JP2000307676A - Device and method for one-to-many communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the communication time of a one-to-many communication device as a whole by reducing the load on a receiving terminal. SOLUTION: A one-to-many communication device confirms delivery with NACK(negative acknowledement) as to the transmission of a file consisting of DTUs(data transfer unit) as transmission units. In this case, a transmitting terminal which transmits a series of DTUs to multiple receiving terminals is equipped with DTU loss state confirming means 204 and 205 which confirm the loss state of DTUs of the respective receiving terminals by receiving NACK from the respective receiving terminals and a resending schedule generating means 206 which preferentially resends DTUs to the receiving terminal judged by the DTU loss state confirming means to have the least loss of DTUs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a one-to-many communication apparatus and method such as multicast or broadcast communication, and more particularly, the present invention relates to a one-to-many communication that performs communication while confirming delivery from a transmitting terminal to each receiving terminal. The present invention relates to a communication device and a method.

[0002]

2. Description of the Related Art In order to implement a reliable one-to-many communication apparatus, if a transmitting terminal does not have any procedure when transmitting data to each receiving terminal, the transmitting terminal sends the data to a sink.
If an error occurs in the data received at the receiving terminal,
Recovery is impossible. Therefore, it is necessary for the transmitting terminal to perform acknowledgment of transmission of the transmitted data with each receiving terminal and perform communication while confirming the reception status of the transmitting data of each receiving terminal.

[0003] As a conventional example of the delivery confirmation in the above one-to-many communication apparatus, UDP / IP (User Data) published as an Internet draft in January 1997 was used.
Gram Protocol / Internet Pr
Multicast as a protocol for simultaneously and reliably transferring files to a large number of recipients of a multicast IP network.
ast File Transfer Protocol
1 (MFTP).

[0004] A delivery confirmation method from a transmitting terminal to each receiving terminal in MFTP is based on NACK (Negative A).
This is a knowledgement (negative confirmation) method, and the outline of the method is as follows. FIG. 7 shows MF
FIG. 6 is a diagram illustrating a method of dividing a file in a TP. As shown in this figure, when a file to be transmitted occurs, one file is divided into a plurality of blocks 1, 2, 3,... M. One more block is the data transfer unit DT
The data is transmitted by being divided into a plurality of transmission units called U (Data Transfer Unit).

[0005] Each of the DTUs 1, 2, 3, ... n has a serial number (1) used at the time of file restoration,
(2), (3),... (N) are given. The serial number given to the last DTU of the block m is (m × n).
FIG. 8 is a diagram illustrating transmission of a series of DTUs from a transmitting terminal. In MFTP, transmitting a series of DTUs from a transmitting terminal is called a path. As shown in this figure,
In the first pass, the entire file and a Status Request message requesting a delivery response from each receiving terminal are transmitted. The Status Request message may be transmitted at any timing, but is usually transmitted in block units as shown in FIG. In the example of this figure, the transmission file is divided into five blocks, and one block is provided with five DTUs. In addition, MFTP may be of any type of full-duplex line or half-duplex line, but in the description of the present invention, the communication line will be described as a full-duplex line.

FIG. 9 is a diagram for explaining a delivery response NACK from the receiving terminal. As shown in this figure, when each receiving terminal receives a Status Request message, it receives an NA as a delivery response for the DTU that failed to receive.
Returns a CK message. Note that NACK is a status R that the transmitting terminal transmits at the end of each block.
request message. If there is no DTU for which reception has failed, no NACK message is transmitted.

FIG. 10 is a diagram for explaining retransmission from a transmitting terminal. Even if the transmitting terminal receives a NACK message from each receiving terminal during the first pass, retransmission is not performed immediately, and only the retransmission schedule (retransmission DTU transmission preparation processing in the second and subsequent passes) is performed. Actual retransmission is performed in the second and subsequent passes. For the second and subsequent passes,
D which received a retransmission request from each receiving terminal during the previous pass
A new block number and a new DTU number are assigned to the TU in ascending order of the block number and the DTU number in the previous pass, and the Status Request is assigned to each new block.
Perform retransmission while sending a message. Although each block number and DTU number change for each pass, when the receiving terminal restores a file, a series of fixed numbers different from the above-mentioned numbers are assigned to each DTU, and these numbers are used as a basis. Is restored.

