JP5616801B2 - User terminal and distribution topology reassignment program - Google Patents

Description

  The present invention relates to a content distribution system, and in particular, a user terminal used by a user who views content, and a user terminal that participates in a distribution tree in which a plurality of user terminals are connected hierarchically with a distribution server at the top. The present invention relates to a distribution topology rearrangement program for causing a distribution topology rearrangement process indicating an order on a distribution tree to be executed.

  In recent years, streaming video distribution services have become widespread on the Internet. In addition to the one-to-one distribution service such as VOD (Video On Demand) that selects the content to be viewed at the receiving terminal and receives the selected content from the distribution server, the same content is simultaneously transmitted to many receiving terminals. A one-to-many (broadcast type) distribution service for transmission is known. Furthermore, IP multicast is known as a method for efficiently performing a broadcast-type moving image distribution service in an IP network. However, in this IP multicast method, a dedicated network for the communication carrier is required, and it is difficult to provide a service across a plurality of carriers.

  Against this background, a distributed content distribution technology using peer-to-peer technology has been devised in order to enable a broadcast-type video distribution service that spans multiple carriers without requiring a dedicated network for carriers. Such a technique realizes multicast (one-to-many communication) by creating a logical tree between user terminals requesting content, and application software operating on the terminals mutually transfers data. For example, the stream data distributed delivery method described in Patent Document 1 can be cited.

  In the stream data distribution and delivery method described in Patent Document 1, each node transmits and receives stream data between nodes in a network environment such as the Internet, and each node has topology information indicating a connection relationship between an upstream node and a downstream node. And the stream data is relayed from the upstream node to the downstream node. In this stream data distributed delivery method, in order to exchange topology information between the nodes, each node has a function of performing management such as autonomously storing and updating topology information and further providing it.

  Moreover, the technique of nonpatent literature 1 is disclosed as another example of such a content delivery system. In the technique of Non-Patent Document 1, streaming media is fragmented into a plurality of data packets in the distribution server (the fragmented data is called a chunk). Each terminal dynamically detects a terminal having a necessary chunk, receives a chunk in a pull type from the detected terminal, and reconfigures the received chunk to obtain a desired streaming medium. it can. An example of such a content distribution system is shown in FIG. In the example of the content distribution system 100 shown in FIG. 1, among the chunks obtained by dividing the content into six (1) to (6) by the distribution server 103, odd-numbered chunks are even-numbered along the solid line. The chunks are transferred along the broken lines to show that all the chunks have been delivered to the six terminals (user terminals) 101a to 101f shown in the figure.

  In such a hierarchical content distribution system 100, the efficiency of the entire system changes depending on where in the distribution tree the user terminals of which performance are arranged. For example, among a plurality of user terminals, a user terminal that has a sufficient transmission capacity of the connected Internet line and can distribute a stream to many terminals can be further connected by being closer to the distribution server. Stable content can be distributed to many terminals. In addition, if a user who uses a terminal in the distribution tree stops viewing and the distribution tree is divided (when a disconnection occurs), it immediately establishes a connection relationship with another terminal in the distribution tree. It is possible to improve stability by re-enabling the stream transfer so as not to be interrupted.

JP 2003-169089 A JP 2009-124662 A

Xinyan Zhang, Jiangchuan Liu, Bo Li, and Tak-Shing Peter Yum, “CoolStreaming / DoNet: A Data-Driven Overlay Network for Efficient Live Media Streaming”, In Proc. Of the 24th IEEE INFOCOM, March 2005, p.2102- 2111

  However, in the content distribution system 100, even a user terminal having a sufficient transmission capacity (transmission capability) of the Internet line cannot always be connected to a user terminal close to the distribution server 103. One reason is that at the timing when the user starts viewing at each user terminal, the terminal newly connects to the distribution tree and starts receiving content. In addition, another reason is that the number of user terminals that can be connected to one user terminal (the number of connectable terminals) is usually limited.

  Also, in the content distribution system 100, once a connection is established between user terminals, the connection is maintained unless content transmission / reception is interrupted. Therefore, once a user terminal with sufficient transmission capacity (transmission capacity) is connected to the downstream of the distribution tree, the user is close to the distribution server due to the disconnection of other user terminals. Even when there is room for connection to the terminal, there is a problem that a user terminal with a margin maintains the current state.

  With respect to such a problem, in Patent Document 2, for example, two parent nodes are connected to the downstream of the soot node located on the upstream side of the tree, and two child nodes are connected to the downstream of one parent node. A technique for improving stability of the entire system by dealing with a case where there is room for connection in the configuration tree is disclosed. In this technique, when the connection of the other parent node is released, the heel node notifies one parent node that the connection has been released. Then, one parent node transmits a connectable notification indicating that the connection to the saddle node is possible to one of the two downstream child nodes. Thereby, any of the child nodes can be newly connected to the soot node.

However, when assuming a system in which each node device (user terminal) autonomously constructs a distribution topology, in the technique of Patent Document 2, before the child node that has received the connectable notification is connected to the 爺 node, There is a possibility that another newly joined node device will connect to the node.
It is not always possible to perform connection switching processing as intended. For this reason, connection switching may not be established, resulting in useless processing.

  Furthermore, the user terminal that constitutes the distribution tree is, for example, a PC (Personal computer), and the PC installed in a general home or company is connected to the Internet via a NAT (Network Address Translation) router. There are many. Such a PC can establish a connection with another terminal (PC or server) on the Internet by making a connection request from itself (own terminal), and can communicate with the other terminal from another terminal on the Internet. Since the connection request is blocked by the NAT router, it cannot be accepted and a connection cannot be established. The technique described in Patent Document 2 does not consider this point. Therefore, if the saddle node described in Patent Document 2 is connected to the Internet via a NAT router and cannot accept a connection request, a new connection request cannot be made from the child node to the saddle node. .

  The present invention has been made in view of the above problems, and provides a user terminal and a distribution topology reassignment program that can stably distribute contents to terminals belonging to a distribution tree that distributes contents. This is the issue.

In order to solve the above-mentioned problem, the user terminal according to claim 1 of the present invention is a plurality of user terminals used by a user who views the content with the content distribution server being a content distribution source at the top. In a content distribution system that forms a hierarchically connected distribution tree and distributes the content, a plurality of user terminals on the distribution tree can accept connection requests from other user terminals A user terminal and a user terminal that cannot be accepted, and redistributing a distribution topology indicating a terminal connection order on the distribution tree between the user terminals according to a communication environment of the user terminal Communication environment information acquisition means, distribution topology reconfiguration terminal selection means, connection reconfiguration instruction means, connection reconfiguration request means , It was decided and a connection switching unit.

According to this configuration, the user terminal indicates whether or not the communication environment information acquisition unit can accept a connection request from another user terminal connected to its own terminal on the distribution tree. Information indicating the communication environment including availability information is acquired. Then, the user terminal selects any two terminals from among a plurality of other user terminals connected to the terminal as a target of the process of rearranging the distribution topology by the distribution topology rearrangement terminal selection unit. One of the two selected terminals is determined as a reassignment request terminal, and the other is determined as a reassignment reception terminal. Here, reclassification reception terminal is configured to establish a connection one with the accepting requests for reclassification from a selected one, to perform the exchange connection assembly for cutting the own terminal performing the decision. Further, the reassignment request terminal requests the connection reassignment to the other selected. Furthermore, the distribution topology reclassification terminal selection means, when selecting the second terminal, at least one terminal selects a user terminal the arrival permission information is reached Friendly, before Symbol arrival permission information is a reach-friendly The user terminal is determined to be the reassignment reception terminal, the recombination reception terminal is selected from either the upstream side or the downstream side on the distribution tree, and the reassignment request terminal is selected on the distribution tree. Select from the other of the upstream and downstream sides . A terminal whose reachability information is reachable can accept a connection request from another terminal on the Internet. And a user terminal performs the connection reassignment request | requirement with respect to the determined said rearrangement reception terminal with respect to the determined recombination request | requirement terminal by a connection reassignment instruction | indication means not via a self-terminal. To instruct. Then, the user terminal, when functioning as the reclassification request terminal, the connection reclassification request unit, a user terminal to instruct to perform the connection set exchange request to the reclassification request terminal reclassification The instruction is received from the instruction terminal, and a request for connection reassignment is made by notifying the reassignment reception terminal of a reassignment request message including identification information of the reassignment instruction terminal. When the user terminal functions as the reassignment receiving terminal, the connection switching unit receives the reassignment request message from the reassignment request terminal and establishes a connection with the reassignment request terminal. At the same time, the connection with the reassignment instruction terminal is disconnected.

  According to such a configuration, the user terminal uses the distribution topology reassignment terminal selection unit to select any one user terminal connected upstream on the distribution tree and any one user terminal connected downstream. It is possible to connect securely and rearrange the distribution topology safely.

