JP2004127074A - File retrieval method in p2p network, terminal, program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the number of Query packets to be transferred when each servant performs file retrieval without using file retrieval technique based on multicast such as Gnutella in a P2P without having a server for retrieving a file. <P>SOLUTION: A servant at a file retrieving origin creates a packet in which retrieval conditions are recorded and transmits it in the P2P network. A servant which receives the packet checks whether or not the present servant holds a file conforming to the retrieval conditions recorded in the received packet (when the servant has the file, informs the servant at the file retrieving origin of a fact according to a predetermined method) and transfers the received packet to other servants. In this case, the packet is successively transferred as tracing tree structure of the network. <P>COPYRIGHT: (C)2004,JPO

Description

例２．
【００３７】
【数２】

例３．
【００３８】
【数３】

なお、関数Ｎ（・）はＴＴＬ値ｔのみに依存する関数でなくてもよい。例えば、ＴＴＬ値ｔの初期値ｔ_０を用いて関数Ｎ（ｔ，ｔ_０）としてもよい。ただし、この場合、各サーバントがｔ_０の値を知るための方法を備えておく必要がある。例えば、Ｑｕｅｒｙパケットにｔ_０の値を記録するという方法などがある。また、関数Ｎ（・）は各サーバント毎に変更するようにしてもよい。
【００３９】
なお、本発明は専用のハードウェアにより実現されるもの以外に、その機能を実現するためのプログラムを、コンピュータ読み取り可能な記録媒体に記録して、この記録媒体に記録されたプログラムをコンピュータシステムに読み込ませ、実行するものであってもよい。コンピュータ読み取り可能な記録媒体とは、フロッピーディスク、光磁気ディスク、ＣＤ−ＲＯＭ等の記録媒体、コンピュータシステムに内蔵されるハードディスク装置等の記憶装置を指す。さらに、コンピュータ読み取り可能な記録媒体は、インターネットを介してプログラムを送信する場合のように、短時間の間、動的にプログラムを保持するもの（伝送媒体もしくは伝送波）、その場合のサーバとなるコンピュータシステム内部の揮発性メモリのように、一定時間プログラムを保持しているものも含む。
【００４０】
【発明の効果】
以上説明した本発明によれば、ファイルを検索するためのサーバを持たないＰ２Ｐネットワークにおいて、Ｇｎｕｔｅｌｌａのようなマルチキャストに基づくファイル検索手法を用いずに、各サーバントがファイル検索を行う際に転送するＱｕｅｒｙパケット数を抑制することが可能になる。
【図面の簡単な説明】
【図１】Ｐ２Ｐネットワークにおける木構造の概念図である。
【図２】本発明の第１の実施形態の概念図である。
【図３】第１の実施形態における各サーバントの構成図である。
【図４】第１の実施形態におけるアルゴリズムＡの概念図である。
【図５】アルゴリズムＡのフローチャートである。
【図６】第１の実施形態において、Ｑｕｅｒｙパケットを受信した際の処理を示すフローチャートである。
【図７】第１の実施形態におけるアルゴリズムＢの概念図である。
【図８】アルゴリズムＢのフローチャートである。
【図９】第１の実施形態におけるアルゴリズムＣの概念図である。
【図１０】アルゴリズムＣのフローチャートである。
【図１１】本発明の第２の実施形態における各サーバントの構成図である。
【図１２】第２の実施形態の動作を示すフローチャートである。
【図１３】本発明の第３の実施形態の概念図である。
【図１４】第３の実施形態における各サーバントの構成図である。
【図１５】第３の実施形態の動作を示すフローチャートである。
【符号の説明】
１１　　Ｑｕｅｒｙパケット入力部
１２　　木を行きがけ順でなぞる転送方法実行部
１３　　Ｑｕｅｒｙパケット出力部
２１，２２，３１〜３４，４１〜４９　　ステップ
５１　　Ｑｕｅｒｙパケット入力部
５２　　ＴＴＬ値読み取り部
５３　　ＴＴＬ値比較部
５４　　第１の転送方法実行部
５５　　第２の転送方法実行部
５６　　Ｑｕｅｒｙパケット出力部
６１〜６４　　ステップ
７１　　Ｑｕｅｒｙパケット入力部
７２　　ＴＴＬ値読み取り部
７３　　転送先サーバント数決定部
７４　　転送先サーバント選択部
７５　　ＴＴＬ値変更部
７６　　Ｑｕｅｒｙパケット出力部
８１〜８６　　ステップ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a file search method, a terminal, and a program used in a P2P (peer-to-peer) network (P2P network), and a recording medium on which the program is recorded.
[0002]
[Prior art]
The P2P type network, which has recently attracted attention, differs from the conventional client / server (C / S) type in that computer resources and services are directly shared between systems without relying on a server.
[0003]
For example, as a program constituting a P2P network for exchanging files such as music between terminals, a network using software called "Gnutella" has been conventionally known. Gnutella's network is a pure P2P network to which no server having a file search function is connected. Each terminal connected to the Gnutella network has a file search function and is called a servant.
[0004]
The file search in the Gnutella network is performed as follows (see Non-Patent Documents 1 and 2).
1. The file search source servant transmits a Query packet (“Query” means “inquiry”) to the directly connected servant. In the payload of the Query packet, search conditions such as "minimum communication speed of servant responding to this search request" and "search keyword" are recorded.
2. The servant that has received the Query packet decrements the TTL (Time To Live) value recorded in the header of the Query packet by one, and if it is not 0, all servants connected to the servant (transmit the Query packet). To each other) (not including the servant that has been sent).
3. A servant having a file matching the conditions of the transferred Query packet returns a Query Hit packet. A servant who does not have one simply forwards the packet.
4. The Query Hit packet returns to the transmission source by following the route in which the Query packet was transferred in reverse order. The total number of files that meet the conditions, the TCP port number of the servant that performed the Query Hit, the IP address of the servant that performed the Query Hit, the connection communication speed of the servant that performed the Query Hit, and the name of the file that matches the conditions are included in the payload of the Query Hit packet. And information such as a file size, a file index (a series of numbers assigned on the servant side to indicate which file the file is), and a GUID (Globally Unique Identifier) of the servant that performed the Query Hit.
[0005]
[Non-patent document 1]
Naoki Ito, "P2P Computing: Technical Explanations and Applications" Published by Soft Research Center, Inc. [Non-Patent Document 2]
Edited by Keiichi Komatsu, "P2P, the New Century of the Internet" Published by The Telecommunications Association [0006]
[Problems to be solved by the invention]