[0008] The transmitting terminal repeats retransmission until there is no DTU retransmission request from each receiving terminal or within a transmission limit time set as a parameter and does not exceed the maximum number of retransmissions. If there is no DTU that failed to receive in the path, the receiving terminal sends the Status Request sent last from the transmitting terminal to the end of the path.
In response to the t message, the receiving terminal sends a Done message indicating that all DTUs have been successfully received, and the sending terminal waits for reception of a Completion message to be sent out as a reception confirmation notification of the Done message, and transmits the Completion message. Upon receipt, the communication process ends.

[0009] Upon receiving the first Done message from the receiving terminal, the transmitting terminal immediately sends a Completion message. Thereafter, at a time interval specified by the parameter, the transmitting terminal collectively transmits one Completion message as confirmation for the Done message received between the previous transmission of the Completion message and the next transmission of the Completion message. When the completion message has been successfully transmitted, the communication process ends. Hereinafter, the details of the delivery confirmation of the one-to-many communication device will be described.

FIG. 11 is a diagram for explaining an operation example of the delivery confirmation. As shown in the figure, when a file to be transmitted is generated, one file is divided into a plurality of blocks, and one block is further divided into a plurality of DTUs.
And transmitted to the receiving terminal. At the transmitting terminal, first, the entire file is transmitted as path 1. Next, in order to know the DTU that needs to be retransmitted while the path 1 is being performed, the transmitting terminal requests a status response requesting a delivery response.
A Request message is transmitted to the receiving terminal. The receiving terminal that has received the Status Request message receives a NACK related to the DTU that could not be received.
Is returned to the sending terminal.

[0011] The Status Request message transmitted from the transmitting terminal to the receiving terminal is usually transmitted in block units. Upon receiving the NACK, the transmitting terminal schedules retransmission of the DTU, and retransmits it on the next path.

FIG. 12 is a diagram showing a relationship between a transmitting terminal and a plurality of receiving terminals, and FIG. 13 is a diagram showing a specific example of a NACK transmitting operation. A Status Request message is transmitted from the transmitting terminal shown in FIG. 12 to receiving terminals A, B, and C. The receiving terminals A, B, and C receive a Status Request message from the transmitting terminal. After this reception, as shown in FIG. 13, NACK is not returned individually from the receiving terminals A, B, and C to the transmitting terminal. That is, a waiting time from reception to NACK transmission is set for each of the receiving terminals A, B, and C. This waiting time is set by a parameter, and is randomly determined every time after reception within the range of the maximum value. Note that the waiting time increases as the number of connections of the receiving terminal increases.

Each of the receiving terminals A, B, and C monitors the response of the other receiving terminal during a random waiting time until NACK transmission (NACK monitoring period of the other receiving terminal). For example, when NACK transmission is performed by the receiving terminal A, each of the receiving terminals B and C receives the NACK of the receiving terminal A. In each of the receiving terminals B and C, the NA of the receiving terminal A
If NACK is to be transmitted similarly after receiving CK, that is, NACK of receiving terminal A is
If the own response status is satisfied, the transmission of NACKs of the receiving terminals B and C is stopped.

Returning to FIG. 11, the description will be continued. If retransmission is scheduled at the end of pass 1 at the transmitting terminal, the DT for which retransmission is required
U is transmitted. Thereafter, the transmitting terminal determines whether there is no DTU retransmission request from each receiving terminal, whether the transmission limit time set in the parameters of the transmitting terminal has timed out,
Alternatively, the path is repeated until the maximum number of retransmissions is reached. That is, while there is a retransmission request, the transmission time limit,
The path is repeated within the maximum number of retransmissions. However,
As parameters, there are a transmission limit time for the transmission terminal and a reception limit time for the reception terminal. If the transmission or reception terminal processing is not completed in each terminal within each time limit, the file transfer processing is forcibly terminated.

FIG. 14 is a diagram showing a specific example of the operation of transmitting a Done message and a completion message of MFTP. As shown in this figure, if the receiving terminal A succeeds in receiving a file from the transmitting terminal in one or a plurality of passes, a Done message is transmitted from the receiving terminal A to the transmitting terminal. Each of the receiving terminals A, B, C, and D receives the Do message from the transmitting terminal that has received the Done message.
complete message as confirmation notification
Tion message is transmitted.

