JP2012078903A - Node device, program for node device and information processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distribution system in which, when newly determining a storage destination of contents, the storage destination can be determined so as to promptly and smoothly distribute the contents.SOLUTION: In a plurality of routers Rm or the like of a distribution system S where contents are stored while being distributed to the routers Rm or the like by an overlay network comprised of the routers Rm or the like, a use state of a communication line for connecting a router Rm or the like to a network NW is acquired and it is determined whether or not that communication line is being used equal to or more than a first threshold value. When the communication line is being used equal to or more than the first threshold value, a router Rm or the like to newly store contents therein is determined from among the other routers Rm or the like. A session is set up with the determined router Rm or the like, and a use state of a communication line to which that router Rm or the like is being connected is acquired. On the basis of the acquired use state, a router Rm or the like for which a use state of a communication line is less than or equal to a second threshold value is determined as a new storage destination of the contents.

Description

  The present application belongs to a technical field of a node device, a program for the node device, and an information processing method. In the following description, the “node device” is appropriately referred to as a “node”.

  2. Description of the Related Art In recent years, techniques for distributing content such as movies and moving images via a peer-to-peer (P2P) type network have been developed. In the following description, a P2P type network is simply referred to as a “P2P network”. In a P2P network, content is distributed and stored in each node existing in the P2P network. Each node transmits and receives each other while sharing content between the nodes. The P2P network is disclosed in detail, for example, in Patent Document 1 below. According to such a P2P network, even when the data amount of content to be distributed increases, it is possible to avoid a distribution failure caused by an increased load on the server device included in the conventional client-server system. In the following description, “server device” is appropriately referred to as “server”.

  On the other hand, in a P2P network, when distribution requests concentrate on a node that stores specific content, distribution from that node is delayed. In order to eliminate such a delay, a copy of the content is stored in another node. Content is also distributed from the node where the copy is stored. As a method for creating such a replica, for example, there is a technique disclosed in Patent Document 2 below. In an example of the technique disclosed in Patent Document 2, a round trip delay time with another node is detected, and another node that stores a copy is searched based on the detected round trip delay time.

JP 2006-197400 A JP 2005-227842 A

  When a copy of content is stored in a node in the P2P network, it is necessary to start distribution using the copy quickly and smoothly. However, in the P2P network described in Patent Document 2, when searching for the storage destination of the replica, the usage state of the search target node is not considered. For this reason, for example, when the line connected to the node is congested, the distribution cannot be started quickly and smoothly even if the copy is stored.

  Therefore, the present invention has been made in view of the above problems, and an example of the purpose is to determine that a content storage destination is quickly and smoothly distributed when a storage destination of the content is newly determined. The present invention provides a node device, an information communication method, and a node device program executed in the node device.

  In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that content is distributed to the plurality of node devices by an overlay network including a plurality of node devices that can communicate with each other via a network. In the node device of the communication system to be stored, a storage unit such as a storage unit that stores the content, and a use state of a communication line to which the node device including the storage unit is connected to connect to the network The communication line is used above a predetermined first threshold based on a first acquisition unit such as a control unit that acquires first state information indicating the first state information and the first state information acquired by the first acquisition unit. A determination unit such as a control unit for determining whether the communication line is used above the first threshold, and the overlay network A first determination unit such as a control unit that determines a node device that is a candidate for a node device that stores the content from among the participating node devices, and a connection to the node device determined by the first determination unit A second controller such as a control unit that acquires second state information indicating a use state of the communication line to which the connected node device is connected from a connection unit such as a control unit and the node device connected by the connection unit; Based on the second state information acquired by the acquisition unit and the second acquisition unit, among the node devices connected by the connection unit, the use state of the communication line connected to the node device is: And a second determination unit such as a control unit that determines the node device having a predetermined second threshold value or less as a storage destination of the content.

  In order to solve the above problem, the invention according to claim 7 is characterized in that content is distributed to the plurality of node devices by an overlay network including a plurality of node devices that can communicate with each other via a network. In an information processing method executed in a stored communication system, a first acquisition step of acquiring first state information indicating a use state of a communication line to which the node device is connected in order to connect to the network; A determination step of determining whether the communication line is used above a predetermined first threshold based on the acquired first state information; and when the communication line is used above the first threshold, Among node devices participating in the overlay network, nodes that are candidates for node devices for storing the content A first determination step of determining a device; a connection step of connecting to the determined node device; and a second indicating a use state of the communication line to which the connected node device is connected from the connected node device A second acquisition step of acquiring state information; and, based on the acquired second state information, a use state of the communication line connected to the node device among the connected node devices is a predetermined first A second determination step of determining the node device having a threshold value of 2 or less as a storage destination of the content.

  According to the invention described in claim 1 or claim 7, based on the second state information acquired from another node device, the node device whose use state of the communication line connected thereto is equal to or less than the second threshold value Determine the content storage destination. By storing the content in the node device whose communication line usage state is equal to or less than the second threshold value, the stored content can be quickly and smoothly distributed.

  The invention according to claim 2, wherein the first determination unit randomly determines a node device that is a candidate for a node device that stores the content from among the plurality of node devices that participate in the overlay network. Configured.

  According to the second aspect of the present invention, the storage destination candidates are determined at random from among the node devices in which the content to be stored is not stored. Therefore, the number of messages for the determination can be reduced while searching for storage destination candidates at random with a simple configuration.

  In the invention according to claim 3, in the communication system, the storage and distribution of the content is performed by sending and receiving a message between the plurality of node devices via the overlay network. When the communication line connected to the node device is used more than the first threshold, further comprising search means such as a control unit for searching the overlay network for the node device that has stored the content, The first determination unit is configured to determine a node device that is a candidate for a node device that stores the content from among node devices other than the node device searched by the search unit.

  According to the third aspect of the present invention, a node device that is a candidate for a storage destination node device is determined by excluding a node device that has already stored content to be stored. Therefore, the number of messages for searching and storing can be reduced as compared with the case of searching for a storage destination candidate regardless of whether or not it has been stored.

  5. The invention according to claim 4, wherein said free capacity information is managed by capacity determining means such as a control unit for determining the free capacity of said storage means, and free capacity information indicating the free capacity determined by said capacity determining means. A transmission unit such as a communication unit that transmits to the node device of the overlay network, and a third unit such as a control unit that acquires the free capacity information about the other node device from the node device that manages the free capacity information. Acquisition means, wherein the first determination means sequentially stores the contents based on the free capacity information acquired by the third acquisition means in order from the node device having the largest free capacity indicated by the free capacity information. The node device is configured to be determined as a node device to be stored.

