JP2011151701A - Server system, client device, program, and information storage medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a server system, client device, program, information storage medium and the like in which stable communication is enabled in a P2P relay system. <P>SOLUTION: A server system includes: a receiver for receiving information from each of nodes on a distribution network; a transmitter for transmitting information to each of the nodes; and a node management section for performing node management processing over the distribution network. Contents are distributed from a content distribution source node on the distribution network to a content distribution destination node in accordance with a P2P relay system. When a communication velocity at a novel participant node requesting content distribution is determined as meeting a communication velocity condition of requested contents, the node management section retrieves a connection destination candidate node of the novel participant node from among participant nodes on the distribution network. The transmitter transmits, to the novel participant node, notification information mediating the retrieved connection destination candidate node as a distribution source node of the requested contents. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a server system, a client device, a program, an information storage medium, and the like.

  In recent years, services that distribute stream data of contents such as video and audio via a distribution network such as the Internet are increasing. In such a content distribution service, it is desired to further increase the bandwidth of the distribution network, but the cost of the distributor managing the server is heavy. For example, high-quality video content compatible with full high-definition is provided to viewers. It was difficult to provide it.

  In order to solve such a problem, as disclosed in Patent Document 1, for example, there is a system that distributes content by a so-called P2P (Peer to Peer) relay system (bucket relay system, cash and toss system). Proposed. In the technique of this patent document 1, in order to perform transmission / reception of stream data between nodes of a distribution network, each node exchanges topology information indicating a connection relationship between an upstream node and a downstream node, and the upstream node and the downstream node Relaying stream data to

  In such a P2P relay system, each node is incorporated into a distribution network and acquires data. In this case, it is possible to acquire data itself, but the communication speed of the line used by each node participating in the distribution network varies. Therefore, there is a problem that it is difficult to perform communication at a stable speed and it is difficult to provide a service that depends on the speed.

JP2003-169089

  According to some aspects of the present invention, it is possible to provide a server system, a client device, a program, an information storage medium, and the like that enable stable communication in a P2P relay system.

  One aspect of the present invention includes a receiving unit that receives information from each node of a distribution network, a transmission unit that transmits information to each node of the distribution network, and node management that performs node management processing of the distribution network. Content is distributed from a content distribution source node of the distribution network to a content distribution destination node by a P2P (Peer to Peer) relay method, and the node management unit requests content distribution. When it is determined that the communication speed at the newly participating node satisfies the communication speed condition of the requested content, the connection candidate node of the new participating node is searched from among the participating nodes of the distribution network. The transmitting unit relates to a server system for transmitting notification information for mediating the searched connection destination candidate node as a distribution source node of the requested content to the new participating node. To.

  According to an aspect of the present invention, content data is distributed from a distribution source node to a distribution destination node by a P2P relay method. When it is determined that the communication speed of the new participation node satisfies the communication speed condition of the requested content, the server system searches for a connection destination candidate node of the new participation node and arranges the searched connection destination candidate node. Send notification information to the new participating node. In this way, the communication speed of the nodes participating in the distribution network can be maintained at a communication speed level equal to or higher than a certain level, and stable communication can be realized in the P2P relay system.

  In one aspect of the present invention, a plurality of contents having different image quality are prepared as the requested contents, and the node management unit selects an image quality according to the communication speed at the new participating node, and the plurality of contents The connection destination candidate node may be searched from among the participating nodes of the distribution network that distributes the content of the selected image quality.

  In this way, it is possible to select the image quality corresponding to the communication speed of the new participating node, and to provide the content by allowing the new participating node to participate in the distribution network corresponding to the content of that image quality.

  Also, in one aspect of the present invention, the node management unit determines that the communication speed at the newly participating node is that the requested content stream playback is not possible but the download playback is possible. The connection destination candidate node may be searched from among the participating nodes of the distribution network that downloads and reproduces the requested content.

  In this way, when the communication speed of the new participating node is not capable of stream playback of the requested content, the content is provided to the new participating node by download playback when the download playback is possible. become able to.

  In the aspect of the invention, the node management unit may determine that the new participation node has first to Kth (K is an integer of 2 or more) communication speed levels based on the communication speed of the new participation node. It is determined to which of the groups it belongs, and it is determined that the new participating node belongs to the i-th communication speed level group (1 ≦ i ≦ K) of the first to K-th communication speed level groups. In this case, the connection destination candidate node may be searched from among the participating nodes of the distribution network corresponding to the i-th communication speed level group.

  According to another aspect of the present invention, a receiving unit that receives information from each node of the distribution network, a transmission unit that transmits information to each node of the distribution network, and node management processing of the distribution network are performed. A node management unit, wherein content is distributed from a content distribution source node of the distribution network to a content distribution destination node by a P2P (Peer to Peer) relay method, and the node management unit distributes the content Based on the requested communication speed at the new participating node, it is determined which of the first to Kth communication speed level groups (K is an integer of 2 or more). When it is determined that the newly participating node belongs to the i-th communication speed level group (1 ≦ i ≦ K) of the first to K-th communication speed level groups, the i-th communication speed Rebellion Search for a connection destination candidate node of the new participation node from among the participation nodes of the distribution network corresponding to the group, and the transmission unit arranges the searched connection destination candidate node as the distribution source node of the requested content. This relates to a server system that transmits notification information to the new participating node.

  According to another aspect of the present invention, it is determined that the new participation node belongs to the i-th communication speed level group among the first to K-th communication speed level groups based on the communication speed at the new participation node. Then, the connection destination candidate node of the new participation node is searched from the participation nodes of the distribution network of the i-th communication speed level group. Then, notification information that mediates the searched connection destination candidate node is transmitted to the new participation node. In this way, it becomes possible to distribute the content by allowing the newly participating node to participate in the distribution network of the communication speed level group corresponding to the communication speed, and to realize stable communication in the P2P relay system. It becomes like this.

  In another aspect of the present invention, the first communication speed level group among the first to Kth communication speed level groups is based on stream reproduction of content of a first image quality level and the first image quality level. The second communication speed level group of the first to Kth communication speed level groups is the first image quality level. The group may be capable of downloading and reproducing the content of the content and stream reproduction of the content of the second image quality level.

  In this way, for example, the first image quality level content and the second image quality level content can be provided by stream reproduction to the first communication speed level group node having a high communication speed. On the other hand, for the nodes of the second communication speed level group whose communication speed is slower than that of the first communication speed level group, contents of the first image quality level are provided by download reproduction and contents of the second image quality level are provided. Can be provided by stream playback.

  In another aspect of the present invention, the node management unit may be configured such that a node that belongs to the first communication speed level group and plays a stream of content of the first image quality level is connected with a decrease in communication speed. When the affiliation is changed to the second communication speed level group, the content of the first image quality level that was being reproduced in the stream reproduction of the first communication speed level group is the second communication. The speed level group may be downloaded and played back.

  In this way, even when the communication speed is reduced during the stream reproduction of the content of the first image quality level, the node affiliation is changed to the second communication speed level group and the reproduction is in progress. It becomes possible to provide the content of the first image quality level by download reproduction.

  In another aspect of the present invention, the third communication speed level group among the first to Kth communication speed level groups may be a group capable of downloading and reproducing content of the second image quality level. Good.

  In this way, it is possible to provide the content of the second image quality level by download reproduction to the nodes of the third communication speed level group having a low communication speed.

  In another aspect of the present invention, the node management unit may be configured such that a node that belongs to the second communication speed level group and plays a stream of content of the second image quality level is caused by a decrease in communication speed. When the affiliation is changed to the third communication speed level group, the content of the second image quality level that was being reproduced in the stream reproduction of the second communication speed level group is the third communication. The speed level group may be downloaded and played back.

  In this way, even when the communication speed drops during the stream reproduction of the content of the second image quality level, the node affiliation is changed to the third communication speed level group and the reproduction is in progress. Content of the second image quality level can be provided by download reproduction.

  In another aspect of the present invention, the receiving unit receives line quality measurement result information from each node of the distribution network, and the node management unit receives the received measurement result information. Based on the above, the communication speed at each of the nodes may be determined.

  In this way, the line quality is measured at each node, and the server system can determine the communication speed of each node based on the measurement result information.

  In another aspect of the present invention, the node management unit searches for a cooperative node capable of cooperating with the measurement of the line quality, and the transmission unit informs the searched cooperative node to each of the nodes. To each of the nodes, and the receiving unit is configured to measure the channel quality when the nodes communicate with the cooperating node and transmit the channel quality measurement result information. Then, the transmitted measurement result information may be received, and the node management unit may determine a communication speed at each node of the distribution network based on the received measurement result information.

  In this way, each node can measure the line quality by connecting to the cooperative node arranged from the server system and measuring the line quality, thereby improving the measurement accuracy of the line quality. For example, the cooperation node is a node that has received the content data but has been turned on and can be connected to the distribution network.

  In another aspect of the present invention, the node management unit distributes the node as a cooperating node so that each node communicates with both a distribution source node and a distribution destination node and the line quality is measured. The first cooperative node that is the original node and the second cooperative node that is the distribution destination node are searched, and the transmission unit arranges both the searched first and second cooperative nodes to the respective nodes. Notification information to be transmitted may be transmitted to each of the nodes.

  In this way, it is possible to measure the line quality by reproducing the same communication environment as at the time of content distribution.

  In another aspect of the present invention, the receiving unit receives, from the new participation node, reception start timing specification information of the requested content at the new participation node, and the node management unit receives the received reception start timing. The expected reception start timing of the requested content at the new participating node is obtained based on the specific information, and the connection destination candidate node is searched from the participating nodes of the distribution network based on the obtained expected reception start timing. Then, the transmission unit may transmit notification information for mediating the searched connection destination candidate node as a distribution source node of the requested content to the new participation node.

  In this way, it is possible to arrange an appropriate connection destination candidate node according to the assumed reception start timing with respect to the new participation node, and it is possible to maintain the distribution network in an appropriate state.

  According to another aspect of the present invention, the storage unit stores a plurality of assumed reception start timings corresponding to a plurality of participating nodes of the distribution network, and the node management unit stores the plurality of nodes stored in the storage unit. The assumed reception start timing is searched for an assumed reception start timing that is earlier than the assumed reception start timing of the new participating node and that is closest to the assumed reception start timing of the new participating node. The participating node corresponding to the assumed reception start timing may be determined as the connection destination candidate node.