Further, the user terminal according to claim 2 is the user terminal according to claim 1 , wherein the communication environment information acquisition means receives the reachability information as information indicating a communication environment from another user terminal. And the transmission capacity information of the terminal, and when the distribution topology reassignment terminal selection unit selects the two terminals, it connects to its own terminal at the upstream position on the distribution tree. One user terminal and one user terminal having the largest transmission capacity and connected to the own terminal at the downstream position on the distribution tree, and selecting either one of the two selected terminals The reachability information is reachable.

  According to such a configuration, the user terminal preferentially selects the upstream terminal and the user terminal having the largest transmission capacity among the downstream terminals by the distribution topology reassignment terminal selection unit. A certain downstream terminal can be reliably connected to the upstream terminal, and the distribution topology can be safely rearranged. As a result, since a terminal having a sufficient transmission capacity can be brought closer to the content distribution server, the stability of content distribution can be improved.

The user terminal according to claim 3 is the user terminal according to claim 1 or 2 , wherein the distribution topology recombination terminal selection means is a target of processing for reconfiguring the distribution topology. The process of selecting the reassignment receiving terminal and the reassignment requesting terminal is started when the own terminal leaves the distribution tree.

  According to such a configuration, when the user terminal leaves the distribution tree, the user terminal performs a process of rearranging the distribution topology. Therefore, the connection relationship between the two terminals that are connected to the terminal and are not connected to each other After building, the terminal can leave. For this reason, in the distribution tree, even if the terminal is disconnected, the transfer of the stream from the content distribution server can be prevented from being interrupted, and the stability can be improved.

The user terminal according to claim 4 is the user terminal according to claim 1 or 2 , wherein the distribution topology recombination terminal selection means is a target of processing for recombination of the distribution topology. The process of selecting and selecting the reassignment receiving terminal and the reassignment request terminal is started at an arbitrary timing set in advance.

  According to such a configuration, the user terminal performs processing for rearranging the distribution topology at an arbitrary timing set in advance, so that the user terminal is connected regardless of whether the user of the user terminal is viewing the content. It is possible to establish a connection relationship between two terminals that are not connected to each other. For this reason, even if the transmission capacity of the terminal itself is no longer sufficient, the stream transfer from the content distribution server can be prevented from being interrupted, and the stability can be improved.

The distribution topology reassignment program according to claim 5 is a distribution tree in which a plurality of user terminals used by users who view the content are hierarchically connected with the content distribution server as a content distribution source at the top. In the content distribution system configured to distribute the content by configuring a plurality of user terminals on the distribution tree, user terminals that can accept connection requests from other user terminals cannot be accepted In order to recombine the distribution topology indicating the connection order of the terminals on the distribution tree between the user terminals according to the communication environment of the user terminal, Computer, communication environment information acquisition means, distribution topology reconfiguration terminal selection means, connection reconfiguration instruction means, connection reconfiguration request Stage, was to be a program for functioning as a connection switching means.

According to such a configuration, the distribution topology reassignment program determines whether or not the communication environment information acquisition unit can accept a connection request from another user terminal connected to the own terminal on the distribution tree. Information indicating the communication environment including the reachability information shown is acquired. Then, the distribution topology reassignment program selects any two terminals from among a plurality of other user terminals connected to the own terminal as a target of the process of reordering the distribution topology by the distribution topology reconfiguration terminal selection means. One of the two selected terminals is determined as a reassignment request terminal, and the other is determined as a reassignment reception terminal. Here, the distribution topology reclassification terminal selection means, said in selecting the second terminal, at least one terminal selects a user terminal the arrival permission information is reached Friendly, before Symbol arrival permission information reaches Allowed A user terminal is determined as the reassignment reception terminal, the reassignment reception terminal is selected from either the upstream side or the downstream side on the distribution tree, and the reassignment request terminal is selected on the distribution tree. To select from the other of the upstream and downstream sides . Then, the distribution topology reassignment program sends a connection reassignment request to the determined reassignment receiving terminal to the determined recombination requesting terminal by the connection reassignment instructing means without going through its own terminal. Instruct to run. The distribution topology reassignment program receives the instruction from the reassignment instruction terminal which is a user terminal that instructs the reassignment request terminal to execute the connection reassignment request by the connection reassignment request unit. Then, the reassignment request message including the identification information of the reassignment instruction terminal is notified to the reassignment reception terminal to request connection reassignment. The distribution topology reassignment program receives the reassignment request message from the reassignment request terminal by the connection switching means, establishes a connection with the reassignment request terminal, and communicates with the reassignment instruction terminal. Disconnect the connection.

According to the invention described in claim 1 or claim 5 , the user terminal is a terminal to which the own terminal is connected according to the communication environment of another user terminal connected to the own terminal in the distribution tree. Thus, a connection relationship can be established between the two terminals that are not connected to each other. Therefore, content can be stably distributed to terminals belonging to a distribution tree for distributing content.

According to the invention described in claim 1, claim 2 or claim 5 , the user terminal reliably connects the user terminal connected downstream of the user terminal and the user terminal connected upstream in the distribution tree. Connect and securely redistribute distribution topologies.

According to the invention described in claim 3 or claim 4 , the user terminal can prevent the stream transfer from the content distribution server from being interrupted even if the terminal is disconnected in the distribution tree. Stability can be improved.

It is a figure which shows the structural example of the conventional content delivery system. It is a figure which shows an example of a structure of the content delivery system by the user terminal and delivery topology rearrangement method which concern on embodiment of this invention. It is a block diagram which shows the user terminal which concerns on embodiment of this invention. An example of the terminal information memorize | stored in the user terminal which concerns on embodiment of this invention is shown. It is explanatory drawing which shows the function of the connection control means of the user terminal which concerns on embodiment of this invention. It is a block diagram which shows the structural example of the delivery topology recombination terminal selection means of the user terminal which concerns on embodiment of this invention. It is a sequence diagram which shows an example of the procedure at the time of a new user terminal joining a delivery group in the content delivery system which concerns on embodiment of this invention. It is a figure which shows an example of the delivery tree formed by the delivery group in the content delivery system which concerns on embodiment of this invention. It is a sequence diagram which shows the flow of the connection switching operation | movement between each user terminal in the content delivery system which concerns on embodiment of this invention. It is a flowchart which shows the detail (the 1) of the delivery topology recombination terminal selection process which concerns on embodiment of this invention. It is a flowchart which shows the detail (the 2) of the delivery topology recombination terminal selection process which concerns on embodiment of this invention. It is a figure which shows an example of the delivery topology rearrangement process by the user terminal which concerns on embodiment of this invention, Comprising: (a) has each shown before connection rearrangement and (b) after connection rearrangement.

  Hereinafter, embodiments for carrying out the present invention will be described. 1. Overview of content distribution system 2. Details of user terminals; 3. Configuration example of distribution topology recombination terminal selection means The operation will be described in detail with reference to the drawings divided into chapters of the operation of the user terminal.

[1. Overview of content distribution system]
In the content distribution system S shown in FIG. 2, a plurality of user terminals 1 (1G, 1R, 1N) used by users who view content are hierarchically connected with the content distribution server 3 that is a content distribution source as the apex. The distribution tree is configured to distribute contents. Therefore, in the content distribution system S, the user terminal 1 can obtain desired streaming media in the same manner as the content distribution system 100 shown in FIG. However, in the content distribution system S, the user terminal 1 is connected to a network (Internet, local network) in three different forms and has different functions.

The user terminal 1G, the terminal management server 2, and the content distribution server 3 are directly connected to the Internet 4.
Each local network 7 is connected to the Internet 4 via a port openable NAT router 5.
Each local network 8 is connected to the Internet 4 via a NAT router 6 that cannot open a port.
The user terminal 1R is indirectly connected to the Internet 4 via the local network 7 and the port openable NAT router 5.
The user terminal 1N is indirectly connected to the Internet 4 via the local network 8 and a port router that cannot open ports.

  Here, the port openable NAT router 5 corresponds to a port open function by UPnP (Universal Plug and Play), for example, and a connection request from the outside of the router (Internet 4) is sent to a user terminal in the local network 7. It is a router that can transfer to 1R. Therefore, the user terminal 1R connected to the port openable NAT router 5 via the local network 7 is connected to the terminal management server 2, the content distribution server 3, other user terminals 1R via the Internet 4 and TCP / It is possible to request connection with each other using a communication protocol such as IP, and also accept connection requests (can be reached), and can send and receive data after establishing a connection. Shall.

On the other hand, the NAT router 6 that cannot open a port does not support, for example, the UPnP port opening function or the like, but disables the function even if it supports, so connection from the outside of the router (Internet 4) The router cannot transfer the request to the user terminal 1N in the local network 8. Therefore, the user terminal 1N connected to the NAT router 6 through which the port cannot be opened via the local network 8 is connected to the terminal management server 2, the content distribution server 3, and the user terminal 1R via the Internet 4. It is possible to establish a connection and send / receive data by making a connection request, but it is not possible to accept connection requests (for example, TCP connections) of these devices and other user terminals 1N.
In FIG. 2, the terminal management server 2 and the content distribution server 3 are shown as individual devices, but one device may have all the functions.