  According to the fourth aspect of the present invention, the storage destination candidates are determined in order from the node device having the largest free space in the storage means for the node device in which the content to be stored is not stored. Therefore, contents can be stored by effectively using the storage means of each node device.

  6. The invention according to claim 5, wherein in the determination of the storage destination of the content by the second determination unit, the use state of the communication line connected to each of the node devices connected by the connection unit is the second threshold value. If higher, after waiting for a predetermined threshold time, the connection means reconnects to the node device determined by the first determination means, and the second acquisition means reconnects by the connection means The second state information is re-acquired from the node device thus obtained, and the second determination means is a node that is a storage destination of the content based on the second state information re-acquired by the second acquisition means Configured to determine a device;

  According to the fifth aspect of the present invention, when the use state of the communication line connected to each connected node device is higher than the second threshold value, the reconnection process and the determination process are performed after waiting for the threshold time. The possibility that the storage destination of the content can be searched is increased, and unnecessary message exchange can be prevented as compared with the case where the reconnection is performed immediately.

  In order to solve the above problem, the invention according to claim 6 is configured such that content is distributed to the plurality of node devices by an overlay network including a plurality of node devices that can communicate with each other via a network. The node device of the communication system to be stored, the node device including the storage means for connecting to the network to a computer included in the node device including storage means such as a storage unit for storing the content A step of acquiring first state information indicating a use state of a communication line to which a communication line is connected, and whether the communication line is used above a predetermined first threshold based on the acquired first state information. Determining and joining the overlay network when the communication line is used above the first threshold Determining a node device that is a candidate node device for storing the content from among the node devices, connecting to the determined node device, and connecting the connected node device to the connected node device A step of acquiring second state information indicating a use state of the communication line to which the device is connected, and the node device connected to the node device among the connected node devices based on the acquired second state information. And determining the node device whose usage state of the communication line is equal to or less than a predetermined second threshold as the storage destination of the content.

  According to the sixth aspect of the present invention, based on the second state information acquired from another node device, the node device whose use state of the communication line connected to it is equal to or less than the second threshold is stored in the content storage destination. Let the computer function to determine. By storing the content in the node device whose communication line usage state is equal to or less than the second threshold value, the stored content can be quickly and smoothly distributed.

  According to the present invention, by storing content in a node device whose communication line usage state is equal to or less than the second threshold, it is possible to quickly and smoothly distribute the stored content.

It is a figure showing the outline composition of the distribution system of an embodiment. It is a block diagram which shows schematic structure, such as a router of embodiment. FIG. 2A is a block diagram illustrating a schematic configuration of a router according to an embodiment. FIG. 2B is a block diagram illustrating a schematic configuration of nodes other than the user terminal and the router according to the embodiment. It is a flowchart which shows the process in the router of embodiment. (A) is a flowchart which shows the whole process in a router. (B) is a flowchart showing content request acceptance processing in the router. It is a flowchart which shows the process in the router etc. of embodiment. (A) is a flowchart which shows the storage destination search process in a router. (B) is a flowchart showing a copy storage process in a node. It is a flowchart which shows the process in the router etc. of a deformation | transformation form. (A) is a flowchart which shows the replication preservation | save process in a node. (B) is a flowchart showing storage destination search processing in the router.

  Next, modes for carrying out the present invention will be described based on the drawings. Embodiments and modifications described below are embodiments when the present invention is applied to a distribution system that distributes content such as moving images from nodes in a P2P network to user terminals outside the P2P network.

(I) Embodiment First, an embodiment of the present invention will be described with reference to FIGS. 1 is a diagram illustrating a schematic configuration of the distribution system according to the embodiment, and FIG. 2 is a block diagram illustrating a schematic configuration of a router and the like according to the embodiment. 3 and 4 are flowcharts showing processing in the router and the like of the embodiment.

(A) General Configuration of Distribution System First, the general configuration of the distribution system according to the embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a schematic configuration of a distribution system S according to the embodiment. The delivery system S is a CDN (Contents Delivery Network system) to which DNS (Domain Name System) is applied. As shown in FIG. 1, in the distribution system S, a plurality of base networks NLm (m is a natural number; the same applies hereinafter) are connected to a network NW. These network NW and each base network NLm are real-world communication networks.

  The network NW is a network for interconnecting the base networks NLm. This network NW is, for example, a WAN (Wide Area Network). The network NW is constructed by, for example, IX (Internet eXchange), ISP (Internet Service Provider), DSL (Digital Subscriber Line) line provider equipment, FTTH (Fiber To The Home) line provider equipment, communication lines, and the like. . The network NW may be a network dedicated to the distribution system S.

  Each base network NLm is a network constructed in the site of the base Pm. The base Pm is a base where an organization such as a company, a school, a hospital, a public organization, or a management body of a karaoke box operates. The base network NLm is constructed by, for example, a LAN (Local Area Network) or the like. A plurality of user terminals Tm-n (n is a natural number; hereinafter the same) are connected to each base network NLm. The user terminal Tm-n is, for example, a personal computer. In FIG. 1, illustration of some base networks NLm and illustration of user terminals Tm-n connected to the base networks NLm are omitted.

  A web server SW, an organization DNS server SO, and a P2P DNS server SP are also connected to the network NW. The web server SW is a server for distributing, for example, various contents of a website operated by the organization having the base Pm described above to the user terminal Tm-n. In FIG. 1, only one web server SW is shown, but the web server SW is installed for each organization, for example. Each web server SW is individually assigned a domain name.

  The organization DNS server SO is a DNS server that resolves a domain name. The organization DNS server SO accepts an IP (Internet Protocol) address inquiry from the user terminal Tm-n. In FIG. 1, only one organization DNS server SO is shown, but the organization DNS server SO may be installed for each organization, for example. The DNS server SP for P2P is also a DNS server that resolves domain names. The P2P DNS server SP accepts an IP address inquiry from the organization DNS server SO. A unique domain name is assigned to the P2P DNS server SP.

  A router Rm is steadily connected to each base network NLm. This router Rm interconnects the base network NLm and the network NW. The router Rm is, for example, a firewall having a router function, a broadband router, or the like. The router Rm corresponds to an example of a “node device” in the present invention.

