JP2005018727A - Communication device and program for realizing the device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a significant load is generated in a server for providing a content when requests from clients are concentrated on the server. <P>SOLUTION: The communication device 100 requests a content from a content providing device 12. When an error message is received from the content providing device 12, the communication device 100 retries it after the lapse of a predetermined period. When the error message is received again, the communication device 100 adjusts the retry time according to the inclination of the receiving frequency of the error message. According to this, concentration of requests on the content providing device 12 can be avoided to reduce the load caused in the content providing device 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a communication technique, and more particularly to a technique for adjusting a timing at which a client transmits a request for a predetermined content to a server.

  With the development of network technology, server / client systems have become widespread. The server and the client are connected to a network such as a LAN (Local Area Network) or a WAN (Wide Area Network) and configured to be able to communicate with each other. The server holds contents such as document files, image data, audio data, and video data and various data, and provides them in response to requests from clients. The server can distribute data to a plurality of clients at the same time, but the number depends on, for example, the size of a buffer for receiving a request from the client, the ability to transmit data, etc. It will be decided. For this reason, when there are accesses from an allowable number or more of clients, the server cannot transmit the requested data, for example, transmits an error message indicating that transmission is not possible to the client. When the requested data cannot be received, the client retries, but since the interval until the retry is determined in advance, the retry is also performed at the same time, resulting in a situation where the retry is repeated many times.

Such a situation often occurs when a plurality of clients simultaneously send requests to the server, for example, when the client accesses the server in response to a broadcast message. In order to avoid such a situation, there is a technique for avoiding the concentration of requests on the server by changing the interval until the client retries for each client. (Patent Document 1)
JP 2000-90040 A

  The technique disclosed in Patent Document 1 avoids the concentration of requests by distributing the timing of retrying by clients that have transmitted requests to the server at the same time. However, considering the communication efficiency in the network, it cannot be said that efficient communication is always performed with the technology. For example, assuming a network in which a plurality of switching hubs are present, it is more efficient in that traffic is reduced in order from the client near the server. Even if the retry period is simply distributed as in the technique disclosed in Patent Document 1, the load on the server can be reduced, but the entire network may become inefficient. Also, there are terminals with high communication capability and terminals with low communication capacity on the network, and there may be a difference in time until distribution ends depending on the distribution order.

  The present invention has been made in view of these points, and an object of the present invention is to provide a technology that enables efficient communication while avoiding concentration of requests on a server.

  One embodiment of the present invention is an apparatus that acquires data from a server that holds predetermined data. This device has a means for accepting a data acquisition request from a server holding predetermined data, a request means for requesting the data to the server in response to the acquisition request, and if data cannot be acquired in response to the request, Means for instructing to request data again after a predetermined period of time, and adjusting means for dynamically adjusting the predetermined period in consideration of the communication capability of the device based on the response from the server Prepare. Accordingly, an appropriate retry period can be set according to the communication capability of the apparatus in the network.

  “Communication capability” is the capability for communication depending on individual factors related to communication, such as the distance on the network from the device to the server, the performance of hardware such as a network card, the performance of the CPU, and the traffic of the network. is there. As a result of the influence of individual factors, for example, the time from receiving a signal broadcast from a server to generating a request is determined. If the timing for transmitting a request is delayed from that of another device, the other device has already started accessing the server, and the allowable number of servers is exceeded. At this time, since an error message is returned from the server, it can be determined that the communication capability is inferior to that of other devices on the network, depending on whether or not the error message is received.

  The response used by the adjustment means is information indicating that data cannot be transmitted, that is, an error message (hereinafter also referred to as “error response”). May be adjusted dynamically. Thereby, according to the number of times of receiving an error response, it is possible to indirectly grasp the communication capability of the apparatus and set a retry period so that requests are not concentrated on the server. Further, since the retry period can be set according to the communication capability, efficient communication is possible.

  When the number of error response receptions tends to increase, the adjustment unit may adjust the predetermined period to be longer. When the number of error response receptions tends to decrease, the adjustment unit may adjust the predetermined period to be shorter. In this way, by adjusting the retry period gradually according to the trend of the number of error response receptions, the retry period is avoided according to the communication capability of each device existing in the entire network, while avoiding a sudden change in the number of retries. Can be optimized.

