JP2009151531A - Contents delivery system, contents delivery method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a contents delivery system utilizing a peer-to-peer (P2P) network capable of making user who wants to immediately browse the contents browse a movie as quickly as possible. <P>SOLUTION: When immediately adding a high-priority-download-peer which browses the movie to the peer-to-peer (P2P) by disciminating the high-priority-download-peer, a low-priority-download-peer, and an upload-exclusive-peer; the contents delivery system suppresses the relative number of high-priority-download-peers by concurrently adding the low-priority-downlaod-peer and the upload-exclusive-peer to provide a high priority download processing to the high-priority-download-peer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a content distribution system, and more particularly to a content distribution system in which a peer that receives content transmits and receives content between receiving peers as well as a content distribution server.

Recently, various video services are provided on the Internet, but the service forms can be roughly classified into the following three types.
(1) Broadcast type streaming service (2) On-demand stream playback service (3) Download type service

(1) Broadcast-type streaming service The broadcast-type streaming service is a service that provides a user with a certain program at a certain time. In general, a broadcast-type streaming service is mainly provided as an ISP (Internet Service Provider) service. In the broadcast streaming service, the same program is transferred to a large number of users at the same time. Therefore, by using a network device that supports a multicast function, it is possible to efficiently distribute high-quality moving images within the network. If the network can be completely controlled like ISP, it is possible to construct a network suitable for moving picture multicast distribution, but it is difficult to provide a high-quality multicast service over the entire Internet. In addition, among the users who have contracted with the ISP, the moving image distribution service is often a limited user who has paid an additional fee in addition to the basic contract fee. Therefore, since the number of users is limited and fluctuations are small, the number of accesses and the amount of traffic are less likely to fluctuate abruptly compared to the case where services are provided free of charge to the entire Internet, and control is easy.

(2) On-demand stream playback service The on-demand stream playback service is a service in which a user selects a video that the user wants to browse and browses on the spot. In on-demand stream playback, playback starts when a certain amount of video is downloaded by the video browsing client. Compared with the broadcast streaming service, the user can freely select the video that he / she wants to watch and can browse freely when he / she wants to watch it.

  A representative example of the on-demand stream reproduction service is “Youtube (registered trademark)” (Non-patent Document 1). Recently, with the rapid spread of “YouTube (registered trademark)”, Internet users can easily view moving images on the Internet. The image quality provided by “Youtube (registered trademark)” is a relatively low-quality moving image with a resolution of “320 × 240”, a frame rate of “30 fps”, and a data rate of “320 kbps”. However, it is said that the network line of 100 million yen or more is used every month in order to provide such a low-quality video, and how expensive it is to provide a video service to a large number of users over the Internet. Can be seen. This is because the access load is concentrated on the distribution server that provides moving images, and it is necessary to use a large-capacity network line that satisfies the total download bandwidth of each user from the distribution server.

(3) Download-type service The download-type service is a method in which a video to be viewed is completely downloaded and then viewed and reproduced later. Since it is not necessary to reproduce immediately, it is not necessary to guarantee a download band higher than the operation reproduction rate, and the constraint conditions are loose compared to other methods. Recently, video media distribution services using a peer-to-peer (P2P) network have emerged as a method for realizing download-type services at low cost. Here, peer refers to a node on a peer-to-peer (P2P) network. In a moving image distribution service using peer-to-peer (P2P), each peer not only downloads moving image content from a server, but also reduces the load on the server by transmitting and receiving content between peers. As a result, it is possible to greatly reduce the equipment installation cost and network cost for the service provider to provide the moving image content distribution service.

  Hereinafter, as an example of a conventional content distribution system, a content distribution system using “BitTorrent (registered trademark)” (Non-Patent Document 2), which is widely used as a peer-to-peer (P2P) protocol for file distribution, will be described.

  In “BitTorrent (registered trademark)”, a peer-to-peer (P2P) network called a swamp is constructed for each content. Peers belonging to a peer-to-peer (P2P) network are managed by a server called a tracker. A peer wishing to download content requests the tracker to join a peer-to-peer (P2P) network. The tracker returns a list of peers. The content is divided into pieces of fixed length size. Each peer transmits and receives data in pieces. Each peer connects with the other peer and obtains information about what piece of content the other peer has. Each peer notifies the connected peer whether or not it wants to download by “Interest flag”. Next, each peer checks the “Interest flag” received from each connected peer, selects a peer to be uploaded from among peers that have requested download, and sends “choke / unchoke flag”. Here, in “choke / unchoke flag”, “choke” indicates download permission, and “unchoke” indicates upload permission. When selecting the upload target peer, it is an important feature that an operation of selecting a user who downloads a lot of content to the user is performed. This is called a “Tit-for-Tat strategy”. According to the “Tit-for-Tat strategy”, the upload target peers are periodically updated, and the contents are mutually transmitted and received, thereby improving the transfer throughput of the entire network. In reality, however, there are also upload dedicated peers that have all of the content and perform only uploading. Such an upload-only peer is called a seed. Such an upload-only peer is selected in preference to a peer with a high upload speed.

  Next, the peer that has obtained the upload permission from the connected peer selects and downloads the piece with the smallest number of peers among the pieces that it wants to download. This mechanism is referred to as a “Rarest First mechanism”. By using the “Rarest First mechanism”, all pieces are distributed evenly over the network, so that it is possible to prevent a situation where a specific piece is insufficient and the overall download efficiency deteriorates.

  “BitTorrent (registered trademark)” using this “Tit-for-Tat strategy” and “Rarest First mechanism” is used as a de facto standard protocol as a P2P content distribution method realizing high total transfer throughput. ing.

As a related technique, Japanese Patent Application Laid-Open No. 2004-072603 (Patent Document 1) discloses a “failure recovery system”.
In this related technique, the first peer leaves the system for some reason. The second peer detects the departure of the first peer and the failure recovery process is started. The second peer searches whether the standby peer is registered and obtains address information of the standby peer. The second peer notifies the standby peer of the occurrence of the leaving peer, and the standby peer immediately takes over. Takeover means exchanging peer information with adjacent peers and updating the contents of each adjacent peer information storage table.

Japanese Patent Laying-Open No. 2004-246790 (Patent Document 2) discloses a “content distribution method”.
This related technology implements peer-to-peer content distribution. The component controls the connection relationship between the content distribution server device that divides the content into packets and distributes the client device group that receives the content transmitted from the content distribution server device, and the content distribution server device and the client device. It consists of a topology control device. Each client device included in the client device group distributes content to other client devices when requested by other client devices.

Japanese Patent Laying-Open No. 2004-260279 (Patent Document 3) discloses a “peer group configuration method”.
In this related technique, a new participation peer makes a peer group participation request to an arbitrary member of the peer group to be joined. The peer that has received the peer group participation request determines whether the peer group attribute information passed from the newly participating peer matches the peer group attribute information that it owns. Returns a response.