(B) P2P network outline configuration In the distribution system S, a P2P network PW, which is a P2P network for distributing content, is constructed. The P2P network PW corresponds to an example of a “communication system” in the present invention. As shown in FIG. 1, the P2P network PW is a logical overlay network constructed on the network NW. This P2P network PW includes a plurality of routers Rm constituting the distribution system S, a P2P DNS server SP, and other devices Nr (r is a natural number; the same applies hereinafter) other than the router Rm and the P2P DNS server SP. It is a network formed by participation. The other device Nr is specifically a personal computer, an STB (Set Top Box), a television receiver, or the like. The router Rm, the P2P DNS server SP, and other devices Nr that participate in the P2P network PW are hereinafter referred to as “nodes”. Here, “participation” in the P2P network PW means that various messages can be transmitted / received to / from other nodes based on a routing table using DHT (Distributed Hash Table) disclosed in Patent Document 1, for example. It means becoming a state. This routing table is hereinafter referred to as “DHT routing table”.

  The P2P network PW is realized by a specific algorithm, for example, an algorithm using DHT. Each node connected to the P2P network PW is assigned a node ID, which is unique identification information consisting of a predetermined number of digits. The P2P network PW shown in FIG. 1 shows the ID space of the node ID as a ring. The position of each node shown in the ring-shaped ID space in FIG. 1 corresponds to each node ID.

  Each node holds a DHT routing table. The DHT routing table defines various message transfer destinations on the P2P network PW. Specifically, in the DHT routing table, a plurality of pieces of node information including node IDs, IP addresses, and port numbers of nodes that are moderately separated in the ID space are registered. The DHT routing using the DHT routing table is well known in the above-mentioned Patent Document 1 and the like, and thus detailed description is omitted.

  In the P2P network PW, a node that stores content in a distributed manner is hereinafter referred to as a “holding node”. Each content is assigned a content ID, which is identification information unique to each content. The content stored and saved in the holding node is content distributed to the user terminal Tm-n. The user terminal Tm-n acquires content from the P2P network PW instead of the web server SW by using the organization DNS server SO.

  The location of content distributed and stored in a plurality of holding nodes is stored as index information by the node managing the location of the content. A node that manages the location of content is hereinafter referred to as a “root node”. The index information includes a set of the node information of the holding node and the content ID of the content stored therein. Since the root node is known from the above-mentioned Patent Document 1 and the like, detailed description thereof is omitted.

  When a certain node tries to acquire content, the node transmits a search message. A node from which content is to be acquired is hereinafter referred to as a “user node”. The search message includes the content ID of the content to be acquired, the IP address of the user node, and the like. The search message is a message for searching for holding nodes. The user node transmits a search message to other nodes according to the DHT routing table stored in the user node. As a result, the search message finally arrives at the root node by DHT routing using the content ID as a key.

  The root node that has received the search message transmits index information corresponding to the content ID included therein to the user node. The user node transmits a content request message including the content ID to one of the holding nodes based on the IP address and port number included in the received index information. The holding node uploads content corresponding to the content ID included in the received content request message to the user node. Thus, the user node can download the content.

  The user node transmits a publish message when content is acquired and stored from the holding node. The publish message is a message for informing the root node that the content has been saved. The publish message includes the content ID of the content and the node information of the holding node that stores the content. Similar to the search message, the publish message arrives at the root node by DHT routing using the content ID as a key. The root node stores index information including a set of node information and content ID included in the received publish message in the index cache area. Thus, the user node becomes a new holding node that holds the content.

(C) Content Distribution to User Terminal Next , content distribution to the user terminal Tm-n in the distribution system S will be described with reference to FIG. The user terminal Tm-n acquires a URL (Uniform Resource Locator) of the content to be downloaded based on an operation by the user. The user terminal Tm-n that acquired the URL makes an inquiry about the IP address. For example, as shown in FIG. 1, it is assumed that the user terminal T1-1 in the site P1 acquires the domain name of the web server SW from the URL. The user terminal T1-1 transmits a name resolution request including the acquired domain name to the organization DNS server SO (see FIG. 1 (1)). The organization DNS server SO holds a database in which domain names and IP addresses are registered in association with each other. Thereby, the organization DNS server SO acquires the domain name of the P2P DNS server SP from the database. Further, the organization DNS server SO acquires an IP address corresponding to the domain name of the P2P DNS server SP from the database. Then, the organization DNS server SO transfers the received name resolution request to the P2P DNS server SP based on the acquired IP address (see FIG. 1B).

  When receiving the name resolution request transmitted from the user terminal T1-1, the P2P DNS server SP searches the holding node corresponding to the domain name included in the name resolution request using the overlay network (FIG. 1 ( 3)). Thereby, the DNS server SP for P2P acquires the index information from the router Rm as the root node (see FIG. 1 (4)).

  The P2P DNS server SP selects one of the holding nodes based on the index information stored in the index cache area. Then, the DNS server SP for P2P returns the IP address of the selected holding node to the organization DNS server SO (see FIG. 1 (5)). In the case illustrated in FIG. 1, it is assumed that the IP address returned to the organization DNS server SO is the IP address of the router R2.

    The organization DNS server SO that has received the IP address of the router R2 transfers this IP address to the user terminal T1-1 (see FIG. 1 (6)). Then, the user terminal T1-1 transmits a content request message to the router R2 based on the received IP address (see FIG. 1 (7)). The router R2 uploads content corresponding to the received content request message to the user terminal T1-1 (see FIG. 1 (8)). Through the series of processes described above, the user terminal T1-1 that has transmitted the name resolution request can acquire the content corresponding to the name resolution request from the P2P network PW.

(D) Configuration and Function of Router and the like Next, the configuration and function of the router Rm and the like of the embodiment will be described with reference to FIG. FIG. 2A is a block diagram showing a schematic configuration of the router Rm. FIG. 2B is a block diagram showing a schematic configuration of the user terminal Tm-n and another device Nr.

(D-1) Configuration of Router As shown in FIG. 2A, the router Rm of the embodiment includes a storage unit 11, a control unit 12, and a communication unit 13. The storage unit 11, the control unit 12, and the communication unit 13 are interconnected via a bus 14 so that data can be exchanged. This control unit 12 is an example of “first acquisition means”, an example of “determination means”, an example of “first determination means”, an example of “connection means”, an example of “second acquisition means”, “second It corresponds to an example of “determination means”, an example of “search means”, an example of “capacity detection means”, and an example of “third acquisition means”, respectively. The storage unit 11 corresponds to an example of “storage means”. Further, the communication unit 13 corresponds to an example of “transmission means”.