When a file search method such as Gnutella is used in a P2P network without a server for searching for a file, a packet in which file search conditions are recorded (hereinafter, a Query packet) is relayed by each terminal (hereinafter, a servant). Each time it is replicated and continues to increase. This leads to a line bandwidth associated with the file search or a load on the CPU of the servant.
[0007]
It is an object of the present invention to provide a P2P network in which a plurality of terminals are connected and which do not have a server for retrieving a file. An object of the present invention is to provide a file search method, a terminal, its program, and a recording medium on which the program is recorded, which suppresses the number.
[0008]
[Means for Solving the Problems]
In the first aspect of the present invention, when a Query packet is transferred, the packet is not transferred (multicast) to all terminals connected to the own terminal (not including the terminal that transmitted the Query packet), but is transferred to the network. Are sequentially transferred so as to trace the tree structure of. According to the second aspect of the present invention, when a Query packet is transferred, the TTL is not transferred (multicast) to all the terminals connected to the own terminal (excluding the terminal that transmitted the Query packet), but the TTL is transferred. Change the transfer method based on the value.
[0009]
When a file search method such as Gnutella is used in a P2P network that does not have a server for searching for a file, the Query packet is copied and continuously increased each time relayed at each terminal.
[0010]
According to the present invention, in a P2P network having no server for retrieving a file, each terminal is transferred by tracing a Query packet so as to trace the tree structure of the network or by changing a transfer method based on a TTL value. Suppresses the number of Query packets to be transferred when performing a file search.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0012]
First, a tree structure in a P2P network will be described with reference to FIG.
[0013]
The servant connected to the servant corresponding to the root is defined as a node connected to the root, with the servant of the file search source as the root. As a result, a tree structure having a depth of 1 is obtained. Further, a servant connected to the servant corresponding to the node connected to the root (excluding the servant corresponding to the root) is set as a node of the node connected to the root. Thereby, a tree structure having a depth of 2 is obtained. By repeating this process, a tree structure having a depth d is obtained. However, when the number of connected servants is insufficient, a tree structure having a depth d may not be formed. Note that this tree structure is obtained by successively connecting servants with a TTL value of d, a servant of a file search source as a root, and a servant through which a Query packet passes when using the file search method in Gnutella as a node. Is equivalent to
[0014]
[First Embodiment]
A method of transferring a Query packet in the present embodiment will be described.
[0015]
The servant of the file search source transmits only one Query packet with the TTL value set to d. This Query packet traces the above tree structure in the order of the destination (for example, see “Data Structure and Algorithm”, AV Eho, JE Hopcroft, JD Ullman, Baifukan, 1990). (FIG. 2). Thus, the same servant as in the case of using the file search method in Gnutella can be searched by one Query packet, with the TTL value set to d.
[0016]
As shown in FIG. 3, each servant has a Query packet input unit 11, a transfer method execution unit 12 for tracing the tree in the order of traversing the tree, and a Query packet output unit 13.
[0017]
Next, the operation of each servant in the present embodiment will be described.
[0018]
First, an operation until the servant of the file search source transmits a Query packet will be described. Here, the servant of the file search source is set to S.
[0019]
Algorithm A (Figs. 4 and 5)
1. All servants to which the file search source servant S is connected (in this example, it is assumed that there are n servants) are indexed according to a predetermined method, and are indexed by S ₁ , S ₂ ,. , put an _{S n} (step 21, Figure 4).
2. Create a Query packet (TTL value is set to d), the forward Query packets to _{S 1} (step 22).
[0020]
Next, an operation when a certain servant S (not necessarily a file search source servant) receives a Query packet will be described. The operation performed when the servant S itself receives the same Query packet as the servant created as the file search source (when the Query packet created by the servant S returns between the servants) is algorithm B. The operation upon reception is algorithm C (FIG. 6).
[0021]
Algorithm B (Figs. 7 and 8)
1. The same Query packet created as the servant of the file search source is received (step 31).
2. It determines the source _{S k} of the received Query Packet (step 32).
3. If k = 1,..., n−1 ((1) in FIG. 7), the TTL value of the Query packet is reduced by _one , transferred to _{Sk + 1} , and the processing ends (step 33).