Japanese Patent Laying-Open No. 2005-235177 (Patent Document 4) discloses “architecture for controlling access to services by clients existing simultaneously”.
In this related art, the system includes a rule component that facilitates enforcing one or more rules for the applicant's account. The rule includes, for example, a limit on the number of clients connected simultaneously.

Japanese Patent Laying-Open No. 2006-148648 (Patent Document 5) discloses a “user terminal connection control method and apparatus”.
In this related technology, the user management table provided in the authentication server includes a priority MAC address, the maximum number of connections, and the like. The priority MAC address indicates the MAC address of the user terminal to be preferentially connected to the Internet.

JP 2004-072603 A JP 2004-246790 A JP 2004-260279 A JP 2005-235177 A JP 2006-148648 A <Http: // www. youtube. com /> <Http: // www. bittorrent. org / protocol. html> “Incentives Build Robustness in BitTorrent”, B.M. Cohen, In Proc. of 1st Works on Economics of Peer-to-Peer Systems (June 2003)

  In providing a content distribution system, in order to provide a service without incurring costs for network server devices and network lines, “BitTorrent (registered trademark)” that transmits and receives content between peers that download content. The use of a content distribution method using a peer-to-peer (P2P) network such as

  However, for example, “Tit-for-Tat strategy” and “Rarest First mechanism” introduced to improve transfer efficiency in “BitTorrent (registered trademark)” are suitable for streaming playback of video content. Not.

  First, in the “Tit-for-Tat strategy”, content cannot be downloaded at a sufficient download rate unless it is a peer capable of sufficiently uploading content. In addition, since the “Rarest First mechanism” cannot download contents in order, the contents cannot be reproduced unless all pieces are arranged.

  From the above characteristics, in content distribution systems using peer-to-peer (P2P), it is generally provided as a download type service, and it is difficult to realize an on-demand stream reproduction service.

  In addition, even when providing a download-type service as a basic service, there are users who want to view videos immediately and users who do not need to browse immediately. For a user who wants to view a moving image immediately, it is necessary to be able to view the moving image as soon as possible.

  The object of the present invention is to provide a video content in a content distribution system such that (1) a user who wants to view the content immediately, (2) a user who is likely to browse in the future, (3) a user who is less likely to browse, etc. To provide a content distribution system, a content distribution method, and a program that enable a user who wants to view content immediately to view a moving image as soon as possible when various users coexist.

  The content distribution system of the present invention includes a plurality of peers classified for each attribute class, a peer management server that manages the state of each of the plurality of peers, and the number of peers for each attribute class satisfies the attribute class peer addition management condition. Multiple peers are managed, and when a request for adding to a given attribute class is made from a given peer among multiple peers, if the peer addition request condition cannot be satisfied, the peer management server is queried. From the peer management server, obtain a support peer list created based on peers of other attribute classes selected to satisfy the peer addition request condition, and within the support peer list and the peer that made the addition request And a tracker that adds a peer to a peer-to-peer (P2P) network. Here, the peer addition request condition is “the number of high priority download peers <(the number of low priority download peers × α) + (the number of upload dedicated peers × β)”, and the attribute class peer addition management condition is “(low priority download peers”). The number of peers × α) + (the number of dedicated peers for uploading × β)> = 1 ”. However, actually, it is not limited to these examples.

  The tracker according to the present invention includes request class check means, inquiry means, and inquiry result confirmation means. The request class checking means checks the peer request class in response to a download request from the peer, and if the request class is a low priority download, adds the request class as a low priority download peer to the peer-to-peer (P2P) network. If it is a high priority download, it is checked whether or not the peer addition requirement is satisfied. If the peer addition requirement is satisfied, it is added to the peer-to-peer (P2P) network as a high priority download peer. When the inquiry means does not satisfy the peer addition request condition, the peer management server that manages the state of the peer inquires whether the low priority download peer and the upload dedicated peer can be added so as to satisfy the peer addition request condition. I do. The inquiry result confirmation means confirms the inquiry result to the peer management server, and if there are low priority download peers and upload dedicated peers that satisfy the peer addition requirement condition, the low priority download peers and upload dedicated peers included in the peer management table are determined. Add to peer-to-peer (P2P) network as supporting peer.

  The peer management server according to the present invention comprises table management means, peer search means, and condition check means. The table management means manages an idle peer management list indicating idle peers that can be added to a peer-to-peer (P2P) network, and a support peer list indicating support peers. The peer search means refers to the idle peer management list, searches for a peer holding the content of the content ID notified from the tracker, and if there is a peer holding the content, the peer list for supporting the peer holding the content Add to The condition checking means checks whether or not the support peer list satisfies the support peer number condition. If the support peer list satisfies the support peer number condition, the support peer list is determined and the support peer list is determined. The list is notified to the tracker, and the peer added to the supporting peer list is deleted from the idle peer management list.

  The content distribution method of the present invention includes a step of managing the state of each of a plurality of peers classified for each attribute class, and managing a plurality of peers so that the number of peers for each attribute class satisfies an attribute class peer addition management condition If a peer addition request condition is not satisfied from a given peer among a plurality of peers and the peer addition request condition cannot be satisfied, the other attribute class is set to satisfy the peer addition request condition. Selecting a peer to create a support peer list; and adding the requesting peer and the peers in the support peer list to a peer-to-peer (P2P) network.

  The program of the present invention is a program for causing a computer to function as a tracker, and checks a peer request class in response to a download request from a peer. If the request class is a low priority download, the low priority download peer If the request class is high-priority download, it is checked whether or not the peer addition requirement is satisfied, and if the peer addition requirement is satisfied, as a high-priority download peer Steps of adding to a peer-to-peer (P2P) network, and if the peer addition requirement is not satisfied, the peer management server managing the state of the peer is configured with the low priority download peer and the upload dedicated peer so as to satisfy the peer addition requirement. Inquire about whether it can be added And if the low priority download peer and upload dedicated peer satisfying the peer addition requirement condition exist, the low priority download peer and upload dedicated peer included in the peer management table are supported. And adding to a peer-to-peer (P2P) network as a peer for use in a computer.

  Another program of the present invention is a program for causing a computer to function as a peer management server, which is an idle peer management list indicating idle peers that can be added to a peer-to-peer (P2P) network, and support indicating a support peer. A peer list for the content, and a search for peers having content ID notified from the tracker by referring to the idle peer management list, and if there is a peer having content, the peer having the content is determined. Step to add to the support peer list and check whether the support peer list satisfies the support peer number condition, and if the support peer list satisfies the support peer number condition, confirm the support peer list The step of notifying the tracker of the support peer list and the support peer list And a step to remove the added peers, the idle peer management list, a program for causing a computer to execute.

  In a content distribution system using a peer-to-peer (P2P) network, a user who wants to view content immediately can view a moving image as soon as possible.

Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a configuration example of a content distribution system 100 in the present embodiment.
The content distribution system of the present invention includes a peer 1, a distribution server 2, a peer management server 3, and a tracker 4.

  Peer 1 (1-i, i = 1 to n: n is the number of peers) is a peer connected to the content distribution system, and downloads a content group. The distribution server 2 has a content group to be distributed on the content distribution system. Since the distribution server 2 is an upload dedicated peer, it can be a peer connected to the content distribution system in the same manner as the peer 1. The peer management server 3 manages peers connected to the content distribution system. The tracker 4 constructs a peer-to-peer (P2P) network called a swamp. A swamp is a group of peers that download or upload some content. At this time, the tracker 4 manages a list of peers (peer list) for each content. The peer list is a list of peers included in a peer-to-peer (P2P) network managed by the tracker 4 itself. Here, the case where the peer management server 3 includes the tracker 4 is also conceivable. In this case, the peer management server 3 and the tracker 4 have functions implemented on the same server. The functions of the peer management server 3 and the tracker 4 may be realized on a dedicated server, but the functions are distributed by using a distributed hash table (DHT) on a peer-to-peer (P2P) network. May be realized. In fact, in “BitTorrent (registered trademark)”, in addition to mounting the tracker 4 on a server, there is also an implementation using DHT.

  The peer management server 3 creates a peer management table and manages the state of the peer 1. The peer management table has, as table entries, a peer ID for uniquely identifying the peer and a retained content ID list for uniquely identifying the content held by the peer 1. The peer management table is preferably idle, ie a list of peers 1 that can be added to a peer-to-peer (P2P) network. However, in practice, the peer management table may be a list including peers other than the idle state. In this case, the peer management table further has a status indicating the state of the peer as a table entry. By providing an item indicating the peer status in the peer management table, the peer management server 3 can determine an idle peer and can use the peer management table as an idle peer management list. The peer management server 3 may create an idle peer management list indicating the idle peers separately from the peer management table.

FIG. 2 shows an example of the peer management table.
The peer management table has “peer ID” and “owned content ID List”. The “peer ID” is identification information for uniquely identifying the peer 1 managed by the peer management server 3. “Owned content ID List” indicates the owned content ID for uniquely identifying the content held by the peer 1. Here, the peer management table displays only idle peers. Although not shown, the peer management table may further have a “status”. “Status” is status information indicating the state of the peer 1.

  The tracker 4 exists for each distribution content and manages the peer 1 that transmits and receives pieces of content. A content ID is assigned to each distribution content. Therefore, the tracker 4 can be identified by the content ID.

  It should be noted that a plurality of contents can be regarded as one group content by combining the plurality of contents into one. The management target of the tracker 4, that is, the target to which the content ID is assigned is assumed to be such a group content unit. Therefore, the management target of the tracker 4 is not strictly limited to one content file.

  When the peer 1 identifies that the content needs to be downloaded, the peer 1 requests the tracker 4 managing the peer list of the content to download the content.

  Users browse video content using a dedicated peer. Video content can be browsed by selecting the content to be viewed on the spot and playing it immediately, or by downloading a video previously downloaded in some way. There are two ways to browse slowly. For example, if the user has previously browsed and registered a program of a certain genre, when a program of the corresponding genre is issued, a moving image is automatically downloaded to the user's peer. The user checks and browses the downloaded video later.

With reference to the flowchart of FIG. 3, the operation of the peer addition process when the peer 1 requests the tracker 4 to download content will be described.
(1) Step S101
The peer 1 makes a content download request to the tracker 4. That is, the peer 1 makes a request for addition to the peer-to-peer (P2P) network as a download peer to the tracker 4.
(2) Step S102
The tracker 4 checks the request class of the peer 1 in response to the download request. Here, the tracker 4 checks whether the request class of the peer 1 is high priority download.
(3) Step S103
If the request class is a low priority download, the tracker 4 permits an additional request to the peer-to-peer (P2P) network as a low priority download peer. Here, if the request class is not the high priority download, the tracker 4 adds the peer 1 to the peer list as a low priority download peer. The peer list is a list of peers included in a peer-to-peer (P2P) network managed by the tracker 4 itself. At this time, the tracker 4 may create a peer list in which only the low priority download peers are registered, and add the peer 1 to the end of the peer list.
(4) Step S104
If the request class is a high-priority download, the tracker 4 next checks whether or not the peer addition request condition is satisfied.
The peer addition request condition is, for example, the following expression.
“High-priority download peers <(Low-priority download peers × α) + (Number of dedicated upload peers × β)”
Here, α = 0.5 and β = 2. The values of α and β can be arbitrarily set. At this time, the tracker 4 may calculate or select the values of α and β. For example, the tracker 4 monitors the traffic of the peer-to-peer (P2P) network managed by the tracker 4 and calculates or selects the values of α and β according to the traffic when a download request is made. good.
(5) Step S105
When the tracker 4 satisfies the peer addition request condition, the tracker 4 permits the addition request to the peer-to-peer (P2P) network as a high priority download peer. Here, the tracker 4 adds the peer 1 to the peer list as a high priority download peer. At this time, the tracker 4 may create a peer list in which only high priority download peers are registered, and add the peer 1 to the end of the peer list.
(6) Step S106
When the tracker 4 does not satisfy the peer addition request condition, the tracker 4 inquires of the peer management server 3 whether or not the low priority download peer and the upload dedicated peer can be added so as to satisfy the peer addition request condition. Here, the tracker 4 inquires whether or not a low priority download peer and an upload dedicated peer that satisfy the peer addition request condition exist in the peer management table of the peer management server 3.
(7) Step S107
When receiving the inquiry result from the peer management server 3, the tracker 4 checks the inquiry result. Here, the tracker 4 refers to the inquiry result and confirms whether or not there is a low priority download peer and an upload dedicated peer that satisfy the peer addition request condition in the peer management table.
(8) Step S108
When there are low priority download peers and upload dedicated peers that satisfy the peer addition request condition in the peer management table, the tracker 4 uses the low priority download peers and upload dedicated peers included in the peer management table as peer lists as support peers. Add to At this time, the tracker 4 may request the peer management server 3 to add the support peer to the support peer list managed on the peer management server 3 side.
(9) Step S109
The tracker 4 adds the requesting peer 1 to the peer list as a high priority download peer.
(10) Step S110
The tracker 4 rejects the peer addition request of the peer 1 in the inquiry result to the peer management server 3 when the low priority download peer and the upload dedicated peer that satisfy the peer addition request condition do not exist in the peer management table.
(11) Step S111
When the tracker 4 rejects the peer addition request of the peer 1, the tracker 4 checks whether or not the low priority download is performed instead of the high priority download. At this time, the tracker 4 may make an inquiry to the peer 1 as to whether or not to perform low priority download. Further, when the tracker 4 rejects the peer addition request of the peer 1, the tracker 4 may automatically perform the low priority download.
(12) Step S112
When performing the low priority download, the tracker 4 adds the peer 1 as a low priority download peer to the peer list.
(13) Step S113
If the low priority download is not performed, the tracker 4 ends without adding the peer 1.

