored in a plurality of nodes. Since the technique shared between the apparatuses 1 is described in detail in the application, description thereof will be omitted.

<2. Processing operation of node device>
Next, a specific processing operation of each node device 1 will be described with reference to the drawings.

<2-1. Main processing>
FIG. 8 is a flowchart showing an example of the main process in the node device 1. This process is executed based on the control of the control unit 11, and the node device 1 is turned on. Is started by instructing participation in the content distribution system S.

  First, table information reading processing (step S1), cache information reading processing (step S2), and catalog information reading processing (step S3) are performed. In each reading process, if the user has participated in the content distribution system S in the past, the information can be acquired from the hard disk storage unit 22 and read into the RAM of the control unit 11. The processing of steps S1 to S3 will be described in detail later.

  Next, it is determined whether or not the power is turned off (step S4). If not turned off (step S4: No), “other processing” is performed (step S5). Note that “other processing” means processing for transmitting own table information in accordance with “participation message” transmitted from another node device 1, and “search message transmitted from other node device 1. ”Content search processing (search for a node device holding content), content distribution processing performed in response to a content distribution request transmitted from another node device 1, or various message transfer processing, etc. It is processing of.

  And the control part 11 functions as a 1st memory | storage control means, and performs the process which preserve | saves the table information, cache information, and catalog information memorize | stored in RAM at the hard disk memory | storage part 22 (step S6). Then, the process proceeds to step S4.

  In this way, the processes in steps S5 and S6 are repeated until it is determined in step S4 that the power is off.

  Steps S1 to S3 are processes performed before participating in the content distribution system S, and steps S4 to S6 are processes performed when participating in the content distribution system S.

<2-2. Reading process of each information>
Next, the table information, cache information, and catalog information reading process executed in steps S1 to S3 will be described with reference to FIGS.

2-2-1. Table Information Reading Process FIG. 9 is a flowchart illustrating an example of the “table information reading process” executed in step S1.

  First, it is determined whether or not the table information is stored (stored) in the hard disk storage unit 22 (step S11). When the table information is not stored in the hard disk storage unit 22, such as when the user has never participated in the content distribution system S in the past or when the table information stored in the hard disk storage unit 22 has been deleted (step S11). : No), as shown in FIG. 6A, a “participation message” is transmitted to the contact node device 1CC, the table information is acquired (received), and the table information is stored in the RAM (step). S12).

  On the other hand, when the table information is stored in the hard disk storage unit 22 (step S11: Yes), the control unit 11 functions as a third storage control unit, and the table information stored in the hard disk storage unit 22 is stored. For the work, it is once read (transcribed) into the RAM (step S13), and the storage time indicating the time when the table information is stored in the hard disk storage unit 22 is also acquired from the hard disk storage unit 22 (step S14).

  And the control part 11 functions as a 2nd preservation | save time judgment means, and determines whether the time (elapsed time) which passed from the preservation | save time to the present time is in a 2nd predetermined preservation | save time (for example, 2 hours). However, if it is longer than the second predetermined storage time (step S15: No), the table information stored in the hard disk storage unit 22 (each node information) remains as it is when participating in the system this time. Since the information is not the latest information that can be used, the process proceeds to the processing after step S16, that is, the processing that causes the table information to be copied from the node device (including the contact node device 1CC) currently participating in the system.

  Next, in step S16, the control unit 11 functions as a first storage time determination unit, and a time (elapsed time) elapsed from the storage time to the current time is a second predetermined target whose determination target is step S15. It is determined whether it is within a first predetermined storage time (for example, 10 days) longer than the storage time (step S16). When the elapsed time is longer than the first predetermined storage time (step S16: No), a “participation message” is transmitted to the contact node device 1CC, and table information is acquired (received) from the contact node device 1CC. Then, the table information is stored in the RAM (step S12). Thus, when the elapsed time is longer than the first predetermined storage time, the table information stored in the hard disk storage unit 22 is old information, so a participation message is transmitted to the node device in the table information. However, the possibility of failure is high. Therefore, the table information is acquired from the contact node device 1CC.

