JP3732671B2 - Transmission device, transmission method, and recording medium recording transmission software - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in technology related to multicast communication in a distributed system. More specifically, the present invention ensures message transmission with excellent reliability by guaranteeing a period for holding a refusal for retransmission of transmission messages. It is a thing.
[0002]
[Prior art]
In recent years, with the spread of computer technology, a distributed system in which a plurality of computers are connected by a communication path such as a local area network (LAN) is becoming widespread, and each computer connected to such a distributed system and its communication device is becoming popular. An example in which messages are exchanged by multicast is also known.
[0003]
In multicast, unlike conventional unicast, it is difficult to confirm that all reception devices have received, and the following technique is used to guarantee message arrival. In other words, the transmission device on the transmission side adds information (referred to as a communication count) serving as a serial number to each message and transmits it, and stores a retransmission copy of the transmitted message in a storage area such as a finite buffer. .
[0004]
When the receiving device on the receiving side has a missing communication count attached to the received message, it requests the sending side to resend the message with the missing number, and the sending side uses the stored copy for retransmission. Resend message based on
[0005]
In this case, since the storage area is also finite on the transmission side, each time a new message is transmitted, a new storage area for retransmission is secured by sequentially erasing from the oldest retransmission memory.
[0006]
[Problems to be solved by the invention]
However, in the conventional technique as described above, the larger the number of messages transmitted per unit time, the shorter the number of messages to be retransmitted for each message, so that a storage area for new messages to be retransmitted is secured. It had been. In this case, depending on the amount of communication and the frequency of retransmission, the message is deleted in a short time, so that it is not possible to respond to the retransmission request, and the reliability of communication may be reduced.
[0007]
In particular, when a re-transmission request occurs, the load on the network or the receiving device is often high in the first place, and there is a high possibility that a re-transmitted message or a message after the re-requested message will be lost. There was a potential desire for improved reliability. In addition, the conventional technique has a problem that it is difficult to control the flow rate of communication because transmission / reception of new messages is not restricted even when the load is high.
[0008]
In order to solve these problems, it may be possible to send the next message after at least a certain time after sending the previous message. In this case, however, the responsiveness deteriorates. There was a point.
[0009]
The present invention has been proposed in order to solve the above-described problems of the prior art, and its purpose is to guarantee a period for holding a retransmission record of a transmission message, thereby ensuring excellent reliability of the message. Communicate Transmission device, transmission method, and recording medium recording transmission software Is to provide.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 is a transmitter for multicast transmission of messages to a plurality of receivers connected by a network, and each message is transmitted together with a communication count which is information indicating a transmission order. Means for transmitting to each of the receiving devices, a retransmission copy for each transmitted message, and Associating the message origination time with the minimum retention period of the message Storage means for storing; receiving means for receiving a message retransmission request from the receiving device; and means for resending a message based on a stored retransmission copy in response to the retransmission request; When trying to send a new message, Based on the current time, the oldest transmission time stored in the storage means, and the minimum holding period stored in association with the transmission time, the retransmission copy corresponding to the oldest transmission time has the minimum holding period. Judge whether or not it has passed Means for suppressing the transmission of the new message until the minimum holding period of the rescheduled copy has passed, and when resending the message based on the stored resend copy, Means for extending the minimum retention period of such a message by a predetermined time When It is provided with. Also, The fourth aspect of the invention is based on the first aspect of the invention from the viewpoint of a method, and the seventh aspect of the invention is based on the viewpoint of the recording medium on which the software is recorded.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention (hereinafter referred to as “embodiments”) will be described below with reference to the drawings. Note that it is generally considered that the present invention is realized by controlling a computer having a peripheral device with software. In this case, the software is created by combining instructions according to the description of this specification, and the method described in the prior art is used in common with the prior art described above. The software includes not only the program code but also data prepared in advance for use when executing the program code.
[0015]
The software uses physical resources such as a processing device such as a CPU, a coprocessor, and various chip sets, an input device such as a keyboard and a mouse, a storage device such as a memory and a hard disk device, and an output device such as a display and a printer. The effect of the present invention is realized.
[0016]
However, specific software and hardware configurations for realizing the present invention can be variously changed. For example, there are various types of software, such as a compiler, interpreter, and assembler. In order to exchange information with the outside, a variety of removable recording media such as a floppy disk can be considered. In addition, a recording medium such as a CD-ROM in which software or a program for realizing the present invention is recorded is an embodiment of the present invention alone. Furthermore, a part of the functions of the present invention can be realized by a physical electronic circuit such as an LSI.