  In this configuration, the control unit 12 includes a CPU (Central Processing Unit) having an arithmetic function, a working RAM (Random Access Memory), a ROM (Read Only Memory) storing various data and a P2P program, and the like. The storage unit 11 includes an HD (hard disk) or the like for storing and storing various data and various programs. Further, the communication unit 13 controls communication of information with the other router Rm, the P2P DNS server SP, the other device Nr, the user terminal Tm-n, and the like through the network NW and the base network NLm.

  Specifically, the storage unit 11 stores the IP address and port number of the P2P domain server SP. The storage unit 11 stores a DHT routing table, index information, the current number of connected terminals, and the like. The storage unit 11 stores the downloaded content in association with the content ID. A content cache area in which content is stored is allocated to the storage unit 11. Further, the storage unit 11 stores a P2P program for transmitting / receiving various messages to / from other nodes based on the DHT routing table. The P2P program may be downloaded from a predetermined server, for example. The P2P program may be recorded on a recording medium such as a DVD (Digital Versatile Disc), for example, and read from the recording medium via a drive (not shown). The control unit 12 performs overall control of each unit of the router Rm of the embodiment by reading and executing a program including the P2P program stored in the storage unit 11 or the like by the CPU.

(D-2) Configuration of User Terminal Tm-n and Other Device Nr The user terminal Tm-n and the other device Nr in the embodiment basically have the same configuration. The user terminal Tm-n and the other device Nr are hereinafter referred to as “user terminal Tm-n etc.”.

  As shown in FIG. 2B, the user terminal Tm-n includes a control unit 21, a storage unit 22, a buffer memory 23, a communication unit 24, a decoder unit 25, an input unit 26, a video processing unit 27, and a display unit 28. The audio processing unit 29 and the speaker 30 are provided. The control unit 21, the storage unit 22, the buffer memory 23, the communication unit 24, the decoder unit 25, and the input unit 26 are interconnected via a bus 31 so that data can be exchanged.

  In this configuration, the control unit 21 includes a CPU having an arithmetic function, a RAM that stores various data, and a ROM that stores programs including various data and P2P programs. The storage unit 22 includes an HD or the like for storing and storing various data and various programs. The buffer memory 23 temporarily stores content acquired via the communication unit 24. The decoder unit 25 decodes encoded video data, audio data, and the like included in the content. The video processing unit 27 performs a predetermined drawing process on the decoded video data or the like and outputs it as a video signal. The display unit 28 including a liquid crystal display displays an image corresponding to the video signal output from the image processing unit 27. The audio processing unit 29 D / A converts the decoded audio data into an analog audio signal, amplifies it, and outputs it to the speaker 30. The speaker 30 outputs the audio signal output from the sound processing unit 29 as a sound wave. The input unit 26 receives an instruction from the user and outputs an instruction signal corresponding to the instruction to the control unit 21. The input unit 26 is realized by, for example, a keyboard, a mouse, an operation panel, or the like. The communication unit 24 included in the user terminal Tm-n performs communication control of information between the router Rm and other user terminals Tm-n via the base network NLm. The communication unit 24 included in another device Nr communicates information with the router Rm, the P2P DNS server SP, and other devices Nr other than the other device Nr including the communication unit 24 via the network NW. Take control.

  The storage unit 22 stores a program including the P2P program of the embodiment, a file as content, a DHT routing table, and the like. In the above configuration, the control unit 21 performs overall control of the entire user terminal Tm-n and the like when the CPU reads and executes the P2P program stored in the storage unit 22 or the ROM. In addition, the control unit 21 of the other device Nr can execute at least the user node, the root node, the holding node, or the like described above by executing the P2P program after the other device Nr participates in the P2P network PW. It functions as one of the nodes.

(E) Processing of Distribution System Next, processing of the distribution system S in the embodiment will be described using FIG. 3 and FIG. 3 and 4 are flowcharts showing processing in the control unit 12 of the router Rm. The process shown in FIG. 3A is started when, for example, the P2P program of the router Rm is activated. First, the control unit 12 checks whether or not a power switch (not shown) of the router Rm is turned off after completion of the predetermined initialization process (step S1). When the power switch is turned off in the confirmation in step S1 (step S1; NO), the control unit 12 ends the process as the router Rm. On the other hand, when the power switch is not turned off in the confirmation in step S1 (step S1; NO), the control unit 12 next confirms whether or not there is a content request from the user terminal Tm-n (step S2). Specifically, the control unit 12 confirms Step S2 by confirming whether or not a content request message from the user terminal Tm-n has been received (see FIG. 1 (7)). If there is a content request from any of the user terminals Tm-n as a result of confirmation in step S2 (step S2; YES), the control unit 12 executes a content request reception process described later (step S3). Thereafter, the control unit 12 proceeds to the confirmation in step S1. On the other hand, when there is no content request in the confirmation in step S2 (step S2; NO), the control unit 12 next confirms whether or not there is an instruction to store and copy the content from another router Rm (step S4). Specifically, the control unit 12 confirms Step S4 by confirming whether or not a copy storage instruction message has been received from another router Rm. The copy save instruction message is a message instructing to save a copy of the content indicated by the content request message. If there is a copy storage instruction from another router Rm as a result of confirmation in step S4 (step S4; YES), the control unit 12 executes a later-described copy storage process corresponding to the copy storage instruction (step S5). Thereafter, the control unit 12 proceeds to the confirmation in step S1. In addition, also when there is no copy preservation | save instruction | indication in the confirmation of step S4 (step S4; NO), the control part 12 transfers to the confirmation of said step S1.

  Next, the content request acceptance process in step S3 will be described in more detail with reference to FIG. When there is a content request in the confirmation in step S2 (step S2; YES), the control unit 12 first transmits information indicating the current use status of the upload bandwidth in the router Rm including the control unit 12 to the communication unit. 13 (step S30). Here, the “upload bandwidth usage state” is specifically the total number of user terminals Tm-n that are currently connected to the router Rm and are receiving content uploads. In the base network NLm connected to the router Rm, the communication unit 13 uses the total value of the current transmission speed of each content addressed to each user terminal Tm-n as information indicating the use state of the upload band at that time. You can also get it from Next, the control unit 12 confirms whether or not the use state of the upload band acquired by the process of step S30 is equal to or more than a preset first threshold value (step S31). That is, the control unit 12 confirms whether or not the usage state of the communication line is equal to or more than the first threshold based on the information indicating the usage state of the upload band. This first threshold value is a threshold value set in advance corresponding to whether or not content can be immediately uploaded from the router Rm to the user terminal Tm-n that has transmitted the content request message. Specifically, the first threshold is set in advance as the maximum number of user terminals Tm-n that are simultaneously connected to the router Rm and can receive content uploads. When the total value of the transmission speeds of the contents addressed to each user terminal Tm-n is set to the upload band usage state, the first threshold value is set in advance as the upper limit value of the total value. In the confirmation in step S31, when the use state of the upload band is not equal to or greater than the first threshold (step S31; NO), the control unit 12 starts uploading the content to the user terminal Tm-n that has transmitted the content request message. (Step S32; see FIG. 1 (8)). Thereafter, the control unit 12 proceeds to the process of step S1 of FIG.