  On the other hand, in step S16, when the elapsed time is within the first predetermined storage time (step S16: Yes), the table information is obtained from the node device 1 selected based on the table information. Specifically, first, the control unit 11 functions as node information presence / absence determination means, and determines whether there is node information in the RAM table information (step S17). When the node information is included in the RAM table information (step S17: Yes), the control unit 11 functions as a node information selection unit and a participation notification unit, selects the node information from the RAM table information, and selects the node information. A “participation message” is transmitted to the node device 1 according to (step S18).

  The control unit 11 functions as a participation notification transmission permission determination unit, and determines whether or not the transmission of the “participation message” is successful. Specifically, it is determined whether or not the table information has been received from the node device that is the transmission destination of the “participation message” (step S19). The node device to which the “participation message” is sent is the node device to which the message has arrived by routing using the node ID (selected in step S18) included in the “participation message” as a key.

  If the table information cannot be received as a result of the determination (step S19: No), the control unit 11 functions as a deletion unit, deletes the node information selected in step S18 from the table information (step S20), and step S17. Return to. Since the table information stored in the hard disk storage unit 22 is the table information used when the node device 1 performing the process participates in the previous content distribution system S, the time since the previous participation is obtained. When a considerable amount of time elapses, the node device that participated in the system at the previous participation has also left the system over time. As described above, when the node device 1 that first receives the “participation message” has already withdrawn, or when a communication error occurs when the “participation message” is relayed through the plurality of node devices 1. For example, table information cannot be received. In step S18, node information in the table information is selected again, and it is determined that there is no node information in the table information (step S17: No) or reception of the table information is confirmed (step S19). : Yes), the processes of steps S17 to S19 are repeated.

  And the control part 11 functions as a link information receiving means, and reception of table information is confirmed (step S19: Yes), the control part 11 functions as a 2nd memory | storage control means, and for work by step S13 Instead of the table information transferred (stored) in the RAM, the received table information is stored in the RAM (step S21).

  If it is determined in step S17 that there is no node information in the table information (step S17: No), the process proceeds to step S12 in the same manner as when participating in the content distribution system S for the first time, and the contact node A “participation message” is transmitted to the device 1CC, table information is received, and the table information is stored in the RAM.

  Subsequently, it is determined whether or not the content to be shared with other node devices 1 participating in the system is stored (possessed) in the storage unit 12 (step S22). If it is not stored in the storage unit 12 (step S22: No), the process is terminated. If it is stored (step S22: Yes), the control unit 11 functions as a public notification means and possesses it. For each content, a “public message” is transmitted based on the table information stored in the RAM in step S12 or S21 (step S23), and the process is terminated.

  If it is determined in step S15 that the time (elapsed time) elapsed from the storage time to the current time is within the second predetermined storage time (step S15: Yes), steps S24 to S26 are performed. Move on to processing. In other words, if the table information acquired from the hard disk storage unit 22 in step S13 is new (such as when the user rejoins the system immediately after leaving the system (for example, within 2 hours)), it joins the previous system. Since the table information used at that time (the information on each node) is still likely to be the latest information, the table information used last time is used as it is.

  Then, it is determined whether or not the content to be shared with the other node devices 1 participating in the system is stored (held) in the storage unit 12 (step S24), and the content to be shared is stored. If it is not stored in the unit 12 (step S24: No), the process is terminated. If it is stored in the storage unit 12 (step S24: Yes), the control unit 11 functions as a public notification means. Then, for each content possessed, a “public message” is transmitted based on the table information stored in the RAM in step S13 (step S25).

  Next, the control unit 11 functions as a disclosure notification transmission availability determination unit, and determines whether or not the transmission of the “public message” is successful (step S26). Specifically, when a reception confirmation notification is received from the node device that is the first transmission destination of the “public message”, it is determined that the message transmission is successful, and the reception confirmation notification is the first transmission destination node. If the message is not transmitted even after waiting for a predetermined waiting time (timeout), it is determined that the message transmission has failed. In the example shown in FIG. 7, the node device that is the first transmission destination of the “public message” is the node device 1b. If the transmission of the “public message” is successful (step S26: Yes), the process is terminated. If the transmission of the “public message” fails (step S26: No), the table stored in step S13 is stored. The information is deleted from the RAM, the process proceeds to step S12, and the table information is acquired from the contact node device 1CC and stored in the RAM.