Next, the operation when the tracker 4 performs the support peer addition request inquiry process to the peer management server 3 will be described with reference to the flowchart of FIG.
(1) Step S201
The tracker 4 performs a support peer addition request inquiry process to the peer management server 3. At this time, the tracker 4 notifies the peer management server 3 of the attribute class peer addition management condition and the content ID at the time of inquiry processing.
The attribute class peer addition management condition is as follows, for example.
“(Number of low-priority download peers x α) + (Number of upload dedicated peers x β)> = 1”
Here, α = 0.5 and β = 2. The values of α and β can be arbitrarily set. At this time, the tracker 4 may calculate the values of α and β. For example, the tracker 4 monitors the traffic of the peer-to-peer (P2P) network managed by the tracker 4 and calculates or selects the values of α and β according to the traffic when a download request is made. good.
(2) Step S202
The peer management server 3 searches for an upload dedicated peer (seed). Specifically, the peer management server 3 finds a peer that has the content of the content ID requested from the tracker 4 and exists in the idle peer management list. Here, the idle peer management list is a peer management table. When there are a plurality of peers 1 that satisfy the condition, the peer management server 3 preferentially selects, for example, a peer with less content. The reason for selecting a peer with less retained content is that peer 1 with more retained content is more likely to be used as a seed for other content.
(3) Step S203
When the peer management server 3 finds a peer that exists in the idle peer management list, the peer management server 3 adds the corresponding peer as a support peer to the support peer list, and the support peer list after adding the corresponding peer sets the support peer number condition. Check if you are satisfied. The support peer number condition is set to satisfy the attribute class peer addition management condition and the peer addition request condition. For example, in the above attribute class peer addition management condition, if “high priority download peer number = 5”, “low priority download peer number = 5”, “upload dedicated peer number = 1”, “(low priority download peer number”) × α) + (number of upload dedicated peers × β) = 4.5 ”, which is smaller than“ the number of high priority download peers = 5 ”, and does not satisfy the peer addition requirement. Therefore, it is necessary to add a supporting peer for satisfying the peer addition requirement condition.
In the above case, the support peer number condition is as follows, for example.
"(Number of low-priority download peers x α) + (Number of dedicated upload peers x β)>0.5"
Here, α = 0.5 and β = 2.
(4) Step S204
When the support peer list satisfies the support peer number condition, the peer management server 3 determines the support peer list and returns a response to the tracker 4.
(5) Step S205
The peer management server 3 searches for low priority download peers when the number of upload dedicated peers satisfying the support peer number condition cannot be found and the support peer list does not satisfy the support peer number condition.
(6) Step S206
The peer management server 3 checks whether there are low priority download peers that satisfy the support peer number condition. Here, when the peer management server 3 finds a low-priority download peer, it adds the corresponding low-priority download peer as a support peer to the support peer list, and the support peer list after the corresponding low-priority download peer is added supports Check whether the number of peers requirement is satisfied.
(7) Step S207
When there is no low priority download peer that satisfies the support peer number condition, the peer management server 3 returns a response to the tracker 4 as the condition is not reached.
(8) Step S208
When the low priority download peer that satisfies the support peer number condition can be found, the peer management server 3 adds all upload exclusive peers and low priority download peers that have been found in the search so far to the support peer list. In the state, the support peer list is confirmed and a response is returned to the tracker 4. At this time, the peer management server 3 deletes the peer added to the swamp as a support peer from the idle peer management list. Here, swamp refers to a peer-to-peer (P2P) network built for certain content.

  Next, how content distribution is controlled using peer-to-peer (P2P) for a certain content in the content distribution system of the present invention will be described.

  The tracker manages a list of peers (peer list) belonging to a certain content. Each peer is classified as one of a transfer class of a high priority download peer, a low priority download peer, and an upload dedicated peer. Data transfer between peers is basically the same transfer process as the operation of the “BitTorrent (registered trademark)” protocol, except that priority control is realized between a high priority download peer and a low priority download peer. And In this embodiment, an example in which a priority control function is added to the “BitTorrent (registered trademark)” protocol is shown, but the peer-to-peer (P2P) transfer protocol is limited to “BitTorrent (registered trademark)”. It is not a thing.

  Each peer acquires a peer list from the tracker when participating in the swamp. Content is divided into fixed-length pieces and transferred in pieces. The peer connects to each peer in the peer list, and acquires information on the pieces that each peer has.

  Next, from the piece information held by each peer, the peer notifies the information on whether or not it has a piece that it does not have as “Interest flag”. By exchanging “Interest flag” between peers, a peer can determine whether each peer connected to it has a piece that it wants to download from itself.

  The peer then authorizes the download for a preset number of connected peers. In “BitTorrent (registered trademark)”, download permission is called “unchoke”. A difference from the normal “BitTorrent (registered trademark)” is that a peer selects a low-priority download peer over a high-priority download peer when selecting a peer that permits download. As a selection method, a method that always gives priority to the high-priority download peer, a method that selects the high-priority download peer and the low-priority download peer at a certain rate, and the like can be considered.

  When a download permission is issued from the connected peer, the peer determines which piece to select and actually permits the download. In “BitTorrent (registered trademark)”, in piece selection, the piece with the fewest peers called “Rarest First” is downloaded so that all pieces are evenly distributed on the network. High priority download peers may follow different piece selection rules. For example, when a high-priority download peer downloads moving image content, it is possible to realize stream reproduction even if all the content is not obtained by downloading pieces in order from the top.

  In "BitTorrent (R)", the "Rarest First" algorithm is an important principle for promoting even distribution of pieces and improving the transfer efficiency of the entire swamp, and high priority download peers behave differently from this principle. At first glance, it seems to reduce the overall transfer efficiency of the swamp. However, in the content distribution system of the present invention, the number of high-priority download peers, the number of low-priority download peers, and the number of dedicated upload peers in the swamp are controlled so as to comply with predetermined conditions. Even with the behavior that hinders the even distribution of the low-priority download peer, the low-priority download peer selectively downloads fewer pieces so that the pieces are evenly distributed. Therefore, if there are a sufficient number of low-priority download peers compared to high-priority download peers, it is possible to maintain a state in which pieces are evenly distributed throughout the network.