  In the confirmation in step S31, when the use state of the upload band is equal to or greater than the first threshold (step S31; YES), the upload of the content from the router Rm including the control unit 12 may be started immediately at that time. Can not. Therefore, the control unit 12 searches for the holding node of the content requested by the content request message in the P2P network PW in which the router Rm in which the control unit 12 is included participates (step S33). Specifically, the control unit 12 generates a search message including the content ID of the content, and searches for a holding node of the content using the P2P network PW. Thereafter, the control unit 12 confirms whether or not one or more holding nodes can be searched by the process of step S33 (step S34). When the holding node can be searched in the confirmation in step S34 (step S34; YES), the control unit 12 connects to any one of the searched holding nodes via the communication unit 13 (step S35). . The connection process of step S35 is a process of establishing a so-called session with the searched holding node. Next, the control unit 12 inquires the connected holding node about the current use status of the upload band in the holding node (step S36). As this inquiry, the control unit 12 transmits an inquiry message of the use state of the upload band to the connected holding node via the network NW. Here, when acquiring the current usage status of the upload bandwidth in each holding node, every time the upload bandwidth usage status of each node changes, a method of transmitting a message indicating the usage status after the change from each node Is also possible. However, in this method, a state in which the P2P network PW is occupied by the message may occur. In this case, for example, there may be a problem that content distribution is delayed. Therefore, in the embodiment, when the use state of the current upload band in the router Rm including the control unit 12 is equal to or more than the first threshold, a session is established and connected to the searched holding node (step S35). Then, the control unit 12 inquires of the holding node that has established the session about the current use status of the upload bandwidth (step S36). As a result, the number of messages exchanged in the P2P network PW can be reduced as compared to the case where a message indicating the changed usage state is transmitted in real time each time the usage state of the upload bandwidth of each node changes. . The use status of the upload band inquired by the process of step S36 is specifically the total number of other routers Rm and other devices Nr that are currently connected to the connected holding node and are receiving content uploads. It is. It should be noted that the total value of the current transmission speeds of the contents addressed to other routers Rm and the like in the communication line of the network NW connected to the holding node may be used as the upload band usage status at that time. Next, the control unit 12 determines whether or not the use state is equal to or less than a second threshold value set in advance based on the use state of the upload band transmitted from the holding node in response to the inquiry in step S36. Confirm (step S37). This second threshold value is a threshold value set in advance corresponding to whether or not content can be uploaded immediately from the holding node. Specifically, the second threshold is set in advance as the maximum number of other routers Rm or other devices Nr that are simultaneously connected to the holding node and can receive content uploads. When the total value of the transmission rates of content from the holding node is set to the upload band usage state, the second threshold value is set in advance as the upper limit value of the total value. The second threshold value may be the same value as the first threshold value used for the confirmation in step S31 or may be a different value. When the use state of the upload band of the holding node is equal to or smaller than the second threshold value in the confirmation in step S37 (step S37; YES), the control unit 12 transfers the content request message received in the confirmation in step S2 to the holding node. (Step S38). Thereby, the content is uploaded from the holding node. Thereafter, the control unit 12 proceeds to the confirmation in step S1 of FIG.

  On the other hand, if the use state of the upload bandwidth is not less than or equal to the second threshold value in the confirmation in step 37 (step S37; NO), the uploading of the content from the holding node cannot be started immediately at that time. Therefore, the control unit 12 confirms whether or not there is a holding node other than the currently connected holding node among the holding nodes searched in the process of step S34 (step S39). In the confirmation in step S39, when there is another holding node other than the currently connected holding node (step S39; YES), the control unit 12 executes the processing of steps S35 to S38 for the holding node. If there is no other holding node other than the currently connected holding node in the confirmation in step S39 (step S39; NO), the control unit 12 next executes a storage destination search process (step S40). The process of step S40 is a process of searching a storage destination of a new copy of the content indicated by the content request message received in the confirmation of step S2 from another router Rm or another device Nr in the P2P network PW. The process of step S40 will be described in detail later with reference to FIG. Thereafter, the control unit 12 confirms whether or not a new copy storage destination has been found in the process of step S40 (step S41). If a new storage location for the copy can be found in the confirmation in step S41 (step S41; YES), the control unit 12 proceeds to the process in step S38 and transfers the received content request message to the storage location. As a result, the content is uploaded from another router Rm or another device Nr that is the storage destination. When a new copy storage destination cannot be found in the confirmation in step S41 (step S41; NO), the control unit 12 waits for a preset threshold time (step S42). Thereafter, the control unit 12 executes the processes from step S30 to S42 again.

  In addition, if the holding node of the requested content cannot be searched in the confirmation in step S34 (step S34; NO), the control unit 12 proceeds to the storage location search process in step S40 and searches for a storage location for a new copy. To do.