  In this way, a plurality of assumed reception start timings corresponding to a plurality of participating nodes are stored in the storage unit of the server system, and the connection destination candidate node is made a new participating node by managing these assumed reception start timings. It becomes possible to realize the node management processing to arrange.

  Another aspect of the present invention includes a receiving unit that receives information from a server system, a transmitting unit that transmits information to the server system, and a communication management unit, from a content distribution source node of the distribution network. When content is distributed to a content distribution destination node by a peer-to-peer (P2P) relay method, and the receiver searches for a cooperative node capable of cooperating with the measurement of the line quality, the cooperation is found. The notification information for mediating the node is received from the server system, the communication management unit is connected to the cooperative node mediated by the notification information, measures the line quality, and the transmission unit includes: The present invention relates to a client apparatus that transmits the line quality measurement result information to the server system. The present invention also relates to a program that causes a computer to function as each of the above-described units, or a computer-readable information storage medium that stores the program.

  According to another aspect of the present invention, the client device receives notification information for mediating a cooperation node for line quality measurement from the server system. Then, the communication quality is measured by connecting to the cooperated node, and the measurement result information is transmitted to the server system. In this way, the client apparatus can measure the line quality by communicating with the cooperative node arranged from the server system and measure the line quality, thereby improving the measurement accuracy of the line quality.

  In another aspect of the present invention, the communication management unit measures the channel quality to obtain a communication speed in a state where the cooperation node is in communication connection, and the transmission unit obtains the obtained communication The line quality measurement result information including the speed may be transmitted to the server system.

  In this way, on the server system side, for example, it is possible to determine whether or not the communication speed of the client device satisfies the communication speed condition and perform various processes.

  In another aspect of the present invention, the communication management unit measures the channel quality to obtain a communication speed in a state where the cooperation node is in communication connection, and the obtained communication speed is the requested content. The transmission unit distributes the requested content when it is determined that the calculated communication speed satisfies the communication speed condition of the requested content. Notification information for requesting may be transmitted to the server system.

  In this way, on the client device side, it is determined whether or not the communication speed of the client device satisfies the communication speed condition, and if the communication speed condition is satisfied, the server system is requested to distribute the requested content. It becomes possible.

  In another aspect of the present invention, the receiving unit mediates, as the cooperation node, a first cooperation node that is a content distribution source node and a second cooperation node that is a content distribution destination node. From the server system, the communication management unit measures the line quality and obtains the communication speed in a state where both the first and second cooperative nodes are connected to communicate with each other. Good.

  In this way, it is possible to measure the line quality by reproducing the same communication environment as at the time of content distribution.

The structural example of the server system of this embodiment. 2A and 2B show other examples of the distribution network topology. 2 is a configuration example of a client device according to the present embodiment. FIGS. 4A and 4B are explanatory diagrams of problems when a new participating node participates in a P2P relay distribution network. 5A and 5B are explanatory diagrams of the node connection management method of the present embodiment. The flowchart for demonstrating the process of this embodiment. The data flow figure for demonstrating the process of this embodiment. 8A and 8B are explanatory diagrams of a node connection management method based on the communication speed level. 9A and 9B are explanatory diagrams of a communication speed level group. 10A and 10B are explanatory diagrams of a node connection management method based on a communication speed level. FIG. 11A and FIG. 11B are explanatory diagrams of a switching method from high-quality stream reproduction to high-quality download reproduction. FIG. 12A and FIG. 12B are explanatory diagrams of a switching method from standard image quality stream reproduction to standard image quality download reproduction. FIGS. 13A to 13E are explanatory diagrams of a method for performing a line quality measurement process using a cooperative node. 6 is a flowchart for explaining a line quality measurement process according to the embodiment. The data flow figure for demonstrating the measurement process of the line quality of this embodiment. FIGS. 16A and 16B are explanatory diagrams of problems when a new participating node participates in a P2P relay distribution network. FIGS. 17A to 17C are explanatory diagrams of a node connection management method according to the assumed data holding amount. 18A and 18B are explanatory diagrams of a node connection management method using an assumed reception start time (assumed reception start timing). 19A and 19B are explanatory diagrams of a node connection management method when the reception start time specifying information (reception start timing specifying information) is a data holding amount. Explanatory drawing of a node connection management method in case reception start time specific information (reception start timing specific information) is assumption reception elapsed time. Explanatory drawing of the node connection management method using assumption data retention amount. The flowchart for demonstrating the process of this embodiment. The data flow figure for demonstrating the process of this embodiment.

  Hereinafter, this embodiment will be described. In addition, this embodiment demonstrated below does not unduly limit the content of this invention described in the claim. In addition, all the configurations described in the present embodiment are not necessarily essential configuration requirements of the present invention.

1. Server System FIG. 1 shows a configuration example of a server system realized by this embodiment. This server system is connected to a distribution network 10 having a plurality of nodes N1 to N10 serving as clients.

  The distribution network 10 (network, communication line) is, for example, a communication path using the Internet. In addition to a dedicated line (dedicated cable) for direct connection, a LAN using Ethernet (registered trademark), a telephone communication network or a cable network. Or other communication networks. The communication method may be wired / wireless. The distribution network 10 includes a plurality of nodes N1 to N10 that are connected to communicate with each other, and each node is configured by a client device having a function of connecting to the Internet or the like.

  The distribution network 10 of FIG. 1 includes a basic node sequence KNL that is a sequence of basic nodes N1, N3, N6, and N10 connected in series (connected) from a content distribution source (server system, content distribution unit). That is, these basic nodes N1, N3, N6, and N10 are connected in series in a line from the server system in the downward direction (first direction).

  Further, the distribution network 10 includes a series of branch nodes BNL1, BNL2, and BNL3 connected in series (connected) to each basic node (starting node) of the basic node string KNL. Specifically, the branch nodes N2, N4, and N7 constituting the branch node row BNL1 are connected in series to the backbone node N1. That is, the branch nodes N2, N4, and N7 are connected in series in a line without branching from the trunk node N1 in the horizontal direction (second direction orthogonal to the first direction). The same applies to the branch nodes N5 and N8 constituting the branch node string BNL2 and the branch node N9 constituting the branch node string BNL3.

  Note that the numbers of the nodes N1 to N10 represent content distribution order numbers (node addition order). Specifically, the starting node N1 (higher node) receives content from a server (server system, content distribution unit) that is the content distribution source. The received content is relayed and transmitted (retransmitted) to the content distribution destination nodes N2 and N3 (lower nodes). Upon receiving the content from the content distribution source node N1, the node N2 (higher node) relays the content and transmits it to the content distribution destination node N4 (lower node). Similarly, when the node N3 (higher node) receives the content from the content distribution source node N1, the node N3 relays the content and transmits it to the content distribution destination nodes N5 and N6 (lower node).

  The distribution network to which this embodiment is applied is not limited to the topology of FIG. For example, FIG. 2A shows an example of an ordered distribution network as a distribution network to which the present embodiment is applied.

  In FIG. 2A, nodes N1, N2, and N3 are connected in series in the distribution order (node addition order) to the server that is the content distribution source. That is, in FIG. 2A, when receiving the content from the server, the node N1 relays the received content and transmits it to the node N2. When receiving the content from the node N1, the node N2 relays the received content and transmits it to the node N3. In the sequential distribution network of FIG. 2A, when the client that is the node N2 is excluded from the distribution network due to the end of viewing or line disconnection, N1 and N3 that are the nodes before and after the connection are connected, Maintain distribution network.

  FIG. 2B shows an example of a binary tree distribution network as a distribution network to which the present embodiment is applied. According to the distribution network having the binary tree structure in FIG. 2B, since the nodes are branched, the time lag of the distribution time at the terminal node can be shortened compared to the distribution network in FIG. There is. However, when a specific node is excluded from the distribution network due to the end of viewing or line disconnection, there is also a disadvantage that the load of the process of reconfiguring the topology of the node that does not break the distribution order is large.

  In this regard, according to the topology of the distribution network of FIG. 1, the time lag of the distribution start at the end nodes N7, N8, N9, and N10 can be reduced compared to FIG. 2A when compared with the same number of nodes. . In addition, there is an advantage that the processing load of topology reconstruction for maintaining the distribution order can be reduced as compared with FIG.

  The server system of the present embodiment includes a content distribution unit 110, a reception unit 120, a transmission unit 130, a node management unit 140, and a storage unit 170. Note that the server system is not limited to the configuration shown in FIG. 1, and various modifications such as omitting some of these components (for example, the content distribution unit) and adding other components are possible.

  The storage unit 170 stores various information necessary for content distribution, server management, and node management, and can be realized by a relational database (database server) such as MySQL. The storage unit 170 stores, for example, distribution management information, server management information, node management information, user information, and the like. Specifically, the storage unit 170 includes a content storage unit 172 and a management information storage unit 174. The content storage unit 172 stores content such as video and audio to be distributed. The management information storage unit 174 stores node management information (node information, distribution network information, etc.) for node management processing.

  The content distribution unit 110 (content server, content distribution source) is a video (movie), audio (music), still image, text, game program, or game data stored in the content storage unit 172 (content database) of the storage unit 170. The content distribution process (stream distribution) is performed. Specifically, the content that is distributed from the content distribution source node of the distribution network 10 to the content distribution destination node by the P2P (Peer to Peer) relay method is used as the basic node starting from the basic node sequence KNL. Send to N1. Then, the core node N1 that has received the content from the content distribution unit 110 distributes (stream transfers) the content as a content distribution source to the content distribution destination nodes N2 and N3 by a relay method. In this case, if necessary, the content distribution unit 110 performs content encryption processing using a common key encryption method such as DES or AES, or a public key encryption method. Each node that is a client performs a decryption process on the encrypted content. Each node performs content decryption processing and playback processing, and also performs relay processing for redistributing content to lower-order nodes at the subsequent stage.

  The receiving unit 120 performs information reception processing. For example, a process of receiving information from each node (or server) of the distribution network 10 is performed. The transmission unit 130 performs information transmission processing. For example, a process of transmitting information to each node of the distribution network 10 is performed. The receiving unit 120 and the transmitting unit 130 perform various processes necessary for communication according to a protocol such as the Internet.