The Completion message is Do
rather than being notified each time a ne message is received,
Promptly responds to the first received Done message
The completion message is notified, and thereafter, the completion message is periodically transmitted. In the message, the name of the receiving terminal confirmed until the completion message is transmitted is written.
The transmission of the file is completed for all receiving terminals.
The process ends when an ion message is notified.

FIG. 3A shows the first Complete.
An example of the content of the second Co is shown in FIG.
An example of the contents of the “pletion” is shown. Figure 15 shows the MFT
It is a figure which shows the specific example of P Abort message and Quit message transmission operation | movement. As shown in FIG. 9A, in the transmitting terminal, when the transmission time limit times out or the maximum number of retransmissions is reached, Abort for stopping the file transfer from the transmitting terminal to each receiving terminal.
The message is notified. Thereafter, the file transmission to the receiving terminal is stopped.

Similarly, the reception terminal also has a reception limit time, and if the file cannot be received normally within the reception time limit, a Quit message is transmitted from the reception terminal to the transmission terminal, and the file reception fails. Is notified, and the communication process ends. Thereafter, the file transfer to the receiving terminal is stopped.

[0019]

However, the above prior art has the following problems. First, in a receiving terminal having a low processing capability, when a plurality of transmitting terminals simultaneously perform transfer file receiving processing and the like, the plurality of communication processings become very heavy loads, and therefore, individual communication processing is performed as much as possible. I wanted to finish in a short time. However, the transmitting terminal transmits a DTU for which a retransmission request has been issued in ascending order of the block number and the DTU number in the previous path. Therefore, even in a terminal having good reception status, if the latter half of the block number fails to receive, the desired DTU
There is a problem that the communication process is not completed until the communication is received.

Second, the values of various timers set by parameters are fixed. Therefore, when the number of connections of the receiving terminal increases, various timer values are set to a relatively large value, and the overall communication time tends to be long. The reasons for increasing the various timer values are as follows. Complete in the above method
The following describes an example of an on message transmission interval. Consider the case where the number of connected receiving terminals is 5 and the case where the number is 50. If it takes 1 second for the transmitting terminal to receive a Done message per receiving terminal, it takes 5 seconds even if the Done message can be received ideally. Assuming that this 5 seconds is the transmission interval of the Done message, one Completion message is assumed to be ideally able to receive a Done message if the transmission interval of 5 seconds is applied when the number of connected receiving terminals is 50. Also, the transmission of the Completion message occurs ten times. This interval is not very efficient, and in a low-speed communication line, such careless transmission of control data may have an effect such as a decrease in throughput. This is because it is better to increase the timer value.

[0021] Accordingly, it is an object of the present invention to provide a one-to-many communication apparatus which reduces the load on a receiving terminal and shortens the overall communication time to perform delivery confirmation.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a point-to-multipoint communication apparatus which confirms the transmission of a file using a DTU as a transmission unit by NACK. The transmitting terminal transmitting to the receiving terminal of the receiving terminal receives a NACK from each of the receiving terminals and checks the DTU loss status of each of the receiving terminals. A one-to-many communication apparatus characterized by comprising retransmission schedule generating means for retransmitting a DTU preferentially to the least number of receiving terminals.

By this means, it has become possible to end the communication of the receiving terminal having a better receiving condition earlier than the receiving terminal having a bad receiving condition. Therefore, the burden on the receiving terminal is reduced. Further, the present invention provides a point-to-multipoint communication device that performs delivery confirmation using NACK for transmission of a file in which a DTU is a transmission unit, wherein a transmission terminal that transmits a series of the DTUs to a plurality of reception terminals includes: Parameter setting / changing means for setting a waiting time for the NACK to be received, and changing the setting of the waiting time to be shorter with a decrease in the number of connections of the receiving terminal requesting retransmission to the transmitting terminal; Receiving a Done message indicating that all DTUs have been successfully received, and
There is provided a point-to-multipoint communication apparatus, comprising: a Done receiving means for giving the parameter setting / change means the information on the decrease in the number of connections of the receiving terminal by receiving a message.

