JP5160405B2 - P2P distribution system and distribution method - Google Patents

Description

  The present invention relates to a peer-to-peer (hereinafter referred to as P2P) distribution system and distribution method in a network, and in particular, a P2P distribution system and distribution that enable high-speed file exchange and suppress network load. Regarding the method.

  With the spread of Internet connection using high-speed ADSL and FTTH in recent years, large-capacity content files such as movies and music can be exchanged between computer terminals by P2P communication without using a server instead of the conventional client / server type service form. Service to replace is increasing. In particular, P2P communication such as BitTorrent in which content files are subdivided into pieces and a plurality of peers share the files in a distributed manner is rapidly increasing.

  In P2P communication using BitTorrent, content files such as movies and music are divided into multiple pieces (multiple pieces of pieces) and meta information files (links to trackers described later and hash values of each piece) on the network. Distributed to each peer, and one peer (requesting peer address) requests peer information from the tracker to obtain a peer information list (peer list), and each piece from each peer on the network based on this peer list Are collected and the file is reconstructed.

  When content distribution using P2P communication is frequently performed, a phenomenon occurs in which traffic increases. In the content distribution service by P2P communication such as BitTorrent currently being provided, the amount of traffic output from the content holder server is reduced by the P2P technology even if the number of users increases. However, for ISPs, the amount of traffic continues to increase, and the backbone is very under pressure.

As an attempt to solve this problem, a technology is disclosed in which a plurality of ISPs disclose network information, use this information on the P2P distribution service side, and the ISP and the distribution service cooperate with each other to perform efficient distribution for both sides. 1 is proposed.
In this technology, in addition to the distribution control server, an information management server that holds the network status is installed in each ISP. When the peer requests content, the distribution control server notifies the information management server of connectable peer information when creating a peer list in which the connectable peers are described in order of priority, and the network between the peers. It has a function of obtaining the upper distance (P4P-distance) and notifying the distribution control server.
P4P: Provider Portal for Applications http: // www. cs. washington. edu / homes / arvind / papers / p4p. pdf

  In this case, when obtaining the priority between peers (creating a peer list), it is necessary to use the same network information until the latest network information is updated. The change in network status is not reflected in the priority between peers.

  In addition, the distribution control server creates and transmits a peer list in which the peers that can be connected are listed in order of priority to the peer that requested the content. When there is a distribution control server, there is a problem that the priority of peers created by other distribution control servers is not considered. For this reason, when the peers are selected from the peer list, the same peer may be selected a plurality of times, and there is an inconvenience that the route to be selected is biased.

In P2P distribution, each peer has a line contract such as FTTH or ADSL, and further uses a wireless LAN, so the communication speed between the peers is very important.
However, with the technology described in Non-Patent Document 1, the network status between ISP routers is acquired by OSPF, BGP, etc., the line speed is acquired by SNMP (Simple Network Management Protocol), and distribution control with peers is performed. Although the communication speed between the servers is acquired, the communication speed between the peers is not notified to the distribution control server and reflected.

  In the technology described in Non-Patent Document 1, BitTorrent also measures the download / upload speed and performs peer selection (Tit-for-tat) based on it. Priority is given to peers that have been fast in the past t (default is t = 20) seconds for nodes that have become peers. is not.

  The present invention has been proposed in view of the above circumstances, and enables high-speed file exchange by using an ISP line and performing peer selection using the current network information and past distribution results. In addition, an object of the present invention is to provide a hybrid P2P distribution system and distribution method that can suppress the load on the network.

In order to achieve the above object, the present invention collects all network information in an ISP from a router or the like and centrally manages it in a P2P application in order to select a peer considering the network topology. Server)
A topology information management server (n-Tracker) that collects network information from the network information providing server (n-Server) and determines the priority of peers in response to a peer list request from the distribution control server (p-Tracker). ,
Is provided.

That is, according to claim 1, the file is divided into a meta information file and a plurality of pieces and distributed on the network, and one peer (requested peer address) obtains a peer list, and based on this peer list, the network In a P2P distribution system that collects pieces by P2P communication from each of the above peers and reconstructs the file,
A network information providing server (n-Server) that collects and centrally manages various types of information related to routes on the network;
Topology information management server (n-Tracker) that creates a priority peer list based on an evaluation value calculated based on information about the peer address from which the piece is acquired for the requested peer address from the network information providing server (n-Server) When,
A distribution control server (p-Tracker) that obtains a priority peer list from the topology information management server and distributes the priority peer list to the requested peer address, and
The topology information management server (n-Tracker) has correction means for determining the priority order by reflecting creation history information during route creation or selection history information for route selection when creating a priority peer list. It is characterized by comprising.