  The node management unit 140 (node management server, mediation server) performs node management processing of the distribution network 10. For example, a process of adding a new participating node to the distribution network 10, a process of removing a node that has been viewed or disconnected from the distribution network 10, a process of rearranging the connection of node rows, or a process of responding to various requests from the node And processing for issuing various requests to the node. For example, when a new participating node is added to the distribution network 10, the node management unit 140 selects the node with the oldest addition order (distribution order) to the distribution network 10 among the nodes that can be connected to the content distribution destination node. It is also possible to search and connect a new participating node to the searched node. In addition, the node management unit 140 excludes the branch node from the distribution network 10 due to the end of viewing or disconnection, and when there is a lower branch node as the content distribution destination node of the excluded branch node, Is connected to the lower branch node. On the other hand, when the main node is excluded from the distribution network 10 due to the end of viewing or disconnection, and there is a branch node as the content distribution destination node of the excluded main node, the branch node is moved up to become a new main node. Set.

  In this embodiment, content data is transferred from a content distribution source node (for example, N1) of the distribution network 10 to a content distribution destination node (for example, N2 or N3) by a P2P (Peer to Peer) relay method. For example, it is delivered in order from the top data. For example, the server system sequentially distributes the content data to the node N1 from the top data of the content to the final data in order. Then, the node N1 sequentially distributes the content data to the distribution destination nodes N2 and N3 from the top data of the content received from the server system to the final data in order. Then, the node N2 sequentially distributes the content data to the distribution destination node N4 from the top data of the content received from the node N1 to the final data in order.

  When the node management unit 140 determines that the communication speed at the new participating node that has requested the content distribution satisfies the communication speed condition of the requested content, the node management unit 140 selects a new one from among the participating nodes of the distribution network 10. Search for connection destination candidate nodes of participating nodes. For example, when the communication speed at the newly participating node has reached the minimum guaranteed communication speed of the distribution network 10 that distributes the requested content, it is determined that the communication speed condition is satisfied, and the distribution node of the requested content Search for candidate connection destination nodes. Here, whether or not the communication speed of the newly participating node has reached the minimum guaranteed communication speed may be determined on the server system side or on each node side (client device side). Further, the new participation node may be a node that already holds part of the data of the requested content by the previous content distribution, or a node that does not yet hold the data of the requested content Good.

  Then, the transmission unit 130 transmits notification information for mediating the searched connection destination candidate node as a distribution node of the requested content to the new participation node. That is, notification information including information for specifying the searched connection destination candidate node is transmitted to the new participation node.

  In the present embodiment, a plurality of contents with different image quality (contents with different compression rates and compression methods) are prepared as requested contents. For example, high-quality content in MPEG (content of a first image quality level in a broad sense), standard image quality content (content in a second image quality level lower than the first image quality level in a broad sense), and low-quality content (in a broad sense) Is prepared with a third image quality level content that is lower in image quality than the second image quality bell. Alternatively, stream reproduction content and download reproduction content at each image quality of high image quality, standard image quality, and low image quality (first to third image quality levels in a broad sense) are prepared.

  Then, the node management unit 140 selects an image quality corresponding to the communication speed at the new participating node, and searches for connection destination candidate nodes from participating nodes of the distribution network that distributes the content with the selected image quality. For example, when the communication speed of the new participating node is capable of reproducing high-quality content, a connection destination candidate node is searched from among the participating nodes of the distribution network that distributes the high-quality content. When the standard quality content can be reproduced, the connection destination candidate node is searched from among the participating nodes of the distribution network that delivers the standard quality content. In addition, when it is determined that the requested content stream playback is not possible but the download playback is possible, the communication speed at the new participating node is from among the participating nodes of the distribution network that downloads and plays the requested content. Search for connection destination candidate nodes. For example, if high-quality content stream playback is not possible, but high-quality content download playback is possible, search for connection destination candidate nodes from among the participating nodes of the distribution network that downloads and plays back high-quality content. . In addition, stream playback of standard definition content is not possible, but when download playback of standard definition content is possible, a connection destination candidate node is searched from participating nodes of a distribution network that downloads and plays back standard definition content. .

  Further, the node management unit 140 determines which of the first to Kth communication speed level groups (K is an integer of 2 or more) the new participation node belongs based on the communication speed at the new participation node. . These first to Kth communication speed level groups are groups having different minimum guaranteed communication speeds, for example. When it is determined that the newly participating node belongs to the i-th communication speed level group (1 ≦ i ≦ K) of the first to K-th communication speed level groups, the i-th communication speed level group The connection destination candidate node is searched from among the participating nodes of the distribution network in which the node is participating. For example, the communication speed of the newly participating node is measured by a line quality measurement process described later. Then, it is determined whether the measured communication speed belongs to which speed range of each communication speed level group. Then, the transmission unit 130 transmits notification information for mediating the searched connection destination candidate node as a distribution node of the requested content to the new participation node.

  Here, the first communication speed level group among the first to Kth communication speed level groups is, for example, stream reproduction of high-quality content (content of the first image quality level) and standard-quality content (second image quality level). In the group). The second communication speed level group is a group that can download and play high-quality content (content of the first image quality level) and stream playback of standard-quality content (content of the second image quality level). Further, the third communication speed level group is a group capable of downloading and reproducing standard-definition content.

  Then, a node that belongs to the first communication speed level group and plays a stream of high-quality content (content of the first image quality level) is changed to belong to the second communication speed level group due to a decrease in the communication speed. Suppose that That is, it is assumed that a decrease in communication speed due to a change in the communication environment or the like is measured during the reproduction of a high-quality content stream, is excluded from the first communication speed level group, and the affiliation is changed to the second communication speed level group. . In this case, the node management unit 140 downloads the second communication speed level group for the high-quality contents (contents of the first image quality level) that were being reproduced by the stream reproduction of the first communication speed level group. Let it play. For example, the high-quality content can be viewed by download playback from the point at which the stream playback is interrupted.

  Also, the node that belongs to the second communication speed level group and plays the stream of the standard definition content (the second image quality level content) is changed to belong to the third communication speed level group due to a decrease in the communication speed. Suppose that In this case, the node management unit 140 downloads and reproduces the third communication speed level group for the standard quality content (content of the second image quality level) that was being reproduced by the stream reproduction of the second communication speed level group. To do. For example, the standard-definition content can be viewed by download reproduction from the point of interruption of stream reproduction.

  Further, the node management unit 140 may perform a process of excluding (excluding) from the distribution network 10 a node determined (evaluated) that the communication speed is slower than the minimum guaranteed communication speed of the distribution network 10. For example, even if a node whose communication speed is equal to or higher than the minimum guaranteed communication speed at the time of participation of the distribution network 10 is a node whose communication speed does not reach the minimum guaranteed communication speed due to a change in the communication environment, 10 so that communication connection to the distribution network 10 is disabled. In this case, for example, the distribution source node of the content of the distribution network having the lowest minimum guaranteed communication speed may be arranged (introduced) so that the distribution network having the minimum guaranteed communication speed lower than the distribution network 10 can participate. .

  Various methods can be considered as methods for evaluating the communication speed of each node participating in the distribution network 10. For example, in the present embodiment, the receiving unit 120 receives measurement result information (measurement communication speed information) of line quality (quality such as communication speed) at each node from each node of the distribution network 10. Based on the received measurement result information, the node management unit 140 determines whether the communication speed at each node of the distribution network 10 satisfies the communication speed condition. For example, it is determined whether or not the minimum guaranteed communication speed has been reached. If the communication speed condition is not satisfied, the node is determined to be excluded from the distribution network 10.

  More specifically, the node management unit 140 searches for cooperative nodes that can cooperate with the measurement of the line quality. Here, the cooperative node capable of cooperating with the measurement of the line quality is, for example, a node that has already received the content data. For example, the reception of content data has been completed and the communication connection with the distribution network 10 has been terminated, but the power source is turned on and the node (client device) capable of communication connection with the distribution network 10 has been turned on. Search for cooperation nodes from among them. Such cooperative nodes do not transmit or receive content data. Therefore, if such a cooperative node and each node are connected in communication and measure the line quality, it is possible to obtain an appropriate line quality measurement result. In addition, it is possible to select a node that cooperates in the measurement of the line quality of each node while maintaining the communication stability of the distribution network 10.

  Then, the transmission unit 130 transmits notification information for introducing (introducing) the searched cooperation node to each node. Each node communicates with the cooperative node to measure the line quality, and transmits line quality measurement result information. Then, the receiving unit 120 receives the transmitted measurement result information. Then, the node management unit 140 determines whether or not the communication speed at each node of the distribution network 10 satisfies the communication speed condition based on the received measurement result information (communication speed and communication speed measurement result of each node). to decide. For example, it is determined whether the communication speed is equal to or higher than the minimum guaranteed communication speed. If the communication speed condition is not satisfied, the node is determined as a candidate for exclusion.

  In addition, the node management unit 140 serves as a first cooperation node that is a distribution source node as a cooperation node so that each node is connected to both the content distribution source node and the distribution destination node to measure the line quality. Then, the second cooperative node that is the distribution destination node is searched. Then, the transmission unit 130 transmits, to each node, notification information that mediates (introduces) both the searched first and second cooperative nodes to each node. That is, information for specifying these first and second cooperative nodes is transmitted to each node.

  The receiving unit 120 receives reception start timing specifying information (reception start time specifying information in a narrow sense) of the requested content at the new participating node from the new participating node that has requested the content distribution. That is, a new participation node to the distribution network 10 transmits request content reception start timing specifying information together with a content distribution request, for example, and the server system receives the information.

  Then, the node management unit 140 obtains the expected reception start timing (assumed reception start time in a narrow sense) of the requested content at the new participation node based on the reception start timing specification information received from the new participation node. Then, based on the assumed reception start timing (virtual reception start timing, reception start time) obtained, a connection candidate node (a mediation node) of the new participation node is searched (specified) from among the participation nodes of the distribution network 10. To do.

  Here, the assumed reception start timing (assumed reception start time) is specified from, for example, the set communication speed (the minimum guaranteed communication speed in a narrow sense) of the distribution network 10 or the current time, and the virtual content reception start at the node is performed. Timing (reception start time). The set communication speed is a communication speed set in the distribution network 10. Specifically, for example, it is a minimum communication speed required for a node participating in the distribution network 10. For example, a communication speed at a node participating in the distribution network 10 is determined by a line quality measurement process described later. It is guaranteed that the communication speed exceeds the set communication speed (minimum guaranteed communication speed).