According to this means, when the number of connections with the receiving terminal at the time of retransmission is reduced, the waiting time for NACK is reduced, so that the communication time can be shortened as a whole. Further, the present invention provides a method for transmitting a file in DTU as a transmission unit.
In a point-to-multipoint communication device that performs acknowledgment by ACK, a transmitting terminal that transmits a series of the DTUs to a plurality of receiving terminals includes:
DTU loss status checking means for receiving a NACK from each of the receiving terminals and checking the DTU loss status of each of the receiving terminals; and preferentially giving priority to the receiving terminal having the least DTU loss by the DTU loss status checking means. Retransmission schedule generating means for retransmitting a DTU, setting a waiting time for the NACK received from each of the receiving terminals, and setting the waiting time with a decrease in the number of connections of the receiving terminal requesting the transmitting terminal to retransmit. Parameter setting / changing means for setting short, a Done message indicating that the receiving terminal has successfully received all DTUs, and
There is provided a point-to-multipoint communication apparatus, comprising: a Done receiving means for giving the parameter setting / change means the information on the decrease in the number of connections of the receiving terminal by receiving a message.

By this means, not only the communication of the receiving terminal with good reception status can be ended early and the load on the receiving terminal can be reduced, but also the number of connections with the receiving terminal with good reception status at the time of retransmission is reduced, and the NACK wait time is reduced. Preferably, the communication time is shortened so that the communication time can be shortened as a whole. Preferably, a NACK is sent to each of the receiving terminals, and a NACK response is monitored for other receiving terminals for a certain period of time.
CK transmitting / receiving means, Completion receiving means for receiving a Completion message from the transmitting terminal indicating the end of communication with the receiving terminal,
a parameter setting / changing unit that changes the setting of the fixed period to be short to monitor the NACK response in the NACK transmitting / receiving unit as the number of connections of the receiving terminal decreases from the reception of the etion message.

By this means, when the receiving terminal having a good receiving condition is disconnected, the period of the response monitor of the receiving terminal itself is also shortened, so that the communication time can be shortened. Preferably, the retransmission schedule generating means is configured to transmit the DTU
The retransmission is performed by the loss status confirmation means in accordance with the transmission order of the series of DTUs to the receiving terminals having the same DTU loss. As described above, when there is no particular receiving terminal having a good receiving condition and the DTU loss is almost the same, the conventional retransmission method is followed.

Further, according to the present invention, delivery confirmation is performed by NACK for the transmission of a file in DTU as a transmission unit.
In the point-to-multipoint communication method, a step of transmitting the series of DTUs from transmission / reception to a plurality of receiving terminals, a step of receiving a NACK from each of the receiving terminals to confirm a loss status of the DTU of each of the receiving terminals, DT with loss status confirmation means
DTU with priority given to the receiving terminal with the least U loss
And a step of retransmitting the one-to-many communication method. According to this step, it is possible to obtain the same operation and effect as the above invention.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram showing a transmission terminal according to the present invention. As shown in the figure, a transmitting terminal 1 performs a process for performing one-to-many communication with a file input unit 1 for setting a file to be transmitted.
It comprises a multi-communication transmitting unit 2 and a communication line input / output unit 3 which is an interface with a communication line.

The one-to-many communication transmitting unit 2 divides one file into a plurality of blocks, further divides the file into a plurality of transmission units called DTUs, and a DTU generated by the file dividing unit 201. Is transmitted to each receiving terminal via the communication line input / output unit 3, and S
Status Request for requesting a transmission response of each receiving terminal to the Status Request sending means 203
DTU sending means 202 for giving a message sending instruction;
Status Request from DTU sending means 202
Status Request based on the st message transmission instruction
status request sending means 203 for sending an e-mail message to each receiving terminal via the communication line input / output unit 3, and receiving a NACK from each receiving terminal, and sending the contents of the DTU for which each receiving terminal failed to receive a DTU. NACK receiving means 204 for notifying loss status confirming means 205
Based on the notification from the NACK receiving means 204, the DTU loss status checking means 205 for generating a DTU loss status list for each receiving terminal, and the DTU loss status list for each receiving terminal generated by the DTU loss status checking means 205 are used. In addition, a retransmission schedule is created so as to preferentially retransmit from a DTU requested by a receiving terminal having a good reception condition,
The retransmission schedule means 206 for instructing the transmission means 202 to transmit a retransmission DTU, and a Done message indicating that all the DTUs have been successfully received from each receiving terminal are received, and the Done message is transmitted to the completion transmission means 208. Comp is a receipt confirmation notification of
A Done receiving unit 207 for issuing a transmission instruction of the contention message, and a Com for transmitting a completion message based on the instruction from the Done receiving unit 207.
Pletion sending means 208, Abort sending means 209 for sending an Abort message, which is a message for the sending terminal to notify each receiving terminal of the suspension of the communication process currently being performed, On the other hand, a Quit receiving means 210 for receiving a Quit message, which is a message for notifying the suspension of the communication processing currently being performed, and setting a parameter at the start of communication, or setting the number of connections of each receiving terminal during communication processing Parameter setting / changing means 211 for changing to an opportunity due to a decrease or the like.