  The apparatus further comprises means for holding identification information for identifying the communication apparatus, and specifying means for specifying any one of a plurality of predetermined control values according to the characteristics of the identification information, The adjusting means may calculate the predetermined period using the number of times of reception of the response and the control value. Thereby, a predetermined period can be distributed.

  The apparatus further includes holding means for holding different prime numbers as control values in association with the characteristics of the identification information, and the specifying means specifies the control value by referring to the holding means based on the characteristics of the identification information. May be.

  The specifying means may convert the identification information into a numerical value of a plurality of digits and select a control value based on the numbers in the lower digits.

  The identification information is an IP address, and the holding means holds a different prime number in association with each number in decimal numbers, and the specifying means sets the prime number corresponding to the last digit of the IP address, The control value may be specified by referring to the holding means.

  The requesting unit may start timing when the acquisition request is received, and may make an initial request to the server after a period calculated based on the control value has elapsed.

  Another aspect of the present invention is a program that is executed by a computer to acquire data from a server that holds predetermined data. This program is based on means for requesting data from the server, means for instructing to request data again after a predetermined period of time has passed, and response from the server if data cannot be acquired in response to the request. In consideration of the communication capability of the apparatus, a means for dynamically adjusting a predetermined period is realized.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, it is possible to avoid the concentration of requests from clients on a server in a network and to perform efficient communication.

<First Embodiment>
FIG. 1 is a configuration diagram of a communication system 10 according to the first embodiment. The content providing apparatus 12 may be, for example, an MFP (Multi Functional Peripheral), a facsimile apparatus, a document management apparatus, a file server, and the like, and communicates contents such as image data, document data, video data, and data used in various applications. An apparatus provided to the system 10. In the present embodiment, a case where the content providing apparatus 12 is an MFP (Multi Functional Peripheral) will be described as an example. For example, when a new facsimile document is received, the content providing apparatus 12 sends information notifying that effect (hereinafter simply referred to as “connection instruction notification”) as a broadcast or multicast packet.

  First communication device 100a, second communication device 100b, and third communication device 100c (hereinafter simply referred to as “communication device 100”) are connected to network 14 and acquire image data of a facsimile document from content providing device 12. . First, when receiving a connection instruction notification, the communication device 100 requests the content providing device 12 to provide image data. As described above, in a system in which the communication device 100 accesses the content providing device 12 based on information transmitted by broadcast or multicast, requests concentrate on the content providing device 12 and a response cannot be made. Specifically, when the number of communication devices 100 that transmitted a request is larger than the allowable number that can deliver image data of the content providing device 12 at the same time, the communication device 100 that cannot acquire image data occurs. Such a communication device 100 is supplied with an error message from the content providing device 12 as a response. The communication device 100 that has received the error message appropriately changes the time period until the retry and distributes access to the content providing device 12 in time, thereby avoiding concentration of access to the content providing device 12.

  The communication apparatus 100 that has received the error message waits until a predetermined time (hereinafter simply referred to as “retry period”) elapses, and then requests image data from the content providing apparatus 12 again. When the error message is received again as a response to the retry, the communication apparatus 100 changes the retry period, waits until the period elapses, and then requests the content providing apparatus 12 for the content again. As described above, the communication device 100 can adjust the timing of transmitting a request to the content providing device 12 by appropriately changing the retry period. As a result, the communication device 100 can smoothly acquire image data, reduce traffic on the network 14, and reduce the load on the content providing device 12. As a result, in order to increase the allowable number of accesses, it is not necessary to increase the specifications of the part related to the communication function of the content providing apparatus 12, leading to cost reduction of the content providing apparatus 12.

  FIG. 2 is an internal configuration diagram of the communication apparatus 100 of FIG. Each component of the communication device 100 is, in terms of hardware components, a CPU of any computer, a memory, a program that realizes the components of this figure loaded in the memory, a storage unit such as a hard disk that stores the program, Although it is realized centering on a network connection interface or the like, it will be understood by those skilled in the art that there are various modifications in the implementation method and apparatus. Each figure to be described below shows functional unit blocks, not hardware unit configurations.