  The storage unit 170 (management information storage unit) stores a plurality of assumed reception start timings corresponding to a plurality of participating nodes participating in the distribution network 10. That is, the assumed reception start timing of each of the nodes N1 to N10 participating (communication connection) in the distribution network 10 in FIG. 1 is stored.

  The node management unit 140 has a plurality of assumed reception start timings (assumed reception start timings N1 to N10) stored in the storage unit 170, more than the assumed reception start timing (assumed reception start time) of the new participating node. An assumed reception start timing that is earlier in timing (time) and closest to the assumed reception start timing of the new participating node is searched. And the participating node corresponding to the searched assumption reception start timing is determined as a connection destination candidate node. Then, the transmission unit 130 transmits notification information for mediating the determined connection destination candidate node as a distribution source node to the new participation node.

  Various information can be assumed as the reception start timing specifying information. For example, the reception unit 120 may receive the data retention amount (data accumulation amount, data retention rate) of the requested content received and held in the past by the new participating node from the new participating node as reception start timing specifying information. Good. In this case, the node management unit 140 determines the expected reception start timing of the new participating node based on the received data holding amount (including information equivalent to the data holding amount) and the minimum guaranteed communication speed of the distribution network 10. Ask. For example, assuming that the data holding amount (bit) of the new participating node is DQ, the current time is TC, and the minimum guaranteed communication speed (bps) is VL, the assumed reception start timing TS is, for example, TS = TC-DQ / It can be obtained from the relational expression of VL.

  Alternatively, based on the data retention amount of the requested content received and held in the past by the new participating node and the minimum guaranteed communication speed of the distribution network 10, the expected reception elapsed time of the requested content is determined for each node (client device). ). In this case, the receiving unit 120 receives the expected reception elapsed time of the requested content from the new participating node as reception start timing specifying information. For example, DQ / VL is received from the new participating node as the assumed reception elapsed time. And the node management part 140 calculates | requires the assumption reception start timing (for example, TS = TC-DQ / VL) of a new participating node based on the received assumption reception elapsed time (DQ / VL).

  Alternatively, each node (client device) may obtain the expected reception start timing of the requested content based on the data holding amount, the minimum guaranteed communication speed, and the current time. In this case, the receiving unit 120 receives the expected reception start timing of the requested content from the new participating node as reception start timing specifying information. For example, TS = TC-DQ / VL is received from the newly participating node as the assumed reception start timing. And the node management part 140 searches the connection destination candidate node of a new participating node based on the received assumption reception start timing.

  The receiving unit 120 may receive the assumed data retention amount specifying information (data retention amount) of the requested content at the new participation node from the new participation node. In this case, the node management unit 140 compares the assumed data holding amount at the new participating node specified based on the received assumed data holding amount specifying information with the assumed data holding amount of the participating node of the distribution network 10. . Based on the comparison result, the connection destination candidate node of the new participation node is searched from the participation nodes of the distribution network 10. Specifically, a node having an assumed data retention amount that is larger than the assumed data retention amount of the new participating node and that has an assumed data retention amount that is closest to the assumed data retention amount of the new participating node is determined as a connection destination candidate node. Search for. Then, the transmission unit 130 transmits notification information that mediates the connection destination candidate nodes searched in this way.

2. Client Device FIG. 3 shows a configuration example of a client device (game device, portable terminal, information processing device, etc.) provided in each node of the distribution network 10. This client device includes a processing unit 200, an operation unit 260, a storage unit 270, an information storage medium 280, a display unit 290, a sound output unit 292, and a communication unit 296. The client device according to the present embodiment is not limited to the configuration shown in FIG. 3, and various modifications such as omitting some of the components or adding other components are possible.

  The processing unit 200 performs various processes. Specifically, the decryption process of the encrypted content, the reproduction process of video and audio, and the like are performed. Also, a process of buffering (caching) content data received from a content distribution source node in the storage unit 270 and retransmitting the buffered content data to a content distribution destination node by a relay method (bucket relay method) Etc. The function of the processing unit 200 can be realized by a processor such as a CPU, a program that operates on the processor, or the like.

  The operation unit 260 is used for the viewer to perform various inputs necessary for viewing the content, and can be realized by, for example, a keyboard, a mouse, a game controller, or the like.

  The storage unit 270 functions as a work area for the processing unit 200 and the communication unit 296, and the function can be realized by a RAM, an HDD, or the like. The storage unit 270 includes a content storage unit 272 and a management information storage unit 274.

  The content storage unit 272 functions as a cache memory for content data received from a content distribution source node. The management information storage unit 274 stores management information such as information on its own node and information on other nodes.

  An information storage medium 280 (a computer-readable medium) stores programs, data, and the like, and functions thereof by an optical disk (CD, DVD), HDD (hard disk drive), memory (ROM, etc.), and the like. realizable. The processing unit 200 performs various processes of the present embodiment based on a program (data) stored in the information storage medium 280. That is, in the information storage medium 280, a program for causing a computer (an apparatus including an operation unit, a processing unit, a storage unit, and an output unit) to function as each unit of the present embodiment (a program for causing the computer to execute processing of each unit). Is memorized.

  The display unit 290 displays content video and the like, and its function can be realized by a CRT, LCD, touch panel display, HMD (head mounted display), or the like. The sound output unit 292 outputs a sound of content and the like, and the function can be realized by a speaker, a headphone, or the like.

  The communication unit 296 performs various communication control processes for data transmission / reception with other nodes and servers. Specifically, various processes necessary for communication according to a protocol such as the Internet are performed. The function of the communication unit 296 can be realized by a communication ASIC or firmware.

  The processing unit 200 includes a reception unit 220, a transmission unit 230, a communication management unit 240, and a content reproduction unit 250.

  The receiving unit 220 performs information reception processing, and performs processing for receiving information from, for example, a server system. It also performs processing for receiving information from other nodes. The transmission unit 230 performs information transmission processing, for example, performs processing for transmitting information to the server system. In addition, processing for transmitting information to other nodes is also performed.

  The communication management unit 240 performs various management processes related to communication. For example, management processing of communication connection to other nodes and server systems is performed.

  The content playback unit 250 performs playback processing of the distributed content. For example, a process for decrypting encrypted content received from another node (or server system) and displaying a video of the decrypted content on the display unit 290, or a sound of the decrypted content is sounded. Processing for output by the output unit 292 is performed.

  In this embodiment, when a cooperation node that can cooperate with the measurement of the line quality is searched, the receiving unit 220 receives notification information that mediates the searched cooperation node from the server system. For example, when the client device requests the server system to assist the cooperation node, the server system searches for the cooperation node and transmits notification information including information for identifying the cooperation node to the client device.

  Then, the communication management unit 240 performs communication connection with the cooperation node that has been intervened by the notification information, and measures the line quality. For example, it is determined whether or not the communication speed of the line in the client device has reached the minimum guaranteed communication speed of the distribution network 10 to which the node of the client device belongs. Then, the transmission unit 230 transmits line quality measurement result information to the server system.

  Specifically, the communication management unit 240 measures the line quality and obtains the communication speed in a state where the cooperative nodes are connected for communication. Then, the transmission unit 230 transmits line quality measurement result information including the obtained communication speed to the server system. Then, on the server system side, it is determined whether or not the communication speed included in the measurement result information satisfies the communication speed condition. For example, it is determined whether or not the minimum guaranteed communication speed of the distribution network 10 has been reached.

  Alternatively, the communication management unit 240 on the client device side obtains the communication speed in a state where the cooperative node is in communication connection, and determines whether the obtained communication speed satisfies the communication speed condition of the requested content. Also good. Then, when it is determined that the requested communication speed satisfies the request content communication speed condition, the transmission unit 230 transmits notification information for requesting distribution of the request content to the server system.

  In addition, the receiving unit 220 receives, from the server system, notification information that mediates the first cooperation node that is the content distribution source node and the second cooperation node that is the content distribution destination node as the cooperation node. Then, the communication management unit 240 measures the line quality and obtains the communication speed in a state where both the first and second cooperative nodes are connected for communication. As a result, the line speed can be measured in a communication environment similar to the communication environment for content distribution.

  Furthermore, when the client device requests content distribution, the transmission unit 230 may transmit the reception start timing specification information (reception start time specification information) of the requested content to the server system.

  Then, the server system searches for a connection destination candidate node from among the participating nodes of the distribution network 10 based on the reception start timing specification information, and notifies the connection destination candidate node thus searched as a distribution node of the requested content. Send information. Then, the receiving unit 220 receives notification information transmitted from the server system. And the communication management part 240 performs the process which carries out communication connection with respect to the connection destination candidate node arranged by notification information. In other words, the communication unit 296 is controlled to execute various protocol processes for communication connection of the node corresponding to the client device to the connection destination candidate node arranged from the server system.

3. 3. Method according to this embodiment 3.1 Node connection management based on communication speed Next, a node connection management method according to this embodiment will be described in detail. Hereinafter, the server system and the client device are appropriately referred to as a server and a client. In the following, the reception start timing specification information is the reception start time specification information, the reception start timing (assumed reception start timing) is the reception start time (assumed reception start time), and the set communication speed of the distribution network is guaranteed to be the lowest Although the case of communication speed will be described as an example, the present embodiment is not limited to this. For example, the reception start timing specifying information, the reception start timing, and the set communication speed are information equivalent to the reception start time specifying information, the reception start time, and the minimum guaranteed communication speed. Information). In addition, the communication speed in the present embodiment may be a communication speed itself such as a communication amount per hour, for example, or a communication speed level or a communication amount when the communication speed is divided into levels. It may be information equivalent to the communication speed that substantially represents the speed.

  As shown in FIG. 4A, in this embodiment, content data is sequentially transmitted between nodes (clients) connected in series by a P2P relay method (bucket relay method, cache and toss method). Hand it over.

  In such a P2P relay distribution network, in order to achieve proper content distribution, the communication speed (line speed) at the nodes participating in the distribution network needs to satisfy a predetermined communication speed condition. is there.