Claim 2 is the P2P distribution system of claim 1,
The correction means of the topology information management server (n-Tracker)
When creating a priority peer list with an evaluation value calculated based on information from the network information providing server (n-Server),
If the evaluation values in the priority peer list are the same, it is determined whether or not the same route is included in the route from the request peer address to the acquisition peer address, and the acquisition peer address including a different route is given priority. It is characterized by having means for creating a priority peer list in consideration of creation history information during route creation to be selected.

Claim 3 is the P2P distribution system of claim 1,
A plurality of the delivery control server (p-Tracker),
While the topology information management server (n-Tracker) has a recording means for recording the priority peer list created in the past,
The correction means includes
When creating a priority peer list with an evaluation value calculated based on information from the network information providing server (n-Server),
By selecting a route with a low usage count from the information of multiple priority peer lists created in the past in response to requests from multiple distribution control servers (p-Trackers), the priority history information is reflected to reflect the priority history information. It is characterized by having means for creating a list.

Claim 4 is the P2P distribution system of claim 1,
Each peer notifies the distribution control server (p-Tracker) at the end of the download about the transfer speed between peers that downloaded or uploaded the content during content distribution in the network, and the distribution control server (p-Tracker) notifies the topology information. While having a means to notify the management server (n-Tracker),
The correction means of the topology information management server (n-Tracker)
When creating a priority peer list with an evaluation value calculated based on information from the network information providing server (n-Server),
It is characterized by comprising means for assigning priorities reflecting the transfer speed between peers as selection history information for route selection.

According to a fifth aspect of the present invention, the file is divided into a meta information file and a plurality of pieces and distributed on the network, and one peer (requested peer address) acquires the peer list, and based on the peer list, In a P2P distribution method of collecting pieces from each peer of P2P communication by P2P communication and reconstructing the file,
Collect various information about routes on the network,
When creating a priority peer list based on an evaluation value calculated based on information on the peer address from which the piece is acquired for the requested peer address, the creation history information for route creation or the selection history information for route selection is reflected. Determine the priority of the peers,
Each piece is distributed from a plurality of acquisition destination peer addresses based on the priority of peers in the priority peer list with respect to the requested peer address.

According to the present invention, when creating the priority peer list, the correction means reflects the creation history information of route creation or the selection history information of route selection, and determines the priority of the acquisition destination peer. The network can be efficiently exchanged at high speed and the load on the network can be suppressed.
In addition, when there are multiple distribution control servers (p-Trackers), it is possible to use the same network as much as possible without frequently changing the network information by reflecting the history information of route creation and route selection. Can be avoided.

  Specifically, when creating a priority peer list, consider route creation history information to preferentially select acquisition peer addresses including different routes, or create multiple priority peer lists created in the past. The selection history information of route selection is reflected so as to select a route with a small number of uses from the above information.

In addition, when creating a priority peer list, by assigning priorities reflecting the transfer speed between peers as route selection selection history information, it is possible to identify users who had high download speeds in the past when content was downloaded. It becomes possible to select as an acquisition destination peer.
As a result, when the user with the requested peer address downloads a file, it is more likely that the same type of content will be downloaded than the user's preference. By becoming a peer, the user with the requested peer address can download content at high speed.

A P2P distribution system according to an embodiment of the present invention will be described with reference to the network model diagram of FIG. 1 and the functional block diagram of FIG.
The present invention is a P2P distribution system for selecting a peer with good distribution efficiency based on network information when a peer performs content distribution using the P2P technology in a network topology having a hierarchy as shown in FIG.
The P2P distribution system includes a plurality of distribution control servers (p-Trackers) 10, a topology information management server (n-Tracker) 20, and a network information providing server (n-) in a network 2 constructed via the Internet 1. Server) 30, a content server 40, and a plurality of peers 50 including a requesting peer for requesting content and an acquisition destination peer.