[0017]
As described above, various aspects of implementing the present invention using a computer are conceivable. In the following, the present invention and implementation are performed using virtual circuit blocks that implement individual functions included in the present invention and embodiments. The form will be described.
[0018]
[1. Constitution〕
[1-1. Configuration of distributed system]
FIG. 1 shows an example of a distributed system to which the present invention is applied. That is, in this distributed system, three computers 1a, 1b, and 1c are connected by a local area network (LAN) that is a communication path, and a message transmitted from a certain computer is transmitted to all three computers. On the other hand, it is broadcasted or multicasted.
[0019]
FIG. 2 shows another example of the distributed system to which the present invention is applied. In this distributed system, a plurality of partial networks N1, N2, and N3 are connected to each other via a gateway or router, and a plurality of computers C are connected to each of the networks N1, N2, and N3. In this example, multicast communication is performed between a plurality of computers C across the networks N1, N2, and N3.
[0020]
Each computer C connected to the same network N1, N2 or N3 is assigned the same multicast address, and can be considered logically communicating in the same environment as in FIG. . For this reason, the following description is based on the premise of the distributed system as shown in FIG.
[0021]
[1-2. Configuration for sending messages]
First, FIG. 3 is a functional block diagram illustrating a configuration example of a computer that transmits a message among computers connected to the network illustrated in FIGS. 1 and 2. That is, the computer 1 that transmits a message is a transmission device for multicast transmission of a message to a plurality of reception devices connected by a network, and includes a main body processing unit 11 and a transmission processing unit 12.
[0022]
The main body processing unit 11 is a part that performs information processing by executing a program such as an application program that runs on the computer 1, and a part that requests message transmission, such as such a program, is a message processing unit. 311. The transmission processing unit 12 is a part for transmitting a message to a network or another computer based on a transmission request from a program in the main body processing unit 11.
[0023]
Note that a computer including such a transmission processing unit 12 for transmitting a message is called a transmission device or a transmission side, and a computer having a configuration for receiving a transmitted message is called a reception device or a reception side.
[0024]
The transmission processing unit 12 receives a message retransmission request sent from the receiving device via the network when the message does not reach the receiving device provided in the computer that performs reception. The message processing unit 11 is configured to guarantee the arrival of the message to the main body processing unit 11 by performing retransmission processing of the message.
[0025]
That is, the transmission processing unit 12 includes a message transmission unit 301, a retransmission request reception unit 302, a communication count management unit 303, a transmission message storage unit 304, a retransmission unit 305, a round trip time measurement unit 306, and a round trip time recording. A unit 307, a period extension unit 308, a current time measurement unit 309, and a suppression unit 310.
[0026]
Among these, the communication count management unit 303 is a part that provides a communication count that is information indicating a transmission order for each message (referred to as a transmission message) to be transmitted. The message transmission unit 301 transmits a message to the communication count. And means for transmitting to each receiving apparatus. The transmission message storage unit 304 is a transmission message storage unit for storing a retransmission memo such as a message body and a corresponding minimum retention period for each transmitted message.
[0027]
The retransmission request receiving unit 302 is a receiving unit for receiving a message retransmission request from the receiving device. The retransmission unit 305 is a retransmission unit stored in the transmission message storage unit 304 in response to the retransmission request. It is a means for resending a message based on a copy.
[0028]
Further, when the suppression unit 310 attempts to transmit a new message, the transmission message storage unit 304 cannot store the retransmission memo for the new message unless the retransmission memo for the retention minimum period has expired. This is a means for suppressing the transmission of the new message.
[0029]
The period extension unit 308 is a means for extending the minimum retention period of the message related to retransmission by a predetermined time. The round trip time measuring unit 306 and the round trip time recording unit 307 are parts that need to be provided or activated when extending the minimum message holding period based on the round trip time of the message and the retransmission request. This can be omitted when only a predetermined period, ie, a predetermined value is extended.
[0030]
That is, the round trip time measuring unit 306 is a means for measuring the round trip time of the message and the retransmission request based on the transmission time of the retransmission request and the transmission time of the message related to the retransmission request. The extension unit 308 is configured as means for extending the minimum message retention period related to the retransmission request based on the measured round trip time.