  Next, the storage destination search process in step S40 will be described in more detail with reference to FIG. This storage destination search process is started when there is no other holding node in the confirmation in step S39 shown in FIG. 3B, or when the holding node cannot be searched in the confirmation in step S34 shown in FIG. . As shown in FIG. 4A, in the process of step S40, the control unit 12 determines a node for newly storing content from among nodes participating in the P2P network PW. That is, the control unit 12 randomly determines other nodes in the P2P network PW (step S400). In the process of step S400, the control unit 12 excludes the holding node searched by the process of step S33 shown in FIG. 3B in the P2P network PW and removes one from other routers Rm or other devices Nr. Is determined at random. Specifically, the control unit 12 randomly generates one node ID other than the node ID indicating the holding node searched by the process of step S33. The control unit 12 generates a search message including the generated node ID, and transmits the search message to another node of the closest P2P network PW in the DHT routing table. Thereafter, this search message is transferred between the nodes by DHT routing. As a result, the search message arrives at the node with the node ID included therein or the node with the node ID closest to the node ID. The node to which the search message has arrived returns its own node ID and the like to the router Rm, whereby the node is randomly determined in step S400. Moreover, the control part 12 which started the process of step S400 starts the time measurement by the timer which is not shown in figure from the start timing. Next, the control unit 12 connects to the determined node via the communication unit 13 (step S401). The connection process in step S401 is a process of establishing a so-called session with the determined node. Next, the control unit 12 inquires of the connected node about the current use status of the upload bandwidth in the node (step S402). This inquiry process is a process for transmitting an inquiry message of the use state in the same manner as in step S36 shown in FIG. In the inquiry from step S400 to step S402, the control unit 12 establishes and connects a session to a randomly determined node, and transmits an inquiry message. Therefore, as in the case of the inquiry in step S36, the number of messages exchanged within the P2P network PW can be reduced. In addition, the upload band usage status inquired by the processing of step S401 is specifically the total number of other routers Rm and other devices Nr that are currently connected to the determined node and are receiving content uploads. . Note that the total value of the current transmission speeds of the contents addressed to other routers Rm and the like on the communication line of the network NW connected to the node may be the use state of the upload band at that time. Next, the control unit 12 confirms whether or not the usage state is equal to or less than the second threshold based on the information indicating the usage state of the upload bandwidth transmitted from the node in response to the inquiry in the process of step S401. (Step S403). In the confirmation in step S403, when the use state of the determined upload bandwidth of the node is equal to or smaller than the second threshold (step S403; YES), the control unit 12 determines the node as a new storage destination of the content copy. . Then, the control unit 12 instructs the node to copy and store the content indicated by the content request message (step S404). Specifically, the control unit 12 transmits a copy storage instruction message via the network NW to the nodes connected by the process of step S401. Note that the copy storage process (step S5 in FIG. 3A) in a node that is another router Rm or the like that has received this copy storage instruction message will be described later with reference to FIG. 4B. Next, the control unit 12 requests the user terminal Tm-n that has downloaded the content from the router Rm including the control unit 12 to upload the content (step S405). The upload request in step S405 is a process of transmitting an upload request message for the node that transmitted the copy storage instruction message in step S404 to the user terminal Tm-n via the base network NLm to which the router Rm is connected. The upload request message includes a content ID for identifying the content to be uploaded and an IP address indicating the node that transmitted the copy save instruction message. The control unit 21 of the user terminal Tm-n that has received the upload request message uploads the content with the content ID included in the received upload request message. Specifically, the control unit 21 uploads the content indicated by the content ID included in the upload request message to the node indicated by the IP address included in the upload request message via the network NW. After the process of step S405, the control unit 12 of the router Rm proceeds to the process of step S41 shown in FIG. In the confirmation in step S41 following step S405, the control unit 12 determines that a new copy storage destination has been found (see step S41; FIG. 3A; YES), and performs subsequent processing.

  On the other hand, in the confirmation in step S403, if the use state of the upload bandwidth of the node is not less than or equal to the second threshold (step S403; NO), the control unit 12 confirms that a predetermined time set in advance by the timer has elapsed. Whether or not it is shown is confirmed (step S406). When the confirmation in step S406 indicates that the predetermined time has not elapsed (step S406; NO), the control unit 12 proceeds to the process of step S400 and makes a random determination of other nodes. On the other hand, when the confirmation in step S406 indicates that a certain time has elapsed (step S406; YES), the control unit 12 proceeds to the process of step S41 shown in FIG. Note that, in the confirmation in step S41 following the confirmation in step S406; YES, the control unit 12 determines that a new copy storage destination has not been found (see step S41; NO in FIG. 3A), and performs subsequent processing. .

  Next, the copy storage process (step S5 in FIG. 3 (a)) in a node that is another router Rm or the like that has received the copy storage instruction message in step S404 will be described in more detail with reference to FIG. 4 (b). To do. The process shown in FIG. 4B is the same when the other router Rm receives the copy storage instruction message and when the other device Nr receives it. Therefore, in the following description, a case where another router Rm receives a copy save instruction message will be described. As shown in FIG. 4B, the control unit 12 of the other router Rm that has received the copy storage instruction message uploads the content from the user terminal Tm-n corresponding to the process in step S405 of FIG. Wait (step S50). Moreover, the control part 12 which started the process of step S50 starts the time measurement by the timer which is not shown in figure from the start timing. Next, the control unit 12 confirms whether or not the content upload started during the standby process in step S50 is completed (step S51). When the upload is completed in the confirmation in step S51 (step S51; YES), the control unit 12 next acquires meta information corresponding to the content that has been uploaded from the router Rm that has transmitted the copy save instruction message (step S51; YES). Step S52). This meta information includes division instruction information for dividing the content that has been uploaded and storing and saving it as a chunk. This division instruction information includes, for example, a data amount corresponding to one chunk, information indicating a delimiter of each chunk, and the like. Next, the control unit 12 creates a chunk by dividing the content that has been uploaded based on the division instruction information included in the acquired meta information, and stores the chunk in the storage unit 11 (step S53). Thereafter, the control unit 12 proceeds to the process of step S1 of FIG.

  On the other hand, when the upload is not completed in the confirmation in step S51 (step S51; NO), the control unit 12 indicates whether or not the time measured by the timer during the time measurement indicates that a predetermined time has elapsed. Is confirmed (step S54). When the confirmation in step S54 indicates that the predetermined time has not elapsed (step S54; NO), the control unit 12 proceeds to the process of step S50 and waits for completion of the upload. On the other hand, when the confirmation in step S54 indicates that a certain time has elapsed (step S54; YES), the control unit 12 downloads the content to be copied from the router Rm that has transmitted the copy save instruction message. (Step S55). The process of step S55 is a process of downloading the content from the router Rm that has transmitted the copy storage instruction message because the upload from the user terminal Tm-n is not performed. Thereafter, the control unit 12 proceeds to the process of step S1 of FIG.

  As described above, according to the processing of the distribution system S of the embodiment, as illustrated in steps S403 and S404 in FIG. 4A, the use state of the upload bandwidth acquired from other nodes in the P2P network PW is A node that is equal to or smaller than the second threshold is determined as a storage destination for a new copy of the content. By newly storing a copy of the content in a node whose upload band usage state is equal to or less than the second threshold, the stored content can be quickly and smoothly distributed to the user terminal Tm-n.

  Further, as illustrated in step S400 of FIG. 4A, the storage destination is randomly determined from the nodes in which the content to be stored newly is not stored. Therefore, it is possible to reduce the number of messages in the P2P network PW for selection while searching for a new storage destination of a replica at random with a simple configuration.