FIG. 2 is a schematic block diagram showing a receiving terminal according to the present invention. As shown in the figure, the receiving terminal includes a file output unit 4 for outputting a received file,
It comprises a one-to-many communication receiving unit 5 for performing a process for implementing the many-to-many communication, and a communication line input / output unit 6 which is an interface with a communication line.

The one-to-many communication receiving unit 5 checks the DTU that has been successfully received to the original file based on the message sequence number, and checks whether the received DTU has an error. If the DTU reception fails, the DTU reception means 502 notifies the DTU loss status confirmation means 504 that the DTU reception has failed.
a status request receiving unit 503 that receives the request message and notifies the DTU loss status checking unit 504, and a DTU received from the DTU receiving unit 502
A DTU loss status list is created based on the notification regarding the failure of the DTU, and a DTU loss status described later is transmitted from the status request receiving unit 503 to the NACK transmission / reception unit 50 based on the status request message reception notification.
5, the DTU loss status confirmation means 504 for notifying
Based on the notification from the loss status confirmation means 504, NACK from another receiving terminal is monitored for a certain period of time, and if NACK equivalent to NACK to be transmitted is received, NA
If transmission of CK is stopped and reception is not possible, NAC
The NACK transmitting / receiving means 505 for transmitting the K and the DTU transmission for receiving a notification from the DTU loss status confirming means 504 when the loss of the DTU has disappeared, that is, when all the DTUs have been successfully received, and transmitting a Done message. When the completion message is received and the confirmation message is not the confirmation message for the Done message issued by the receiving terminal, the retransmission instruction of the Done message is issued again to the Done sending unit 506. Completi that issues a transmission instruction to the file output unit for the file restored in 501
on receiving means 507, a Quit sending means 508 for sending a Quit message and stopping communication processing,
Abo for receiving t message and stopping communication processing
An rt receiving unit 509 and a parameter setting / changing unit 510 for setting parameters at the start of communication or changing parameters during communication processing due to a decrease in the number of receiving terminals or the like.

Next, the overall operation of the present embodiment will be described with reference to FIGS. First, the operation of the transmitting terminal will be described using FIG. 1, FIG. 3, and FIG. FIGS. 3 and 4 are flowcharts illustrating the operation of the transmitting terminal of FIG. In step A1, various parameters are set by the parameter setting / change means 211 at the start of communication. In step A2, the file input by the file input / output unit 1 is
Is set to 1, the file is divided into multiple blocks,
The DTU is further divided into a plurality of DTUs, and a series of numbers (from No. 1 to [the number of blocks × the number of DTUs in one block]) are used for the DTUs.

In step A3, the DTU sending means 2
02 confirms that the transmission limit time and the maximum number of retransmissions set as parameters have not been exceeded. If the transmission time limit and the maximum number of retransmissions have been exceeded, the process proceeds to step A22,
An ort message is transmitted to notify that the communication has been stopped. In step A4, if the transmission time limit and the maximum number of retransmissions have not been exceeded by the DTU sending means 202 in step A3, the DTU is transmitted via the communication confirmation input / output unit 3,
It is sent to each receiving terminal. In step A5, DT
It is checked whether the DTU sent by the U sending means 202 is the last DTU in the block.

If the last DTU in the block is not the last DTU in step A6, the processing in steps A3 to A5 is repeated, and if the last DTU in the block has been transmitted in step A5, the status request transmission unit 202 transmits the status request. Means 203 is instructed to send a Status Request message, and the Status Request
The sending unit 203 sends a Status Request message to each receiving terminal via the communication line input / output unit 3.

In step A7, DTU sending means 2
02, it is checked whether the transmitted DTU is the last DTU in the path. If it is not the end of the pass, the process returns to step A3 and the above processes are repeated. In step A8, if it is the end of the path, the NACK receiving means 204 receives a NACK from each receiving terminal, and checks in step A8 whether a retransmission request has been issued. In step A9, if there is a retransmission request, NACK receiving means 204
The TU loss status confirmation means 205 is notified of the DTU reception failure of each receiving terminal, and the DTU loss status confirmation means 205 creates a DTU loss status list for each receiving terminal.