[0031]
The round trip time recording unit 307 is a means for storing a history of measured round trip times. In this case, the period extension unit 308, for example, sets a minimum message retention period related to retransmission to at least the round trip time. The recording unit 307 is configured to extend the average value of each round trip time stored as a history. The current time measurement unit 309 is a part for obtaining the current time using a system built-in clock or the like for the above-described round trip time measurement.
[0032]
[1-3. Configuration for message reception]
Next, FIG. 4 is a functional block diagram illustrating a configuration example of a computer that receives a message among the computers connected to the network illustrated in FIGS. 1 and 2. That is, the computer 2 includes a main body processing unit 21 and a reception processing unit 22, and the main body processing unit 21 includes a message processing unit 407 that performs information processing based on a received message by a program or the like that operates on the computer. It has been realized.
[0033]
In addition, the reception processing unit 22 receives a message from the network, passes the message to the message processing unit 407 of the main body processing unit 21, and when detecting a message omission, the reception processing unit 22 sends a retransmission request for the message. It is configured to send to the transmitting device.
[0034]
Specifically, the reception processing unit 22 includes a message reception unit 401, a message missing detection unit 403, a message order adjustment unit 404, a reception history storage unit 405, a received message save storage unit 406, and a retransmission request transmission unit. 402. Among these, the message receiving unit 401 is a part that receives a transmitted message from the network, and the reception history storage unit 405 is a part that stores a communication count history of the received message.
[0035]
In addition, the message drop detection unit 403 transmits the received message based on the communication count of the received message and the reception history of the communication count stored in the reception history storage unit 405 for the messages received so far. This is a means for detecting a message that has not been received, that is, a missing message.
[0036]
In other words, such a missing message is detected by receiving a message after the communication count is one or more when viewed from the message received immediately before. In this way, the message is stored by storing the message after the communication count is one and the subsequent message.
[0037]
The message order adjustment unit 404 is a part for adjusting the order of messages, and the retransmission request transmission unit 402 is a means for requesting retransmission of a message that has not been received to the transmission apparatus on the transmission side.
[0038]
The transmitter shown in FIG. 3 and the receiver shown in FIG. 4 together form a communication system, and each computer included in the distributed system as shown in FIG. 1 and FIG. It is also conceivable that all or part of the configuration includes both the configuration for message transmission shown in FIG. 3 and the configuration for message reception shown in FIG.
[0039]
[2. data structure〕
Next, in this embodiment as described above, an example of a data structure used for exchanging messages and retransmission requests and storing other information will be shown.
[2-1. (Outgoing message structure)
First, FIG. 5 shows an example of the structure of a transmission message that is a message transmitted from the transmission apparatus. That is, in the communication count 500, a communication count indicating how many times the message is transmitted from the transmitting device is registered as information indicating the order of message transmission. Further, in the transmission device ID 501, transmission source information indicating from which transmission device the message is transmitted is registered. For example, a transmission source computer ID is considered as a specific example of the transmission source information.
[0040]
As the transmission time 502, the current time is registered when a message is transmitted. In the message body 503, the body of a message that is information sent from the transmission device to the reception device is registered. In the case of resending a message, the current time at the time of resending is registered as the sending time 502, not the sending time at which the message was first sent.
[0041]
[2-2. (Retransmission request structure)
FIG. 6 is a diagram illustrating an example of the structure of a retransmission request sent from the receiving apparatus to the transmitting apparatus. That is, in the transmission device ID 600, the transmission device ID 501 of the transmission device that has transmitted the message received by the reception device is registered. The received message transmission time 601 is necessary only when the round trip time is measured, and the latest message transmission time 502 received by the receiving device is registered or received for such a transmission time. The time corrected by adding a value obtained by subtracting the time at which the retransmission request is transmitted from the time at which the device last received the message is registered. With this correction, the transmission device can calculate the round trip time by subtracting the reception message transmission time during the retransmission request from the reception time of the retransmission request.
[0042]
Note that since the transmission time 502 in FIG. 5 and the reception message transmission time 601 in FIG. 6 are used only when measuring the round-trip time of the message, the message retention minimum period of the transmission message storage unit 304 is extended. In addition, it is necessary only when the round trip time between the message and the retransmission request is used, and can be omitted when only the default value is extended.
[0043]
[2-3. (Structure for storing outgoing messages)
FIG. 7 is a diagram illustrating an example of a structure of information stored in the transmission message storage unit 304 in FIG. Among these, (a) is an example in the case where the main body of the message is taken out and stored in the transmission message storage unit 304, and (b) is an example of the message having the structure shown in FIG. It is an example in the case of memorizing.