  Further, as illustrated in step S400 of FIG. 4A, a node where a content to be newly saved has been saved is excluded and a new saving destination node is determined. Therefore, the number of messages in the P2P network PW for the search and storage can be reduced as compared with the case of searching for a new storage destination candidate regardless of whether or not it has been stored.

  Furthermore, as exemplified in step S42 of FIG. 3B, when a new storage destination is not searched, the connection process and the determination process are performed again after waiting for a predetermined time. The possibility of searching for a new storage destination is increased, and unnecessary message transmission / reception within the P2P network PW can be prevented as compared with the case where reconnection is immediately performed.

  In addition, as illustrated in steps S50 to S53 in FIG. 4B, content to be stored in a new copy is acquired from the user terminal Tm-n outside the distribution system S, so that data in the distribution system S is exchanged. Can be reduced.

  In the copy storage process (see FIG. 5A) of the embodiment, the content to store the copy is acquired from the user terminal Tm-n or the router Rm that has transmitted the copy storage instruction message. The content may be acquired from a server that manages the content. Further, in the P2P network PW, the duplicate may be obtained from another node by the same method as the conventional method.

(II) Modified Embodiment Next, a modified embodiment of the present invention will be described with reference to FIG. FIG. 5 is a flowchart showing processing in a modified router or the like. In FIG. 5, the same steps as those in FIG. 4 are denoted by the same step numbers, and detailed description thereof is omitted.

  In the distribution system S of the embodiment, when selecting a node where a copy of the content is to be newly stored, the storage destination is randomly determined from the nodes in which the content is not stored (see step S400 in FIG. 4A). ). On the other hand, in the modified distribution system S, a new storage destination is determined in consideration of the free capacity of the content cache area in the storage unit 11 or 22 of the node. Note that the hardware configuration of a router or the like included in the modified distribution system is basically the same as the hardware configuration of the router Rm or the like included in the distribution system S of the embodiment. Therefore, in the following description, the processing of the modified distribution system will be described with reference to the member numbers in the router Rm and the like included in the distribution system S of the embodiment. Further, the processing of the distribution system S according to the modified embodiment is different from the distribution system S according to the embodiment only in copy storage processing (see FIG. 5A) and storage destination search processing (see FIG. 5B). Therefore, only these different processes will be described below. Furthermore, the copy storage process shown in FIG. 5A is the same when the other router Rm receives the copy storage instruction message (see step S404 in FIG. 4A) and when the other device Nr receives it. . Therefore, in the flowchart shown in FIG. 5A, a case where another router Rm receives a copy storage instruction message will be described.

  As shown in FIG. 5A, in the copy storage process of the modified form (see step S5 in FIG. 3A), the control unit 12 firstly performs step S50 of the copy storage process of the embodiment (see FIG. 4B). To S55 are executed. Next, when the content chunk (step S53) or the downloaded content is stored and stored in the storage unit 11 (step S55), the control unit 12 performs a free space information disclosure process (step S56). This free capacity information disclosure process is a process of transmitting a publish message including free capacity information indicating the free capacity of the content cache area in the storage unit 11 after storage to a node in the P2P network PW. In the free capacity information disclosure process of the modified form, the free capacity of the content cache area in each node in the P2P network PW is divided into a plurality of ranges in advance. The control unit 12 stores, for example, a value of a free capacity range divided into four. For example, the control unit 12 stores a free capacity of 30 gigabytes or more as a first range and a free capacity of 20 gigabytes or more and less than 30 gigabytes as a second range. The control unit 12 stores a free space of 10 gigabytes or more and less than 20 gigabytes as a third range and a free space of less than 10 gigabytes as a fourth range. When the content is stored, the control unit 12 detects the free capacity of the content cache area in the storage unit 11 after the storage. Thereafter, the control unit 12 hashes the character string indicating the range of the free space including the detected free space with the same hash function as that used when generating the content ID, for example. For example, if the detected free capacity is 40 gigabytes, the control unit 12 hashes a character string of “30 gigabytes or more” or “first range” indicating the range to which the free capacity belongs using a hash function. The control unit 12 transmits a publish message including the hashed character string to the root node of the node ID corresponding to the character string. This root node is a free capacity management root node for managing a node having a free capacity content cache area belonging to the free capacity range. The publish message arrives at the free capacity management route node as the destination by DHT routing. As a result, the other router Rm and the other device Nr have the free capacity range of the storage unit 11 of the router Rm managed by the free capacity management route node or the free capacity of the storage unit 22 of the other device Nr. This range can be referred to. Thereafter, the control unit 12 proceeds to the process of step S1 of FIG.

  Next, a storage search process according to a modified embodiment will be described with reference to FIG. In the storage search process according to the modified embodiment, the control unit 12 first sets the free space range to the highest first range (step S410). Next, the control unit 12 searches the P2P network PW for a node having free capacity in the content cache area corresponding to the free capacity range set at that time (step S411). Specifically, the control unit 12 transmits a search message including a character string indicating the hashed free space range to the root node for free space management corresponding to the free space range. Then, the control unit 12 acquires a reply including the IP address of the holding node corresponding to the search message from the root node for free capacity management. As a result, the control unit 12 searches for a node having a free capacity in the corresponding content cache area. Next, the control unit 12 checks whether or not one or a plurality of corresponding nodes can be searched by the process of step S411 (step S412). When the corresponding node can be searched in the confirmation in step S412, the control unit 12 randomly determines one of the searched nodes (step S413). In the process of step S413, the control unit 12 excludes the holding node searched by the process of step S33 shown in FIG. 3B in the P2P network PW, and applies from the other router Rm or another apparatus Nr. Determine the node to be used. Moreover, the control part 12 which started the process of step S413 starts the time measurement by the timer which is not shown in figure from the start timing. Thereafter, the control unit 12 executes processing similar to the processing from step S401 to S406 of the storage destination search processing (see FIG. 4A) of the embodiment. After the process of step S405 or when it is shown in the confirmation of step S406 that a certain time has elapsed (step S406; YES), the control unit 12 proceeds to the process of step S41 shown in FIG. . On the other hand, when the confirmation in step S406 indicates that the predetermined time has not elapsed (step S406; NO), the control unit 12 determines that the currently connected node among the nodes searched in the process of step S412. It is confirmed whether there is another node other than (step S417). If it is confirmed in step S417 that there is another node other than the currently connected node (step S417; YES), the control unit 12 performs the processes of steps S413 and S401 to S406 on the node. If there is no other node other than the currently connected node in the confirmation in step S417 (step S417; NO), the control unit 12 proceeds to the process in step S414 described later.