Each peer 50 is a node in the network, and is connected to the router 3 every plural number. In addition, a plurality of content servers 40 that provide content file distribution services such as movies and music are connected in the network 2. For example, when a content file is downloaded from the content server 40 (content server X) to a node (peer) for the first time, all files are downloaded from the content server 40 (content server X). Such a content file is divided into a plurality of pieces (a large number of piece-like file pieces) and a meta information file and distributed to each peer on the network.
When one peer (requested peer address) downloads a content file, the meta information file is first acquired by P2P distribution, and the peer list is requested and acquired from the distribution control server managing the content in the meta information file. To do. Based on this peer list, pieces are collected from each peer on the network, and the entire content file is reconstructed.
Each peer 50 is notified to the distribution control server 10 at the end of the download about the transfer speed between peers at which the content is downloaded or uploaded at the time of content (piece) distribution from the content acquisition destination peer in the network. 10 is provided with means for notifying the topology information management server 20.

The network information providing server (n-Server) 30 collects and centrally manages various information related to the distance on the network regarding each peer in the network.
That is, the network information providing server (n-Server) 30 is connected to each router 3 to which an arbitrary number of peers 50 are connected, for each link, distance, bandwidth, bandwidth usage rate, cost, circuit (FTTH / (ADSL) or the like, and an information detection unit 31 that constantly detects information and an information management unit 32 that manages the information.
The network information providing server (n-Server) 30 is configured to transmit and receive network information to and from the topology information management server (n-Tracker) 20.

The topology information management server (n-Tracker) 20 sends a piece (content file file) corresponding to the requested peer address from the network information providing server (n-Server) 30 in response to a peer list request from the distribution control server (p-Tracker) 10. Information acquisition unit 21 that acquires information on the peer address (distance, bandwidth, bandwidth usage rate, cost, line) in the network, and evaluation value calculation that calculates an evaluation value based on this information Unit 22 and a priority peer list creation unit 23 that creates a priority peer list based on the evaluation value, and manages the requested peer for the priority peer list created by the priority peer list creation unit 23 Is sent back to the distribution control server (p-Tracker) 10. The priority peer list creation unit 23 has a recording unit for recording a priority peer list created in the past.
The topology information management server (n-Tracker) 20 reflects the creation history information of route creation or the selection history information of route selection when the priority peer list creation unit 23 creates the priority peer list. The correction means 24 for determining the priority order is provided.
The distance information between peers described above includes parameters related to the transfer rate such as the number of routers interposed between peers.

  Each distribution control server (p-Tracker) 10 manages a plurality of peer groups connected to each router 3, while a topology information management server when any of the managed peers 50 becomes a requesting peer. After requesting the peer list to the (n-Tracker) 20, the priority peer list created by the priority peer list creating unit 23 of the topology information management server (n-Tracker) 20 is acquired and distributed to the address of the requested peer The peer list distribution unit 11 is configured.

Next, a procedure from when a peer in the network starts downloading content using a P2P application to selecting a piece acquisition destination peer will be described with reference to the processing flow of FIGS.
The peer (peer # 1) requesting the download of the content file activates the application and performs a content download start operation (step 101).
Peer (peer # 1) requests download control server (p-Tracker) 10 that owns the downloaded content and manages the content (peer list) that is currently participating in the network and can become a peer. To do. At this time, the address of the peer (peer # 1) and the number of peers (p-count) included in the peer list are transmitted to the distribution control server (p-Tracker) 10 (step 102).

  The distribution control server (p-Tracker) 10 has an IP address of a peer (p-Tracker peer list) that can be downloaded by the peer (peer # 1) 50 managed by itself and an IP address of the peer (peer # 1) 50. The address is transmitted to the topology information management server (n-Tracker) 20 (step 103).

  The topology information management server (n-Tracker) 20 receives a notification from the network information providing server (n-Server) 30 periodically and when changing the network information (Step 301). That is, when there is a network information update notification, the topology information management server (n-Tracker) 20 requests network information from the network information providing server (n-Server) 30 (step 302) and receives the network information (step 302). Step 303).

  On the topology information management server (n-Tracker) 20, the evaluation value between each peer of the peer list (p-Tracker peer list) of the peer (peer # 1) 50 and the distribution control server (p-Tracker) 10 is Calculation is performed based on the information (step 201), and a priority peer list in which peers are arranged in the order of evaluation values is created (step 202).