[0044]
In any case, it is assumed that the data structure in the transmission message storage unit 304 has a structure in which a plurality of messages can be registered and is reused in order from the old message area. The message is registered in the transmission message storage unit 304 when transmitted from the message transmission unit 301.
[0045]
First, in the case of FIG. 7A, the communication count 700a registers the number of message transmissions from the transmission device as the communication count. In addition, the transmission time 701a is registered with the time when the message is transmitted. When retransmitting a message, the transmission time 701a may be registered as the first transmission time or registered as the current time at the time of retransmission.
[0046]
The minimum message retention period is registered as the minimum period of time until the message is retained without being deleted. Further, the message body 503 to be transmitted is registered in the message body 703a in the message structure of FIG.
[0047]
On the other hand, in FIG. 7B, instead of recording individual elements included in the transmission message such as the message body 503 in addition to the message holding minimum period 700b corresponding to the message holding minimum period 702a of FIG. This is an example in which the message structure illustrated in FIG. 5 is stored as it is.
[0048]
This message structure includes a transmission device ID 501 such as the IP address shown in FIG. Further, in this example, instead of the communication count 700a and the transmission time 701a in FIG. 7, the communication count 500 and the transmission time 502 as shown in FIG. 5 are nested and stored in the message structure 701b, respectively. Will be.
[0049]
[2-4. (Receiving history structure)
FIG. 8 shows an example of the structure of information stored in the reception history storage unit 405 shown in FIG. 4. Specifically, the received message communication count 500 and the transmission device ID 501 shown in FIG. These are stored as a pair of a communication count 801 and a transmission device ID 800, respectively.
[0050]
However, if the communication count 500 of the message received from a certain transmission device is not the latest communication count 801 registered for the transmission device plus 1, the message loss detection unit 403 causes the message to be lost. In this case, it is assumed that the communication count 801 is not updated.
[0051]
[2-5. (Structure for recording round trip time)
FIG. 9 shows an example of the structure of information recorded in the round trip time recording unit 307 shown in FIG. That is, the round trip time 901 calculated by the round trip time measuring unit 306 is registered in the round trip time recording unit 307 for each receiving device ID 900. Of these, as the round trip time 901, the latest measured round trip time, the weighted average of the stored time and the measured value, or the history of a certain number of the latest measured values are stored. To do.
[0052]
[3. Action)
The present embodiment configured as described above operates as follows. It is assumed that the transmission message storage unit 304 has the data structure illustrated in FIG.
[0053]
[3-1. Procedure for sending messages)
First, FIG. 10 is a flowchart illustrating an example of a processing procedure related to message transmission. That is, when the message processing unit 311 attempts to transmit a message to another computer, the message processing unit 311 sends a message transmission request to the message transmission unit 301, and the message transmission unit 301 that has received this transmission request performs the procedure shown in FIG. Execute.
[0054]
In this procedure, first, the message transmission unit 301 secures the transmission message storage unit 304 (transmission message storage unit) by reading out the area having the oldest transmission time 701a (step 1001).
[0055]
Subsequently, the suppression unit 310 receives the current time from a system built-in clock or the like, and determines whether or not the message holding minimum period 702a has already elapsed from the transmission time 701a of the area (step 1002). As a result, if the minimum retention period has not yet elapsed, the suppression unit 310 causes the message transmission unit 301 to wait without transmitting until the minimum retention period elapses (step 1003). It is assumed that no transmission request is accepted.
[0056]
In addition, after the waiting is completed, and when the minimum retention period has already passed in the determination of step 1002, the oldest message 703a is deleted from the secured message area (step 1004), An area for storing a newly transmitted message.
[0057]
Then, a message to be newly transmitted and other information related thereto are registered in the area secured in the transmission message storage unit 304 (transmission message storage means) in this way (step 1005). More specifically, in the message structure, the message body 703a is a message body to be transmitted, and the communication count 700a of the area is the communication count value determined by the communication count management unit 303 of the transmission device. In addition, the current time obtained from the system built-in clock or the like is registered in the transmission time 701a. Further, a predetermined value, for example, 10 seconds is registered in the minimum message holding period 702a.