<Content distribution server>
The content distribution server 3 is a server that is a content distribution source. The content distribution server 3 sequentially distributes content data to the user terminals 1 participating in a distribution tree formed by connecting the content distribution server 3 and the user terminals 1 in a hierarchical manner.
In the following description, the term “terminal” simply refers to the content distribution server 3 or each user terminal 1. A distribution topology constructed by determining the connection relation of each node at a certain point in time with the content distribution server 3 as the vertex of the node is called a distribution tree. A collection of nodes in the distribution tree is called a distribution group.

<Terminal management server>
The terminal management server 2 holds and manages terminal information, which is information related to content distribution of each terminal participating in the content distribution system S, in the terminal information list L. Here, each terminal refers to the content distribution server 3 or each user terminal 1. The terminal information includes information necessary for data transfer such as an IP address and a port number as information associated with the terminal ID for identifying the content distribution server 3 and the user terminal 1.
When the user terminal 1 newly joins the distribution group, the terminal management server 2 receives a connection destination introduction request that is a message including the terminal information of the user terminal 1 from the new user terminal 1.
The terminal management server 2 returns an initial connection destination list in response to the connection destination introduction request. This initial connection destination list is a list including one or more pieces of terminal information of terminals that are candidates for connection destinations to which user terminals 1 newly joining the distribution group can directly connect. Here, the terminal that is a candidate for the connection destination is the content distribution server 3 or another user terminal 1.

<User terminal>
The user terminal 1 is a terminal that is connected to other user terminals 1 belonging to the same distribution tree, and receives and transfers content data packets (referred to as content data).
That is, the user terminal 1 has a function of being a content distribution side and a reception side as a node using the peer-to-peer technology in the distribution tree.

Although details will be described later, the user terminal 1 indicates the connection order of the terminals on the distribution tree between the user terminals 1 (1G, 1N, 1R) according to the communication environment of the user terminal 1. In order to execute a distribution topology reconfiguration process for reconfiguring a distribution topology, for example, as shown in FIG. 9, a function as a reconfiguration request terminal (hereinafter referred to as 1a) that requests connection reconfiguration to another terminal; A function as a reconfiguration accepting terminal (hereinafter referred to as 1p) that accepts a request for connection reassignment from the reassignment request terminal 1a, and a reassignment request for connection to the reconfiguration accepting terminal 1p to the reconfiguration request terminal 1a And a function as a reassignment instruction terminal (hereinafter referred to as 1c) for instructing execution. Details will be given later, but in the distribution tree, reclassification instruction terminal 1c (Nc in FIG. 12 (a)) is set from the user terminal 1 connected to the own terminal replacement request terminal 1a (FIG. 12 (a ) And Na) and the reassignment receiving terminal 1p (Np in FIG. 12A) are determined. In addition, the connection reassignment executed by the reassignment receiving terminal 1p (Np in FIG. 12A) is a request for reassignment to connect to the reassignment request terminal 1a (Na in FIG. 12A). The reconfiguration instruction terminal 1c (Nc in FIG. 12A) is established and indicates reconfiguration (the recombination result is shown in FIG. 12B).

[2. Details of user terminal]
The user terminal 1 is, for example, a general personal computer including an arithmetic device such as a CPU (Central Processing Unit), a storage device such as a memory or a hard disk, and an interface device that transmits and receives various types of information to and from the outside. It consists of a computer.
The user terminal 1 is realized by controlling the hardware resources described above by a program. As shown in FIG. 3, the storage unit 11, the connection partner selection unit 12, the distribution topology recombination terminal selection unit 13, and the like. , Connection reassignment instruction means 14, connection reassignment request means 15, connection switching means 16, connection control means 17, terminal information management means 18, communication environment information acquisition means 19, and connection communication environment measurement means 20. A content data relay unit 21, a content buffer 22, a content playback unit 23, and a communication interface 24.

  The storage unit 11 includes a storage device such as a RAM (Random Access Memory) and a ROM (Read Only Memory), and a hard disk, and includes a terminal information storage unit 111 and a topology information storage unit 112.

  The terminal information storage unit 111 stores terminal information of its own user terminal 1 (own terminal) and terminal information of other user terminals 1 (other terminals) participating in the distribution group and the content distribution server 3. And hold.

  An example of the terminal information is shown in FIG. In the example of FIG. 4, as a terminal information database item in which terminal information of each terminal is converted into a database, a connection standby address 42, reachability 43, transmission capability 44, and connectable number 45 associated with the terminal ID 41, respectively. In addition, the current connection number 46 and the hop number 47 are included.

  The terminal ID 41 is an identifier that uniquely identifies the content distribution server 3 and the user terminal 1. As the terminal ID 41, for example, unique information of each terminal, a MAC address, a universal unique identifier (UUID), or the like may be used.

  The connection standby address 42 indicates a set of an IP address and a port number that can accept a connection request from another terminal. However, when the information of reachability 43 is “unreachable” (“no” in the example of FIG. 4), connection acceptance from other user terminals 1 is impossible, and therefore, in FIG. ----”

  The reachability 43 is information (reachability information) indicating whether a connection request can be accepted via the Internet 4. For example, the value of reachability information is “reachable” when it can be accepted, and the value of reachability information is “unreachable” when it cannot be accepted. A terminal whose reachability information is “reachable” can accept a connection request without a connection request from another terminal on the Internet being blocked by a NAT router (portable NAT router 5: see FIG. 2). . For a terminal whose reachability information is “unreachable”, a connection request from another terminal on the Internet is blocked by a NAT router (port release unusable NAT router 6: see FIG. 2). In the example of FIG. 4, “reachable” and “unreachable” are simply abbreviated as “enabled” and “not allowed”. Further, “reachable” and “unreachable” can be realized by flags “0”, “1”, and the like.

  The transmission capability 44 is information indicating transmission capability related to transmission / reception of content data of the terminal associated with the terminal ID 41. In FIG. 4, as an example, the larger the numerical value, the higher the transmission capability.

  The connectable number 45 is information indicating the maximum number of terminals that can be connected simultaneously when the terminal associated with the terminal ID 41 is connected to the content distribution server 3 or another user terminal 1. The connectable number 45 is, for example, the connectable number when viewed from the user terminal 1 on the connection request receiving side. As the connectable number 45, a predetermined value may be set in advance, or may be sequentially updated according to the communication state of the user terminal 1.

  The current connection number 46 is information indicating the total number of content distribution servers 3 and other user terminals 1 to which the terminal associated with the terminal ID 41 is currently connected. The current connection number 46 is, for example, the connection acceptance number when viewed from the user terminal 1 on the side of accepting the connection request.

  The number of hops 47 is a value indicating the number of relay stages from the content distribution server 3 in the distribution tree. The number of hops 47 indicates the number of stages (minimum number of hops) counted so as to be relayed from the content distribution server 3 in the shortest time. Here, the hop count of the content distribution server 3 is set to 0, the hop count of the user terminal 1 directly connected to the content distribution server 3 is 1, and the hop of the user terminal 1 connected to the user terminal 1 Let the number be 2. Further, when the currently connected content distribution server 3 or other user terminal 1 is changed due to connection or disconnection, the hop count 47 is updated at any time according to the change in the hop count of the connected terminal. be able to.

  The topology information storage unit 112 stores and stores information on the terminal ID of the directly connected terminal as information on the distribution topology constructed by connecting the user terminal 1 directly to another terminal. This distribution topology information is used for transmission / reception of content data via the user terminal 1. The side that transmits content data to the user terminal 1 is referred to as upstream, and the side that receives content data from the user terminal 1 is referred to as downstream.

The connection partner selection unit 12 selects a connection partner candidate from the terminal information stored in the terminal information storage unit 111 based on a predetermined criterion, and the connection control unit 17 is connected to the selected user terminal 1. The connection request is transmitted through the network. Here, as a predetermined reference, for example, a terminal that satisfies all of the following conditions A1 to A3 can be selected as a connection partner candidate.
(Condition A1) The terminal ID is not stored in the topology information storage unit 112.
(Condition A2) The value of the current connection number is smaller than the value of the connectable number.
(Condition A3) The value of the reachability information is “reachable”.