  Specifically, as shown in FIG. 4B, the minimum guaranteed communication speed VL is set in the distribution network, and the communication speeds VN1 to VN5 of the participating nodes N1 to N5 of the distribution network are equal to or higher than the minimum guaranteed communication speed VL. The communication speed condition is satisfied so that That is, if there is a node with a communication speed slower than the minimum guaranteed communication speed VL among the participating nodes N1 to N5, the communication speed of the node becomes rate-determined, and the overall communication speed of the distribution network decreases. There is a risk that. For example, when the communication speed VN1 of the node N1 is slower than the minimum guaranteed communication speed VL, even if the communication speeds VN2 to VN5 of the other nodes N2 to N5 are equal to or higher than the minimum guaranteed communication speed VL, the communication speed of the node N1 is eventually obtained. There is a risk that content distribution to other nodes may be delayed because the rate is limited by VN1. Therefore, the minimum guaranteed communication speed VL is set in the distribution network of FIG. 4B, and nodes that do not satisfy the communication speed condition are excluded from the distribution network.

  In FIG. 4B, the new participating node NX requests content distribution to a server that distributes content through such a distribution network. In this case, in this embodiment, the server determines whether or not the communication speed VNX at the newly participating node NX that has requested content distribution satisfies the communication speed condition of the requested content (distribution network). For example, it is determined whether or not the communication speed VNX is equal to or higher than the minimum guaranteed communication speed VL of the requested content.

  Then, as shown in FIG. 5A, when it is determined that the communication speed VNX at the new participating node NX is equal to or higher than the minimum guaranteed communication speed VL and the communication speed condition is satisfied, the participating node of the distribution network The connection candidate node of the new participation node is searched from N1 to N5. For example, in FIG. 5A, among the nodes N1 to N5, the node N2 with the oldest addition order to the distribution network (the node with the youngest addition order) is searched as a connection destination candidate node of the node NX. Then, notification information that mediates the searched connection destination candidate node N2 as a distribution source node is transmitted to the new participation node NX. As a result, the newly participating node NX can communicate with the node N2 and receive the content data by the P2P relay method with the node N2 as the distribution source node.

  On the other hand, in FIG. 5B, it is determined that the communication speed VNX at the newly participating node NX is slower than the minimum guaranteed communication speed VL and does not satisfy the communication speed condition. In this case, the server does not search for a connection destination candidate node of the new participation node NX, and notifies the new participation node NX that the requested content cannot be used, for example. Alternatively, as described later, when there are a plurality of communication speed level groups, the communication speed level group to which the communication speed VNX of the newly participating node NX belongs is selected. Then, a connection destination candidate node is searched from among the participating nodes of the distribution network corresponding to the selected communication speed level group.

  In FIG. 5A, the node with the oldest addition order to the distribution network is determined as the connection destination candidate node, but the present embodiment is not limited to this. For example, as will be described later, when a new participation node has already accumulated a part of the requested content data, the new participation node is based on the assumed reception start time (assumed data retention amount) at each node. The connection destination candidate node of the node NX may be determined.

  Next, details of the processing of this embodiment will be described with reference to the flowchart of FIG.

  First, the client (new participating node) requests the server to arrange a content distribution source node (step S61).

  Then, the server determines whether or not the client has a communication speed level at which the requested content can be used (step S62). For example, it is determined whether or not the communication speed of the client is equal to or higher than the minimum guaranteed communication speed of the requested content. If the client does not have a communication speed level at which the requested content can be used and does not satisfy the communication speed condition, the client is notified that the requested content cannot be used (step S63). .

  On the other hand, if the client has a communication speed level at which the requested content can be used and satisfies the communication speed condition, an image quality corresponding to the communication speed level is selected (step S64). For example, an image quality such as high image quality, standard image quality, or low image quality is selected. Alternatively, it is selected whether it is stream playback or download playback.

  Then, a connection destination candidate node is searched from the distribution network that distributes the requested content with the selected image quality (step S65). For example, a communication speed level group corresponding to the selected image quality is selected from a plurality of communication speed level groups as will be described later, and a connection destination is selected from among the participating nodes of the distribution network corresponding to the selected communication speed level group. Search for candidate nodes. Then, the connection destination candidate node obtained as a result of the search is notified to the client (step S66).

  FIG. 7 is a data flow diagram showing the sharing of processing between the client and the server. When the client makes a mediation request for the content distribution source node in step S71, the server checks in step S72 whether the requested content can be used based on the communication speed level of the client. If the use is not possible, the server notifies the client in step S73 that the requested content cannot be used and cannot be distributed. On the other hand, if it can be used, in steps S74 and S75, the server selects the image quality from the communication speed level of the client, and searches the connection destination candidate node from the distribution network of the content of the selected image quality. In step S76, the server notifies the connection destination candidate node to the client.

  As described above, according to the present embodiment, the new participation node cannot participate in the distribution network of the requested content unless the communication speed satisfies the communication speed condition of the requested content. Accordingly, only nodes satisfying the communication speed condition belong to the distribution network of the requested content. For example, it is ensured that the communication speed of the participating nodes is equal to or higher than the minimum guaranteed communication speed, and the content is distributed by the P2P relay method between nodes satisfying a predetermined communication capability. Therefore, it becomes possible to stably communicate at a speed sufficient for distributing the requested content, and the distribution network can be maintained in an appropriate state.

3.2 Node Connection Management According to Communication Speed Level In this embodiment, a plurality of distribution networks having different communication speed levels are prepared. For example, in FIG. 8A, the delivery network NTA has a minimum guaranteed communication speed VL = 6 Mbps, and the delivery network NTB has a minimum guarantee communication speed VL = 2 Mbps. NTB communication speed levels are different.

  However, in FIG. 8A, the communication speeds of the nodes NB2 and NB3 of the distribution network NTB are 9 Mbps and 6 Mbps, respectively, and the communication speed that should actually belong to the distribution network NTA (VL = 6 Mbps or more) Speed). Even if the nodes NB2 and NB3 having such a high communication speed belong to the distribution network NTB having a low communication speed, the communication speed of the P2P relay method is the low communication speed of the nodes NB1, NB4, and NB5. It will be rate-limited. Therefore, even if the nodes NB2 and NB3 have a high communication speed, content data having a large amount of data such as game data (character data, image data, etc.) cannot be downloaded at high speed.

  Therefore, in the present embodiment, the nodes NB2 and NB3 having a high communication speed are made to belong to the distribution network NTA having a high communication speed level. In other words, groups are grouped into a plurality of communication speed level groups according to the communication speed (line communication speed capability) of each node, and distribution networks that can participate are switched according to the communication speed level. For example, based on the communication speed of each node, it is determined whether each node belongs to a plurality of communication speed level groups (NTA and NTB groups), and each node is included in the distribution network of the corresponding communication speed level group. Node connection management is performed so that communication connection is established.

  In this way, as shown in FIG. 8B, only nodes NA1, NA2, and NA3 having a communication speed of minimum guaranteed communication speed VL = 6 Mbps or higher belong to the delivery network NTA having a high communication speed level. become. Therefore, even when data with a large amount of data, such as game data, is downloaded and distributed, these nodes NA1, NA2, and NA3 can complete the data download at high speed and can be provided with services early. . That is, when the nodes NB2 and NB3 belong to the distribution network NTB as shown in FIG. 8A, the communication speeds of the other nodes NB1, NB4, and NB5 even if the communication speeds of the nodes NB2 and NB3 are fast. Therefore, the data download time of the nodes NB2 and NB3 becomes longer. On the other hand, if the nodes NA1 and NA3 corresponding to the nodes NB2 and NB3 belong to the distribution network NTA having a high communication speed level, the nodes NA1 and NA3 are compared with the case of belonging to the distribution network NTB. Data download can be completed at high speed, and services after data download can be received early.

  Specifically, in this embodiment, each node is assigned to a plurality of groups A, B, and C (first to Kth communication in a broad sense) as shown in FIG. Group into speed level groups). For example, a node having a communication speed of 6 Mbps or higher belongs to group A (first communication speed level group in a broad sense), and a node having a communication speed of 2 Mbps or higher is assigned to group B (second communication speed in a broad sense). Level group). Nodes whose communication speed is less than 2 Mbps belong to group C (third communication speed level group in a broad sense).

  Here, 6 Mbps corresponding to the group A is the minimum guaranteed communication speed of the distribution network in which the group A node participates, and 2 Mbps corresponding to the group B is the minimum guaranteed communication speed of the distribution network in which the group B node participates. is there. Note that the minimum guaranteed communication speed of group C may be set to, for example, about 0.5 Mbps, and the use of the requested content itself may be disabled for the nodes in the group whose communication speed is less than 0.5 Mbps.

  As shown in FIG. 9B, nodes (clients) belonging to group A (first communication speed level group) can perform, for example, high-quality stream playback and standard-quality stream playback. That is, for both high-quality content and standard-quality content, stream playback that requires high communication speed is possible.

  Nodes belonging to group B (second communication speed level group) can perform high-quality download reproduction and standard-quality stream reproduction, for example. That is, in Group B, stream playback is not possible for high-quality content, but download playback is possible. Also, stream playback is possible for standard quality content.

  Further, nodes belonging to the group C (third communication speed level group) can perform standard image quality download reproduction, for example. That is, in the group C, standard quality stream reproduction is not possible, but download reproduction is possible. In stream playback, it is possible to play back content in real time while receiving content data. In download playback, all content data is once downloaded to the storage unit of the client, then the content is based on the downloaded data. Playback will be performed.

  In the present embodiment, it is determined which of the plurality of communication speed level groups the new participation node belongs to based on the communication speed at the new participation node that has requested content distribution. Then, a connection candidate node of the new participation node is searched from among the participation nodes of the distribution network in which the node of the communication speed level group to which the new participation node belongs.

  For example, in FIG. 10A, the new participating node NX requests the server to distribute the content. The communication speed VNX of the newly participating node NX is 2 Mbps ≦ VNX <6 Mbps in FIG. For this reason, it is determined that the newly participating node NX belongs to the communication speed level group (second communication speed level group) of the distribution network NTB whose minimum guaranteed communication speed is VL = 2 Mbps. Therefore, in this case, as shown in FIG. 10B, the server searches for a connection destination candidate node of the new participation node NX from among the participation nodes of the distribution network NTB and arranges them.

  On the other hand, when the communication speed of the new participating node NX is VNX ≧ 6 Mbps, the new participating node NX transmits the communication speed level group (first communication speed) of the distribution network NTA whose minimum guaranteed communication speed is VL = 6 Mbps. Level group). Therefore, in this case, the server searches for a connection destination candidate node of the new participation node NX from among the participation nodes of the distribution network NTA and arranges them.