4. If k = n (FIG. 7 (2)), the query packet is discarded and the process ends (step 34).
[0022]
Algorithm C (FIGS. 9 and 10)
1. A Query packet different from the one created as the servant of the file search source is received (step 41).
2. It is determined whether the same Query packet as the received Query packet has been received in the past (step 42).
3. If not, it is checked whether or not the file has a file that meets the conditions of the received Query packet. If so, the file search source servant is notified according to a predetermined method (step 43). If so, the process proceeds to step 45.
4. Transfer source servant of the received Query packets (not necessarily file search source servant) S ₀ Distant, further, in all the servant (this example S other than S ₀ is connected to n pieces exist relative to) have, indexed according to a predetermined method, it _{S 1,} S 2, ..., put and _{S n} (step 44).
5. It is determined whether the TTL value recorded in the header of the received Query packet is 1 (step 45).
6. TTL value incremented by one the TTL value of the Query packets received if 1, then exit transferred to the transfer source servant _{S O} (step 46).
7. If the TTL value is not 1, judges the source _{S k} of the received Query Packet (step 47).
8. If k = 0, 1,..., n−1, the TTL value is reduced by one, the Query packet is transferred to the servant S _{k + 1} , and the process ends (step 48, FIG. 9 (1)).
9. If k = n, and transfer the Query packet ends by increasing one TTL value to the transfer source servant _{S 0} (step 49, FIG. 9 (2)).
[0023]
When all servants included in the tree structure transfer the Query packets according to the above algorithms A, B, and C, it becomes possible to transfer the Query packets so that the Query packets trace the tree structure in the order in which they are traversed.
[0024]
Further, all servants in the P2P network of interest operate as servants as file search sources and also operate as other servants. Therefore, a file is searched by using algorithms A, B, and C as appropriate. File search that suppresses the number of Query packets in a P2P network that does not have a server for use.
[0025]
[Second embodiment]
In the first embodiment, only the method of transferring Query packets so as to trace the tree structure in a traversal order is used, but in the second embodiment, the transfer method of Gnutella is also used based on the TTL value. (FIG. 12).
[0026]
As shown in FIG. 11, each servant executes a query method input unit 51, a TTL value reading unit 52, a TTL value comparison unit 53, a Gnutella transfer method execution unit 54, and a transfer method for tracing a tree in a traversal order. And a Query packet output unit 56.
[0027]
Based on a TTL value t of a Query packet held by the own servant (a case where the own servant creates a Query packet as a search source servant and a case where it is received from another servant) and a predetermined value s, Thus, the transfer direction of Gnutella is used together (steps 61 to 64).
[0028]
If s < t, use Gnutella's transfer method.
[0029]
If t <s, use the transfer method that traces the tree.
[0030]
The algorithm for tracing the tree is the same as in the first embodiment.
[0031]
[Third Embodiment]
Although the transfer method of the present embodiment is based on the transfer method of Gnutella, a query packet to be held (a case where the own servant is a Query packet created as a search source servant and a case where the query packet is received from another servant) The transfer method is different in that the transfer destination servant and the number of transfer destination servants change based on the TTL value t) (FIG. 13).
[0032]
As shown in FIG. 14, each servant includes a Query packet input unit 71, a TTL value reading unit 72, a destination servant number determining unit 73, a destination servant selection unit 74, a TTL value changing unit 75, and a Query packet output unit 76. Have.
[0033]
The operation algorithm of each servant in the present embodiment is as follows (FIG. 15).
1. The TTL value reading unit 72 reads the TTL value t of the held Query packet (step 81).
2. The transfer destination servant number determination unit 73 determines the transfer destination servant number as N (t) based on a predetermined function N (·) (step 82). N (t) takes a value equal to or less than the number of servants that can be transferred.
3. Based on a predetermined method, N (t) servants as transfer destinations are selected (step 83).
4. It is determined whether the TTL value t is 1 (step 84).
5. If the TTL value is 1, the Query packet is discarded and the process ends (step 85).
6. If the TTL value is 1, the TTL value t is set to t-1 (the TTL value is not changed in the case of the file search source servant), and the Query packet is transferred to the servant selected in step 82 (step 86).
[0034]
In step 83, a random selection method or the like may be used.
[0035]
Hereinafter, specific examples of the function N (•) will be listed. However, let n be the number of servants to which the servant of interest is directly connected.
Example 1
[0036]
(Equation 1)