The user terminal 1 shown in FIG. 3 has, for example, functions such as the connection control means 17 depending on which one of the functions of the reassignment instruction terminal 1c, reassignment request terminal 1a and reassignment reception terminal 1p shown in FIG. Will be different. FIG. 5 shows a block diagram in which each unit shown in FIG. 3 is made to correspond to these three functions and a part thereof is extracted.
The reassignment instruction terminal 1c shown in the lower right of FIG. 5 has Nc as an ID when executing this function. Further, in the drawing, “c” is added to distinguish the reference numerals of the respective means for executing this function.
The reassignment request terminal 1a shown in the upper right of FIG. 5 has Na as an ID when executing this function. Further, in the drawings, “a” is added to the reference numerals of the respective means for executing this function for distinction.
The reassignment receiving terminal 1p shown on the left in FIG. 5 has Np as an ID when executing this function. Further, in the drawings, “p” is added to distinguish the reference numerals of the respective means for executing this function. Hereinafter, with reference to FIG. 5 (refer to FIG. 3 as appropriate), the description of the configuration of each means of the user terminal 1 will be continued.

<Recomposition instruction terminal>
As shown in FIG. 5, the reassignment instruction terminal 1c has, as main components, a distribution topology reconfiguration terminal selection means 13 (indicated as 13c in FIG. 5) and a connection reassignment instruction means 14 (indicated as 14c in FIG. 5). And connection control means 17 (indicated as 17c in FIG. 5).

The distribution topology recombination terminal selection means 13 selects any two terminals from among a plurality of other user terminals 1 connected to the own terminal as a target of processing for redistributing the distribution topology, and the selected two terminals Of these, the selected one is determined as the reassignment request terminal 1a, and the other is determined as the reassignment reception terminal 1p.
When this distribution topology recombination terminal selection means 13 selects two terminals, it selects the user terminal 1 with reachability information reachable as one of them, and the receptive reception terminal 1p is reachable with reachability information. Is determined to be a user terminal.

  Here, when selecting two terminals, the distribution topology reassignment terminal selection means 13 connects to any one user terminal connected to the own terminal at an upstream position and to the own terminal at a downstream position. At the same time, the user terminal having the largest transmission capacity is selected. A terminal connected upstream is a terminal having a smaller hop count from the content distribution server 3 than its own terminal, and a terminal connected downstream has a larger hop count from the content distribution server 3 than its own terminal. It is a terminal.

In this embodiment, the distribution topology reassignment terminal selection unit 13 selects the distribution topology reconfiguration from the user terminals 1 whose terminal IDs are stored in the topology information storage unit 112 based on transmission capability and reachability information. Two target user terminals 1 are selected, one is determined to be the reassignment request terminal 1a, and the other is determined as the reassignment reception terminal 1p, and the terminal IDs of these user terminals 1 are assigned to the reassignment request terminal ID (= Na ) And output to the connection reassignment instruction means 14 as the reassignment reception terminal ID (= Np).
Details will be described later.

The connection reassignment instruction unit 14 connects the reconfiguration request terminal 1a determined by the distribution topology reconfiguration terminal selection unit 13 to the reconfiguration receiving terminal 1p determined by the distribution topology reconfiguration terminal selection unit 13 This is an instruction to execute a replacement request.
Here, the connection reassignment instruction means 14 is the reassignment request terminal ID (= Na), reassignment reception terminal ID (= Np), and the terminal ID of its own terminal input from the distribution topology reconfiguration terminal selection means 13. A reassignment instruction message is generated and transmitted using a certain reassignment instruction terminal ID (= Nc).
In the present embodiment, the connection reassignment instruction unit 14 includes a reassignment instruction message transmission unit 141. The reassignment instruction message transmission unit 141 sends a recombination instruction message including a reassignment reception terminal ID (= Np) and a reassignment instruction terminal ID (= Nc) to the reassignment request terminal 1a with a predetermined communication interface. 24.

  The connection control unit 17 (denoted as 17c in FIG. 5) includes a connection request unit 171, a connection reception unit 172, and a disconnection unit 173, and the connection reception unit 172 functions. In FIG. 5, the non-functioning sub-block is indicated by a broken line frame.

  The connection reception unit 172 (indicated as 172c in FIG. 5) receives a disconnection request to be described later transmitted from the reconfiguration reception terminal 1p in response to the connection instruction and the connection request, and when disconnected, the terminal of the disconnected other terminal The ID is deleted from the topology information storage unit 112 (see FIG. 3) of the storage unit 11c, and the current connection number is decremented in the terminal information of the own terminal stored in the terminal information storage unit 111 (see FIG. 3) (1 Subtract).

<Reclassification request terminal>
As shown in FIG. 5, the reassignment request terminal 1a includes, as main components, a connection reassignment request means 15 (denoted as 15a in FIG. 5) and a connection control means 17 (denoted as 17a in FIG. 5).

The connection reassignment request unit 15 receives a connection reassignment instruction (recombination instruction message) from the reassignment instruction terminal 1c, and includes a reassignment request message including the ID (identification information = Nc) of the reassignment instruction terminal 1c. Is notified to the reassignment receiving terminal 1p to request connection reassignment.
In the present embodiment, the connection reassignment request unit 15 includes a reassignment instruction message receiving unit 151. The reconfiguration instruction message receiving unit 151 receives a reconfiguration instruction message from the reconfiguration instruction terminal 1c via the communication interface 24.
The connection reassignment request means 15 extracts the reassignment instruction terminal ID (= Nc) and reassignment reception terminal ID (= Np) from the received reassignment instruction message, and the reassignment instruction terminal ID (= Nc) and the recombination instruction terminal ID (= Nc). A reassignment request message including an exchange request terminal ID (= Na) is generated and transmitted to the reassignment reception terminal 1p via the connection control means 17.

  The connection control means 17 (indicated as 17a in FIG. 5) includes a connection request unit 171, a connection reception unit 172, and a disconnection unit 173, and the connection request unit 171 and the connection reception unit 172 function. In FIG. 5, the non-functioning sub-block is indicated by a broken line frame.

  The connection request unit 171 (indicated as 171 a in FIG. 5) makes a connection request under the instruction of the connection reassignment request unit 15. When the connection is established, the connection request unit 171a (see FIG. 5) adds the terminal ID of the established other terminal to the topology information storage unit 112a (see FIG. 5) and the terminal information storage unit 111a (see FIG. 5). The number of current connections and the number of hops are updated in the terminal information stored in the reference). For example, the following method can be used to calculate the updated value of the number of hops. Specifically, assuming that the current number of connections is “3” and the value of each hop number is “h1”, “h2”, “h3”, the number of current connections after the update is “4”, the number of hops after the update can be calculated by an operation of “Min (h1, h2, h3) +1”.

The connection accepting unit 172 (indicated as 172a in FIG. 5) receives the reconfiguration response transmitted by the reconfiguration accepting terminal 1p in response to the connection request, and when established, the connection request unit 171a (see FIG. 5). ). As a result, the connection request unit 171a (see FIG. 5) updates the topology information storage unit 112a ( see FIG. 5) and the terminal information storage unit 111a (see FIG. 5).

<Reclassification reception terminal>
As shown in FIG. 5, the reclassification receiving terminal 1p includes, as main components, connection switching means 16 (indicated as 16p in FIG. 5) and connection control means 17 (indicated as 17p in FIG. 5).
The connection switching unit 16 receives a reassignment request message from the reassignment request terminal 1a, establishes a connection with the reassignment request terminal 1a, and disconnects the connection with the reassignment instruction terminal 1c. In the present embodiment, the connection switching means 16 inputs a reassignment request from the reassignment request terminal 1a via the connection control means 17, and the reassignment request terminal ID (= Na) and reassignment instruction terminal ID (= Nc) is extracted, a reassignment response indicating that recombination is successful is transmitted to the reassignment request terminal 1a, and a disconnection request is made to the reassignment instruction terminal 1c through the connection control means 17.

The connection control unit 17 (indicated as 17p in FIG. 5) includes a connection request unit 171, a connection reception unit 172, and a disconnection unit 173.
The connection request unit 171 (indicated as 171p in FIG. 5) makes a connection request under the instruction of the connection reassignment request unit 15. In this case, the connection request unit 171p (see FIG. 5) transmits a reassignment response indicating that recombination is successful to the reassignment request terminal 1a.

The connection reception unit 172 (indicated as 172p in FIG. 5) receives a connection request (recombination request) from another terminal and determines whether or not to establish a connection based on a predetermined standard. Here, as a predetermined standard, for example, when both of the following conditions B1 and B2 are satisfied, a connection can be established. Of course, it is assumed that the reachability information is “reachable”.
(Condition B1) The value of the number of current connections of the terminal information of the own terminal (the user terminal 1 functioning as the reclassification receiving terminal 1p) is smaller than the value of the connectable number.
(Condition B2) The terminal ID of the other terminal (the user terminal 1 functioning as the reassignment request terminal 1a) is not stored in the topology information storage unit 112.

  In addition, when the connection is established, the connection receiving unit 172p (see FIG. 5) adds the terminal ID of the established other terminal to the topology information storage unit 112p (see FIG. 5) and the terminal information storage unit 111p (see FIG. 5). In the terminal information stored in (5), the number of current connections and the number of hops are updated.