  As described above, when the table information stored in the hard disk storage unit 22 is used after rejoining the system, it is determined whether or not the table information can be used depending on whether or not the “public message” can be transmitted. If the transmission of the public message fails, it is determined that there is a high possibility that the node device 1 related to the remaining node information of the table information stored in the hard disk storage unit 22 is not participating in the system. The latest table information is obtained from the contact node device 1CC.

  In step S13, the table information stored in the hard disk storage unit 22 is once read into the RAM, and various operations such as selecting node information from the table information are performed. Instead, the CPU 11 accesses the table information stored in the hard disk storage unit 22 via the bus 23 while the table information is stored in the hard disk storage unit 22, so that the control unit 11 functions as a node information reading unit. Then, the node information included in the table information stored in the hard disk storage unit 22 may be read and a “participation message” may be transmitted to the node device related to the node information.

2-2-2. Cache Information Reading Process Next, the cache information reading process in step S2 will be described with reference to a flowchart showing an example of the “cache information reading process” in FIG.

  First, it is determined whether or not the cache information is stored (stored) in the hard disk storage unit 22 (step S31). If the cache information has not been saved in the hard disk storage unit 22 (eg, if the user has never participated in the content distribution system S in the past) (step S31: No), the process is terminated.

  On the other hand, when the cache information is stored in the hard disk storage unit 22 (step S31: Yes), the control unit 11 functions as a second storage control unit, and the cache information stored in the hard disk storage unit 22 is stored in the RAM. (Step S32), and the process ends.

2-2-3. Catalog Information Reading Processing Next, the catalog information reading processing in step S3 will be described with reference to a flowchart showing an example of “catalog information reading processing” in FIG. This process is the same as the “cache information reading process” described above.

  First, it is determined whether or not the catalog information is stored (stored) in the hard disk storage unit 22 (step S41). If the catalog information has not been saved in the hard disk storage unit 22 (eg, if the user has not participated in the content distribution system S in the past) (step S41: No), the process ends.

  On the other hand, when the catalog information is stored in the hard disk storage unit 22 (step S41: Yes), the control unit 11 functions as a second storage control unit, and the catalog information stored in the hard disk storage unit 22 is stored in the RAM. (Step S42), and the process ends.

<2-3. Saving information>
Next, the table information, cache information, and catalog information storage processing executed in step S6 will be described with reference to FIGS. 11 and 12. FIG.

  While participating in the content distribution system S, the table information, cache information, and catalog information that are stored and used in the RAM of the control unit 11 are stored (stored) in the hard disk storage unit 22 at a predetermined timing. It has become.

  Here, when the table information, the cache information, and the catalog information are updated due to the method of saving to the hard disk storage unit 22 every predetermined time and the exchange of information with other node devices, the hard disk storage unit 22 How to save to will be described.

2-3-1. Method for Saving Every Predetermined Time A method for saving table information, cache information, and catalog information to the hard disk storage unit 22 every predetermined time will be described. FIG. 11 is a flowchart illustrating an example of “a process of saving the table information, cache information, and catalog information stored in the RAM to the hard disk storage unit 22” executed in step S6.

  First, it is determined whether or not a predetermined time has elapsed since the previous storage process in the hard disk storage unit 22 (step S61). When the predetermined time has not elapsed (step S61: No), the process is terminated, and when the predetermined time has elapsed (step S61: Yes), the control unit 11 functions as a first storage control unit, The RAM table information and the storage time are stored in the hard disk storage unit 22 (step S62), and the process proceeds to step S63. At this time, if table information stored in the past is stored in the hard disk storage unit 22, it is overwritten and saved.