Next, with reference to the flowchart of FIG. 5, an operation of processing in which the peer 1 completes downloading of content and requests the tracker 4 to delete from the swamp will be described.
(1) Step S301
When the download of the content is completed, the peer 1 inquires of the tracker 4 whether or not it can leave the corresponding swamp. Here, the peer 1 makes a withdrawal request to the tracker 4 after the content download is completed.
(2) Step S302
The tracker 4 adds the peer 1 that has made a withdrawal request to the end of the deletion reservation list. Here, the tracker 4 adds the peer 1 to the end of the deletion reservation list in response to the withdrawal request from the peer 1.
(3) Step S303
The tracker 4 checks whether or not the peer deletion management condition is satisfied.
The peer deletion management condition is defined as follows, for example.
"(High priority download peers + γ) <(Low priority download peers x α) + (Number of upload dedicated peers x β)"
Here, α = 0.5, β = 2, and γ = 3. The values of α, β, and γ can be arbitrarily set. At this time, the tracker 4 may calculate the values of α, β, and γ. For example, the tracker 4 monitors the traffic of the peer-to-peer (P2P) network managed by the tracker 4 and calculates or selects the values of α, β, and γ according to the traffic when a download request is made. May be. In the above example, if γ = 0, the peer addition request condition and the peer deletion management condition are the same. The peer addition request condition and the peer deletion management condition may be the same, but by setting the peer deletion management condition strictly, it is possible to add a certain number of high priority download peers unconditionally.
(4) Step S304
When the tracker 4 does not satisfy the peer deletion management condition, the process ends.
(5) Step S305
When the tracker 4 satisfies the peer deletion management condition, the tracker 4 checks whether an entry exists in the deletion reservation list. The entry indicates a peer added to the deletion reservation list, that is, a peer that has made a withdrawal request.
(6) Step S306
When there is no entry in the deletion reservation list, the tracker 4 ends the process.
(7) Step S307
When there is an entry in the deletion reservation list, the tracker 4 deletes the first entry from the management target of the tracker 4 as a deletion target.
(8) Step S308
The tracker 4 registers the entry to be deleted in the peer management table of the peer management server 3 as being capable of supporting the peer.

  The peer deletion process from the deletion reservation list is repeatedly executed until the peer deletion condition is not satisfied or no entry exists from the deletion reservation list.

  The second embodiment of the present invention will be described below.

  In the present embodiment, the peer management server 3 has a peer relationship table for determining whether or not the users who use each peer are acquainted with each other. Peer 1 notifies whether other peer 1 is his acquaintance.

  Here, the peer management server 3 manages the relationship of each peer using the peer relationship table. The relationship between the peers is information such as that users are acquainted and registered. Here, it is assumed that the relationship between each peer is represented by the number of hops of acquaintance indicating how many people can pass through the acquaintance. Note that the peer management server 3 may automatically calculate the number of acquaintance hops based on the relationship between the peers. However, actually, it is not limited to these examples.

  When there are a plurality of candidates for selecting a low priority download peer, the peer management server 3 preferentially assigns a peer that is acquainted and registered with the peer that requested the high priority download. If there is no direct acquaintance among the low-priority download candidates, a peer having an “acquaintance acquaintance” relationship with the high-priority download peer is selected.

  The peer 1 that requested the high priority download is more likely to browse the content immediately and introduce the content to acquaintances with similar preferences, so it is better to assign peers of acquaintances as low priority download peers In the future, it is considered likely to browse the content.

  With reference to FIG. 6, the structural example of the peer 1, the peer management server 3, and the tracker 4 in the content delivery system of this invention is demonstrated. However, these are only examples, and are not actually limited to these examples.

  The peer 1 (1-i, i = 1 to n) includes a peer addition request unit 11, a piece management unit 12, and a relationship notification unit 13.

  The peer addition request means 11 (11-i, i = 1 to n) makes a request to add to the peer list as a download peer by making a content download request to the tracker 4. Further, the peer addition request means 11 makes a request for addition to the deletion reservation list by making a withdrawal request to the tracker 4 after the content download is completed.

  The piece management means 12 (12-i, i = 1 to n) manages pieces of content and transmits / receives pieces between peers. A piece is obtained by dividing content into fixed-length sizes. Here, the piece management unit 12 acquires all the pieces constituting the content, and determines that the download of the content is completed when the content is reconfigured from the acquired pieces.

  The relationship notification means 13 (13-i, i = 1 to n) notifies the peer management server 3 about the relationship of each peer. Note that the relationship notification unit 13 may update the relationship between peers.

  Note that the configuration example of the distribution server 2 may be the same as that of the peer 1. In the case of the distribution server 2, the peer addition request unit 11 does not make a content download request to the tracker 4, but makes an addition request to the peer list as an upload dedicated peer.

  The peer management server 3 includes a table management unit 31, a peer search unit 32, a condition check unit 33, and a relationship management unit 34.

  The table management unit 31 manages a peer management table 311, a peer relationship table 312, an idle peer management list 313, and a support peer list 314. The peer management table 311 has, as table entries, a peer ID for uniquely identifying the peer and a retained content ID list for uniquely identifying the content held by the peer 1. The peer relationship table 312 indicates whether users who use each peer are acquainted with each other. Here, the peer relationship table 312 has the number of acquaintance hops indicating how many acquaintances can be reached. The idle peer management list 313 is a list of peers 1 that can be added to an idle state, that is, a peer-to-peer (P2P) network. The idle peer management list 313 may be the same as the peer management table 311. The support peer list 314 shows support peers. The supporting peer is a peer of another attribute class selected to satisfy the attribute class peer addition management condition and the peer addition requirement.

  The peer search means 32 searches for an upload dedicated peer (seed). For example, the peer search means 32 finds a peer having the content with the content ID notified from the tracker 4 from the peers existing in the idle peer management list 313. At this time, when the peer search means 32 finds the corresponding peer in the idle peer management list, the peer search means 32 adds the corresponding peer to the support peer list 314. The peer search means 32 searches for a low-priority download peer when the support peer list 314 does not satisfy the support peer number condition.

  The condition check means 33 checks whether the support peer list 314 satisfies the support peer number condition. In addition, when the support peer list 314 satisfies the support peer number condition, the condition check means 33 confirms the support peer list 314 and responds to the tracker 4 to notify the confirmed support peer list 314. return it. In addition, when there is no low priority download peer that satisfies the support peer number condition, the condition check unit 33 returns a response to the tracker 4 as the condition is not achieved. Further, when the low priority download peer that satisfies the support peer number condition can be found, the condition checking means 33 adds the upload dedicated peer and the low priority download peer that have been found to the support peer list 314, and the support peers 314 The list 314 is confirmed, and a response is returned to the tracker 4 to notify the confirmed support peer list 314. At this time, the condition check means 33 deletes the peer added to the swamp as a support peer from the idle peer management list 313. That is, the condition check unit 33 deletes the peer added to the support peer list 314 from the idle peer management list 313.

  The relationship management means 34 manages the relationship of each peer using the peer relationship table 312. When there are a plurality of candidates for selecting a low priority download peer, the relationship management means 34 preferentially assigns a peer that is acquainted and registered with the peer that requested the high priority download. When there is no direct acquaintance among the low-priority download candidates, the relationship management unit 34 selects a peer that has an “acquaintance acquaintance” relationship with the high-priority download peer. Further, the relationship management unit 34 updates the peer relationship table 312 based on the notification from the relationship notification unit 13.

