JP2007065714A - Method for dynamically controlling replica for pure p2p communication, device having it, and its program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the number of replicas in consideration of a demand degree at a certain time for every file and to smooth loads regarding a certain file. <P>SOLUTION: When a value of congestion state C<SB>k</SB>(G<SB>N</SB>äS(t)}) of a certain file k is checked near a predetermined core servant S and the value is larger than a threshold value α1 (Step 103), the servant S distributes the load by performing replication on the file k and increasing the number of replicas (Step 104). When the value is smaller than a threshold value α2 (Step 105), a value of a rating function θ is compared to the threshold value (Step 109) and if it is smaller than the threshold value, its replica is deleted from a memory and the replica held by itself is eliminated (Step 110). As a result, the number of replicas can be optimized. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention prevents concentration of search and download loads on a servant within a short period of time when performing so-called P2P (Peer-to-Peer) type communication on an IP (Internet Protocol) network. Executes replication of files that are requested to be downloaded in advance to prevent load congestion by reducing the number of replicas when the congestion level is low. The present invention relates to a dynamic replica control method in pure type P2P communication for the purpose of equalizing loads in the network, an apparatus including the dynamic replica control method, and a program thereof.

P2P type communication is roughly divided into the following two types. That is,
Napster type: A type with a dedicated server that collectively manages the location of target information.
Gnutella type: A type that makes inquiries about the location of purpose information one after another using a message game system.
The former tends to be a server bottleneck because search request packets from each servant concentrate on a dedicated server. Further, the latter inquires the adjacent servant for the existence of the target information one after another up to the hop number range set in the TTL, and in each servant, only the “arm” extended to the adjacent servant. The packet is sent after being branched.

  When such information retrieval packets are transmitted in parallel from a large number of servants, the number of packets in the network increases explosively, and congestion over a wide area in the network is expected. In addition, when performing P2P communication in an IP network, a copy (replica) of the content is sent to another servant in order to improve the hit rate for the content (file), and the load of the servant or the line (Replication) (see Non-Patent Documents 1 to 3 for this).

Q. Lv, P.M. Cao, E .; Cohen, K.M. Li, Li, and S.R. Schenker, “Search and replication in unstructured peer-to-peer networks,” productions of 16th ACM International Conference on Supercomputing (ICS'02). Goto, Ata, Murata: “Replication placement method for improving service stability in P2P networks,” IEICE Technical Report NS2002-152, Oct, 2002. Nogami, Uchida: “About File Search and Replication in Pure P2P”, Shingaku Sodai 2004 (March 2004).

  In the replication method, when multiple contents are targeted, the memory in each servant is limited, so if many content replicas are replicated many times, there is not enough free memory space to Can no longer be created. In such a case, for a replica that has become old and is no longer referenced or searched by another servant, delete that replica to secure memory space, reserve memory space for the most recently needed replica, and reverse In addition, when there are many file search and transfer requests, it may be possible to support the replication system by creating replicas and distributing the load by executing replication.

(the purpose)
An object of the present invention is to control the number of replicas for each file in consideration of the degree of request at that time, and to perform dynamic replica control in pure P2P communication capable of smoothing a load related to a certain file. To provide a method, an apparatus including the method, and a program thereof.

The dynamic replica control method in the pure type P2P communication according to the present invention is based on the congestion degree C _k (G _N {S (t)}) of a certain file k in the vicinity of a predetermined nuclear servant S. When the condition is higher than a certain threshold value α1, the servant S replicates the file k and increases the replicas to distribute the load. When the condition is lower than the certain threshold value α2, the servant S deletes its own replica. Thus, the number of replicas is optimized, and as a result, the load is averaged.

In P2P type communication, when certain file search and transfer requests are likely to be concentrated at a certain time, replication is performed so that "load distribution on a physical space (network)" is performed as much as possible. good. However, performing replication uses memory in each servant, and therefore uses extra resources.
Therefore, control is performed so that the optimum number can always be maintained by dynamically changing the number of replicas as much as necessary according to the number of requests. In addition, a method of defining the “congestion degree” at that time and performing control based on the value is used.

  A device that performs dynamic replica control in pure-type P2P communication according to the present invention and is used as each servant is a means for managing the number of hits in its own neighborhood (neighbor 1 and neighborhood 2 (these definitions will be described later)). Means for calculating the degree of congestion for each file owned by itself, means for calculating the rating of each replica file at the present time, means for executing replication by comparing the threshold value α1 with the degree of congestion, and a threshold value α2. And a means for erasing the replica by comparing the degree of congestion.