  The disconnecting unit 173 (indicated as 173p in FIG. 5) makes a disconnection request to the reassignment instruction terminal 1c according to the connection switching means 16 when the connection accepting unit 172p (see FIG. 5) receives the reassignment request. It is. The disconnecting unit 173 generates and transmits a disconnection request message including the reassignment receiving terminal ID (= Np). The disconnecting unit 173 deletes the terminal ID of the disconnected other terminal from the topology information storage unit 112.

Returning to FIG. 3, the description of the configuration of each means of the user terminal 1 will be continued.
As illustrated in FIG. 3, the terminal information management unit 18 includes a terminal information generation unit 181, a terminal information transmission unit 182, and a terminal information reception unit 183.
The terminal information generation unit 181 generates terminal information including the terminal ID of the own terminal and stores it in the terminal information storage unit 111.
The terminal information transmission unit 182 reads the terminal information of the own terminal from the terminal information storage unit 111, and other users whose terminal management server 2 or terminal ID is stored in the terminal information storage unit 111 via the communication interface 24. Transmit to terminal 1.
The terminal information receiving unit 183 receives terminal information including the terminal ID from the terminal management server 2 or another user terminal 1 via the communication interface 24, and associates the terminal information with the terminal ID in the terminal information storage unit 111. save. It is also possible to transfer the terminal information of the other terminal received by the terminal information receiving unit 183 to another terminal stored in the terminal information storage unit 111 using, for example, gossip type multicast. Shall.

The communication environment information acquisition means 19 determines the communication environment of the terminal including reachability information indicating whether or not a connection request can be received from another user terminal 1 connected to the terminal on the distribution tree. Information to be obtained is acquired.
The communication environment information acquisition unit 19 acquires reachability information and transmission capacity information of the terminal as information indicating the communication environment from other user terminals 1.
In this embodiment, the communication environment information acquisition unit 19 acquires transmission capability and reachability information from the terminal information of other terminals acquired by the terminal information management unit 18 and outputs the transmission capability and reachability information to the distribution topology rearrangement terminal selection unit 13. It was.

The connected communication environment measurement unit 20 includes a reachability determination unit 201 and a band measurement unit 202. The reachability determination unit 201 determines whether or not the own terminal can accept a connection request from another terminal. For example, when the own terminal is directly connected to the Internet 4, the reachability information can be registered in the terminal information storage unit 111 as “reachable”.
In addition, for example, when it is assumed that the terminal is connected to the router via the local network, if the router can transfer a connection request from the outside (Internet 4) to the terminal, it is reachable. When the information is “reachable” and the router cannot transfer a connection request from the outside to the own terminal, the reachability information can be set to “impossible”.
The reachability determination unit 201 determines whether or not the own terminal can accept a connection request from another terminal with reference to the terminal information stored in the terminal information storage unit 111, and uses the determination result as the connection control unit 17. To the connection accepting unit 172 (see FIG. 5).

  The bandwidth measuring unit 202 measures the transmission capability related to transmission / reception of content data of the terminal itself. For example, the bit rate (bit / sec) can be measured from the number of bytes transmitted at the time of relaying content data sequentially and the time required for transmission, and the value can be used as the transmission capability. Alternatively, the specified value can be set as the transmission capability based on the contract line type information to which the terminal is connected. As specified values, for example, FTTH = “3”, ADSL = “2”, and mobile line = “1” may be set for FTTH / ADSL / mobile line. Note that the terminal information shown in FIG. 4 corresponds to this specified value.

  The content data relay unit 21 sequentially receives the content data from the connection destination terminal via the communication interface 24 based on the topology information (terminal ID stored in the topology information storage unit 112a). To the connected terminal. The content data relay unit 21 stores the received content data in the content buffer 22. For example, the content data relay unit 21 continuously outputs a signal corresponding to the received data relay state to the distribution topology rearrangement terminal selection unit 13 and stops the signal when the relay of the received data stops. Thus, it is possible to notify the distribution topology reconfiguration terminal selection means 13 whether or not the user terminal 1 has left the distribution tree.

  The content reproduction unit 23 is a reproduction unit that extracts content data from the content buffer 22 and sequentially decodes and reproduces the content data. For example, an ON / OFF signal or the like according to a user operation is input to the content reproduction unit 23. For example, when an ON signal is input, the content is reproduced, and when an OFF signal is input, the reproduction of the content is stopped, the relay of the content data being received is stopped, and the distribution tree can be withdrawn.

  The user terminal 1 can be realized by operating a general computer with a program that functions as each of the above-described means. This program (distribution topology reassignment program) can be distributed via a communication line, or can be distributed by writing on a recording medium such as a DVD or CD-ROM.

[3. Configuration example of distribution topology recombination terminal selection means]
Next, a configuration example of the distribution topology reassignment terminal selection unit will be described with reference to FIG. 6 (see FIG. 3 as appropriate). In the example shown in FIG. 6, the distribution topology reassignment terminal selection means 13 includes a timing determination means 31, a downstream terminal selection control means 32, an upstream terminal selection control means 33, and a reassignment terminal determination means 34. did.

<Timing determination means 31>
The timing determination unit 31 determines whether or not the current time is the processing start timing of the distribution topology reassignment process. The determination result as to whether or not it is the processing start timing is output to a transmission capability determination unit 321 and a terminal ID extraction unit 322, which will be described later, on the downstream terminal selection control unit 32. Here, the timing determination unit 31 includes a reception end detection unit 311 and a set time detection unit 312.

  The reception end detection unit 311 detects whether or not the current state is the end (removal) of the reception process, and determines that it is the processing start timing in the case of the separation, and notifies the terminal ID extraction unit 322 to that effect. On the other hand, if it is not a departure, the fact is notified to the set time detection unit 312. Note that the reception end detection unit 311 can detect that the reception is terminated, for example, when the signal from the content data relay unit 21 is interrupted.

The set time detection unit 312 detects whether or not the current time is the set time if it is not a departure, determines that it is the processing start timing if it is the set time, and notifies the transmission capability determination unit 321 to that effect. On the other hand, if it is not the set time, it waits. The set time may be determined in advance, or the user may be able to update the set time as needed from an input device (not shown). The timing of the set time may be arbitrary and may be irregular timing or periodic timing. In the case of regular timing, a fixed time interval such as every second may be used, or a plurality of time intervals such as 1 second and 2 seconds may be sequentially used in a fixed rhythm.
The timing determination unit 31 may include only one of the reception end detection unit 311 and the set time detection unit 312.

<Downstream terminal selection control means 32>
The downstream terminal selection control unit 32 selects one of the two terminals to be subjected to the distribution topology reassignment process from the downstream terminals connected to the downstream of the distribution topology when viewed from the own terminal, A transmission capability determination unit 321, a terminal ID extraction unit 322, a terminal ID sort unit 323, a terminal ID acquisition control unit 324, and a reachability determination unit 325 are provided.

  When the transmission capability determination unit 321 receives a notification of the determination result indicating that it is the processing start timing from the set time detection unit 312 of the timing determination unit 31, the transmission capability determination unit 321 has a transmission capability in the topology information storage unit 112 that is higher than that of its own terminal. It is determined whether or not there is a high downstream terminal. The terminal ID extraction unit 322 is notified of the determination result as to whether or not there is a downstream terminal having a higher transmission capability than the own terminal. The transmission capability determination unit 321 acquires the transmission capability in the terminal information of each terminal from the communication environment information acquisition unit 19 and uses it for the determination. The same applies to the terminal ID extraction unit 322.

The terminal ID extraction unit 322 extracts all the terminal IDs of the downstream terminals from the topology information storage unit 112 when receiving the notification of the determination result indicating the processing start timing from the reception end detection unit 311 of the timing determination unit 31. And output to the terminal ID sorting unit 323.
On the other hand, if the terminal ID extraction unit 322 receives a notification from the transmission capability determination unit 321 that a downstream terminal having a higher transmission capability than the own terminal is present, the terminal ID extraction unit 322 is stored in the topology information storage unit 112. The terminal ID of the downstream terminal having a higher transmission capability than that of the own terminal is extracted and output to the terminal ID sorting unit 323.

The terminal ID sorting unit 323 sorts the terminal IDs of downstream terminals extracted by the terminal ID extracting unit 322 in descending order of transmission capability, and outputs the sorted terminal IDs to the terminal ID acquisition control unit 324.
The terminal ID acquisition control unit 324 controls repetitive processing in which the downstream terminal selection control unit 32 and the upstream terminal selection control unit 33 are linked. The terminal ID acquisition control unit 324 selects one downstream terminal as a downstream terminal candidate to be selected in accordance with the number of downstream terminal IDs extracted by the terminal ID extraction unit 322. The terminal ID of the terminal is acquired and output to the reachability determination unit 325.