The characteristic configuration of the present invention is that when the topology information management server (n-Tracker) 20 creates the above-described priority peer list, creation history information during route creation or route selection selection It has a correcting means for determining the priority order reflecting the history information. That is, the correction means provided in the topology information management server (n-Tracker) 20 rearranges the peer addresses of the acquisition destination peers in the priority peer list (step 203).
The rearrangement of peer addresses by the correcting means includes (1) avoiding duplicate link selection in the route as creation history information during route creation, and (2) priority peer list (priority) created in the past as route selection selection history information. Peer list) Reflecting information, (3) Reflecting the actual value of the transfer rate between peers, or a combination thereof is performed.

When the priority peer list creating unit creates a sorted priority peer list (priority peer list), the topology information management server (n-Tracker) 20 creates a priority peer list. (priority peer list) is notified to the distribution control server (p-Tracker) 10 (step 204).
The delivery control server (p-Tracker) 10 extracts the number of peers (p-count) included in the peer list requested by the peer (peer # 1) from the top of the received priority peer list (priority peer list) ( In step 104), this is transmitted as a peer list to the peer (peer # 1) 50 (step 105).
The peer (peer # 1) 50 becomes a peer and downloads contents in the order described in the received peer list (step 106).

  Details of the transmission and reception of network information between the topology information management server (n-Tracker) 20 and the network information providing server (n-Server) 30 (procedure surrounded by a dotted line in FIG. 3) will be described with reference to FIG. explain.

In the network information providing server (n-Server) 30, network information (link ID, bandwidth, usage rate, state) is detected from the router 3 at regular intervals, updated, and recorded. That is, the network information providing server (n-Server) 30 receives network information from the router 3 at regular intervals (step 310), updates and sets the received network information in a table (step 311), and links the network. The connection state is recalculated (step 312), the cost and route for every network are calculated (step 313), and the latest information of the network is grasped.
The table described above is divided into (a) a link status table and (b) an inter-cluster cost table, and network information is managed. As shown in each table in FIG. In the inter-cluster cost table, the cost, path, and link (Link ID) for the acquisition peer (cluster Src) and request peer (cluster Dst) are set for the bandwidth, usage rate, cluster ID, and status.

  When the IP address of peer (peer # 1) 50 is transmitted to topology information management server (n-Tracker) 20 (step 103), topology information management server (n-Tracker) 20 receives peer (peer # 1). ) Calculation 1 for calculating the link address, link ID, and cluster ID of 50 and calculation 2 for calculating the link address, link ID, and cluster ID of the distribution control server (p-Tracker) peer list are performed (step 210).

The topology information management server (n-Tracker) 20 receives a notification from the network information providing server (n-Server) 30 about updating of network information at regular intervals (step 301), and determines whether or not network information is updated (step 301). 211).
When the topology information management server (n-Tracker) 20 has received notification that the network information has been updated, the topology information management server (n-Tracker) 20 requests network information from the network information providing server (n-Server) 30 (step 302), and has been described above ( Network information of a) link state table and (b) intercluster cost table is received (step 303).

The topology information management server (n-Tracker) 20 that has received this information is information corresponding to the link addresses, link IDs, and cluster IDs of the calculations “1” and “2” registered in the tables (a) and (b). (Step 212), and an evaluation value is calculated for each peer in the peer list of the peer (peer # 1) 50 and the distribution control server (p-Tracker) 10 using a desired formula (step 213).
Then, a priority peer list in which peers are arranged in the order of evaluation value is created, and the peer address of the acquisition destination peer in the priority peer list (priority peer list) is rearranged by the correction means (priority change) (Step 214), and a priority peer list is created (step 215).
The topology information management server (n-Tracker) 20 stores the created priority peer list (priority peer list) n times (step 216), and stores the latest priority peer list (priority peer list) in the distribution control server ( p-Tracker) 10 is notified (step 204).

  Next, a description will be given of the above-described priority change procedures (1) to (3) performed when the priority peer list is created using the correcting means.

First, a correction example (correction taking into account creation history information during route creation) by avoiding duplicate link selection in the route of (1) will be described.
In the network of FIG. 5, when the requesting peer for downloading the content file is peer # 3 (peer 50), the priority peer list created from the evaluation value (priority peer list before the priority ranking is changed by the correcting means) ) Is as shown in FIG.