[0058]
In addition, the message transmission unit 301 sets necessary information such as a message body in the message structure that is actually a transmission target (step 1006). For example, in the case of the message structure shown in FIG. 5, the communication count 500 is set to the value of the communication count 700 a stored in the transmission message storage unit 304 or the value of the communication count reread from the communication count management unit 303. .
[0059]
Also, an identifier such as the IP address of the transmission device is registered in the transmission device ID 501, and the transmission time 701 a registered in the transmission message storage unit 304 or the current time received from the system built-in clock or the like is registered in the transmission time 502. To do. The message body to be transmitted is set in the message body 503.
[0060]
Note that the order in which the registration to the transmission message storage unit 304 (step 1005) and the creation of the message structure to be transmitted (step 1006) are performed first is arbitrary, as shown in FIG. In the example, the message structure is created first (step 1006), but it is also possible to do it in the reverse order.
[0061]
In the transmission device, the communication count of the communication count management unit 303 is incremented by 1 (step 1007), and the message structure is transmitted to the communication path (step 1008).
[0062]
[3-2. (Receiving and resending request procedure)
Next, a procedure for receiving a message transmitted as described above and receiving the message and requesting retransmission is shown in the flowchart of FIG. That is, in this procedure, when the message receiving unit 401 receives a message (step 1101), the message dropout detecting unit 403 is stored in the reception history storage unit 405 for each received message communication count and the transmission device ID of the received message. It is determined whether or not the message has been lost by comparing the communication count with the current communication count (step 1102).
[0063]
If the received message has already been received, the received message is discarded (step 1103), and the procedure ends. As a case where a message that has already been received is received in this way, a message that has already been received for a certain receiving device may be multicast again according to a retransmission request from another receiving device having the same multicast address. .
[0064]
If the received message is missing in the determination at step 1102, the communication count to be retransmitted is extracted (step 1109), a retransmission request is transmitted (step 1111), and the message received at step 1101 is saved in the received message. It memorize | stores in the memory | storage part 406 (step 1112), and complete | finishes a procedure.
[0065]
Note that the role of the message order adjustment unit 404 is to pass messages to the message processing unit 407 in the order of transmission when the messages are not received in the order of transmission due to loss or retransmission of the messages. It is done.
[0066]
If it is determined in step 1102 that there is no omission in the received message, the received message is passed to the message processing unit 407 and processed (step 1104). In this case, 1 is added to the communication count 801 stored in the reception history storage unit 405 (step 1105).
[0067]
If there is a desired evacuation message in the received message evacuation storage unit 406, that is, a message to be processed next by the message processing unit 407 (step 1106), the message is processed according to the message ID (step 1106). 1107) The procedure of adding 1 to the communication count 801 each time (step 1108) is repeated until there is no desired message (step 1106).
[0068]
That is, since the retransmission request is transmitted when the communication count of a certain message and the next message that has arrived thereafter is 1 or more, the next message is received message saving storage unit 406 at the time of the retransmission request. Stored or saved (step 1112).
[0069]
The next message saved in this way can be processed after the message corresponding to the portion of the communication count is received according to the retransmission request and processed in step 1104. For this reason, after the received message is processed in step 1104, the saved message is processed in steps 1106 to 1108.
[0070]
[3-3. Example of procedures for resending messages]
Next, FIG. 12 shows an example of a procedure in which the transmission apparatus retransmits a message in response to the retransmission request transmitted as described above. Here, in order to show an example in which the minimum retention period of a message related to retransmission is extended by a predetermined value without measuring the round trip time, step 1202 is not included, and step 1202 will be described later. Another example will be described.
[0071]
That is, in this procedure, first, when retransmission request receiving section 302 receives a message retransmission request having the structure shown in FIG. 6 (step 1201), retransmission section 305 of the receiving transmitting apparatus sends the retransmission request to the transmitting apparatus. Is determined based on the transmission device ID 600 for which retransmission is requested (step 1203). In this determination, if the retransmission request is addressed to another transmission apparatus other than the transmission apparatus, the retransmission request is only discarded (step 1208), and the procedure is terminated.
[0072]
On the other hand, when the retransmission request is addressed to itself, that is, to the transmission device (step 1203), the retransmission unit 305 transmits the desired message, that is, the communication specified by the retransmission request from the transmission message storage unit 304 (transmission message storage unit). A message having the same communication count 700a as the count 602 is searched (step 1204). At this time, if the desired message does not exist in the transmission message storage unit 304 due to elapse of the minimum holding period (step 1205), the retransmission request is discarded (step 1208), and the procedure is terminated.