Example 2.
[0037]
(Equation 2)

Example 3
[0038]
[Equation 3]

Note that the function N (•) may not be a function that depends only on the TTL value t. For example, the function N (t, t ₀ ) may be set using the initial value t ₀ of the TTL value t. However, in this case, it is necessary to each servant should provide a way to know the value of t _0. For example, there is a method that records the value of _{t 0} to Query packets. Further, the function N (•) may be changed for each servant.
[0039]
In addition, the present invention records a program for realizing the function other than that realized by dedicated hardware on a computer-readable recording medium, and stores the program recorded on the recording medium in a computer system. It may be read and executed. The computer-readable recording medium refers to a recording medium such as a floppy disk, a magneto-optical disk, a CD-ROM, or a storage device such as a hard disk device built in a computer system. Further, the computer-readable recording medium is one that dynamically holds the program for a short time (transmission medium or transmission wave), such as a case where the program is transmitted via the Internet, and serves as a server in that case. It also includes those that hold programs for a certain period of time, such as volatile memory inside a computer system.
[0040]
【The invention's effect】
According to the present invention described above, in a P2P network that does not have a server for searching for a file, each servant transfers a query when performing a file search without using a file search method based on multicast such as Gnutella. It is possible to reduce the number of packets.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a tree structure in a P2P network.
FIG. 2 is a conceptual diagram of the first embodiment of the present invention.
FIG. 3 is a configuration diagram of each servant in the first embodiment.
FIG. 4 is a conceptual diagram of an algorithm A according to the first embodiment.
FIG. 5 is a flowchart of algorithm A.
FIG. 6 is a flowchart illustrating processing when a Query packet is received in the first embodiment.
FIG. 7 is a conceptual diagram of an algorithm B according to the first embodiment.
FIG. 8 is a flowchart of algorithm B.
FIG. 9 is a conceptual diagram of an algorithm C according to the first embodiment.
FIG. 10 is a flowchart of algorithm C.
FIG. 11 is a configuration diagram of each servant according to the second embodiment of the present invention.
FIG. 12 is a flowchart illustrating the operation of the second embodiment.
FIG. 13 is a conceptual diagram of a third embodiment of the present invention.
FIG. 14 is a configuration diagram of each servant in the third embodiment.
FIG. 15 is a flowchart showing the operation of the third embodiment.
[Explanation of symbols]
11 Query packet input unit 12 Transfer method execution unit 13 tracing a tree in a traversal order 13 Query packet output units 21, 22, 31 to 34, 41 to 49 Step 51 Query packet input unit 52 TTL value reading unit 53 TTL value comparison unit 54 1 transfer method execution unit 55 second transfer method execution unit 56 Query packet output units 61 to 64 Step 71 Query packet input unit 72 TTL value read unit 73 Transfer destination servant number determination unit 74 Transfer destination servant selection unit 75 TTL value change Unit 76 Query packet output units 81 to 86 Step