  According to the present invention, when P2P type communication is performed, replication is performed on a target file in which inquiries and download requests in the network are likely to concentrate, and when the number of file transmission requests and search requests is still large. In addition, replication is performed to distribute the load. Conversely, when the number of file requests and search requests decreases, the lifetime of the file is measured, and if that value falls below a certain level, the servant Erase the replica in By executing the above, it is possible to smooth the load related to a certain file.

The principles and embodiments of the present invention will be described below in detail with reference to the drawings.
(Definition)
In the P2P network, the vicinity of a certain servant is defined as follows.
[Neighboring definition 1]
This refers to all servants within the range from the servant to the N-hop ahead servant. At this time, it is particularly referred to as “N-position vicinity servant of servant S”.

[Neighboring definition 2]
The servant refers to all servants that send Ping information at a certain time and have a time (hereinafter referred to as “response time”) until Pong returns within t1 seconds.
Here, a servant included in the vicinity of a certain servant S is referred to as a “servant S's t1-time vicinity servant”.

Also, the servant at the center of the neighborhood is called “nuclear servant” and is defined as follows.
[Definition of nuclear servant]
The “level M kernel servant” means a servant whose degree (the number of arms directly extending to the adjacent servant) is M or more, and a “neighbor” can be defined around the servant.
(Other nuclear servants may be included in the vicinity of the nuclear servant S).

Here, a set of N-neighbor servants of the servant S at a certain time t is represented as G _N {S (t)}. At this time, the degree of congestion C _k ( _GN {S (t)}) regarding the file k of the servant S at time t is evaluated as follows.
That is, when a certain index regarding the degree of congestion of the file k of a certain servant i (εG {S (t)}) is C _{i, k} (t),
The degree of congestion related to file k of servant S is
C _k (G _N {S (t)}) = ΣC _{i, k} (t)
iεG _N {S (t)}
It shall be given by
At this time, the number of replicas is controlled using this value as a threshold (see claim 1).

Example 1
Here, the following items can be considered as C _{i, k} (t) in the degree of congestion.
(1) The number m1 of Ping and Pong related to the file k passing through the servant per unit time,
(2) The number m2 of queries related to the file k passing through the servant per unit time,
(3) The number m3 of Query Hits related to the file k passing through the servant per unit time,
(4) The average value m4 of the latest N unit times of the CPU usage rate of the servant,
(5) Number of executions m5 of downloading (providing side) file k hit in the servant,
And so on. Of these, the prominent ones are considered to be (3) and (5) above.

  Now, when m3 (or m5) is adopted as the degree of congestion, the value of the degree of congestion m3 (or m5) of a certain file k is seen, and if this value is higher than a predetermined threshold value α1, the servant S has the file Replication is performed for k, and the load is distributed by increasing the number of replicas. When the value of the congestion degree m3 (or m5) is lower than a predetermined threshold value α2, the replica of the servant S itself is deleted. Optimize the number of replicas.

(Example 2)
FIG. 3 is an explanatory diagram showing a replica file erasing method using a finite-surviving file according to the second embodiment of the present invention.
In the second embodiment, when replication is performed by each servant that performs P2P communication, a time TTL that remains in the memory after the replica is generated is defined, and a function F (t) that decays with time for the file When this file is searched and the function F (t) is reset every time it is hit to give a predetermined value, attenuation continues again, and the value of the file becomes 0 Delete that file.

FIG. 3 shows two types of calculation examples, Example 1 and Example 2, as a replica file erasing method using a finite-lived file.
The time (file TTL) to be kept in the memory for each replica is determined by two kinds of methods (Example 1 and Example 2), and when the time has come, the replica file is deleted. Example 1 is a case where the decay function F (t) is used, and Example 2 is a case where the lifetime τ (k) is given based on the observation of the number of hits.

(Example 1)
In the case of the decay function F (t), a function F (t) that decays with time is defined for the file k, and the value of the function F (t) is set to 1 every time the file is searched and hit. to add. In FIG. 3 (example 1), since the search hits at times t ₁ , t ₂ , and t ₃ , 1 is added to the attenuated value. After 1 is added, attenuation continues again, and when the value reaches 0, file k is deleted. In Example 1, t ₁ is the time when the replica is created, t ₂ and t ₃ are the times when the replica is referenced and downloaded, and the total lifetime is t ₄ −t ₁ .

(Example 2)
In this case, it is a method of giving the lifetime τ (k) based on the observation of the number of hits, taking into account the number of searched, hit and downloaded within a certain time from the time when the file was generated. Determine the length of time until file deletion. In FIG. 3 (example 2), the file has been deleted after a given lifetime τ (k) since it has been searched and downloaded k times. In this case, the lifetime is represented by τ (k) = √k * t ₀ , and the total lifetime is represented by t ₃ −t ₁ .