  The receiving unit 102 receives a connection instruction notification, image data, and the like from the content providing apparatus 12 and supplies them to the analyzing unit 104. The analysis unit 104 analyzes the data supplied from the reception unit 102 and determines a connection instruction notification, image data or an error message included in a response described later. If the data is a connection instruction notification and an error message, the analysis unit 104 outputs that fact to the adjustment unit 112. Hereinafter, outputting the connection instruction notification to the adjustment unit 112 is referred to as “normal instruction”. Outputting an error message to the adjustment unit 112 is referred to as a “retry instruction”.

  When the data received by the receiving unit 102 is image data, the analyzing unit 104 stores the image data in the storage unit 106. For example, the analysis unit 104 makes a determination based on a character string included in the data, and notifies the adjustment unit 112 when the data includes a character string or an error code indicating a connection instruction notification. In other cases, the analysis unit 104 may store the received data as image data in the storage unit 106, or may determine the file format and store the received data in the storage unit 106 in the case of image data. . The processing unit 108 is a functional block that performs predetermined processing using the image data held in the storage unit 106. For example, the processing unit 108 decodes the image data and displays it on the monitor, or edits the image. Process.

  Although details will be described later, the adjustment unit 112 instructs the request unit 110 to transmit a request in accordance with the notification content from the analysis unit 104. The request unit 110 transmits a request for requesting image data to the content providing apparatus 12 at a timing instructed by the adjustment unit 112. For example, the request unit 110 transmits a request according to HTTP (Hyper Text Transfer Protocol). The above-described receiving unit 102 receives the response of the request according to HTTP.

  When the notification content from the analysis unit 104 is a normal instruction, the adjustment unit 112 instructs the request unit 110 to immediately transmit the request. When the notification content from the analysis unit 104 is a retry instruction, the adjustment unit 112 waits until the retry period held in the retry period holding unit 116 elapses, and then instructs the request to the request unit 110. When a retry instruction is received from the analysis unit 104 again, the adjustment unit 112 calculates a new retry period. Then, the adjustment unit 112 writes the newly calculated retry period in the retry period holding unit 116. As described above, the retry period stored in the retry period holding unit 116 is rewritten every time it is newly calculated. When the communication apparatus 100 is activated, a basic retry period, for example, a period of about 5 seconds is stored in the retry period holding unit 116 as a default value.

  The adjustment unit 112 may calculate a new retry period as, for example, basic retry period + retry count × difference time. The difference time may be set to a fixed value of about 10 seconds, for example, or may be set in the communication apparatus 100 such as the IP (Internet Protocol Address) address of the communication apparatus 100 or the MAC address (Media Access Control address) of the network connection device. It may be generated based on unique information. The number of retries is held in the retry number holding unit 114. The adjustment unit 112 increments the number of retries each time a retry instruction is received from the analysis unit 104, for example, and stores it in the retry number holding unit 114. Then, the adjustment unit 112 deletes the retry count held in the retry count holding unit 114 at the timing when the image data is received. The adjustment unit 112 stores the new retry period calculated in this way in the retry period holding unit 116. Thus, the adjustment unit 112 can dynamically change the retry period each time a retry instruction is received. The number of retries is almost determined according to the communication capability of the communication apparatus 100. For example, the communication device 100 with high communication capability has a small number of retries, and the communication device 100 with low communication capability has a large number of retries. For this reason, by calculating the retry period according to the number of retries, the retry period according to the communication capability of each communication apparatus 100 is calculated, and efficient communication becomes possible by performing the retry in that period.

  The adjustment unit 112 gradually adjusts the retry period according to the number of retries, that is, the tendency of the number of times the reception unit 102 receives an error message. For example, when the number of times of receiving a retry instruction tends to increase, the adjustment unit 112 gradually increases the retry period. In addition, when the number of retry instruction receptions tends to decrease, the adjustment unit 112 gradually shortens the retry period. As a result, the retry interval can be optimized to be as short as possible.

  FIG. 3 is a diagram showing a method for adjusting the retry period in the adjustment unit 112 in FIG. The adjustment unit 112 lengthens the retry period stepwise according to the number of times the error message is received. In addition, when the number of times that the error message is received tends to decrease, the adjustment unit 112 gradually shortens the retry period. Thereby, it is possible to prevent the number of error message receptions from rapidly increasing by shortening the retry interval. For example, when the retry period is A and an error message is further received, the adjustment unit 112 changes the retry period to B and tries again. If the number of error message receptions tends to decrease, the process shifts from B to A. The adjustment unit 112 dynamically changes the retry period in this way.