The reachability determination unit 325 acquires the terminal information of the downstream terminal of the terminal ID acquired by the terminal ID acquisition control unit 324 from the terminal information storage unit 111, and the reachability information in the acquired terminal information is “reachable”. It is determined whether or not there is. This determination result is output to a terminal candidate determination unit 331 and a terminal ID acquisition unit 332, which will be described later, of the upstream terminal selection control unit 33. The reachability determination unit 325 acquires reachability information in the terminal information of each terminal from the communication environment information acquisition unit 19 and uses it for determination. The same applies to the terminal candidate determination unit 331, the terminal ID acquisition unit 332, and the reachability determination unit 341.
Further, when the reachability determination unit 325 determines that it is “reachable”, the terminal ID (for example, Ndi) of the downstream terminal is output to the ID setting unit 342 described later on the upstream terminal selection control unit 33.

  The upstream terminal selection control means 33 selects one of the two terminals to be subjected to the distribution topology reassignment process from the upstream terminals connected to the upstream of the distribution topology as viewed from the other terminal. A terminal candidate determination unit 331 and a terminal ID acquisition unit 332 are provided.

  The terminal candidate determination unit 331 receives the notification of the determination result that the reachability information is “unreachable” in the terminal information of the downstream terminal candidate from the reachability determination unit 325, and the topology information storage unit 112 In addition, it is determined whether or not there is an upstream terminal whose reachability information is “reachable”. When there is no upstream terminal whose reachability information is “reachable”, the terminal candidate determination unit 331 notifies the terminal ID acquisition control unit 324 to that effect, and when there is an upstream terminal that is “reachable” The terminal ID acquisition unit 332 is notified of this.

The terminal ID acquisition unit 332 receives from the topology information storage unit 112 a notification of reachability when receiving a notification from the terminal candidate determination unit 331 that there is an upstream terminal whose reachability information is “reachable”. The terminal ID (for example, Nui) of any upstream terminal whose information is “reachable” is acquired for one terminal.
On the other hand, when the terminal ID acquisition unit 332 receives from the reachability determination unit 325 a notification of a determination result that the reachability information is “reachable” in the candidate terminal information of the downstream terminal, the topology information storage From the unit 112, the terminal ID (for example, Nui) of an arbitrary upstream terminal is acquired for one terminal.
The terminal ID (for example, Nui) of the upstream terminal acquired by the terminal ID acquisition unit 332 is output to the reachability determination unit 341 which will be described later on the reassigned terminal determination unit 34.

The reassignment terminal determination unit 34 determines two terminals to be subjected to distribution topology reassignment processing, and includes a reachability determination unit 341 and an ID setting unit 342.
The reachability determination unit 341 determines whether the reachability information associated with this Nui is “reachable” based on the terminal ID (for example, Nui) of the upstream terminal acquired from the terminal ID acquisition unit 332. Is. The determination result of whether or not “reachable” is output to the ID setting unit 342.

The ID setting unit 342 sets a reassignment request terminal ID (Na), a reassignment reception terminal ID (Np), and a reassignment instruction terminal ID (Nc).
The ID setting unit 342 sets the own terminal ID read from the terminal information storage unit 111 as the reassignment instruction terminal ID (Nc).
Further, the ID setting unit 342 sets the reassignment request terminal ID (Na) and the reassignment reception terminal ID (Np) according to the determination result of the reachability determination unit 341.
Specifically, when the ID setting unit 342 receives a notification of a determination result indicating that the reachability information associated with Nui is “reachable” from the reachability determination unit 341, the reassignment request terminal ID ( “Ndi” is set in Na), and “Nui” is set in the reassignment receiving terminal ID (Np).
On the other hand, when the ID setting unit 342 receives a notification of the determination result that the reachability information associated with the Nui is “not reachable” from the reachability determination unit 341, the ID setting unit 342 sets the reassignment request terminal ID (Na). “Nui” is set, and “Ndi” is set in the reassignment receiving terminal ID (Np).
The Na, Np, and Nc set here are output to the connection reassignment instruction unit 14.

[4. Operation of user terminal]
Next, the operation of the user terminal is subdivided into five, 4-1. User terminal group subscription processing, 4-2. Example of distribution tree, 4-3. Distribution topology rearrangement processing, 4-4. Distribution topology recombination terminal selection process, 4-5. Each of the specific examples of the distribution topology rearrangement process will be described in detail.

<4-1. User terminal group subscription processing>
First, an example of a procedure for group joining processing performed when a new user terminal 1 joins a distribution group will be described with reference to FIG. 7 (refer to FIG. 3 as appropriate).
In the content distribution system S according to the present embodiment, when the user terminal 1 selects a content that the user wants to view after starting a content viewing application (not shown) according to the user's operation, the terminal of the terminal information management means 18 The information transmission unit 182 transmits a connection destination introduction request including the terminal information of the own terminal to the terminal management server 2 (S001).

The terminal management server 2 extracts the terminal information included in the connection destination introduction request received from the new user terminal 1, updates the terminal information list L (see FIG. 2) managed by the terminal management server 2, and the terminal information list L Then, one or more pieces of terminal information of the user terminal 1 receiving the requested content are extracted (S002), and transmitted to the user terminal 1 as an initial connection destination list (S003).
The user terminal 1 receives the initial connection destination list by the terminal information receiving unit 183 of the terminal information management unit 18 and stores it in the terminal information storage unit 111 (S004).

  The user terminal 1 transmits the terminal information of its own terminal to the other terminals whose terminal IDs are stored in the terminal information storage unit 111 by the terminal information transmission unit 182 of the terminal information management means 18 and distributes itself. Notify other terminals in the distribution group that you have joined the group. Further, the user terminal 1 newly joining the distribution group makes a distribution topology (distribution tree) by making a connection request from the own terminal or accepting a connection request from another terminal by the connection control means 17. can do.

<4-2. Distribution tree example>
Here, in order to explain the distribution topology rearrangement process (connection switching operation) by the user terminal 1, an example of a distribution tree of the content distribution system S assumed will be described. In the example shown in FIG. 8, user terminals 1 belonging to a distribution tree having a structure with the content distribution server 3 as a vertex are indicated by circles. Among these, the user terminal 1 indicated by a white circle indicates that the reachability information of the terminal information is “reachable”, and the user terminal 1 indicated by a black circle is that the reachability information of the terminal information is “unreachable”. It is shown that. The numerical value shown in the circle of the user terminal 1 indicates the transmission capability of each user terminal 1. The line between the user terminals 1 indicates that they are connected to each other (that is, that a distribution topology is constructed), and the arrow points from the terminal that has made the connection request to the terminal that has accepted the connection request. ing.

Each user terminal 1 in the distribution group G is assigned a unique terminal ID.
In FIG. 8, the ID of the user terminal 1 arranged at a predetermined reference position is “Ns”, and this user terminal 1 is its own terminal.
The number of hops of the user terminal 1 with ID = Nu1 and Nu2 is “1”, the number of hops of the user terminal 1 with ID = Ns is “2”, and the number of hops of the user terminal 1 with ID = Nd1 and Nd2 is respectively It shall be “3”.
In addition, terminals having a smaller number of hops than their own terminals (ID = Nu1, Nu2) are referred to as upstream terminals respectively arranged upstream with respect to the reference.
In addition, terminals (ID = Nd1, Nd2) having a larger number of hops than the own terminal are referred to as downstream terminals respectively arranged downstream with respect to the reference.

<4-3. Distribution topology reconfiguration process>
Here, the operation of the distribution topology reconfiguration process (distribution topology reconfiguration method) by the user terminal 1 will be described with reference to the sequence diagram of FIG. 9 (refer to FIGS. 3, 5, and 8 as appropriate). The distribution topology reassignment process is started immediately before the reassignment instruction terminal 1c, which is its own terminal, stops receiving the content and ends (leaves) the process related to the content distribution system S. You can start with timing.

  First, the reconfiguration instruction terminal 1c is a user terminal that makes a reconfiguration request by the distribution topology reconfiguration terminal selection processing in which the distribution topology reconfiguration terminal selection unit 13 selects two terminals that are to be redistributed in the distribution topology. 1 is selected, and a reassignment reception terminal 1p that is a user terminal 1 that is a receptive reception destination. Then, the terminal ID of the terminal selected as the reassignment request terminal 1a is set as the value of the reassignment request terminal ID (Na), and the terminal ID of the terminal selected as the reassignment reception terminal 1p is set as the reassignment reception terminal ID ( Np), and the terminal ID of the own terminal is set to the value of the reassignment instruction terminal ID (Nc) (S101). Details of this distribution topology reassignment terminal selection process will be described later.

Hereinafter, the reassignment request terminal ID may be simply expressed as Na, the reassignment reception terminal ID may be expressed as Np, and the reassignment instruction terminal ID may be expressed as Nc.
Next, the reassignment instruction terminal 1c transmits a reassignment instruction message including Np and Nc to the reassignment request terminal 1a by the reassignment instruction message transmission unit 141 (S102).
The reassignment request terminal 1a receives the reassignment instruction message from the reassignment instruction terminal 1c by the reassignment instruction message receiver 151 (S103), and extracts the Np and Nc from the message by the connection reassignment request means 15. (S104), a reassignment request including Nc and Na is transmitted to the reassignment receiving terminal 1p (S105).

