JP2002199012A - Receiver terminal, transmitter terminal and information retransmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a receiver terminal, a transmitter terminal and an information retransmission system, with which the processing load of the transmitter terminal can be reduced by retransmitting information only to a part of the receiver terminals that can not accurately receive the information in the case the part of the receiving terminals can not receive the accurate information in IP compliant multi-address communication. SOLUTION: This information retransmission system consists of the receiving terminals that return a NAK(negative acknowledge character) to the transmitting terminal to urge the transmitting terminal to retransmit a packet received by the multi-address communication in the case of analyzing the packet and detecting that the packet is not normally received, and return an ACK(acknowledge character) to the transmitting terminal in the case of detecting that the packet which can not be normally received in the multi- address communication is normally received, and the transmitting terminal which retransmits a packet corresponding to the prescribed number of NAKs only to the receiving terminals that have returned the NAKs in the case of receiving the NAKs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IP (Internet P
(rotocol), when some receiving terminals could not receive the correct information in the broadcast based on the information, the information can be retransmitted only to the receiving terminal that could not receive correctly,
The present invention relates to an information retransmission method capable of reducing a processing load on a transmission terminal.

Broadcasting to which the multicast system is applied is widely performed not only in social systems such as disaster prevention command systems, police command systems, and fire command systems, but also in company premises communication systems. It is necessary that accurate information be transmitted to all receiving terminals. That is, high QoS (Quality of Se
rvice) is required.

In particular, since the disaster prevention command system, police command system, fire command system, and the like are systems for protecting the security of society and the safety of people's lives, higher QoS is required.
Is required.

[0004] In recent years, there has been a remarkable spread of IP-based communication, and it is inevitable to use IP in disaster prevention command systems, police command systems, firefighting command systems, and the like. And even if it is IP, disaster prevention command system,
It is necessary to keep the QoS of the police command system and the fire command system high.

[0005]

2. Description of the Related Art Currently, when performing multicast communication to which a multicast method is applied in an IP network, a normal UDP is used.
(User Datagram Protocol) to transfer information.

In addition, TCP (Transmission Control Proto)
col), a normal reception completion signal (hereinafter referred to as “A
CK ". ) Is returned, and retransmission is performed when ACK is not returned.

[0007]

FIG. 10 is a diagram (part 1) for explaining a problem of the prior art, which shows a problem in broadcast communication by UDP. FIG. 10 is based on the assumption that a single transmitting terminal logically broadcasts to three receiving terminals.
The form of the communication network accommodating one receiving terminal is arbitrary.

[0008] Information to be transmitted is digitized, packetized and transferred. That is, the information to be transmitted is divided into a plurality of packets, such as packet # 1, packet # 2, packet # 3,... Shown in FIG. 10, and is sequentially transferred to each receiving terminal.

In FIG. 10, packet # 1 is correctly transmitted to receiving terminal # 1 and receiving terminal # 3, not correctly transmitted to receiving terminal # 2, and packet # 2 is transmitted to receiving terminal # 1. Is correctly transmitted to the receiving terminal # 2, and the receiving terminal # 3
Shows an example that is not transmitted accurately. Generally, the cause of inaccurate transmission is a transmission error and discarding of a packet due to congestion in a link constituting a communication network.

The information to be transmitted is packet #
1, packet # 2, packet # 3,..., Receiving terminal # 2 could not correctly receive packet # 1, and receiving terminal # 3 could not correctly receive packet # 2. Not receiving accurate information.

However, UDP does not have a function of transferring an ACK relating to a received packet. For this reason, the transmitting terminal cannot know whether or not the information to be transmitted has been correctly transmitted, and cannot respond at all even if the information cannot be transmitted accurately. That is, there is no guarantee of QoS.

FIG. 11 is a diagram (part 2) for explaining a problem of the conventional technique, and shows a problem of a method of performing retransmission by ACK control. FIG. 11 also assumes a logical broadcast communication between a single transmitting terminal and three receiving terminals.

The information to be transmitted is digitized, packetized and transmitted. That is, the information to be transmitted is packet # 1, packet # 2,.
The packet is divided into a plurality of packets and sequentially transferred to each receiving terminal. Each time a packet is transferred, the receiving terminal returns an ACK to the transmitting terminal. If a timeout occurs without returning an ACK from any of the receiving terminals even after waiting for a predetermined time, the transmitting terminal returns the ACK to the transmitting terminal. Retransmit the packet.

In FIG. 10, packet # 1 is correctly transmitted to receiving terminal # 1 and receiving terminal # 3, but not accurately transmitted to receiving terminal # 2. The example which is correctly transferred to the terminal is shown. That is,
Receiving terminal # 2 cannot receive accurate information because packet # 1 could not be received correctly.

However, in this method, if even one receiving terminal does not return an ACK, the packet is retransmitted to all receiving terminals by the broadcast method. Therefore, (1) the retransmission packet is also transferred to the receiving terminal that can normally receive, so that the receiving processing load on the receiving terminal that can receive normally increases.

(2) Since it is normal to be able to receive data normally, the transmitting terminal must receive a large number of ACKs, and the ACK processing load on the transmitting terminal increases.