In step A10, if the Quit receiving means 210 has not received the Quit message or the Done receiving means 207 has not received the Done message, the process proceeds to step A13 described later. In step A11, if a Quit message or a Done message has been received, the DTU loss status confirming means 205 is notified of the fact, and the DTU loss status confirming means 205 having received the notification indicates that the DTU loss status of each receiving terminal has been received. Information about the receiving terminal that transmitted the Quit message is deleted from the list.

In step A12, the parameter setting / change means 211 has a parameter management table in which various parameter settings for the number of connected receiving terminals are described. Various parameters are changed to specified values by referring to the table. In steps A13 and A14, the retransmission schedule generating means 206 checks the DTU loss status list of the DTU loss status checking means 205,
A retransmission schedule is set so that a retransmission DTU of a reception terminal having a good U loss situation, specifically, a reception terminal having a small number of failed DTUs is transmitted preferentially, and notified to the DTU sending means 202. . DTU retransmission is step A
The processing is performed by repeating the processing of 3 to A14.

In step A15, if there is no retransmission request in step A8, the Done receiving means 207 checks whether a Done message has been received.
If a Done message has been received, complete
This is notified to the ion sending means 208. In step A16, the parameter setting / change means 211 holds a parameter management table describing the setting of various parameters with respect to the number of connections of the receiving terminal, and refers to the parameter management table as the number of receiving terminals decreases. Various parameters are changed to specified values.

In step A17, step A15
Comp received a notification from the Done receiving means 207 at
The completion sending unit 208 sends a completion message notifying that the reception from the receiving terminal that transmitted the done message has been confirmed. In step A18, the completion transmitting means 208 sends a complete message to all receiving terminals.
It is checked whether or not the transmission message has been transmitted, and if the completion message has been transmitted to all the receiving terminals, the communication process ends.

In steps A19, A20, and A22, if the completion message has not been transmitted, it is checked whether the transmission time limit and the maximum number of transmissions of the status request message have been exceeded.
A message is sent. In step A21, if the transmission time limit does not exceed the maximum number of Status Request messages, the Completion transmission unit 203 issues a Status Request message transmission instruction, and based on the notification, sends a Status Request message.
The Status is sent by the Request sending unit 203.
A Request message is sent. Steps A8 and A15 to A21 are repeated until the completion message is transmitted to all the receiving terminals.

Next, the operation of the receiving terminal will be described with reference to FIG. 2, FIG. 5 and FIG. 5 and 6 are flowcharts for explaining the operation of the receiving terminal in FIG. Step B1
In, various parameters are set by the parameter setting / change means 510 at the start of communication processing. Step B
In 2, the Quit sending means 508 checks whether the reception limit time set as a parameter has been exceeded or the Abort receiving means 509 has not received an Abort message from the transmitting terminal.

In step B21, if the reception limit time has elapsed or an Abort message has been received, the Quit sending means 508 sends the Quit message and the communication processing is stopped. Step B
In step 3, when the DTU is received by the DTU receiving unit 502, the normally received DTU is sent to the file restoring unit 501.
The TU loss status confirmation means 504 is notified of the fact.

In step B4, Stat
us Request by the receiving unit 503
If a s Request message is received, the DTU
The loss status confirmation unit 504 is notified of the fact. Sta
If you do not receive a tus Request message,
Steps B2 to B4 are repeated until a Status Request message is received. In steps B5 and B6, in step B4, Status
Request from the request receiving unit 503 to Status Re
The DTU loss status confirming means 504, which has received the request message reception notification, checks whether there is any DTU that has failed to be received.
A random NACK transmission waiting time is set within the range of the ACK transmission waiting time.

In steps B7 and B8, the NACK transmission / reception means 505 monitors the NACK transmitted from another receiving terminal while the DACK transmission status confirmation means 504 elapses the NACK transmission waiting time, and satisfies the response status of itself. It is checked whether or not the NACK is transmitted from another receiving terminal. If the NACK transmission waiting time has elapsed and a NACK satisfying its own response status has been transmitted from another receiving terminal during that time, the NACK transmitting / receiving means 505
As a result, the transmission of the NACK is stopped, and the process proceeds to step B2.