The reassignment receiving terminal 1p receives a reassignment request from the reassignment request terminal 1a by the connection accepting unit 172 (S106), and extracts Nc and Na (S107).
Next, the reassignment receiving terminal 1p transmits a response to the reassignment request (reassignment response) to the reassignment request terminal 1a by the connection switching unit 16 (S108), and adds Na to the topology information storage unit 112 ( S109).
The reassignment request terminal 1a receives the reassignment response through the connection accepting unit 172 (S110), and adds Np to its own topology information storage unit 112 (S111).

Subsequently, the reassignment reception terminal 1p transmits a disconnection request including Np to the reconfiguration instruction terminal 1c by the disconnection unit 173 (S112), and deletes Nc from its own topology information storage unit 112 (S113).
The reconfiguration instruction terminal 1c receives a disconnection request from the reconfiguration reception terminal 1p through the connection reception unit 172 (S114), deletes Np from its own topology information storage unit 112, and presently connects the terminal information of its own terminal The number is decremented (S115).

  Then, the reconfiguration instruction terminal 1c confirms whether or not there is a downstream terminal by the distribution topology reconfiguration terminal selection means 13 (S116), and if it exists (Yes in S116), selects the distribution topology reconfiguration terminal. Returning to the process (S101), if it does not exist (No in S116), the process ends.

  The reassignment instruction terminal 1c refers to its own terminal information storage unit 111 and topology information storage unit 112 in order to confirm whether or not a downstream terminal exists. At this time, in the terminal information stored in the terminal information storage unit 111, the terminal ID associated with the hop number larger than the hop number of the own terminal and stored in the topology information storage unit 112 is also the terminal ID. If it exists, there is a downstream terminal.

<4-4. Distribution topology recombination terminal selection processing>
Next, the distribution topology reassignment terminal selection process (S101) shown in FIG. 9 will be described with reference to the sequence diagrams of FIGS. 10 and 11 (see FIGS. 3, 6, 8, and 9 as appropriate).
In the reassignment instruction terminal 1c which is its own terminal, the distribution topology reassignment terminal selection means 13 performs the following operation. The timing determination unit 31 determines whether or not the current state is the process start timing due to the end (leave) of the reception process (S201). When it is time to start processing due to detachment (Yes in S201), the terminal ID extraction unit 322 extracts all terminal IDs of downstream terminals from the topology information storage unit 112 (S202). The number of extractions at this time is “W”.

  On the other hand, when the set time detection unit 312 determines that the process start timing is based on the set time instead of the process start timing due to separation in S201 described above (No in S201), the transmission capability determination unit 321 causes the topology information It is determined whether there is a downstream terminal having a higher transmission capability than the own terminal in the storage unit 112 (S203). If there is a downstream terminal having a higher transmission capability than the own terminal (Yes in S203), the downstream terminal is stored in the topology information storage unit 112 by the terminal ID extraction unit 322 and has a higher transmission capability than the own terminal. Is extracted (S204). The number of extractions at this time is “W”. On the other hand, in S203 described above, when there is no downstream terminal having a transmission capability higher than that of the terminal itself (No in S203), the distribution topology reconfiguration terminal selection unit 13 ends this distribution topology reconfiguration process.

Next, the terminal ID sorting unit 323 sorts the terminal IDs of the downstream terminals extracted by the above-described processing of S202 or S204 in descending order of transmission capability (S205).
Next, the terminal ID acquisition control unit 324 sets the value of the variable I to “1” (S206), and determines whether the value of the variable I is smaller than “W” (S207). If the value of variable I is still smaller than “W” (Yes in S207), distribution topology reassignment terminal selection means 13 repeats the following processing as shown in FIG. 11, and the value of variable I becomes “W”. If they are equal (No in S207), the process is terminated.

  Subsequently, as shown in FIG. 11, in S208, the terminal ID acquisition control unit 324 acquires the I-th terminal ID (Ndi) based on the current value of the variable I. Then, the reachability determination unit 325 acquires the terminal information of the terminal having the terminal ID from the terminal information storage unit 111, and determines whether the reachability information in the terminal information is “reachable” (S209). When the reachability information is “reachable” (Yes in S209), the terminal ID acquisition unit 332 acquires only one terminal ID (Nui) of an arbitrary upstream terminal from the topology information storage unit 112 (S210). ).

  On the other hand, when the reachability information is “not reachable” in S209 (No in S209), the terminal candidate determination unit 331 causes the topology information storage unit 112 to store an upstream terminal whose reachability information is “reachable”. It is determined whether or not it exists (S211). When there is an upstream terminal whose reachability information is “reachable” (Yes in S211), any upstream terminal whose reachability information is “reachable” is received from the topology information storage unit 112 by the terminal ID acquisition unit 332 The terminal ID (Nui) is acquired for one terminal (S212).

  On the other hand, in S211, if there is no upstream terminal whose reachability information is “reachable” (No in S211), the terminal candidate determination unit 331 notifies the terminal ID acquisition control unit 324 to that effect, and the terminal ID The acquisition control unit 324 increments the current I value (+1 step) (S213), and returns to the process of S207 illustrated in FIG.

  Subsequently, as shown in FIG. 11, in S214, the reachability determination unit 341 determines whether the reachability is associated with Nui based on the terminal ID (Nui) of the upstream terminal acquired by the process of S210 or S212. It is determined whether or not the information is “reachable”. When the reachability information associated with Nui is “reachable” (S214: Yes), the ID setting unit 342 sets Ndi to the reassignment request terminal ID (Na), and reassignment reception terminal ID (Np) Is set to Nui, and the own terminal ID is set to the reassignment instruction terminal ID (Nc) (S215). On the other hand, when the reachability information associated with Nui is “unreachable” (S214: No), the ID setting unit 342 sets Nui to the reassignment request terminal ID (Na), and the reconfiguration accepting terminal ID ( Ndi is set to Np), and the own terminal ID is set to the reassignment instruction terminal ID (Nc) (S216).

  Then, the distribution topology reassignment terminal selection unit 13 returns to S201 shown in FIG. 10 following the process of S215 or S216. The distribution topology reassignment terminal selection unit 13 outputs the Na, Np, and Nc set by the process of S215 or S216 to the connection reassignment instruction unit 14. As a result, the connection reassignment instruction unit performs the process of S102 (see FIG. 9) using Na, Np, and Nc. As described above, the user terminal 1 can securely connect the user terminal 1 connected downstream of the user terminal 1 and the user terminal 1 connected upstream of the user terminal 1 and can safely rearrange the distribution topology.

<4-5. Specific example of distribution topology reconfiguration processing>
Furthermore, a specific example of the distribution topology rearrangement process shown in FIGS. 10 and 11 will be described with reference to FIG. FIG. 12A illustrates an overview of distribution topology reassignment processing in a similar distribution tree created based on FIG. As in FIG. 8, each user terminal 1 is assigned a unique terminal ID. In the following description, the ID of the user terminal 1 placed at the reference position is “Ns”, and this user terminal 1 is its own terminal. The upstream terminals are two user terminals 1 with ID = Nu1 and Nu2. The downstream terminals are two user terminals 1 with ID = Nd1 and Nd2.

  In this case, the user terminal 1 (self terminal) with ID = Ns selects the two downstream terminals extracted in S204 in descending order of transmission capability in the distribution topology reassignment terminal selection process (S101: see FIG. 9). Sorting is performed (S205: see FIG. 10). When I = “1”, that is, first, the user terminal 1 with ID = Nd1 having the highest transmission capability from the two downstream terminals (transmission capability = “3”). ) Is selected (S208: see FIG. 11). Here, since the reachability information of the user terminal 1 with ID = Nd1 is “unreachable” as indicated by a black circle (No in S209: see FIG. 11), from among the two upstream terminals, Only one terminal ID (= Nu1) of the user terminal 1 (terminal indicated by a white circle) whose reachability information is “reachable” is acquired (S212: see FIG. 11). Furthermore, since the reachability information associated with this ID = Nu1 is “reachable” (Yes in S214: see FIG. 11), “Nd1” is set as the value of the reassignment request terminal ID (Na), and the set “Nu1” is set as the value of the replacement acceptance terminal ID (Np), and “Ns” is set as the value of the reassignment instruction terminal ID (Nc). The correspondence between these setting values and the terminal IDs (Na, Np, Nc) is as illustrated in FIG.

  Next, the reassignment instruction terminal 1c (own terminal) having ID = Ns set as the reassignment instruction terminal ID (Nc) by the procedure of the distribution topology reassignment process shown in FIG. Transmits a reassignment instruction message including “Nu1”) and Nc (set value is “Ns”) to the reassignment request terminal 1a having ID = Nd1 set as the reassignment request terminal ID (Na) (S102). : Refer to FIG.