  FIG. 4 is a sequence diagram between the communication apparatus 100 and the content providing apparatus 12 of FIG. The content providing apparatus 12 broadcasts a connection instruction notification that is a new arrival notification (S10). Based on the notification, the communication device 100 requests image data from the content providing device 12 (S12). In response to the request, the content providing apparatus 12 outputs a response to the communication apparatus 100 (S14). The communication device 100 determines whether the response is an error message (S16). If the response is not an error message in step 16 (N in S16), the communication apparatus 100 stores the response as image data (S22) and performs predetermined processing such as displaying on the monitor (S24). In the case of an error message (Y in S16), the communication device 100 sets a retry period (S18). Then, after waiting for the set retry period (S20), the communication device 100 requests content from the content providing device 12 again. The retry period in step 18 is calculated and set according to the tendency of the number of error message receptions. As described above, by setting the retry period according to the number of times the error message is received, an appropriate retry period can be dynamically set for each communication device 100, and efficient communication is enabled.

<Second Embodiment>
FIG. 5 is an internal configuration diagram of the communication apparatus 100 according to the second embodiment. Configurations denoted by the same reference numerals as those already described in the figure are substantially the same in function and operation as those already described. The following description will focus on points that differ from the functions in the configuration already described.

  The IP address storage unit 150 holds an IP address that identifies the communication device 100 in the network 14 of FIG. In another example, the IP address storage unit 150 may hold information that can identify the communication device 100 such as a MAC address and a name.

  Based on the IP address held in the IP address storage unit 150, the difference time specifying unit 152 assigns the communication device 100 to any of a plurality of groups prepared in advance, and specifies the difference time corresponding to the group. . Then, the difference time specifying unit 152 outputs the specified difference time to the adjustment unit 112. The adjustment unit 112 calculates the retry period described above using this difference time. The difference time table 154 holds a group prepared in advance and a difference time in association with each other.

  The difference time specifying unit 152 specifies a group of the communication devices 100 based on the last digit of the IP address held in the IP address storage unit 150, and refers to the difference time table 154 using the group as a key. Thereby, the differential time specifying unit 152 can specify the differential time as a control value for calculating the retry period based on the IP address. That is, the differential time specifying unit 152 extracts the feature of the identification information based on the identification information held in the IP address storage unit 150, and specifies the group. Then, the difference time specifying unit 152 acquires a control value associated with the specified group from the difference time table 154. The feature extraction method is arbitrary. For example, when the identification information is stored as a character string in the IP address storage unit 150, the difference time specifying unit 152 digitizes the character string based on the character code and prepares it in advance. It may be converted into a numerical expression corresponding to the number of groups being grouped, and the group may be specified based on the last digit. The numerical expression corresponding to the number of groups is, for example, to express the characteristics of the identification information in octal when there are eight groups. In short, the difference time specifying unit 152 may extract a feature of the identification information according to the number of groups based on the identification information and specify the group.

  FIG. 6 is a diagram illustrating an example of a data structure of the differential time table 154 in FIG. The group number column 170 holds information for identifying a group, that is, the characteristics of the identification information extracted by the differential time identifying unit 152 in FIG. In this figure, the last digit of the IP address is held as a feature of the identification information. The difference time column 172 holds a difference time as a control value for each group. Each difference time is a prime number. As a result, it is possible to prevent the retry periods from being the same in a plurality of groups, so that it is possible to prevent many accesses from being concentrated simultaneously on the content providing apparatus 12 of FIG. In another example, the difference time column 172 may hold a difference time other than a prime number.

  Further, the differential time specifying unit 152 may detect the number of other communication devices 100 connected to the network 14 in FIG. 1 and dynamically change the number of groups according to the number of communication devices 100. Good. That is, when the number of communication devices 100 connected to the network 14 is small, the number of groups is reduced correspondingly. When the number of communication devices 100 connected to the network 14 is large, the number of groups is increased correspondingly. Thereby, a big difference does not arise in the retry period in all the communication apparatuses 100.