In step B9, if the packet has not been transmitted, the DTU loss status confirming means 504 notifies the NACK transmitting / receiving means 505 of information on NACK.
An ACK is transmitted by the ACK transmitting / receiving means 505.
In step B10, the completion receiving means 507 checks whether or not a completion message has been received. If not,
Move to the process of step B2. Compl if received
The etion message is parsed. Then, the number of connections of the receiving terminals for which communication has been completed is determined by the parameter setting / change means 5.
10 is notified.

In step B11, the parameter setting / change means 510 having received the notification has a parameter management table in which the setting values of various parameters with respect to the number of connections of the receiving terminal are described as in the transmitting terminal. The parameters that have already been set are changed based on the parameter management table according to the number of connections of the receiving terminals that have not completed communication, and the process returns to step B2. In step B12, if there is no DTU for which reception has failed in step B5, the DTU loss status confirmation unit 504 checks whether the end of the path has been reached.

In step B13, if it is not the end of the path, the completion receiving means 507 checks whether or not a completion message has been received. If not, the process proceeds to step B2. If it has been received, the completion message is analyzed, and the number of connections of the receiving terminal with which communication has been completed is notified to the parameter setting / change means 510. In step B14, the parameters that have already been set by the parameter setting / change unit 510 that has been notified are:
It is changed based on the parameter management table according to the number of connections of receiving terminals that have not finished communication, and the process proceeds to step B2.

Thereafter, the above-described processing steps B2 to B14 are repeated until all DTUs have been successfully received. Step B
In step 15, if the end of the path is reached in step B12, the Done sending unit 506 sends a Done message. In step B16, Complete
A check is made to see if a Tion message has been received. If the completion message has not been received, the process proceeds to step B19 described later.

In step B17, Complete
Complete if an ion message has been received
ion message is parsed and Done sent by itself
It is checked whether reception of the message has been confirmed at the transmitting terminal. If the reception has been confirmed, the communication process is terminated.
The Tion message is analyzed, and the number of connections of the receiving terminal with which communication has been completed is notified to the parameter setting / change unit 510. In step B18, the parameter setting / change unit 510 that has received the notification changes the parameters that have already been set based on the parameter management table in accordance with the number of connections of receiving terminals that have not completed communication. Move on to processing.

In step B19, the Quit sending means 508 checks whether the reception limit time has been exceeded or not.
The rt receiving unit 509 checks whether an Abort message has been received from the transmitting terminal. If there is no problem, the process proceeds to step B20. In step B20, the Status Request receiving unit 503 checks whether or not a Status Request message has been received. If the Status Request message has been received, the process proceeds to step B15.

In steps B9, B10, B11 and B12, the processing of steps B15 to B20 is repeated until the completion message confirming the reception of the Done message sent by itself is received. In step B21, Compl
Before receiving the etion message, step B19
When the reception limit time has elapsed, the Quit sending means 508 sends a Quit message, and the communication processing is stopped.

[0051]

As described above, according to the present invention,
Communication with a receiving terminal having a better receiving condition can be completed earlier than a receiving terminal having a poor receiving condition, and the load on the receiving terminal can be reduced. Also, when the number of connections with the receiving terminal at the time of retransmission decreases, the waiting time for NACK becomes shorter, so that the communication time can be shortened as a whole. Further, when the receiving terminal having a better receiving condition is disconnected, the period of the response monitor of the receiving terminal itself is shortened, so that the communication time can be shortened.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing a transmitting terminal according to the present invention.

FIG. 2 is a schematic block diagram showing a receiving terminal according to the present invention.

FIG. 3 is a flowchart illustrating an operation of the transmitting terminal of FIG. 1;

FIG. 4 is a flowchart illustrating an operation of the transmitting terminal of FIG. 1;

FIG. 5 is a flowchart illustrating an operation of the receiving terminal of FIG. 2;

FIG. 6 is a flowchart illustrating an operation of the receiving terminal of FIG. 2;

FIG. 7 is a diagram illustrating a file division method in MFTP.

FIG. 8 is a diagram illustrating transmission of a series of DTUs from a transmitting terminal.

FIG. 9 is a diagram illustrating a delivery response NACK from the receiving terminal.

FIG. 10 is a diagram illustrating retransmission from a transmitting terminal.

FIG. 11 is a diagram illustrating an operation example of delivery confirmation in conventional one-to-many communication.

FIG. 12 is a diagram illustrating a relationship between a transmitting terminal and a plurality of receiving terminals.