  When replication is performed at each servant in P2P type communication, the priority of replicas at any point in time for each replica file in a finite memory is determined by the number of points at that point (here called rating) To do. It is conceivable that the replica lifetime shown in FIG. 3 is observed and deleted if the rating function θ falls below a certain threshold value α2.

FIG. 1 is a flowchart illustrating a servant replica number control method according to an embodiment of the present invention.
First, set the initial value 0 of the value of K (step 101), the increment value is made (step 102), whether the congestion degree C _K in the vicinity of the servant itself is greater than the threshold α1 Is determined (step 103), and if it is larger than the threshold value α1, the process proceeds to a new replication execution subroutine and executed (step 104). Further, If the congestion degree C _K is smaller than the threshold value [alpha] 1, whether a value greater than or congestion degree C _K threshold α2 in the vicinity of the servant itself is determined (step 105), smaller if the observation subroutine (within the dotted line 107).

If it is determined in the step 105, if the congestion degree _{C K} is larger than the threshold value [alpha] 2, the value of K is compared with Kmax (step 106), if K and Kmax is equal to step 101, if the different value step Fly to 102 respectively.
Within the observation subroutine, observation of the value of the rating function θ relating to this replica starts (step 108), and the process starts again from step 106 independently of this.
In the observation subroutine, the value of the rating function θ is compared with a threshold value (step 109). If the value is smaller than the threshold value, this replica is deleted from the memory (step 110), and the subroutine ends (step 111). If it is larger than the threshold value, the observation is continued (step 112), and the process returns to step 109.

FIG. 2 is a hardware configuration diagram of a servant according to an embodiment of the present invention.
In FIG. 2, reference numeral 1 denotes a servant (terminal device), which is a so-called terminal having a normal PC function, but appears as a servant as a P2P application layer. 2 is a normal timer. An information calculation unit 3 includes a rating function calculation unit 4 and a rating information calculation unit 5. The rating function calculation unit 4 has a function of calculating a rating function θ of each replica file, and the rating information calculation unit 5 has a function of calculating a rating, that is, a score that is a priority of replicas of each file.

  In FIG. 2, reference numeral 6 denotes an information management / transfer unit that includes a replica search information management unit 7, a hit information management unit 8, a neighborhood management unit 9, and a request information transfer unit 10. The replica search information management unit 7 has a function of managing with replica search information from other servants. The hit information management unit 8 has a function of managing information for which the search has hit in the servant 1. The neighborhood management unit 9 has a function of managing neighborhood information of the servant. The request information transfer unit 10 has a function of transferring a hit replica to another servant.

  In FIG. 2, reference numeral 11 denotes a memory unit that includes a memory capacity management / control unit 12 and a memory 13. The memory capacity management / control unit 12 has a control function for managing the remaining capacity of the memory, deleting unnecessary information, and writing new information. The memory 13 is a place for storing / accumulating various types of replication information, hit information, information about held files, IP addresses of servants, and the like.

  In FIG. 2, reference numeral 14 denotes a replication execution unit, which includes a replication information analysis unit 15 and a replication action determination / execution unit 16. The replication information analysis unit 15 has a function of analyzing which file is replicated at what timing. The replication action determination / execution unit 16 has a function of determining and executing an action to be taken for replication.

  In FIG. 2, reference numeral 17 denotes a PAD (packet assembling / decomposing unit), which has a function of converting various types of information into IP packets, and conversely decomposing IP packets into various types of information. A packet transmission unit 18 has a function of transmitting IP packets to other servants. A packet receiving unit 19 has a function of receiving an arrival packet from another servant in the network. Reference numeral 20 denotes an IP network (Internet) to which this servant is connected.

The servant has the following functions.
1) Define a time unit (T). Each time interval has a function of recording the number of hits for each replica file, and calculating the rating of each replica file at the present time.
2) When it is determined that the memory capacity is insufficient when executing replication at a certain time, the replica file having the minimum rating is erased from the memory at that time. The replica files with the lowest rating are deleted one after another until the memory capacity to execute new replication is secured.

3) The file TTL is managed for each replica file, and when the value of the file TTL becomes 0, the corresponding replica file is erased from the memory.
4) It has a function of storing, for each servant, an information set consisting of a time when an inquiry is made in the past and an attenuation function F (t) with respect to the replica held by itself.

5) The servant has a function of arranging these information sets in order of rating. When a new replica is to be stored in the memory and the capacity is insufficient in the memory, it is necessary to store the new replica based on the information of the information set arranged in the above priority order. It has a function of erasing in order from replica files with low priority until the memory capacity can be secured.