  Subsequently, the reassignment request terminal 1a having ID = Nd1 set as the reassignment request terminal ID (Na) includes Nc (set value is “Ns”) and Na (set value is “Nd1”). The request is transmitted to the reassignment receiving terminal 1p having ID = Nu1 set as the reassignment receiving terminal ID (Np) (S105: see FIG. 9).

Next set, reclassification reception terminal 1 p with reclassification reception terminal ID (Np) ID = Nu1 set as the response to the reclassification request (reclassification response), as reclassification request terminal ID (Na) Is transmitted to the reassignment request terminal 1a having the assigned ID = Nd1 to establish a connection (S108: see FIG. 9), and further, the reassignment instruction having ID = Ns set as the reassignment instruction terminal ID (Nc) A disconnection request is transmitted to the terminal 1c (own terminal) to disconnect (S112: see FIG. 9). As a result of the above series of processing, the distribution topology can be rearranged as shown in FIG.

  As described above, according to the user terminal 1 of the present embodiment, even in an environment where there is a user terminal that cannot accept a connection request from another terminal because it is connected to the Internet 4 via a NAT router. The user terminal 1 participating in the distribution tree of the distribution system S securely connects the user terminal 1 connected to the downstream of the user terminal 1 to the user terminal 1 connected to the upstream of the user terminal 1 and securely distributes the distribution topology (tree (Upper order) can be rearranged. Therefore, it is possible to improve distribution stability and reduce wasteful processing related to connection switching.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to this. For example, in the present embodiment, the communication environment information acquisition unit 19 acquires both the reachability information and the transmission capacity information of the terminal as information indicating the communication environment from the other user terminals 1. Only the reachability information may be acquired. In this case, when selecting two terminals, the distribution topology reassignment terminal selection means 13 automatically selects one user terminal connected to the own terminal at the upstream position on the distribution tree and the downstream position. Any one user terminal connected to the terminal may be selected.

In addition, when the distribution topology reassignment terminal selection unit 13 selects two terminals, one of them selects the user terminal 1 whose reachability information is reachable, but the user who can reach both is selected. Even if the terminal 1 is selected, the same effect can be obtained.
The distribution topology reassignment terminal selection means 13 selects one terminal from the upstream and the downstream when selecting two terminals, but both may be selected from the downstream, or both may be upstream. You may choose from.

S content distribution system 1,1G, 1N, 1R user terminal 1a reassignment request terminal 1c reassignment instruction terminal 1p recombination acceptance terminal 2 terminal management server 3 content distribution server 4 internet 5 port openable NAT router 6 port unopenable NAT Router 7 Local network 8 Local network 11 Storage unit 111 Terminal information storage unit 112 Topology information storage unit 12 Connection partner selection unit 13 Distribution topology reconfiguration terminal selection unit 14 Connection reconfiguration instruction unit 141 Reconfiguration instruction message transmission unit 15 Connection reconfiguration Requesting means 151 Reconfiguration instruction message receiving unit 16 Connection switching unit 17 Connection control unit 171 Connection requesting unit 172 Connection receiving unit 173 Disconnecting unit 18 Terminal information managing unit 181 Terminal information generating unit 182 Terminal information transmitting unit 183 Terminal information receiving unit 19 Communication environment information acquisition unit 20 Connection communication environment measurement unit 201 Reachability determination unit 202 Band measurement unit 21 Content data relay unit 22 Content buffer 23 Content playback unit 24 Communication interface 31 Timing determination unit 311 Reception end detection unit 312 Setting time detection unit 32 Downstream terminal selection control unit 321 Transmission capability determination unit 322 Terminal ID extraction unit 323 Terminal ID sort unit 324 Terminal ID acquisition control unit 325 Reachability determination unit 33 Upstream terminal selection control unit 331 Terminal candidate determination unit 332 Terminal ID acquisition unit 34 Reclassification Terminal determination means 341 Reachability determination unit 342 ID setting unit L Terminal information list

Claims (5)

The content delivery server is a content distribution source as the vertex, in the content distribution system in which a plurality of user terminals which users used to view the content to deliver the content to configure the distribution tree hierarchically connected, said The plurality of user terminals on the distribution tree include a user terminal that can accept a connection request from another user terminal and a user terminal that cannot accept the request, and the communication environment of the user terminal A user terminal that rearranges a distribution topology indicating a connection order of terminals on the distribution tree between the user terminals according to
Communication environment information acquisition means for acquiring information indicating a communication environment including reachability information indicating whether or not a connection request can be received from another user terminal connected to the terminal on the distribution tree; ,
As a target of the process of rearranging the distribution topology, any two terminals are selected from a plurality of other user terminals connected to the own terminal, and one of the selected two terminals is used as a reassignment request terminal. A distribution topology reconfiguration terminal selection means for determining and determining the other as a reconfiguration reception terminal;
A connection reassignment instruction means for instructing the determined recombination requesting terminal to execute a connection reassignment request to the determined reassignment receiving terminal without going through its own terminal;
From the reassignment instruction terminal, which is a user terminal that instructs the reassignment request terminal to execute the connection reassignment request, receives the instruction, and receives a reassignment request message including identification information of the reassignment instruction terminal. A connection reassignment request means for requesting a connection reassignment by notifying the reassignment reception terminal;
Receiving the reassignment request message from the reassignment request terminal, establishing a connection with the reassignment request terminal, and connection switching means for cutting off the connection with the reassignment instruction terminal,
The distribution topology recombination terminal selection means, when selecting the two terminals,
At least one terminal selects a user terminal whose reachability information is reachable,
To determine the user terminal before Symbol reaching propriety information is reaching Allowed to the reclassification reception terminal,
Selecting the reassignment receiving terminal from one of upstream and downstream on the distribution tree, and selecting the reassigning request terminal from the other of the upstream and downstream on the distribution tree; A user terminal characterized by The communication environment information acquisition unit acquires the reachability information and the transmission capacity information of the terminal as information indicating a communication environment from another user terminal,
The distribution topology recombination terminal selection means includes:
When selecting the two terminals,
Any one user terminal connected to its own terminal at the upstream position on the distribution tree;
Select one user terminal having the largest transmission capacity while connecting to the terminal at the downstream position on the distribution tree,
The user terminal according to claim 1 , wherein the reachability information of any one of the two selected terminals is reachable. The distribution topology recombination terminal selection means includes:
The process of selecting two terminals that are the targets of the process of redistributing the distribution topology and determining the reassignment receiving terminal and the recombination requesting terminal is started when the own terminal leaves the distribution tree. The user terminal according to claim 1 or 2 . The distribution topology recombination terminal selection means includes:
The process of selecting two terminals that are targets of the process of rearranging the distribution topology and determining the rearrangement receiving terminal and the rearrangement requesting terminal is started at an arbitrary preset timing. The user terminal according to claim 1 or claim 2 . The content delivery server is a content distribution source as the vertex, in the content distribution system in which a plurality of user terminals which users used to view the content to deliver the content to configure the distribution tree hierarchically connected, said The plurality of user terminals on the distribution tree include a user terminal that can accept a connection request from another user terminal and a user terminal that cannot accept the request, and the communication environment of the user terminal In order to rearrange the distribution topology indicating the connection order of the terminals on the distribution tree between the user terminals according to the computer, the computer as the user terminal,
A communication environment information acquisition means for acquiring information indicating a communication environment including reachability information indicating whether or not a connection request can be received from another user terminal connected to the terminal on the distribution tree;
As a target of the process of rearranging the distribution topology, any two terminals are selected from a plurality of other user terminals connected to the own terminal, and one of the selected two terminals is used as a reassignment request terminal. A distribution topology recombination terminal selection means for determining and determining the other as a reconfiguration accepting terminal;
A connection reassignment instruction means for instructing the determined recombination requesting terminal to execute a connection reassignment request to the determined reassignment receiving terminal without going through its own terminal;
From the reassignment instruction terminal, which is a user terminal that instructs the reassignment request terminal to execute the connection reassignment request, receives the instruction, and receives a reassignment request message including identification information of the reassignment instruction terminal. Connection reassignment request means for requesting connection reassignment by notifying the reassignment reception terminal,
A distribution topology for receiving the reassignment request message from the reassignment request terminal, establishing a connection with the reassignment request terminal, and functioning as a connection switching unit for disconnecting the connection with the reassignment instruction terminal A reclassification program,
The distribution topology recombination terminal selection means, when selecting the two terminals,
At least one terminal selects a user terminal whose reachability information is reachable,
To determine the user terminal before Symbol reaching propriety information is reaching Allowed to the reclassification reception terminal,
Selecting the reassignment receiving terminal from one of upstream and downstream on the distribution tree, and selecting the reassigning request terminal from the other of the upstream and downstream on the distribution tree; A distribution topology rearrangement program characterized by:

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