  On the other hand, if the corresponding node cannot be searched in the confirmation in step S412, (step S412; NO), the control unit 12 then lowers the free space range by one step and resets it to the second range (step S414). Next, the control unit 12 confirms whether or not the free space range reset in the process of step S414 is the lowest fourth range among the plurality of free space ranges set (step S415). In the confirmation in step S415, when the reset free space range is not the fourth range (step S415; NO), the control unit 12 performs the above steps S411 to S413 and the reset free space range. The process after S401 is performed. On the other hand, in the confirmation in step S415, if the reset free space range is the fourth range (step S415; YES), the control unit 12 randomly determines one other node in the P2P network PW. (Step S416). In the process of step S416, when the reset free space range becomes the fourth range, it is no longer meaningful to perform a search based on the free space range, so other nodes are randomly assigned in the P2P network PW. This is a process for determining one. The process of step S416 is a random determination process similar to the process of step S400 of FIG. Thereafter, the control unit 12 performs the processes of steps S401 to S406 and S416 on the node selected by the process of step S415.

  According to the processing of the distribution system S of the modified embodiment described above, in addition to the operational effects of the processing of the distribution system S of the embodiment, the control unit 12 sequentially starts from the node with the largest free capacity in the content cache area of the storage unit 11. Then, the storage destination of the content to be newly stored is determined. Therefore, content can be newly stored by effectively using the content cache area of each node. Further, when determining a new storage destination node, the control unit 12 divides the free capacity of the content cache area into a plurality of ranges and uses it as a reference for the determination. Therefore, compared with the case where the free capacity value itself is used as a reference for the sequential search, it is possible to reduce the exchange of messages in the P2P network PW for the determination.

  In the above embodiment and modification, the node device of the present invention is applied to a router. However, the node device of the present invention may be applied to a network device having a function of relaying information, such as a proxy server, a load balancer, and a web accelerator. The node device of the present invention may be applied to a server such as a cache server or an edge server.

  In the above embodiment, the P2P network using DHT is applied to the overlay network. However, the present invention is not limited to this. For example, a system using another P2P network or an overlay network may be applied. An example of a P2P network that does not use DHT is a hybrid P2P network.

11, 22 Storage unit 12, 21 Control unit 13, 24 Communication unit Rm Router SP P2P DNS server SO Organization DNS server NLm Base network NW network PW P2P network S Distribution system

Claims (7)

In the node device of the communication system in which content is distributed and stored in the plurality of node devices by an overlay network configured by a plurality of node devices capable of communicating with each other via a network,
Storage means for storing the content;
First acquisition means for acquiring first state information indicating a use state of a communication line to which the node device including the storage means is connected to connect to the network;
Determination means for determining whether the communication line is used above a predetermined first threshold based on the first state information acquired by the first acquisition means;
First determining means for determining, from among the node devices participating in the overlay network, a node device that is a candidate node device for storing the content, when the communication line is used above the first threshold; ,
Connection means for connecting to the node device determined by the first determination means;
Second acquisition means for acquiring, from the node device connected by the connection means, second state information indicating a use state of the communication line to which the connected node device is connected;
Based on the second state information acquired by the second acquisition means, a use state of the communication line connected to the node device among the node devices connected by the connection means is a predetermined second Second determining means for determining the node device that is equal to or less than a threshold as a storage destination of the content;
A node device comprising:   The first determining unit randomly determines a node device that is a candidate node device for storing the content from among the plurality of node devices participating in the overlay network. Node equipment. In the communication system, the content is stored and distributed by exchanging messages via the overlay network between the plurality of node devices.
When the communication line connected to the node device comprising the storage means is used for the first threshold value or more, it further comprises search means for searching the overlay network for a node device that has stored the content,
The first determination unit determines a node device that is a candidate for a node device that stores the content from among node devices other than the node device searched by the search unit. The node device according to claim 2. Capacity determining means for determining the free capacity of the storage means;
Transmitting means for transmitting free capacity information indicating the free capacity determined by the capacity determining means to the node device of the overlay network that manages the free capacity information;
Third acquisition means for acquiring the free capacity information about the other node apparatus from a node apparatus that manages the free capacity information;
With
The first determination unit includes node device candidates for storing the content in order from the node device with the larger free space indicated by the free space information based on the free space information acquired by the third acquisition unit. The node device according to claim 1, wherein the node device is determined as a node device. In the determination of the storage destination of the content by the second determination unit, when the use state of the communication line connected to each of the node devices connected by the connection unit is higher than the second threshold, only a predetermined threshold time After waiting, the connection means reconnects to the node device determined by the first determination means,
The second acquisition means re-acquires the second state information from the node device reconnected by the connection means,
The second determination unit determines a node device that is a storage destination of the content based on the second state information reacquired by the second acquisition unit. The node device according to any one of the above. The node device of a communication system in which content is distributed and stored in the plurality of node devices by an overlay network composed of a plurality of node devices that can communicate with each other via a network, and stores the content In a computer included in a node device having a storage means,
Obtaining first state information indicating a use state of a communication line to which the node device including the storage unit is connected to connect to the network;
Determining whether the communication line is used above a predetermined first threshold based on the acquired first state information;
Determining a node device as a candidate node device for storing the content from among the node devices participating in the overlay network when the communication line is used at the first threshold value or more;
Connecting to the determined node device;
Obtaining second state information indicating a use state of the communication line to which the connected node device is connected from the connected node device;
Based on the acquired second state information, among the connected node devices, the node device whose use state of the communication line connected to the node device is equal to or less than a predetermined second threshold value, Determining the content storage location;
A program for a node device, characterized in that In an information processing method executed in a communication system in which content is distributed and stored in the plurality of node devices by an overlay network configured by a plurality of node devices capable of communicating with each other via a network,
A first acquisition step of acquiring first state information indicating a use state of a communication line to which the node device is connected in order to connect to the network;
A determination step of determining whether the communication line is used above a predetermined first threshold based on the acquired first state information;
A first determining step of determining, from among the node devices participating in the overlay network, a node device that is a candidate node device for storing the content, when the communication line is used above the first threshold; ,
A connection step of connecting to the determined node device;
A second acquisition step of acquiring second state information indicating a use state of the communication line to which the connected node device is connected, from the connected node device;
Based on the acquired second state information, among the connected node devices, the node device whose use state of the communication line connected to the node device is equal to or less than a predetermined second threshold value, A second determination step for determining a content storage destination;
An information processing method comprising:

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