  The tracker 4 includes a request class check unit 41, a list management unit 42, a condition check unit 43, an inquiry unit 44, and an inquiry result confirmation unit 45.

  The request class check unit 41 checks the request class of the peer 1 in response to the download request from the peer addition request unit 11. If the request class is a low-priority download, the request class check means 41 adds it as a low-priority download peer to the peer-to-peer (P2P) network. If the request class is a high-priority download, the request class check means 41 checks whether or not the peer addition request condition is satisfied. If the request class check means 41 satisfies the peer addition request condition, the request class check means 41 Add to peer-to-peer (P2P) network as preferred download peer. It should be noted that the condition check means 43 may check whether or not the peer addition request condition is satisfied.

  The list management unit 42 manages the peer list 421 and the deletion reservation list 422. The peer list 421 is a list of peers for each content. Here, the peer list 421 is a list of peers included in a peer-to-peer (P2P) network managed by the tracker 4 itself. The list management means 42 adds the peer 1 added to the peer-to-peer (P2P) network to the peer list 421. Note that the peer list 421 may be prepared individually for each of the low priority download peer, the high priority download peer, the upload dedicated peer, and the support peer. The deletion reservation list 422 is a list indicating the peer 1 that has made a withdrawal request. The list management means 42 adds the peer 1 for which a withdrawal request has been made to the end of the deletion reservation list 422.

  The condition check means 43 sets attribute class peer addition management conditions. The condition checking unit 43 calculates the attribute class peer addition management condition values (for example, α and β values) so as to satisfy the peer addition request condition. Further, the condition checking means 43 checks whether or not the peer deletion management condition is satisfied. If the peer deletion management condition is satisfied, the condition checking unit 43 checks whether or not an entry exists in the deletion reservation list 422, and the deletion reservation list 422 is checked. If there is an entry, the first entry is deleted from the management target of the tracker 4. In other words, the condition checking unit 43 deletes the peer in the top entry of the deletion reservation list 422 from the peer-to-peer (P2P) network.

  The inquiry unit 44 makes an inquiry to the peer management server 3. For example, the inquiry means 44 inquires whether or not a low priority download peer and an upload dedicated peer can be added so as to satisfy the peer addition requirement condition.

  When the inquiry result confirmation unit 45 receives the inquiry result from the peer management server 3, the inquiry result confirmation unit 45 checks the inquiry result. For example, the inquiry result confirmation unit 45 refers to the inquiry result and confirms whether or not the low priority download peer and the upload dedicated peer satisfying the peer addition request condition exist in the peer management table 311. The inquiry result confirmation unit 45 supports the low-priority download peer and the upload-dedicated peer included in the peer management table 311 when the low-priority download peer and the upload-dedicated peer satisfying the peer addition request condition exist in the peer management table 311. As a peer to a peer-to-peer (P2P) network.

  According to the present invention, with respect to a swamp related to a predetermined content, the quality of the high-priority download peers is always sufficient by maintaining the number of high-priority download peers sufficiently lower than the number of low-priority download peers and the number of dedicated upload peers. Thus, it is possible to ensure that the content can be downloaded.

  In selecting a low-priority download peer, the peer 1 that has a high possibility of downloading in the future is preferentially selected to propose that the corresponding peer 1 may become a high-priority download peer in the future. It is possible to keep the number of high priority download peers small. It is possible to increase the download speed of other high priority download peers.

That is, the content distribution system of the present invention has the following characteristics.
The content distribution system of the present invention includes a distribution server that is a content distribution source, a plurality of peers that receive the content, a tracker that manages the content or a peer that downloads content for each of a plurality of content groups, and the state of the entire peer And a peer management server for managing the server. A peer-to-peer (P2P) network for each content or content group is configured between peers managed by the tracker. The peer has a function of downloading content not only from the server but also from other peers using the peer-to-peer (P2P) network. In this content distribution system, peers are classified into a plurality of attribute classes. In the group of peers to be managed, the tracker manages the peers so that the number of peers for each attribute class satisfies a preset attribute class peer addition management condition. When the tracker is requested to add to a certain attribute class and cannot satisfy the peer addition request condition, the tracker makes an inquiry to the peer management server. The peer management server selects peers of other attribute classes so as to satisfy the peer addition requirement, creates a support peer list, and responds to the tracker. The tracker maintains the peer addition requirement condition by adding the peer list that has made the addition request and the supporting peer list from the peer management server to the peer-to-peer (P2P) network that it manages. Here, when the peer participates in the swamp, the supporting peer is added from the peer list.

  In the content distribution system of the present invention, when a peer whose content has been downloaded notifies the tracker that the content has been downloaded, the tracker adds the peer to the deletion reservation list, and the tracker satisfies the peer deletion management condition. The peer is allowed to leave the peer-to-peer (P2P) network managed by the tracker. In this case, when the content download is completed, the peer leaves only when the condition is satisfied.

  In the content distribution system of the present invention, there are a high-priority download class, a low-priority download class, and an upload-only class as peer attribute classes, and peers belonging to the high-priority download class are compared to peers belonging to the low-priority download class. Also prioritize downloading content. That is, there are attribute classes dedicated to high priority, low priority, and upload.

  In the content distribution system of the present invention, in the process in which the peer management server selects the support peer, first, the upload dedicated peer is selected, and if the peer addition condition cannot be satisfied only by the upload dedicated peer, then the low priority download is performed. Make a peer selection. That is, an upload-only or low priority peer is selected.

  In the content distribution system of the present invention, in the process in which the peer management server selects a support peer, priority is given to a peer with less content when selecting an upload dedicated peer.

  In the content distribution system of the present invention, in the process of selecting a support peer by the peer management server, a peer with a high possibility of browsing the corresponding content in the future is selected preferentially when selecting a low priority download peer.

  The peer management server has a peer relationship table for determining whether or not users using each peer are acquainted with each other. Peers have a means of notifying whether other peers are acquainted with them. The relationship between peers is expressed by the number of acquaintance hops indicating how many acquaintances can be reached. When selecting a peer having a high possibility of browsing the corresponding content in the future, the peer relationship table is accessed, and a peer having a small number of hops with the high-priority download peer is preferentially assigned as a low-priority download peer.

  In the content distribution system of the present invention, when the distribution server distributes the moving image content and the peer downloads the content, the high priority download peer downloads the content in order from the top.

  As described above, according to the present invention, in constructing a peer-to-peer (P2P) network that performs download processing for predetermined content, peers are classified into high priority download peers, low priority download peers, and upload dedicated peers, and high priority downloads are made. In order to perform control that satisfies the quality required by the user, the peer introduces a mechanism for downloading content in preference to the low-priority download peer.