  Next, in step S63, it is determined whether or not the cache information is stored in the RAM (step S63). If the cache information is stored in the RAM (step S63: Yes), the cache information is stored in the RAM. It is determined whether or not the capacity of the cache information is larger than the storage capacity of the cache information storage area of the hard disk storage unit 22 (step S64).

  If the capacity of the cache information stored in the RAM is within the storage capacity of the cache information storage area of the hard disk storage unit 22 (step S64: No), all the cache information stored in the RAM is stored in the hard disk. If the capacity of the cache information stored in the RAM is larger than the storage capacity of the cache information storage area of the hard disk storage section 22 (step S64), the process proceeds to step S67. : Yes), only the location information of the content having the content ID close to its own node ID among the cache information stored in the RAM is stored in the hard disk storage unit 22 (step S66).

  Subsequently, in step S67, it is determined whether or not the catalog information is stored in the RAM (step S67). If the catalog information is not stored in the RAM (step S67: No), the process is terminated and stored. If yes (step S67: Yes), the catalog information is stored in the hard disk storage unit 22 (step S68), and the process is terminated.

2-3-2. Method of Saving When Updated The table information, cache information, and catalog information will be described as a method of saving the hard disk storage unit 22 when these pieces of information are updated. FIG. 12 is a flowchart showing an example of the “process for saving the table information, cache information, and catalog information stored in the RAM to the hard disk storage unit 22” executed in step S6.

  First, it is determined whether or not the table information stored in the RAM has been updated (rewritten) (step S71). When the table information is updated (step S71: Yes), the control unit 11 functions as a first storage control unit, and stores the table information of the RAM and the storage time in the hard disk storage unit 22 (step S72). If there is past table information in the hard disk storage unit 22, it is overwritten and saved. If the table information has not been updated (step S71: No), the process proceeds to step S73.

  Next, in step S73, it is determined whether or not the cache information has been updated (rewritten) (step S73). If the cache information has not been updated (step S73: No), the process proceeds to step S77. When the information has been updated (step S73: Yes), it is determined whether or not the capacity of the cache information stored in the RAM is larger than the storage capacity of the cache information storage area of the hard disk storage unit 22 ( Step S74).

  If the capacity of the cache information stored in the RAM is within the storage capacity of the cache information storage area of the hard disk storage unit 22 (step S74: No), all the cache information stored in the RAM is stored in the hard disk. When the capacity of the cache information stored in the RAM is larger than the storage capacity of the cache information storage area of the hard disk storage section 22 (step S74), the process proceeds to step S77. : Yes), only the location information of the content having the content ID close to its own node ID among the cache information stored in the RAM is stored in the hard disk storage unit 22 as the cache information (step S76).

  Subsequently, in step S77, it is determined whether or not the catalog information has been updated (rewritten) (step S77). If the catalog information has not been updated (step S77: No), the process is terminated and the catalog information is not updated. If it has been updated (step S77: Yes), the catalog information is stored in the hard disk storage unit 22 (step S78), and the process is terminated.

  In steps S64 and S74, it is determined whether or not the capacity of the cache information stored in the RAM is larger than the storage capacity of the cache information storage area of the hard disk storage unit 22. The number of content location information that can be stored in the cache information storage area is determined, and in the case of cache information having location information larger than this number, only location information of content having a content ID close to its own node ID is stored. The cache information may be stored in the hard disk storage unit 22. In addition, the upper limit of the processing time for storing cache information from the RAM to the hard disk storage unit 22 is determined in advance as a storage processing time (for example, within 2 to 3 minutes), and the content having a content ID close to its own node ID from the RAM The location information may be read sequentially, and the reading may be terminated when a predetermined storage processing time has elapsed.

  Furthermore, in the present embodiment, a method for saving each piece of information stored in the RAM to the hard disk storage unit 22 every predetermined time and a method for saving the information to the hard disk storage unit 22 when each piece of information is updated will be described. However, for example, when the power-off is confirmed in step S4 (step S4: Yes), the information is stored in the hard disk storage unit 22 and then the power is turned off. Also good.