[0073]
If it is determined in step 1205 that a desired message exists, the retransmission unit 305 retransmits the desired message (step 1206). At that time, the same values as those stored in the transmission message storage unit 304 are used for the communication count 500, the transmission device ID 501, and the transmission time 502.
[0074]
When this transmission is completed, the period extending unit 308 extends the minimum holding period by adding a predetermined predetermined value to the minimum holding period 702a of the message stored in the transmission message storage unit 304. In addition, the retransmission request is discarded (step 1208), and the procedure is terminated.
[0075]
[3-4. Other examples of procedures related to message retransmission]
Next, as another example of the procedure for resending a message in response to a resend request, the step of measuring the round trip time between the message and the resend request and extending the minimum message holding period by this round trip time The process including the process 1202 will be described.
[0076]
That is, in this example, when a message retransmission request arrives (step 1201), the round-trip time measuring unit 306 determines whether the message is a retransmission request addressed to the transmission apparatus (step 1203). The round trip time with the received retransmission request is measured and recorded in the round trip time measurement recording unit 307 (step 1202).
[0077]
Specifically, the round trip time measurement unit 306 calculates the round trip time of the message and the retransmission request from the received message transmission time 601 included in the message retransmission request and the current time when the retransmission request arrives. In addition, the specific standard and procedure of calculation are free.
[0078]
For example, the receiving device sends a retransmission request from the time of the latest message received by the receiving device as the received message sending time 602 in the resending request, or from the time when the receiving device last received the message from that time. Register the corrected time by adding the value obtained by subtracting the outgoing time. With this correction, the transmission device can calculate the round trip time by subtracting the reception message transmission time during the retransmission request from the reception time of the retransmission request.
[0079]
In this example, when the minimum retention period of the message is extended (step 1207), the predetermined minimum value is not added to the minimum retention period, but the minimum retention period is based on the round trip time recorded in the round trip time recording unit 307. Is extended. In addition, as the extension of the minimum holding period based on the round trip time, not only the one round trip time itself may be extended but also the time calculated based on one or a plurality of round trip times may be extended. .
[0080]
For example, as the extension time, it is possible to use a time obtained by multiplying the round trip time by a constant, and not only the round trip time to the receiving device that sent the retransmission request, but also the average value of the round trip time for all the receiving devices, or A value obtained by weighted averaging of round trip times between a receiving apparatus that has sent a retransmission request and another receiving apparatus, a maximum round trip time, or the like can also be used.
[0081]
[3-5. Example of network configuration and data)
A specific example of the network configuration of the communication system as described above is shown in FIG. In this example, two transmission devices 1a and 1b and two reception devices 2a and 2b are arranged in three computers. The transmission device 1b and the reception device 2b are one computer. The transmission device 1a and the reception device 2a are arranged on a single computer.
[0082]
In such an example, for example, in the reception history storage unit 405 on the reception device 2a, as illustrated in FIG. 14, for each transmission device, the transmission device ID and the last received message from the transmission device without omission The message communication count is stored. For example, in this example, “6” is recorded as the communication count of the message that has arrived last from the transmission device 1b, and if the communication count of the message that has arrived next from the transmission device 1b is “7”, the omission is detected. However, if the communication count of the next message received from the transmission device 1b is “8”, it can be determined that the message with the communication count “7” has been lost.
[0083]
In the example of FIG. 13, for example, the round trip time recording unit 307 on the transmission device 1a or 1b sends a reception device ID and a message to the reception device for each reception device as illustrated in FIG. The round trip time from when the retransmission request is returned is stored. In this example, for example, when the average of round trip times for each receiving device is used as the round trip time for extending the minimum holding period, this average value is 2.5 milliseconds.
[0084]
[4. effect〕
As described above, according to the present embodiment, for each message retransmission copy, the minimum retention period that is not deleted is managed, and the new message retransmission copy cannot be saved without deleting the retransmission copy that has not expired. Waits for a new message to be sent. As a result, even when there are many transmission messages, retransmission is guaranteed for a certain period of time after transmission, and communication reliability is improved.
Also, in this embodiment, by extending the minimum retention period when retransmitting a message, even if the amount of network communication is large and a re-transmission request is generated, the re-transmission of the message is facilitated, and the communication Reliability can be improved.