  Also, for certain content, when a high priority download is requested so that the peer can immediately view the content, the tracker satisfies the constraints between the high priority download peer, the low priority download peer, and the upload dedicated peer. To check. If the constraints are not satisfied, the peer management server is queried, and by appropriately assigning low priority download peers and upload dedicated peers, uploads with sufficiently low priority download peers compared to high priority download peers. Holds the state where a dedicated peer exists. If the number of high-priority download peers is sufficiently small, even if the high-priority download peer ignores the “Tit-for-Tat strategy” or the “Rarest First mechanism” and downloads content preferentially, The upload-only peer can maintain the state of the network where the content can be downloaded at a statistically sufficient transfer rate for the entire peer-to-peer (P2P) network.

  When the peer management server selects a low-priority download peer, it selects a peer that has a high possibility of browsing the corresponding content in the future. By selecting a peer that has a high possibility of browsing the relevant content, when the relevant peer browses the content, the content has already been downloaded, so there is no need to wait for the download, and user convenience and satisfaction are improved. improves. In addition, since it is not necessary for the corresponding peer to download content as a high-priority download peer, it is possible to reduce the number of high-priority download peers and stabilize the peer-to-peer (P2P) network. .

FIG. 1 is a configuration diagram of a content distribution system of the present invention. FIG. 2 is a diagram illustrating an example of a peer management table. FIG. 3 is a flowchart of processing in the tracker when adding a peer to the swamp. FIG. 4 is a flowchart of peer management server inquiry processing when adding a peer to a swamp. FIG. 5 is a flowchart of processing for deleting a peer from a swamp. FIG. 6 is a block diagram illustrating a configuration example of a peer, a peer management server, and a tracker.

Explanation of symbols

1 (-i, i = 1 to n) ... Peer 11 ... Peer addition request means 12 ... Piece management means 13 ... Relationship notification means 2 ... Distribution server 3 ... Peer management server 31 ... Table management means 311 ... Peer management table 312 ... Peer relationship table 313 ... Idle peer management list 314 ... Supporting peer list 32 ... Peer search means 33 ... Condition check means 34 ... Relationship management means 4 ... Tracker 41 ... Request class check means 42 ... List management means 421 ... Peers List 422 ... Deletion reservation list 43 ... Condition check means 44 ... Inquiry means 45 ... Inquiry result confirmation means 100 ... Content distribution system

Claims (36)