  According to the above-described embodiment, when participating in the content distribution system S, in order to use the table information stored and used in the RAM of the control unit 11 next time when participating in the system, Even after leaving the system (after turning off the power), the stored information is stored in the hard disk storage unit 22 that is not erased, and when the user joins the system again after leaving the system, the hard disk storage unit 22 Since the node device participating in the system for copying the table information (the node device to which the participation message is transmitted) is selected based on the table information stored in the table information, the contact node device 1CC is selected. The latest table information can be acquired from the time of joining the system without imposing a processing burden.

  Further, when selecting a node device currently participating in the system based on the table information (table information stored in the hard disk storage unit 22) used when participating in the system in the past, If a node device related to a node ID relatively far from its own node ID is selected, a “participation message” including its own node information is transferred between a relatively large number of node devices. A relatively large number of node devices can be notified of participation. The node ID relatively far from the own node ID is level 1 because level 1 of the table information (see FIG. 4D) is the farthest from the own node ID and level 8 is the closest to the own node ID. It may be configured to select from among the node IDs described in.

The first storage means of the present invention is not limited to the working RAM, but may be any volatile memory that loses the stored contents when the power is turned off. Further, the second storage means is not limited to the hard disk storage unit 22, and the information stored when participating in the system remains without being erased even after withdrawal from the system (after the power is turned off). Any non-volatile storage means may be used. For example, flash memory, EEPROM (Electronically Erasable and Programmable Read Only)
Memory), flash memory, semiconductor memory with a backup power source, or the like. Further, the second storage means is not limited to the constituent members of the node device 1 such as the hard disk storage unit 22 but may be an external memory connected to the node device 1 or the like.

  In the above embodiment, the description has been made on the assumption that the overlay network 9 is constructed by an algorithm using DHT. However, the present invention is not limited to this and can be applied to other computer network systems. It is.

1 Node device 1CC Contact node device 3 IX
4 ISP
5 DSL line provider's equipment 6 FTTH (Fiber To The Home) line provider's equipment 7 Communication line 8 Network 9 Overlay network 11 Control unit 12 Storage unit 13 Buffer memory 14 Decoder unit 15 Video processing unit 16 Display unit 17 Audio processing Unit 18 speaker 20 communication unit 21 input unit 22 hard disk storage unit 23 bus S content distribution system

Claims (8)