[0085]
Further, in this embodiment, at the time of message retransmission, the minimum holding period is extended based on the round trip time required for the message and the retransmission request to make a round trip with the receiving apparatus that has requested retransmission. As a result, even if the retransmitted message is not received by the receiving device, it is possible to secure a retransmission copy until a re-transmission request is received, thereby improving the reliability of message communication.
[0086]
Also, in this embodiment, by extending the minimum message retention period by at least the average value of each round trip time, it is possible to average the variation in round trip time for each time point and for each computer in the group address, and By extending the minimum retention period by an appropriate time width, excellent performance can be realized.
[0087]
In other words, according to the present embodiment, when exchanging information using, for example, processes between distributed systems in which a plurality of computers are connected by a network, using multicast, the minimum value of the period for holding transmitted messages is set. In addition to guaranteeing, when the retransmission occurs, the time for guaranteeing the storage of the message is dynamically controlled by appropriately extending the period.
[0088]
This reduces retransmission failures and improves communication reliability, suppresses overloading of the network and receiving device, and allows for efficient communication with a short minimum retention period when the load is low. Become.
[0089]
[5. Other Embodiments]
In addition, this invention is not limited to the said embodiment, Other embodiments which are illustrated next are included. For example, in the above-described embodiment, a communication system including both a transmission device and a reception device is shown. However, the present invention can be implemented by a transmission device alone and used in combination with an existing reception device.
[0090]
In addition, the minimum message retention period guarantees a minimum period in which the message resending copy is not deleted. If a new message is not sent or the resending copy storage area is sufficiently large, it is retained. Of course, it is safe to keep a copy for resending beyond the minimum period. Further, the default value for extending the minimum retention period may be configured to vary on a constant basis according to the load state of the network.
[0091]
In addition, for the round trip time measurement, specific criteria and procedures for calculating and combining what numerical values and times are free, and the configuration and data structure shown in the above embodiment, Specific details of the processing procedure and the like can be freely changed.
[0092]
【The invention's effect】
As described above, according to the present invention, a transmission apparatus, a transmission method, and a recording medium on which transmission software is recorded that performs message communication with excellent reliability by guaranteeing a period for holding a retransmission message retransmission copy. In addition, a communication system can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of the configuration of a distributed system in an embodiment of the present invention.
FIG. 2 is a diagram showing another example of the configuration of the distributed system in the embodiment of the present invention.
FIG. 3 is a functional block diagram illustrating an example of a configuration of a transmission device according to an embodiment of the present invention.
FIG. 4 is a functional block diagram showing an example of a configuration of a receiving device according to the embodiment of the present invention.
FIG. 5 is a conceptual diagram showing an example of a data structure of a transmission message in the embodiment of the present invention.
FIG. 6 is a conceptual diagram showing an example of a data structure of a retransmission request in the embodiment of the present invention.
FIG. 7 is a conceptual diagram illustrating an example of a data structure of information stored in a transmission message storage unit of a transmission device in the embodiment of the present invention.
FIG. 8 is a conceptual diagram showing an example of a data structure of information stored in a reception history storage unit of the reception device according to the embodiment of the present invention.
FIG. 9 is a conceptual diagram illustrating an example of a data structure of information stored in a round trip time recording unit of a transmission device according to an embodiment of the present invention.
FIG. 10 is a flowchart illustrating an example of a processing procedure in which a transmission device transmits a message in the embodiment of the present invention.
FIG. 11 is a flowchart showing an example of a processing procedure for processing a message received by the receiving apparatus and performing a retransmission request in the embodiment of the present invention.
FIG. 12 is a flowchart illustrating an example of a processing procedure in which a transmission apparatus retransmits a message according to a retransmission request in the embodiment of the present invention.
FIG. 13 is a diagram showing an example of the arrangement of transmission devices and reception devices in the embodiment of the present invention.
14 is a diagram showing an example of information stored in a reception history storage unit of the receiving device in the example of FIG.
15 is a diagram showing an example of information stored in a round trip time recording unit of the transmission device in the example of FIG.