  In this case, by changing the priority by the correction means, in the priority peer list created based on the evaluation value, if the evaluation value is the same, the peer that uses the link route with a small number of selections is given priority. Change (correct) peer priority to select. In the case of FIG. 6A, before the priority change, the same route (NW2 → NW3) is used in 12, and the route A and the route B from the peer # 2 to the peer # 3 in FIG. The priority order of 2 is lowered and switched to create a priority peer list shown in FIG.

Next, a description will be given of a correction example in which (2) priority evaluation is performed by reflecting priority peer list information created in the past.
In this case, the priority peer list (priority peer list) created in the past is stored n times, and in the case of the same evaluation value, it is used as an index for selecting a link that is used less frequently.
In the network of FIG. 7, when the requesting peer for downloading the content file is peer # 3 (peer 50), the priority peer list created from the evaluation value (priority peer list before the priority ranking is changed by the correcting means) ) Is as shown in FIG.

  In the network of FIG. 7, the requesting peers 1 to 4 times before are peer # 4 (peer 50), peer # 2 (peer 50), peer # 1 (peer 50), and peer # 2 (peer 50), respectively. When the priority peer list created at that time is shown in FIGS. 8A to 8D, the link route (NW0 → NW1) is selected many times, so this priority peer list (priority peer list) In the list), 1 is the route C including the link route (NW0 → NW1) (FIG. 9A), so the priority of the route C is lowered (1 ′), and the link route (NW2 → NW3) is the first. The priority peer list shown in FIG. 9B is created.

Next, a description will be given of a correction example in which (3) the priority order is evaluated by reflecting the actual transfer speed value.
FIG. 10 shows a processing flow for notifying the actual transfer rate value in order to reflect the inter-peer transfer rate actual value. In FIG. 10, steps identical to those in FIG.
When the user executes content distribution, the address, piece size, and transfer time of the peer (acquisition destination peer) that downloaded the piece are recorded in the correction means 24 in a log or the like.

When the peer (peer # 1) and peer (peer # 2) managed by different distribution control servers (p-Tracker) 10 become requesting peers, after the download of each piece ends (step 401), the peer The download piece size and the transfer time are recorded (step 402). When downloading of all pieces is completed, the distribution completion is notified to the distribution control server (p-Tracker) 10 that manages the requesting peer (step 403).
Thereafter, the requesting peer totals the download piece size and transfer time for each acquisition destination peer (step 404), calculates the transfer rate (step 405), and sends it to the distribution control server (p-Tracker) 10 to the acquisition destination peer. Then, the address and transfer rate of the requesting peer (own peer) are notified (step 406).

The distribution control server (p-Tracker) 10 further notifies the topology information management server (n-Tracker) 20 of this information with the current time added (step 407). On the topology information management server (n-Tracker) 20, a transfer rate actual value table (in FIG. 11) displaying transfer times between the requested peer address (Dst) and the acquisition peer address (Src) in order of execution time from the above information. Is created and held (step 408).
The priority peer list creation unit 23 of the topology information management server (n-Tracker) 20 has a high transfer rate based on the information in the transfer rate actual value table when the priority peer list is created. Select peers preferentially.
Whether or not the transfer rate record value is high is determined by a preset threshold value. Whether data with an old execution time is valid is also determined by a threshold. In FIG. 11, when the threshold is 60 Mbps or higher and the execution time is 12/03 after 20:00, only 1 and 2 are determined to be valid.

  By using the transfer rate actual value table that records the transfer time between the request peer address (Dst) and the acquisition destination peer address (Src), the acquisition peer is selected preferentially so that the user of the request peer address Since the possibility of downloading the same type of content is higher than the user's preference, a user whose download speed was high when the content was downloaded in the past can be selected as the acquisition destination peer.

  In addition, the transfer rate actual value table in FIG. 11 displays the transfer rate between the request peer address (Dst) and the acquisition destination peer address (Src), and preferentially selects the acquisition destination peer having a high transfer rate. However, it is also possible to create a transfer rate record table only for the acquisition peer address (Src) side. If the transfer speed between peers when the acquisition peer address (Src) is selected for a certain request peer address is high, the acquisition peer address (Src) will be relative to other request peer addresses. This is because it can be estimated that the transfer speed is high.

  According to the P2P distribution system described above, when creating the priority peer list, the correction means determines the priority order of the acquisition destination peers by reflecting the route creation creation history information or the route selection selection history information. This makes it possible to exchange files efficiently using the network and reduce the load on the network. Even when there are multiple distribution control servers (p-Trackers), the network can be efficiently Can be used.