Claims (9)

A method for searching for a file in a P2P network in which a plurality of terminals are connected and does not have a server for searching for a file,
A first step of receiving a Query packet created by the terminal that is the file search source and transmitted into the P2P network and recording the search conditions;
It checks whether the own terminal holds a file that matches the search condition recorded in the received Query packet, and if so, notifies the file search source terminal according to a predetermined method. A second step to
A file search method including a third step of sequentially transferring received Query packets to another terminal so as to trace a tree structure of a network. The first and second steps include:
Determining whether the received Query packet is the same as the one created as the file search source terminal;
If the Query packet is the same as the one created as the file search source terminal, the transfer source of the received Query packet is not the last terminal in the file transfer order of the terminal group connected to the own terminal. The TTL value of the Query packet is reduced by one, the Query packet is transferred to the terminal in the next file transfer order of the terminal group, and the transfer source of the received Query packet is the last terminal in the file transfer order of the terminal group. Discarding the Query packet, if any;
If the Query packet is different from the one created as the file search source terminal, if the same Query packet has not been received in the past, it is checked whether or not a file matching the conditions of the received Query packet is possessed. If the TTL value of the received Query packet is 1, after the notification, the TTL value is increased by one, the Query packet is transferred to the transfer source terminal, and the TTL value of the received Query packet is notified. Is not 1, the query packet is transferred to the terminal group connected to its own terminal, and if it is not the last terminal in the file transfer order, the Query packet is decremented by one and the TTL value is reduced by one. The file is transferred to the terminal in the next file transfer order, and the transfer destination of the Query packet is connected to the terminal itself. The Query packet if the last terminal in the file transfer sequence of the terminal group in which, comprising the step of transferring the transfer source terminal TTL value is incremented by one, the file search method of claim 1. A method for searching for a file in a P2P network in which a plurality of terminals are connected and does not have a server for searching for a file,
A first step of receiving a Query packet created by the terminal that is the file search source and sent out in the P2P network and recording the search conditions;
It checks whether the own terminal holds a file that matches the search condition recorded in the received Query packet, and if so, notifies the file search source terminal according to a predetermined method. A second step to
A file search method comprising: transferring a received Query packet to another terminal; and, at that time, changing the transfer method based on a TTL value recorded in the Query packet. The third step is a step of reading a TTL value, a step of determining the number of destination terminals based on a predetermined function, and a step of determining the destination terminal based on a predetermined method. A step of selecting the number of terminals, a step of determining whether or not the TTL value is 1; a step of discarding the Query packet if the TTL value is 1; 4. The file transfer method according to claim 3, further comprising transferring the file to a selected terminal. A terminal in a P2P network without a server for retrieving a file,
Means for receiving a Query packet created by the terminal that is the file search source and sent out in the P2P network and recording the search conditions;
It checks whether the own terminal holds a file that matches the search condition recorded in the received Query packet, and if so, notifies the file search source terminal according to a predetermined method. Means to
A terminal having means for sequentially transferring a received Query packet to another terminal so as to trace the tree structure of the network. A terminal in a P2P network without a server for retrieving a file,
Means for receiving a Query packet created by the file search source terminal and transmitted into the P2P network, in which the search condition is recorded;
It checks whether the own terminal holds a file that matches the search condition recorded in the received Query packet, and if so, notifies the file search source terminal according to a predetermined method. Means to
A terminal having means for transferring a received Query packet to another terminal and changing the transfer method based on a TTL value recorded in the Query packet. Means for transferring the query packet to another terminal, means for reading a TTL value of the query packet, means for determining the number of destination terminals based on a predetermined function, and transfer based on a predetermined method. Means for selecting the number of transfer destination terminals to the destination terminal; determining whether the TTL value is 1; discarding the Query packet if the TTL value is 1; decrementing the TTL value by -1 if the TTL value is not 1; The terminal according to claim 6, further comprising: means for outputting a Query packet to the selected terminal. A program for causing a computer to execute the method according to claim 1. A computer-readable recording medium on which the program according to claim 8 is recorded.

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