The servant 1 shown in FIG. 2 is a device that operates under computer control. The information calculation unit 3, the information management / transfer unit 6, the replication execution unit 14, and the memory unit 11 all include a CPU, an arithmetic circuit, a register, and a memory. And so on. In other words, this is a sequential control operation in which a series of pre-programmed instructions are interpreted and executed according to the order, and data used for execution is also stored in the same memory as the instruction word. Various registers, control gates, and the like for arranging data fetching, writing, and processing are sequentially arranged.
Data is transferred between the register and the memory, between the register and the input / output device, and between the register and various functional devices via the bus.

  If the flowchart shown in FIG. 1 is programmed and the completed program is stored in a recording medium such as a CD-ROM, the recording medium is mounted on the computer of the replication execution unit 14 in the servant, and the program is stored in the computer. It is possible to easily implement the replica control method of the present invention by installing and executing the software. In addition, by downloading this program widely to other computers via the Internet, this program can be generalized.

5 is an operation flowchart of a servant replica control method according to an embodiment of the present invention. It is a hardware block diagram of the servant which concerns on one Example of this invention. It is explanatory drawing of the replica file erasing method by the file TTL of finite survival in this invention.

Explanation of symbols

1: Servant 2: Timer 3: Information calculation unit 4: Rating function calculation unit 5: Rating information calculation unit 6: Information management / transfer unit 7: Replica search information management unit 8: Hit information management unit 9: Neighborhood management unit 10: Request information transfer unit 11: Memory unit 12: Memory capacity management / control unit 13: Memory 14: Replication execution unit 15: Replication information analysis unit 16: Replication action determination / execution unit 17: PAD
18: Packet transmitter 19: Packet receiver 20: IP network

Claims (5)

In a computer controlled replica control method for performing replication in each servant device that performs P2P communication,
Information is transmitted / received between the nuclear servant device and the neighboring servant device, and based on the transmitted / received information, in the vicinity of the predetermined nuclear servant, the value of the degree of congestion of a certain file is observed, and the degree of congestion is determined in advance. When higher than a defined first threshold, the nuclear servant performs replication on the file, increasing the number of replicas to distribute the load,
Also, when the congestion level is lower than the second threshold, the dynamic servant control method in pure P2P communication is characterized in that the memory of the nuclear servant device itself is accessed and the replica of the nuclear servant device itself is deleted. . In a servant device that performs dynamic replica control in pure P2P communication,
Management means for managing the number of hits in the vicinity of the servant device;
Means for calculating the degree of congestion for each file of the servant device by being connected to the management means and referring to information on the number of hits of the management means;
Means for calculating a rating of each replica file at the present time by referring to information on the number of hits of the management means connected to the management means;
Means for performing replication by comparing the first threshold and the degree of congestion by referring to information on the number of hits possessed by the management means and connected to the management means;
By referring to information on the number of hits held by the management means and comparing the second threshold and the degree of congestion, the memory means is accessed, and the replica stored in the memory means is And a servant device in pure type P2P communication, characterized by comprising: means for erasing. The servant device according to claim 2,
The congestion degree represents a set of all servants within a range up to the N-hop ahead servant of a servant device at a certain time t as G _N {S (t)}, and relates to the congestion degree of a file k of a servant i. When an index is C _{i, k} (t),
C _k (G _N {S (t)}) = ΣC _{i, k} (t)
iεG _N {S (t)}
A servant device characterized by being given by: The servant device according to claim 2 or 3,
Ci _{, k} (t) in the degree of congestion is the number of Pings and Pongs relating to the file k passing through the servant device per unit time, the number of queries, the number of query hits, or the CPU of the servant device A servant device that selects one of an average value of the most recent N unit times of usage rate or the number of times of execution of downloading a file k hit in the servant.   The computer of the servant device that performs dynamic replica control in pure type P2P communication sets the initial value of the value of the file K, the procedure for incrementing the value of the file K, and the degree of congestion in the vicinity of the servant device is the first. A procedure for determining whether or not the value is larger than the threshold value, and if it is larger than the first threshold value, a procedure for moving to a new replication execution subroutine and executing the subroutine. If the congestion degree is smaller than the first threshold value. For example, a procedure for determining whether or not the degree of congestion in the vicinity of the servant device is a value greater than the second threshold. If smaller, a procedure for moving to an observation subroutine. If the degree of congestion is greater than the second threshold, the value of K. And the procedure for comparing Kmax, and if K and Kmax are the same value, the procedure returns to the initial value setting procedure for file K. If the value is different, the procedure to return to the increment procedure, the procedure to start the observation of the value of the rating function related to the replica in the observation subroutine, the procedure to compare the value of the rating function and the threshold, A replica number control program for executing a procedure for deleting the replica from the memory and a procedure for continuing the observation if the replica is larger than the threshold.

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