  Specifically, the differential time specifying unit 152 holds in advance a threshold value, the number of first groups, and the number of second groups that is greater than the number of first groups, and the number of second groups that are connected is greater than the threshold value. When the number of communication devices 100 is small, the differential time specifying unit 152 sets the number of groups to the number of first groups. When the number of connected communication devices 100 is greater than the threshold value, the differential time specifying unit 152 sets the number of groups to the number of second groups. Thereby, efficient access according to the number of connected communication apparatuses 100 is possible.

  The adjustment unit 112 in the first embodiment instructs the request unit 110 to immediately transmit a request when a normal instruction is received from the analysis unit 104. In this form, initial requests are concentrated on the content providing apparatus 12 of FIG. Therefore, when the adjustment unit 112 in the second embodiment receives a normal instruction from the analysis unit 104, the difference time supplied from the difference time specifying unit 152 or a time calculated based on the difference time has elapsed. The first request may be transmitted to the request unit 110 while waiting. Thereby, it is possible to prevent the initial requests from being concentrated on the content providing apparatus 12.

  The present invention has been described based on the embodiments. The embodiments are exemplifications, and it is understood by those skilled in the art that various modifications can be made to combinations of the respective components and processing processes, and such modifications are within the scope of the invention.

It is a block diagram of the communication system which concerns on 1st Embodiment. It is an internal block diagram of the communication apparatus of FIG. It is a figure which shows the adjustment method of the retry period in the adjustment part of FIG. It is a sequence diagram between the communication apparatus of FIG. 1, and a content provision apparatus. It is an internal block diagram of the communication apparatus which concerns on 2nd Embodiment. It is a figure which shows an example of the data structure of the difference time table of FIG.

Explanation of symbols

  10 communication system, 12 content providing device, 14 network, 100 communication device, 102 receiving unit, 104 analyzing unit, 106 storing unit, 108 processing unit, 110 requesting unit, 112 adjusting unit, 114 retry number holding unit, 116 holding retry period Part, 150 IP address storage part, 152 difference time specifying part, 154 difference time table.

Claims (10)

Means for receiving an acquisition request for the data from a server holding predetermined data;
Request means for requesting the data from the server in response to the acquisition request;
Means for instructing to request the data again after a predetermined period of time if the data cannot be obtained in response to the request;
An adjustment unit that dynamically adjusts the predetermined period in consideration of its own communication capability based on a response from the server;
A communication apparatus comprising:   2. The response is information indicating that the data cannot be transmitted, and the adjusting unit dynamically adjusts the predetermined period according to a tendency of the number of times the response is received. The communication apparatus as described in.   The communication apparatus according to claim 2, wherein when the number of times the response is received tends to increase, the adjustment unit adjusts the predetermined period to be longer.   4. The communication apparatus according to claim 2, wherein when the number of times the response is received tends to decrease, the adjustment unit adjusts the predetermined period to be shorter. Means for holding identification information for identifying the communication device;
A specifying means for specifying any one of a plurality of predetermined control values according to the characteristics of the identification information;
5. The communication apparatus according to claim 2, wherein the adjustment unit calculates the predetermined period using the number of times the response is received and the control value. A holding unit that holds a different prime number as the control value in association with a feature of the identification information;
The communication device according to claim 5, wherein the specifying unit specifies the control value by referring to the holding unit based on a feature of the identification information.   The communication device according to claim 5, wherein the specifying unit converts the identification information into a numerical value and selects the control value based on a number in a lower digit. The identification information is an IP address,
The holding means holds different prime numbers in association with respective numbers in decimal numbers,
The communication device according to claim 7, wherein the specifying unit specifies a prime number corresponding to the last digit of the IP address with reference to the holding unit and sets the prime number as a control value.   8. The request unit starts timing when the acquisition request is received, and makes an initial request to the server after a period calculated based on the control value has elapsed. The communication apparatus in any one of 8-8. On the computer,
Means for requesting the data from a server holding predetermined data;
Means for instructing to request the data again after a predetermined period of time if the data cannot be obtained in response to the request;
Means for dynamically adjusting the predetermined period in consideration of the communication capability of the computer based on the response from the server;
A program to realize

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