  As described above, as shown in FIG. 8B, for example, only the node of group A satisfying VNX ≧ 6 Mbps belongs to the distribution network NTA, and the group satisfying 2 Mbps ≦ VNX <6 Mbps belongs to the distribution network NTB. Only node B belongs. Therefore, as shown in FIG. 9B, it is possible to provide content with image quality corresponding to the communication speed level of each group. For example, with respect to the node of group A, the content can be stably distributed at a speed sufficient to perform stream playback of high-quality content and stream playback of standard-definition content. In addition, with respect to the node of group B, the content can be stably distributed at a speed sufficient for downloading and reproducing high-quality content and stream reproduction of standard-definition content.

  In addition, for example, content data having a large amount of data such as game data or a game program can be downloaded at high speed with a download time corresponding to the communication speed level of each group. For example, the nodes NA1 and NA3 in FIG. 8B can download data at a higher speed than when belonging to the distribution network NTB as shown in FIG. 8A.

  Also, for example, in FIG. 11A, the node NX participates in the high-speed distribution network NTA and performs high-quality content stream playback.

  However, in FIG. 11B, the communication speed VNX of the node NX decreases due to a change in the communication environment due to a communication failure or the like, for example, 2 Mbps ≦ VNX <6 Mbps. In such a case, if the node NX remains connected to the distribution network NTA, the decrease in the communication speed of the node NX adversely affects content distribution to other nodes participating in the distribution network NTA. Specifically, the delivery speed to the lower (downstream) node having the node NX as the content delivery source node is limited by the communication speed VNX of the node NX. Therefore, when such a decrease in communication speed occurs, processing for excluding the node NX from the distribution network NTA is performed as will be described later.

  However, for example, if the node NX is excluded from the distribution network NTA when the node NX is in the middle of the stream reproduction of the high-quality content and the high-quality content cannot be viewed, the user convenience is impaired.

  Therefore, in this embodiment, the node NX that belongs to the group A (first communication speed level group) and plays the stream of the high-quality content can no longer belong to the group A due to the decrease in the communication speed. In this case, as shown in FIG. 11B, the affiliation of the node NX is changed to the group B (second communication speed level group). Then, the group B download reproduction is performed for the high-quality content being reproduced in the stream reproduction. That is, real-time stream playback of high-quality content is not permitted, but download playback that downloads and plays back high-quality content to the storage unit of the client is permitted.

  In this way, the user of the node NX can view the high-quality content that was in the middle of reproduction by download reproduction, although it takes more time than the stream reproduction. That is, the high-quality content data from the point at which playback was interrupted is downloaded once to the storage unit of the client of the node NX, and after the download is completed, the high-quality content can be viewed. It can be improved.

  In FIG. 12A, the node NX participates in the distribution network NTB and plays the stream of the standard-definition content, but the communication speed VNX of the node NX decreases due to a change in the communication environment, for example, VNX < It is 2 Mbps.

  As described above, when the node NX that belongs to the group B (second communication speed level group) and plays the stream of the standard-definition content cannot belong to the group B due to the decrease in the communication speed, FIG. As shown in (B), the affiliation of the node NX is changed to group C (third communication speed level group). Then, the group C download reproduction is performed on the standard-definition content that was being reproduced in the stream reproduction. In other words, real-time stream playback of standard-definition content is not permitted, but download-playback that downloads and plays back standard-definition content to the storage unit of the client is permitted.

  By doing so, the user of the node NX takes time compared with the stream reproduction, but can view the standard-definition content that was in the middle of reproduction by downloading reproduction, and the convenience of the user can be improved.

3.3 Measurement of channel quality Next, a method for measuring channel quality at each node will be described. In this embodiment, the server receives line quality measurement result information from each node of the distribution network. This measurement result information may be, for example, information indicating the communication speed of the line at each node, or may be result information indicating whether the communication speed has reached the minimum guaranteed communication speed.

  Then, the server determines whether the communication speed at each node of the distribution network has reached the minimum guaranteed communication speed based on the received measurement result information. For example, when the measurement result information includes information on the communication speed at each node, it is determined whether or not the minimum guaranteed communication speed has been reached by comparing the communication speed with the minimum guaranteed communication speed. Alternatively, even if the client of each node performs a measurement comparing the communication speed with the minimum guaranteed communication speed, the server determines whether the communication speed has reached the minimum guaranteed communication speed based on the measurement result information. Good.

  For example, as shown in FIG. 13A, the client of the node NX requests the server to arrange a cooperation node for line quality measurement. Then, the server searches for a cooperative node that can cooperate with the measurement of the line quality, and transmits notification information for mediating the searched cooperative node to the node NX, as shown in FIG.

  Here, the cooperation node is selected from, for example, nodes that have already received the content. For example, a client such as a game device is turned on and can be connected to the distribution network, but the content reception itself is selected from the completed nodes. If such a node is selected as a cooperative node, it is possible to minimize a situation in which the communication band of the server is compressed for the measurement of the line quality. The cooperation node can be any node, and its own node can also be a cooperation node.

  Then, as shown in FIG. 13C, the node NX on which the cooperation node has been arranged communicates with the cooperation node to measure the line quality, and transmits the line quality measurement result information to the server. Then, the server determines whether or not the communication speed VNX at the node NX has reached the minimum guaranteed communication speed VL based on the received measurement result information.

  Specifically, in FIG. 13 (D), the server performs the first cooperation as the distribution source node so that the node NX is connected to both the distribution source node and the distribution destination node and the line quality is measured. The node NC1 and the second cooperation node NC2 that is the distribution destination node are searched, and both of these cooperation nodes NC1 and NC2 are routed to the node NX.

  Then, the node NX establishes communication connection with the cooperation node NC1 as a distribution source node and communication connection with the cooperation node NC2 as a distribution destination node. Then, the data for measurement is received from the cooperative node NC1 by the P2P relay method, and the received measurement data is stored in the storage unit and transmitted to the cooperative node NC2.

  In this way, since the line quality at the node NX can be measured in the same connection state as at the time of content distribution by the P2P relay method, the measurement accuracy of the line quality can be improved.

  For example, as a method of the comparative example, a method of measuring line quality by connecting only one cooperative node to the node NX can be considered. However, in a communication environment in which a client such as a game device is connected to a router by a wireless LAN such as half-duplex, in the method of the comparative example, the measured communication speed is an actual value at the time of content distribution. It becomes faster than the communication speed, and accurate measurement of the line quality cannot be realized.

  In this regard, as shown in FIG. 13D, if the cooperation nodes NC1 and NC2 are connected to both the distribution source side and the distribution destination side of the node NX, the communication environment similar to that at the time of content distribution can be reproduced, and more accurately. Can measure the line quality.

  In the distribution network having the topology as shown in FIG. 1, in order to further improve the measurement accuracy of the line quality, it is possible to connect two cooperative nodes NC21 and NC22 as distribution destinations as shown in FIG. desirable. For example, in FIG. 1, two nodes N2 and N3 are connected to the core node N1 as content distribution destinations. The same applies to the core nodes N3 and N6.

  In addition, at the time of participation in the distribution network, the position where each node is arranged in the distribution network is arbitrary, and the node may be arranged at such a position of the basic nodes N1, N3, and N6. Therefore, in order to properly maintain the minimum guaranteed communication speed of the distribution network, even when a node is arranged at such a position of the basic node, the communication speed at that node is equal to or higher than the minimum guaranteed communication speed. It is necessary to. Therefore, when measuring the line quality, as shown in FIG. 13E, it is possible to connect the node NC1 of the distribution source and the two nodes NC21 and NC22 of the distribution destination to the node NX. desirable. By doing so, even in the distribution network having the topology as shown in FIG. 1, the measurement accuracy of the line quality can be improved, and the minimum guaranteed communication speed of the distribution network can be appropriately maintained.

  Although the method for measuring the communication speed of the line at each node using the cooperative node has been described above, the measurement of the communication speed of the line is not limited to the method using the cooperative node. For example, at the time of actual content distribution, a decrease in communication speed or the like at each node may be monitored from a communication state of data of the content at each node (data reception or transmission state). In this way, it is possible to exclude from the distribution network nodes that have a communication speed drop and adversely affect P2P distribution during actual content distribution.

  FIG. 14 is a flowchart for explaining the line quality measurement process. First, the client requests placement of a cooperation node for line quality (step S21). Then, the server searches for nodes that can cooperate (step S22). This cooperating node is searched from among nodes that have joined the content distribution service but have not received the content at the time of the search. Then, the server notifies the client of the mediation information of the searched cooperation node (step S23).

  Next, the client performs line quality measurement with the cooperation node (step S24). Then, the server determines the communication speed level based on the measurement result, and records the determined communication speed level in the storage unit in association with each client (steps S25 and S26).

  FIG. 15 is a data flow diagram illustrating the line quality measurement process. When the client requests the cooperation node in step S31, the server searches for the cooperation node in step S32 and arranges for the client in step S33. In step S34, line quality measurement is performed between the client and the cooperation node.

  In step S35, the client reports the result of the line quality measurement to the server. In step S36, the server determines the communication speed level of the client based on the line quality measurement result, and records it in correspondence with each client in step S37.

  According to the above-described line quality measurement method of the present embodiment, the line speed is measured in a situation closer to the actual usage situation by connecting a plurality of cooperative nodes to each node and measuring the line speed. It becomes possible to do. Also, by performing transmission and reception simultaneously when measuring the line speed, it is possible to accurately evaluate half-duplex communication such as a wireless LAN, and it is possible to obtain a valid evaluation of line quality. Also, by measuring the line speed using P2P, the problem of load concentration on the server in the server client method can be avoided. In addition, the server can manage the node, grasp the capability of the node, and select a cooperation node (cooperation partner), thereby preventing an unauthorized evaluation due to insufficient performance of the cooperation node.

3.4 Node Connection Management Based on Assumed Reception Start Time As shown in FIG. 16 (A), in this embodiment, content data is sequentially transferred between nodes connected in series by the P2P relay method. . For this reason, as shown in FIG. 16B, content data is accumulated in each node as time elapses from the start of reception of content data. In this method, the higher (upstream) node closer to the server has a larger amount of stored data than the lower (downstream) node. That is, the content distribution source node that is an upper node has a larger data holding amount than the content distribution destination node that is a lower node. For example, in FIG. 16B, the data retention amounts (data retention ratios) of the nodes N1, N2, N3, N4, and N5 are 80%, 70%, 60%, 52%, and 40% with respect to all data of the content. It has become.