FIG. 13 is a diagram illustrating a specific example of a NACK transmission operation.

FIG. 14 shows an MFTP Done message and Com.
It is a figure which shows the specific example of a transmission message transmission operation.

FIG. 15: Abort message of MFTP and Qui
It is a figure which shows the specific example of a t message transmission operation | movement.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... File input part 2 ... One-to-many communication transmission part 3 ... Communication line input / output part 4 ... File input part 5 ... One-to-many communication reception part 6 ... Communication line input / output part 201 ... File division means 202 ... DTU transmission means 203: Status Request sending means 204 ... NACK receiving means 205 ... DTU loss status checking means 206 ... Retransmission schedule generating means 207 ... Done receiving means 208 ... Completion sending means 209 ... Abort sending means 210 ... Quit receiving means 211 ... Parameter setting / change Means 501 File recovery means 502 DTU receiving means 503 Status Request receiving means 504 DTU loss status confirmation means 505 NACK transmitting / receiving means 506 Done sending means 507 Completion receiving means 508 Qu t delivery means 509 ... Abort receiving means 510 ... parameter setting / changing means

Claims (6)

[Claims] 1. A one-to-many communication apparatus for performing transmission acknowledgment by NACK for transmission of a file using DTU as a transmission unit, comprising: a transmitting terminal transmitting a series of the DTUs to a plurality of receiving terminals; And a DTU loss status confirmation unit for confirming the DTU loss status of each of the receiving terminals; and a retransmission schedule for preferentially retransmitting the DTU to the reception terminal having the least DTU loss by the DTU loss status confirmation unit. A one-to-many communication device comprising: a generation unit. 2. A one-to-many communication apparatus which performs NACK confirmation of transmission of a file whose transmission unit is a DTU, comprising: a transmitting terminal transmitting a series of the DTUs to a plurality of receiving terminals; Parameter setting / changing means for setting a waiting time of the NACK to be performed and shortening and changing the waiting time with a decrease in the number of connections of the receiving terminal requesting retransmission to the transmitting terminal; And a Done receiving means for receiving a Done message indicating that the DTU has been successfully received, and providing the parameter setting / change means with information on a decrease in the number of connections of the receiving terminal by receiving the Done message. Characteristic one-to-many communication device. 3. A one-to-many communication apparatus for performing transmission acknowledgment by NACK for transmission of a file using DTU as a transmission unit, comprising: a transmitting terminal transmitting a series of the DTUs to a plurality of receiving terminals; And a DTU loss status confirmation unit for confirming the DTU loss status of each of the receiving terminals; and a retransmission schedule for preferentially retransmitting the DTU to the reception terminal having the least DTU loss by the DTU loss status confirmation unit. A parameter setting / change for setting a waiting time for the NACK received from each of the receiving terminals and shortening the waiting time with a decrease in the number of the receiving terminals requesting retransmission to the transmitting terminal; Means for receiving a Done message indicating that the receiving terminal has successfully received all DTUs, and the Done message Number of connections decrease information of the receiving terminal to the parameter setting / changing unit by receiving a one-to-many communications device, characterized in that it comprises a Ataeraru Done receiving means. 4. A NACK transmitting / receiving means for transmitting a NACK to the transmitting terminal to each receiving terminal and monitoring a NACK response for another receiving terminal for a certain period of time, and terminating communication from the transmitting terminal to the receiving terminal. Co meaning
Complete to receive the completion message
ion receiving means; and parameter setting / changing means for setting and changing the fixed period to be shorter to monitor the response of the NACK in the NACK transmitting / receiving means in response to a decrease in the number of connections of the receiving terminal from the reception of the Completion message. The one-to-many communication device according to claim 2 or 3, wherein 5. The retransmission schedule generating means performs retransmission in accordance with the transmission order of the series of DTUs to a receiving terminal having a similar DTU loss in the DTU loss status checking means. Item 1. The one-to-many communication device according to item 1 or 3. 6. A one-to-many communication method for confirming delivery by NACK for transmission of a file using DTU as a transmission unit, comprising: transmitting and receiving a series of the DTUs from transmission / reception to a plurality of receiving terminals; Receiving a NACK and confirming the DTU loss status of each of the receiving terminals, and the DTU loss status confirming means retransmitting the DTU preferentially to the receiving terminal with the least DTU loss A one-to-many communication method.