[Explanation of symbols]
1, 2, ... Calculator
11, 21 ... Main body processing unit
12 ... Transmission processing unit
22. Reception processing unit
301 ... Message transmission unit
302 ... Retransmission request receiver
303 ... Communication count management unit
304: Transmission message storage unit
305 ... Retransmission part
306. Round trip time measurement unit
307: Round-trip time recording unit
308 ... Period extension
309 ... Current time measuring unit
310 ... deterrence part
311, 407 ... Message processing unit
401: Message receiver
402: Retransmission request transmission unit
403 ... Missing message detection unit
404: Message order adjustment unit
405: Reception history storage unit
406 ... Received message saving storage unit
407: Message processing unit

Claims (9)

In a transmission device for multicast transmission of a message to a plurality of reception devices connected by a network,
Means for transmitting each message to each receiving device together with a communication count which is information indicating a transmission order;
For each transmitted message, a storage means for storing a copy for retransmission, a transmission time of the message, and a retention minimum period of the message in association with each other ;
Receiving means for receiving a message retransmission request from the receiving device;
Means for resending the message based on the stored resending copy in response to the resending request;
When trying to send a new message, it corresponds to the oldest outgoing time based on the current time, the oldest outgoing time stored in the storage means and the minimum holding period stored in association with the outgoing time. Means for determining whether or not the retransmission reserve to be passed has passed its minimum holding period and suppressing transmission of the new message until the determined minimum hold duration of the retransmission reserve has elapsed When,
If based on the retransmission copy stored to resend the message, transmitting device the holding minimum duration of the message according to the retransmission, characterized in that a means for extending by a predetermined time .   Based on the reception time of the retransmission request and the transmission time of the message related to the retransmission request, means for measuring the round trip time of the message and the retransmission request, and the minimum retention period of the message related to the retransmission request, The transmission apparatus according to claim 1, further comprising means for extending based on at least the measured round trip time.   Means for storing a history of the measured round trip time, and means for extending a minimum message retention period related to retransmission at least by an average value of each round trip time stored as the history. The transmission device according to claim 2, further comprising: In a transmission method for multicast transmission of a message to a plurality of receiving devices connected by a network,
A step for transmitting each message to each receiving device together with a communication count which is information indicating a transmission order;
For each transmitted message, a step for storing a record for retransmission, a transmission time of the message, and a minimum retention period of the message in association with each other ;
Receiving a message retransmission request from the receiving device;
In response to the retransmission request, retransmitting the message based on a stored copy for retransmission;
When trying to send a new message, it corresponds to the oldest outgoing time based on the current time, the oldest outgoing time stored in the storage means and the minimum holding period stored in association with the outgoing time. A step for determining whether or not the retransmission reservation to be performed has passed the minimum holding period and suppressing transmission of the new message until the determined minimum holding period for the retransmission backup has elapsed. When,
And a step for extending the minimum holding period of the message related to retransmission for a predetermined time when the message is retransmitted based on a stored copy for retransmission. .   A step for measuring a round trip time of the message and the retransmission request based on a reception time of the retransmission request and a transmission time of the message related to the retransmission request; and the minimum holding period of the message related to the retransmission request, The transmission method according to claim 4, further comprising a step of extending based on the measured round trip time.   A step for storing a history of the round trip time measured; and a step for extending a minimum retention period of a message related to retransmission by at least an average value of each round trip time stored as the history. The transmission method according to claim 5, further comprising: In a recording medium recording transmission software for multicast transmission of a message to a plurality of receiving devices connected by a network by controlling a computer,
The software causes the computer to transmit each message to each receiving device together with a communication count that is information indicating the transmission order,
For each message sent, a record for resending, the outgoing time of the message, and the minimum retention period of the message are stored in association with each other ,
Receiving a message retransmission request from the receiving device;
In response to the retransmission request, the message is retransmitted based on the stored copy for retransmission,
When trying to send a new message, it corresponds to the oldest outgoing time based on the current time, the oldest outgoing time stored in the storage means and the minimum holding period stored in association with the outgoing time. To determine whether or not the retransmission hold has passed its minimum holding period, and to suppress transmission of the new message until the determined minimum holding period of the retransmission backup has passed,
A recording medium on which transmission software is recorded, wherein when a message is retransmitted based on a stored copy for retransmission, the minimum holding period of the message related to retransmission is extended by a predetermined time.   The software causes the computer to measure a round-trip time of the message and the retransmission request based on the reception time of the retransmission request and the transmission time of the message related to the retransmission request, and the minimum holding of the message related to the retransmission request. 8. The recording medium recording the transmission software according to claim 7, wherein the period is extended based on the measured round trip time.   The software stores the history of the measured round trip time in the computer, and extends the minimum message retention period related to retransmission by at least the average value of each round trip time stored as the history. A recording medium on which the transmission software according to claim 8 is recorded.

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