  On the other hand, in P2P content distribution, before all content data is accumulated, the user may interrupt viewing of the content and leave the distribution network. Alternatively, the line may be disconnected from the distribution network in the middle of viewing due to disconnection of the line for some reason. In this case, the node corresponding to the user is excluded from the distribution network.

  When such a user newly participates in the distribution network again in order to resume viewing of the interrupted content, content data up to the middle of viewing is stored in the client device of the user's node. ing. For example, in FIG. 16B, 50% of the requested content data has already been accumulated in the new participating node NX.

  As described above, when the newly participating node NX having the data holding amount of 50% is connected to the node N5 having the data holding amount (data holding ratio) of 40%, for example, the data holding amount of the node N5 is 50. The node NX cannot receive the content data until it reaches%. Therefore, the new participating node NX cannot receive the distribution service until the data retention amount of the node N5 reaches 50%, and a waiting time occurs.

  As a comparative example method for solving such a problem, the server inquires all nodes participating in the distribution network about the data retention amount in each node, or each node participating in the distribution network. However, a method of reporting the actual data holding amount in its own node to the server at regular intervals can be considered.

  However, in the methods of these comparative examples, it is necessary to frequently communicate information other than content data between a large number of nodes participating in the distribution network and the server, and the communication band is compressed. For this reason, there is a risk of adversely affecting the distribution of important content data due to the communication of the information.

  In order to solve such a problem, in the present embodiment, a reception start time at each node is assumed based on reception start time specifying information received from each node, and P2P node connection management is performed using the assumed reception start time. I do. In other words, P2P node connection management is performed based on the minimum guaranteed communication speed of the distribution network and the estimated reception elapsed time and assuming the data retention amount that each node should have accumulated at the minimum.

  For example, in order to participate in the distribution network, the communication speed of the communication line at the client (node) needs to be equal to or higher than the minimum guaranteed communication speed set for the distribution network. Then, the newly participating client reports information for specifying the reception start time to the server, and the server records the reception start time assumed by the information. Then, the data retention amount that each client should have accumulated at the minimum can be obtained from the difference between the current time and the reception start time and the minimum guaranteed communication speed.

  When a client that has previously stopped receiving the content receives the content again to view the continuation of the content, the client receives the content based on the amount of data held by the client and the minimum guaranteed communication speed. The virtual reception start time is obtained. Then, a client that has received the content before the reception start time is arranged (introduced) from the server, and the content is received from the client.

  By doing in this way, it becomes possible to maintain the optimal state as the whole delivery network. That is, the server can grasp the accumulated data amount of each client without constantly updating the information. Therefore, it is possible to arrange an optimal distribution source client without squeezing the communication band, and it is possible to maintain the optimal state of the entire distribution network.

  For example, in FIG. 16B, the assumed data retention amount of the new participating node NX is 50%. Therefore, the server arranges a node having a larger assumed data holding amount than the node NX as a connection destination candidate node of the node NX.

  Specifically, as illustrated in FIG. 17A, the node N4 (52%) whose estimated data retention amount is closest to the assumed data retention amount (50%) of the node NX is intervened as a connection destination candidate node. . That is, the node N4 having an assumed reception start time that is earlier than the assumed reception start time of the node NX and closest to the assumed reception start time of the node NX is introduced.

  In FIG. 17B, the assumed data retention amount of the new participating node NX is 68%. Therefore, the node N2 (70%) whose estimated data retention amount is closest to the assumed data retention amount (68%) of the node NX is intervened as a connection destination candidate node. That is, the node N2 having an assumed reception start time that is earlier than the assumed reception start time of the node NX and closest to the assumed reception start time of the node NX is introduced.

  Accordingly, as shown in FIG. 17C, the node NX is arranged between the nodes N2 and N4. That is, the distribution source node of the node NX is N2, and the distribution destination node is N4. By doing so, it is possible to realize P2P content distribution from the node N2 to the NX and P2P content distribution from the node NX to the N4.

  As shown in FIG. 18A, the server stores a plurality of assumed reception start times TS1 to TS5 corresponding to a plurality of participating nodes N1 to N5 of the distribution network in the storage unit 170. For example, TS1 is an assumed reception start time of the node N1, and TS2 is an assumed reception start time of the node N2. The same applies to TS3 to TS5.

  Then, the server receives the request content reception start time specifying information from the newly participating node NX that has requested the content distribution. Next, an expected reception start time TSX at the node NX is obtained based on the reception start time specifying information, and a connection destination candidate node of the node NX is searched based on the obtained expected reception start time TSX. And the notification information which mediates using the searched connection destination candidate node as a distribution source node is transmitted to the node NX.

  Specifically, the expected reception start time that is earlier than the expected reception start time TSX of the node NX and that is closest to TSX among the assumed reception start times TS1 to TS5 stored in the storage unit 170. And a node corresponding to the searched expected reception start time is determined as a connection destination candidate node.

  For example, in FIG. 18B, the assumed reception start time TS4 of the node N4 is earlier than the assumed reception start time TSX of the new participating node NX and is closest to TSX. Therefore, in this case, the server introduces the node N4 as a connection destination to the new participating node NX. Note that in FIG. 18B and FIG. 19B described later, the right direction is the direction in which the time advances toward the drawing.

  According to the method of the present embodiment described above, each node only has to report the reception start time specifying information to the server, for example, when participating in the distribution network. In addition, the server does not need to check the data retention amount of all the nodes in the distribution network when a new participating node joins. Then, it becomes possible to introduce a node having a larger data holding amount than the new participating node to the new participating node as a connection destination. Therefore, it is possible to eliminate the situation where the reproduction of the content is awaited when the node that has interrupted reception receives the continuation without significantly increasing the processing load on the server. Therefore, the optimum connection partner can be introduced to the new participating node without unnecessarily reducing the communication band, and the optimum state of the entire distribution network can be maintained.

  Various information can be considered as the reception start time specifying information received by the server from the node NX. For example, in FIG. 19A, the new participating node NX transmits the data retention amount DQX at the node NX as the reception start time specifying information. This data retention amount DQX is the actual data retention amount of the content that the client of the node NX has received in the past and accumulated and retained in its storage unit.

  When the server receives this data retention amount DQX, the server obtains the expected reception start time TSX of the new participating node NX based on the received data retention amount DQX and the minimum guaranteed communication speed VL of the distribution network. Specifically, assuming that the current time is TC, for example, the expected reception start time TSX of the node NX can be obtained from the relational expression of TSX = TC−DQX / VL.

  In this case, the assumed reception start time of the node N1 that has already participated is also obtained by the relational expression TS1 = TC−DQ1 / VL. The same applies to the assumed reception start times TS2 to TS5 of the other nodes N2 to N5. These assumed reception start times TS2 to TS5 are recorded in the storage unit 170 of the server.

  For example, when the node N1 does not hold the content data received in the past when the node N1 joins the distribution network and DQ1 = 0, TS1 = TC and the current time TC is assumed. It is recorded as the reception start time TS1.

  Then, as shown in FIG. 19B, the assumed reception start time that is earlier than the assumed reception start time TSX of the node NX and closest to the TSX is TS4. Therefore, in this case, the node N4 is searched and is arranged as a connection destination candidate node of the node NX.

  In FIG. 20, the newly participating node NX transmits the assumed reception elapsed time DQX / VL at the node NX as reception start time specifying information. This estimated reception elapsed time DQX / VL is a virtual reception elapsed time specified from the minimum guaranteed communication speed VL.

  When receiving the estimated reception elapsed time DQX / VL, the server obtains the assumed reception start time TSX = TC−DQX / VL of the node NX based on the current time TC and the received expected reception elapsed time DQX / VL. Then, an assumed reception start time that is earlier than the assumed reception start time TSX of the node NX and closest to the TSX is searched, and a node corresponding to the assumed reception start time that has been searched is introduced to the node NX.

  Note that the reception start time specifying information transmitted to the server by the new participating node NX is not limited to the data holding amount or the assumed reception elapsed time. For example, the node NX obtains the expected reception start time TSX itself. The assumed reception start time TSX may be transmitted to the server. In this case, the server searches for a connection destination candidate node of the new participation node NX based on the received expected reception start time TSX.

  18A to 20, the server manages the assumed reception start time of each node and realizes node connection management. However, the server manages the assumed data retention amount of each node and connects the nodes. Management may be realized. Specifically, as illustrated in FIG. 21, the new participation node NX transmits the assumed data retention amount specifying information to the server. Then, the server specifies the assumed data holding amount DQX ′ of the node NX based on the assumed data holding amount specifying information. The assumed data retention amount DQX ′ is, for example, the data retention amount accumulated in the node NX when the node NX participates.

  Then, the server compares the assumed data retention amounts DQ1 ′ to DQ5 ′ of the other participating nodes N1 to N5 with the assumed data retention amount DQX of the new participating node NX, and selects the participating node whose assumed data retention amount is closest to DQX. Search for. More specifically, a search is performed for a participating node that has a data amount that is larger than the assumed data retention amount DQX and that has an assumed data retention amount that is closest to DQX. For example, in FIG. 17A, the node N4 whose estimated data retention amount (52%) is closest to the assumed data retention amount (50%) of the node NX is searched for, and is arranged as a connection destination candidate node. Further, in FIG. 17B, the node N2 having the assumed data holding amount (70%) closest to the assumed data holding amount (68%) of the node NX is searched and is appointed as a connection destination candidate node.

  The node connection management method using the assumed data retention amount as shown in FIG. 21 can also prevent a situation in which a new participation node is connected to a node with a small data retention amount and content reception at the new participation node is awaited. However, in order to reduce the processing load on the server, it is desirable to adopt a node connection management method using the assumed reception start time as shown in FIGS.

  That is, in the method using the assumed data retention amount of FIG. 21, the server needs to update the assumed data retention amount of each node every time. For this reason, the processing load of the server increases by this update process.

  On the other hand, according to the method using the assumed reception start time shown in FIGS. 18A to 20, for example, if the assumed reception start time of the participating node is recorded in the server when participating in the distribution network, It is not necessary to update the recorded expected reception start time. That is, when a new node joins, it is necessary to make a reference to the newly participating node by simply comparing the expected reception start time of the participating node already recorded with the expected reception starting time of the new participating node. You can search for nodes. Therefore, since the update process of the assumed reception start time can be made unnecessary, the processing load on the server can be reduced as compared with the method using the assumed data retention amount.