Multiple peers grouped by attribute class,
A peer management server that manages the state of each of the plurality of peers;
The plurality of peers are managed so that the number of peers for each attribute class satisfies the attribute class peer addition management condition, and when an addition request from a predetermined peer to the predetermined attribute class is made among the plurality of peers If the peer addition requirement cannot be satisfied, the peer management server is queried and created based on peers of other attribute classes selected from the peer management server to satisfy the peer addition requirement. A content distribution system comprising: a peer list for support, and a tracker for adding a peer that has made the addition request and a peer in the support peer list to a peer-to-peer (P2P) network. The content distribution system according to claim 1,
The peer addition request condition is “the number of high priority download peers <(the number of low priority download peers × α) + (the number of upload dedicated peers × β)”,
The content distribution system in which the attribute class peer addition management condition is “(the number of low priority download peers × α) + (the number of upload dedicated peers × β)> = 1”. The content distribution system according to claim 1 or 2,
Upon receiving a download completion notification from a peer whose content has been downloaded, the tracker adds the peer to the end of the deletion reservation list, and the first entry in the deletion reservation list within a range that satisfies the peer deletion management condition Content distribution system that deletes the client from the management target and allows the peer to leave the peer-to-peer (P2P) network. The content distribution system according to claim 3,
The content distribution system in which the peer deletion management condition is “(number of high priority download peers + γ) <(number of low priority download peers × α) + (number of upload dedicated peers × β)”. The content distribution system according to any one of claims 1 to 4,
The peer management server selects an upload-only peer when creating the support peer list, and selects a low-priority download peer when the selected upload-only peer cannot satisfy a peer addition condition. Content distribution system. The content distribution system according to any one of claims 1 to 5,
When creating the support peer list, the peer management server prioritizes peers with less content when selecting a dedicated upload peer. The content distribution system according to any one of claims 1 to 6,
When creating the support peer list, the peer management server preferentially selects a peer that is likely to be viewed in the future when selecting a low-priority download peer. The content distribution system according to claim 7,
The peer management server refers to a peer relationship table for determining whether or not users using each peer are acquainted when selecting a peer that is likely to be viewed in the future, A content distribution system that preferentially assigns a peer with a small number of acquaintance hops with a high-priority download peer as a low-priority download peer based on the number of acquaintance hops indicating how many acquaintances can be reached. In response to a download request from a peer, the peer request class is checked. If the request class is a low priority download, it is added to the peer-to-peer (P2P) network as a low priority download peer, and the request class is a high priority download. If there is a peer addition requirement, the request class check means for adding to the peer-to-peer (P2P) network as a high priority download peer is checked.
If the peer addition requirement is not satisfied, an inquiry is made to the peer management server that manages the status of the peer as to whether a low-priority download peer and upload dedicated peer can be added so as to satisfy the peer addition requirement. Inquiry means to perform,
The inquiry result to the peer management server is confirmed, and when there are low priority download peers and upload dedicated peers that satisfy the peer addition requirement condition, the low priority download peers and upload dedicated peers included in the peer management table are designated as supporting peers. A query result confirmation means for adding to the peer-to-peer (P2P) network as a tracker. The tracker according to claim 9,
The peer addition request condition is “the number of high priority download peers <(the number of low priority download peers × α) + (the number of upload dedicated peers × β)”,
The attribute class peer addition management condition is “(the number of low priority download peers × α) + (the number of upload dedicated peers × β)> = 1” tracker. The tracker according to claim 9 or 10,
A list management means for adding a peer having requested to leave to the end of the deletion reservation list;
Check whether the peer deletion management condition is satisfied, and if the peer deletion management condition is satisfied, check whether there is an entry in the deletion reservation list, and if there is an entry in the deletion reservation list, And a condition check means for deleting a peer in the first entry of the deletion reservation list from a peer-to-peer (P2P) network. The tracker according to claim 11,
The peer deletion management condition is “(high priority download peer number + γ) <(low priority download peer number × α) + (upload dedicated peer number × β)”. A tracker according to any one of claims 9 to 12,
The inquiry unit notifies the peer management server of an attribute class peer addition management condition and a content ID during the inquiry process. A table management means for managing an idle peer management list indicating idle peers that can be added to a peer-to-peer (P2P) network, and a supporting peer list indicating supporting peers;
By referring to the idle peer management list and searching for a peer that possesses the content of the content ID notified from the tracker, and when there is a peer that possesses the content, the peer that possesses the content is added to the supporting peer list. Peer search means to be added;
It is checked whether or not the support peer list satisfies the support peer number condition. If the support peer list satisfies the support peer number condition, the support peer list is determined, and the support peer list is determined. A peer management server comprising condition check means for notifying the tracker of a list and deleting a peer added to the support peer list from the idle peer management list. The peer management server according to claim 14, comprising:
The peer search means searches for low priority download peers when the number of upload dedicated peers satisfying the support peer number condition cannot be found and the support peer list does not satisfy the support peer number condition. Peer management server. The peer management server according to claim 15, wherein
The condition check means, when there is no low priority download peer that satisfies the support peer number condition, returns a response to the tracker as the condition is not reached. The peer management server according to claim 15 or 16, comprising:
When the low-priority download peer that satisfies the support peer number condition is found, the condition check means adds the upload dedicated peer and the low-priority download peer that have been found to the support peer list, and A peer management server that determines a list and notifies the tracker of the supporting peer list. The peer management server according to any one of claims 15 to 17,
When there are multiple candidates for selecting a low-priority download peer, priority is given to a peer with a small number of acquaintance hops with a high-priority download peer based on the number of acquaintance hops that indicate how many people you can reach via acquaintances A peer management server further comprising relationship management means for assigning to the server as a low priority download peer. Managing the state of each of a plurality of peers classified by attribute class;
The plurality of peers are managed so that the number of peers for each attribute class satisfies the attribute class peer addition management condition, and when an addition request from a predetermined peer to the predetermined attribute class is made among the plurality of peers If the peer addition requirement cannot be satisfied, selecting a peer of another attribute class so as to satisfy the peer addition requirement and creating a support peer list;
Adding the peer that has made the addition request and the peer in the supporting peer list to a peer-to-peer (P2P) network. The content distribution method according to claim 19, wherein
The peer addition request condition is “the number of high priority download peers <(the number of low priority download peers × α) + (the number of upload dedicated peers × β)”,
The attribute class peer addition management condition is “(low priority download peer number × α) + (upload dedicated peer number × β)> = 1” content distribution method. The content distribution method according to claim 19 or 20,
When a download completion notification is received from a peer whose content has been downloaded, the peer is added to the end of the deletion reservation list, and the first entry of the deletion reservation list is managed from the management target within a range that satisfies the peer deletion management condition. The content delivery method further comprising the step of deleting and allowing the peer to leave the peer-to-peer (P2P) network. The content distribution method according to claim 21, wherein
The peer deletion management condition is a content distribution method in which “(the number of high priority download peers + γ) <(the number of low priority download peers × α) + (the number of upload dedicated peers × β)”. The content distribution method according to any one of claims 19 to 22,
A content distribution method further comprising: selecting an upload-only peer when creating the supporting peer list, and selecting a low-priority download peer when the selected upload-only peer cannot satisfy a peer addition condition. The content distribution method according to any one of claims 19 to 23, wherein
A content distribution method further comprising the step of giving priority to a peer with less content when selecting a peer dedicated to uploading when creating the support peer list. A content distribution method according to any one of claims 19 to 24,
When creating the support peer list, the content distribution method further includes a step of preferentially selecting a peer that is likely to be viewed in the future when selecting a low-priority download peer. The content distribution method according to claim 25, wherein
When selecting peers that are likely to be viewed in the future, refer to the peer relationship table for determining whether or not the users who use each peer are acquainted with each other. A content delivery method further comprising: preferentially assigning a peer having a small number of acquaintance hops with a high-priority download peer as a low-priority download peer based on the number of acquaintance hops indicating whether it can be reached. A program for causing a computer to function as a tracker,
In response to a download request from a peer, the peer request class is checked. If the request class is a low priority download, it is added to the peer-to-peer (P2P) network as a low priority download peer, and the request class is a high priority download. If there is a peer addition requirement check, and if the peer addition requirement is satisfied, adding to the peer-to-peer (P2P) network as a high priority download peer;
If the peer addition requirement is not satisfied, an inquiry is made to the peer management server that manages the status of the peer as to whether a low-priority download peer and upload dedicated peer can be added so as to satisfy the peer addition requirement. Steps to do,
The inquiry result to the peer management server is confirmed, and when there are low priority download peers and upload dedicated peers that satisfy the peer addition requirement condition, the low priority download peers and upload dedicated peers included in the peer management table are designated as supporting peers. And adding to the peer-to-peer (P2P) network as a program. A program according to claim 27,
The peer addition request condition is “the number of high priority download peers <(the number of low priority download peers × α) + (the number of upload dedicated peers × β)”,
The attribute class peer addition management condition is “(low priority download peer count × α) + (upload dedicated peer count × β)> = 1”. The program according to claim 27 or 28, wherein:
Adding a peer with a withdrawal request to the end of the delete reservation list;
Check whether the peer deletion management condition is satisfied, and if the peer deletion management condition is satisfied, check whether there is an entry in the deletion reservation list, and if there is an entry in the deletion reservation list, A program for causing a computer to further execute a step of deleting a peer in a first entry of the deletion reservation list from a peer-to-peer (P2P) network. A program according to claim 29,
The peer deletion management condition is “(high priority download peer number + γ) <(low priority download peer number × α) + (upload dedicated peer number × β)”. A program according to any one of claims 27 to 30, wherein
A program for causing a computer to further execute a step of notifying an attribute class peer addition management condition and a content ID to the peer management server during inquiry processing. A program for causing a computer to function as a peer management server,
Configuring an idle peer management list indicating idle peers that can be added to a peer-to-peer (P2P) network, and a supporting peer list indicating supporting peers;
By referring to the idle peer management list and searching for a peer that possesses the content of the content ID notified from the tracker, and when there is a peer that possesses the content, the peer that possesses the content is added to the supporting peer list. Adding steps,
It is checked whether or not the support peer list satisfies the support peer number condition. If the support peer list satisfies the support peer number condition, the support peer list is determined, and the support peer list is determined. Notifying the tracker of a list;
A program for causing a computer to execute the step of deleting a peer added to the support peer list from the idle peer management list. A program according to claim 32, wherein
If the number of upload dedicated peers satisfying the support peer number condition cannot be found and the support peer list does not satisfy the support peer number condition, the computer further includes a step of searching for a low priority download peer. A program to be executed. A program according to claim 33, wherein
A program for causing a computer to further execute a step of returning a response to the tracker as unsatisfied when a low priority download peer that satisfies the support peer number condition does not exist. A program according to claim 33 or 34,
When a low-priority download peer that satisfies the support peer number condition can be found, the discovered upload dedicated peer and low-priority download peer are added to the support peer list, the support peer list is confirmed, A program for causing a computer to further execute a step of notifying the tracker of a supporting peer list. A program according to any one of claims 33 to 35, wherein
When there are multiple candidates for selecting a low-priority download peer, priority is given to a peer with a small number of acquaintance hops with a high-priority download peer based on the number of acquaintance hops that indicate how many people you can reach via acquaintances A program for causing a computer to further execute the step of assigning to a computer as a low priority download peer.

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