Information that includes a plurality of node devices that can communicate with each other via a network, and a plurality of shared information shared by the plurality of node devices is distributed and stored by an overlay network composed of the plurality of node devices. In the node device included in the communication system,
Volatile first storage means for storing the link information, which is link information used when communicating with the node device via the overlay network and includes node information indicating a plurality of specific node devices;
When the node device itself including the first storage unit participates in the information communication system, the link information stored in the first storage unit is stored in the nonvolatile second storage unit at a predetermined timing. First storage control means for causing
When the node device itself comprising the first storage means leaves the information communication system and then joins the information communication system again, the node information included in the link information stored in the second storage means A link information acquisition unit that acquires the link information to be stored in the first storage unit using any one of the nodes that reads the node information included in the link information stored in the second storage unit Based on the read node information, participation notification means for transmitting a participation notification notifying the node device related to the node information that the node apparatus participates in the information communication system, and the participation notification Participation notification transmission permission / inhibition determining means for determining whether or not the transmission of the participation notification is successful. If the transmission is determined to be successful, from the participation notification transmission destination of the node device, and the link information obtaining means for obtaining the link information to which the destination node device is stored,
Second storage control means for storing the link information acquired by the link information acquisition means in the first storage means;
A node device comprising: The node device according to claim 1,
The first storage means stores, as the link information, table information including a plurality of the node information used for communication with other node devices included in the information communication system via the overlay network,
The first storage control means stores the table information stored in the first storage means in the second storage means at the predetermined timing,
The node information reading means reads the node information included in the table information stored in the second storage means,
The previous participation notification means transmits the participation notification to the node device related to the node information based on the node information read from the table information by the node information reading means,
If the link information acquisition unit determines that the transmission of the participation notification is successful by the participation notification transmission enable / disable determination unit, the link destination node device of the transmission destination from the node device of the transmission destination of the participation notification Obtain the stored table information,
The node device characterized in that the second storage control means stores the table information acquired by the link information acquisition means in the first storage means. In the node device according to claim 1 or 2,
The first storage unit includes location information indicating a location of the node device that stores the shared information to be managed by the node device itself, and the shared information among the plurality of node devices. Storing shared information related information related to a plurality of shared information,
The first storage control means stores the location information and the shared information related information stored in the first storage means in the second storage means at the predetermined timing,
The second storage control means relates to the location information and the shared information stored in the second storage means when the node device itself withdraws from the information communication system and rejoins the information communication system. A node device which stores information in the first storage means again. In the node apparatus as described in any one of Claims 1 thru | or 3,
The predetermined timing is the link information stored in the first storage means each time a predetermined time elapses or due to the exchange of information with the other node devices included in the information communication system, A node device characterized in that it is at least one of each time the location information or the shared information related information is updated or when the power of the node device itself is turned off. In the node apparatus as described in any one of Claims 1 thru | or 4,
In the information communication system, each node device is connected by an overlay network,
The node information included in the link information includes a node ID for uniquely identifying the node device related to the node information in the identification information space of the overlay network, and destination information of the node device. A node device characterized by the above. In the node apparatus as described in any one of Claims 1 thru | or 5,
The first storage means is a RAM provided in the node device,
The node device, wherein the second storage means is a hard disk, a flash memory, an EEPROM, or a semiconductor memory with a backup power source. Information that includes a plurality of node devices that can communicate with each other via a network, and a plurality of shared information shared by the plurality of node devices is distributed and stored by an overlay network composed of the plurality of node devices. In the computer of the node device in the communication system,
Step of storing link information used when communicating with the node device via the overlay network, the link information including node information indicating a plurality of specific node devices in a volatile first storage unit When,
When the node device itself including the first storage unit participates in the information communication system, the link information stored in the first storage unit is stored in the nonvolatile second storage unit at a predetermined timing. A first storage control step,
When the node device itself comprising the first storage means leaves the information communication system and then joins the information communication system again, the node information included in the link information stored in the second storage means A link information acquisition step for acquiring the link information to be stored in the first storage means using any one of the steps, wherein the node information included in the link information stored in the second storage means is read out When,
A participation notification step of transmitting a participation notification notifying that the node device according to the node information participates in the information communication system based on the read node information;
A participation notification transmission permission determination step for determining whether or not the transmission of the participation notification is successful;
Have
The link information stored in the transmission destination node device from the node device that is the transmission destination of the participation notification when it is determined in the participation notification transmission availability determination step that the transmission of the participation notification is successful. Acquiring the link information;
A second storage control step of storing the acquired link information in the first storage means;
A storage control program for executing Information that includes a plurality of node devices that can communicate with each other via a network, and a plurality of shared information shared by the plurality of node devices is distributed and stored by an overlay network composed of the plurality of node devices. In an information storage method in a communication system,
The link information used when communicating with the node device via the overlay network, the link information including node information indicating a plurality of specific node devices stored in a volatile first storage unit When,
When the node device itself including the first storage unit participates in the information communication system, the link information stored in the first storage unit is stored in the nonvolatile second storage unit at a predetermined timing. A first memory control step,
The node information included in the link information stored in the second storage means when the node device comprising the first storage means itself withdraws from the information communication system and then joins the information communication system again. A link information acquisition step of acquiring the link information to be stored in the first storage means, and reading any of the node information included in the link information stored in the second storage means And a step of transmitting a participation notification notifying that the node device related to the node information participates in the information communication system based on the read node information, and the transmission of the participation notification was successful. A participation notification transmission availability determination step for determining whether or not the participation notification transmission availability determination step determines that the participation notification has been successfully transmitted. Was the case, from the participation notification transmission destination of the node device, and the link information obtaining step of obtaining the link information to which the destination node device is stored,
A second storage control step of storing the acquired link information in the first storage means;
An information storage method characterized by comprising:

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