  Next, details of the processing of this embodiment will be described with reference to the flowchart of FIG.

  First, the client (new participating node) requests the server to arrange a content distribution source node (step S1). At this time, the client transmits reception start time specifying information to the server (step S2).

  Next, the server converts the reception start time specifying information into an assumed reception start time (step S3). For example, as described above, DQ (or DQ / VL), which is reception start time specifying information, is converted into an assumed reception start time TS using the relational expression TS = TC-DQ / VL. Then, the converted assumed reception start time is recorded in the server (step S4).

  Next, the server extracts nodes participating in the content distribution network requested by the client (step S5). Then, based on the assumed reception start time obtained in step S4, an optimum connection destination candidate node is searched from the nodes extracted in step S5 (step S6). For example, the node closest to the assumed reception start time of the newly joined client is searched. Then, the connection destination candidate node obtained as a result of the search is notified to the client (step S7).

  FIG. 23 is a data flow diagram showing the sharing of processing between the client and the server. In step S11, when the client transmits the mediation request of the content distribution source node and the reception start time specifying information, the server converts the reception start time specifying information into the assumed reception start time in steps S12 and S13, and stores the storage unit. To record. Then, the server searches for a connection destination candidate node based on the assumed reception start time in steps S14 and S15, and notifies the connection destination candidate node to the client that has requested the content in step S16.

  Although the present embodiment has been described in detail as described above, it will be easily understood by those skilled in the art that many modifications can be made without departing from the novel matters and effects of the present invention. Accordingly, all such modifications are intended to be included in the scope of the present invention. For example, a term described at least once together with a different term having a broader meaning or the same meaning in the specification or the drawings can be replaced with the different term in any part of the specification or the drawings. Further, the topology of the distribution network, the method of arranging connection nodes, the method of measuring line quality, and the like are not limited to those described in this embodiment, and techniques equivalent to these are also included in the scope of the present invention.

N1-N6, NX node, TS1-TS5, TSX, TS Assumed reception start time,
DQ1-DQ5, DQX, DQ data retention, TC current time,
VL minimum guaranteed communication speed, VN1 to VN5, VNX communication speed,
NTA, NTB distribution network,
10 distribution network, 110 content distribution unit, 120 reception unit, 130 transmission unit,
170 storage unit, 172 content storage unit, 174 management information storage unit,
200 processing unit, 220 receiving unit, 230 transmitting unit, 240 communication management unit,
250 content playback unit, 260 operation unit, 270 storage unit,
272 content storage unit, 274 management information storage unit, 280 information storage medium,
290 display unit, 292 sound output unit, 296 communication unit

Claims (20)

A receiver for receiving information from each node of the distribution network;
A transmitter for transmitting information to each node of the distribution network;
A node management unit that performs node management processing of the distribution network,
Content is distributed from a content distribution source node of the distribution network to a content distribution destination node by a P2P (Peer to Peer) relay method,
The node management unit
When it is determined that the communication speed at the new participating node that has requested content distribution satisfies the communication speed condition of the requested content, the connection destination of the new participating node from among the participating nodes of the distribution network Search for candidate nodes,
The transmitter is
A server system, wherein notification information for mediating the searched connection destination candidate node as a distribution source node of the requested content is transmitted to the new participation node. In claim 1,
A plurality of contents with different image quality are prepared as the requested contents,
The node management unit
The image quality corresponding to the communication speed at the new participating node is selected, and the connection destination candidate node is searched from among the participating nodes of the distribution network that distributes the content of the selected image quality among the plurality of contents. A server system characterized by that. In claim 2,
The node management unit
If it is determined that the requested content stream is not stream-playable but download-playback is possible, the communication speed at the new-participating node is that of the participating node of the distribution network that downloads and plays the requested content. A server system, wherein the connection destination candidate node is searched from among them. In claim 1,
The node management unit
Based on the communication speed at the new participation node, it is determined which of the first to Kth communication speed level groups (K is an integer of 2 or more), and the new participation node When it is determined that the node belongs to the i-th communication speed level group (1 ≦ i ≦ K) among the first to K-th communication speed level groups, the node is assigned to the i-th communication speed level group. A server system, wherein the connection destination candidate node is searched from among participating nodes of a corresponding distribution network. A receiver for receiving information from each node of the distribution network;
A transmitter for transmitting information to each node of the distribution network;
A node management unit that performs node management processing of the distribution network,
Content is distributed from a content distribution source node of the distribution network to a content distribution destination node by a P2P (Peer to Peer) relay method,
The node management unit
Based on the communication speed at the new participating node that has requested the content distribution, it is determined which of the first to Kth (K is an integer of 2 or more) communication speed level groups the new participating node belongs to. If it is determined that the newly participating node belongs to the i-th communication speed level group (1 ≦ i ≦ K) of the first to K-th communication speed level groups, the i-th The connection destination candidate node of the new participation node is searched from among the participation nodes of the distribution network corresponding to the communication speed level group of
The transmitter is
A server system, wherein notification information for mediating the searched connection destination candidate node as a distribution source node of the requested content is transmitted to the new participation node. In claim 4 or 5,
The first communication speed level group of the first to Kth communication speed level groups is a stream reproduction of content having a first image quality level and a second image quality level having a lower image quality than the first image quality level. Of the first to Kth communication speed level groups, the second communication speed level group of the first to Kth communication speed level groups downloads and plays back the first image quality level content and the second communication speed level group. A server system, which is a group capable of stream playback of content of an image quality level. In claim 6,
The node management unit
When a node that belongs to the first communication speed level group and plays a stream of content of the first image quality level is changed to belong to the second communication speed level group due to a decrease in communication speed The second communication speed level group is downloaded and reproduced for the content of the first image quality level that was being reproduced in the stream reproduction of the first communication speed level group. Server system. In claim 6 or 7,
3. The server system according to claim 1, wherein a third communication speed level group among the first to Kth communication speed level groups is a group capable of downloading and reproducing content of the second image quality level. In claim 8,
The node management unit
When a node that belongs to the second communication speed level group and plays a stream of content of the second image quality level is changed to belong to the third communication speed level group due to a decrease in communication speed The third communication speed level group is downloaded and reproduced for the content of the second image quality level that was being reproduced in the stream reproduction of the second communication speed level group. Server system. In any one of Claims 1 thru | or 9,
The receiver is
From each node of the distribution network, receiving the measurement result information of the line quality at each node,
The node management unit
A server system, wherein a communication speed at each of the nodes is determined based on the received measurement result information. In claim 10,
The node management unit
Search for cooperation nodes that can cooperate in the measurement of the line quality,
The transmitter is
Sending notification information to the each node to the searched cooperation node to each node,
The receiver is
Each node performs communication connection with the cooperating node to measure the line quality, and when each node transmits the line quality measurement result information, the transmitted measurement result information is received,
The node management unit
A server system, wherein a communication speed at each node of the distribution network is determined based on the received measurement result information. In claim 11,
The node management unit
As the cooperation node, a first cooperation node that is a distribution source node and a distribution destination node so that each node communicates with both the distribution source node and the distribution destination node and the line quality is measured. Search for a second cooperating node,
The transmitter is
A server system, wherein notification information that mediates both of the searched first and second cooperative nodes to each node is transmitted to each node. In any one of Claims 1 to 12,
The receiver is
From the new participation node, receiving the reception start timing specification information of the requested content at the new participation node,
The node management unit
Obtaining the expected reception start timing of the requested content at the new participation node based on the received reception start timing specifying information, and based on the calculated expected reception start timing, from among the participating nodes of the distribution network Search for connection destination candidate nodes,
The transmitter is
A server system, wherein notification information for mediating the searched connection destination candidate node as a distribution source node of the requested content is transmitted to the new participation node. In claim 13,
A storage unit that stores a plurality of assumed reception start timings corresponding to a plurality of participating nodes of the distribution network;
The node management unit
Among the plurality of assumed reception start timings stored in the storage unit, the timing is earlier than the assumed reception start timing of the new participation node, and the timing is closest to the assumed reception start timing of the new participation node A server system, wherein an assumed reception start timing is searched, and a participating node corresponding to the searched assumed reception start timing is determined as the connection destination candidate node. A receiver for receiving information from the server system;
A transmission unit for transmitting information to the server system;
Including a communication management unit,
Content is distributed from a content distribution source node of the distribution network to a content distribution destination node by a P2P (Peer to Peer) relay method,
The receiver is
When a cooperative node capable of cooperating with the measurement of circuit quality is searched, notification information for mediating the searched cooperative node is received from the server system,
The communication management unit
Communicatively connect with the cooperating node intervened by the notification information, measure the line quality,
The transmitter is
A client apparatus, wherein the line quality measurement result information is transmitted to the server system. In claim 15,
The communication management unit
The line quality is measured, and the communication speed in a state where the cooperation node is connected for communication is obtained.
The transmitter is
A client apparatus, wherein the line quality measurement result information including the obtained communication speed is transmitted to the server system. In claim 15,
The communication management unit
The line quality is measured to determine the communication speed in a state where the cooperative node is in communication connection, and it is determined whether the determined communication speed satisfies the communication speed condition of the requested content,
The transmitter is
When the determined communication speed is determined to satisfy the communication speed condition of the requested content, notification information for requesting delivery of the requested content is transmitted to the server system. apparatus. In claim 16 or 17,
The receiver is
The server system receives notification information for mediating a first cooperation node that is a content distribution source node and a second cooperation node that is a content distribution destination node as the cooperation node,
The communication management unit
A client apparatus, wherein the line quality is measured to determine the communication speed in a state where both the first and second cooperative nodes are in communication connection. A receiver for receiving information from the server system;
A transmission unit for transmitting information to the server system;
As a communication manager
Make the computer work,
Content is distributed from a content distribution source node of the distribution network to a content distribution destination node by a P2P (Peer to Peer) relay method,
The receiver is
When a cooperative node capable of cooperating with the measurement of circuit quality is searched, notification information for mediating the searched cooperative node is received from the server system,
The communication management unit
Communicatively connect with the cooperating node intervened by the notification information, measure the line quality,
The transmitter is
A program characterized by transmitting the line quality measurement result information to the server system.   An information storage medium readable by a computer, wherein the program according to claim 19 is stored.

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