It is a network model figure which shows the structure of the P2P delivery system which concerns on embodiment of this invention. It is a functional block diagram for demonstrating the function of each server in a P2P delivery system. It is processing flow explanatory drawing which shows the procedure from the download start of content to peer selection in a P2P delivery system. It is processing flow explanatory drawing which shows the procedure in the case of producing a priority peer list in a P2P delivery system. It is a network model figure between peers for demonstrating a link duplication selection avoidance process in a P2P delivery system. (A) And (b) is a priority peer list explanatory drawing before and behind a link duplication selection avoidance process. It is a network model figure between peers for demonstrating the process which reflects the priority peer list | wrist produced in the past. (A)-(d) is a priority peer list explanatory drawing of the priority peer list | wrist (for 4 times) created in the past. (A) And (b) is a priority peer list explanatory drawing before and after the process of reflecting the priority peer list created in the past. It is processing flow explanatory drawing which shows the procedure in the case of creating the priority peer list | wrist reflecting the transfer rate performance value between peers in a P2P delivery system. It is a transfer rate actual value table between peers reflected when creating a priority peer list.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Internet, 2 ... Network, 3 ... Router, 10 ... Delivery control server (p-Tracker), 11 ... Peer list delivery part, 20 ... Topology information management server (n-Tracker), 21 ... Information acquisition part, 22 ... Evaluation value calculation unit, 23 ... Priority peer list creation unit, 24 ... Correction means, 30 ... Network information providing server (n-Server), 31 ... Information detection unit, 32 ... Information management unit, 40 ... Content server, 50 ... Peer 50.

Claims (5)

The file is divided into a meta information file and a plurality of pieces and distributed on the network, and one peer (requested peer address) obtains a peer list, and based on this peer list, P2P communication from each peer on the network In a P2P distribution system for collecting pieces and reconstructing the file,
A network information providing server that collects and centrally manages various types of information regarding routes on the network;
A topology information management server that creates a priority peer list based on an evaluation value calculated based on information of the peer acquisition destination peer address for the requested peer address from the network information providing server;
A distribution control server that obtains a priority peer list from the topology information management server and distributes the priority peer list to the requested peer address;
The topology information management server includes a correction unit that determines the priority order by reflecting the creation history information during route creation or the selection history information of route selection when creating the priority peer list. A characteristic P2P distribution system. The correction means of the topology information management server includes:
When creating the priority peer list by the evaluation value calculated based on the information from the network information providing server,
If the evaluation values in the priority peer list are the same, it is determined whether or not the same route is included in the route from the request peer address to the acquisition peer address, and the acquisition peer address including a different route is given priority. 2. The P2P distribution system according to claim 1, further comprising means for creating a priority peer list in consideration of creation history information during route creation to be selected. A plurality of distribution control servers,
While the topology information management server has recording means for recording the priority peer list created in the past,
The correction means includes
When creating the priority peer list by the evaluation value calculated based on the information from the network information providing server,
Means for creating a priority peer list reflecting selection history information by selecting a route with a low usage frequency from information of a plurality of priority peer lists created in the past in response to requests from a plurality of distribution control servers The P2P distribution system according to claim 1, comprising: Each of the peers has means for notifying the distribution control server at the end of download about the transfer speed between peers that downloaded or uploaded the content during content distribution in the network, and the distribution control server notifies the topology information management server,
The correction means of the topology information management server includes:
When creating the priority peer list by the evaluation value calculated based on the information from the network information providing server,
The P2P distribution system according to claim 1, further comprising means for assigning a priority order reflecting the transfer rate between peers as selection history information for route selection. The file is divided into a meta information file and a plurality of pieces and distributed on the network, and one peer (requested peer address) obtains a peer list, and based on this peer list, P2P communication from each peer on the network In the P2P delivery method of collecting pieces and reconstructing the file,
Collect various information about routes on the network,
When creating a priority peer list based on an evaluation value calculated based on information on the peer address from which the piece is acquired for the requested peer address, the creation history information for route creation or the selection history information for route selection is reflected. Determine the priority of the peers,
A P2P distribution method, wherein each piece is distributed from a plurality of acquisition destination peer addresses based on the priority of peers in the priority peer list with respect to the requested peer address.

Images