(3) If the ACK processing load on the transmitting terminal increases, there is a possibility that the packet of the information to be transmitted cannot be transferred continuously, and a specific link is congested by the ACK. As a result, the packet of information to be transmitted may not be transferred continuously. The problem is caused.

In view of the above problems, the present invention retransmits information only to a receiving terminal that failed to receive the correct information when some of the receiving terminals could not receive the correct information in the IP-based broadcast. It is therefore an object of the present invention to provide an information retransmission method capable of reducing the processing load on the transmitting terminal.

[0019]

According to a first aspect of the present invention, a packet received by broadcast is analyzed, and when it is detected that the packet is not normally received, an abnormal reception signal (NAK) is generated. The packet is returned to the transmitting terminal to urge retransmission of the packet, and a normal reception completion signal (ACK) is returned to the transmitting terminal when it is detected that the packet which has not been received normally in the broadcast is received normally by retransmission. The receiving terminal.

According to the first aspect, the receiving terminal analyzes the packet received by the broadcast communication, and returns a NAK to the transmitting terminal when detecting that the packet is not normally received. The retransmission of the packet is promoted, and when it is detected that the packet which was not received normally by the broadcast is normally received by the retransmission, the normal reception completion signal (AC
K) is returned to the transmitting terminal.

Therefore, the receiving terminal returns NAK only when the packet by the broadcast cannot be normally received,
Since the ACK may be returned when the retransmission packet is normally received, the load on the receiving terminal for returning the NAK or the ACK is reduced.

Also, since the number of returned NAKs or ACKs is reduced, the processing load on the transmitting terminal is reduced, and the possibility that a specific link is congested by the returned NAKs or ACKs is also reduced.

According to the second invention, when a predetermined number of NAKs are received, only the receiving terminal that has returned the NAKs receives the NAKs.
This is a transmitting terminal that retransmits a packet corresponding to AK.

According to the second aspect, when the transmitting terminal receives a predetermined number of NAKs, the transmitting terminal retransmits the packet corresponding to the NAK only to the receiving terminal that has returned the NAK.

Therefore, generally, the load of the retransmission process at the transmitting terminal is reduced, and the load of the NAK or ACK reception process is also reduced.

According to a third aspect of the present invention, the packet received by the broadcast is analyzed, and when it is detected that the packet is not normally received, the NAK is returned to the transmitting terminal to prompt retransmission of the packet. If it is detected that a packet that has not been received normally in broadcast
A receiving terminal that returns the CK to the transmitting terminal, and a predetermined number of NAKs
This is an information retransmission method in a communication network constituted by only a receiving terminal that has returned the NAK when receiving the NAK and a transmitting terminal that retransmits a packet corresponding to the NAK.

According to the third aspect, the receiving terminal analyzes the packet received by the broadcast communication, and returns a NAK to the transmitting terminal when detecting that the packet is not normally received. It prompts retransmission of the packet and returns a normal reception completion signal ACK to the transmitting terminal when it detects that the packet which was not received normally by the broadcast is normally received, and the transmitting terminal transmits a predetermined number of NAKs. When receiving, the NAK is returned only to the receiving terminal that has returned the NAK.
Is retransmitted.

Therefore, the receiving terminal returns a NAK only when a packet by broadcast cannot be normally received,
Since the ACK may be returned when the retransmission packet is normally received, the load on the receiving terminal for returning the NAK or the ACK is reduced.

Also, since the number of returned NAKs or ACKs is reduced, the processing load on the transmitting terminal is reduced, and the possibility that a specific link is congested by the returned NAKs or ACKs is also reduced.

Further, the load of the retransmission processing on the transmitting terminal is generally reduced.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the technology of the present invention will be described below with reference to a configuration diagram of a transmitting terminal and a receiving terminal, and a flowchart showing processing contents and procedures of the transmitting terminal and the receiving terminal. The configuration of the transmitting terminal and the receiving terminal is based on a disaster prevention command system, a police command system, or a fire command command system. However, there is essentially no difference in a local communication system or the like.

FIG. 1 shows the configuration of a receiving terminal, and also shows a speaker that outputs a command by voice.

In FIG. 1, 1 is an input / output port for receiving an IP packet and transmitting a NAK or ACK,
A received information storage database for storing received packets and sequence numbers of the packets (in the figure, "reception information storage DB"; hereinafter, "database" is abbreviated as "DB" in the figure), 3 Performs a detection of a missing sequence number of a received packet or a checksum error of a received packet with reference to the received information storage database 2 and a predetermined timer when a missing of a sequence number or a checksum error is detected. A packet error detection circuit for setting a value (in the figure, it is described as “packet error detection circuit” but is the same);
Reference numeral 4 denotes a packet reception processing circuit for receiving and processing a packet in which the packet error detection circuit 3 has not detected a checksum error and converting the packet into voice (analog data). A timer for setting a timer value of NAK 6 is a NAK for generating and transmitting a NAK with reference to the timer value of timer 5
In the transmitting circuit, a receiving terminal is configured by the above components.

Reference numeral 7 denotes a speaker that outputs a command by voice. Although FIG. 1 shows only a speaker as a means for outputting command information, it is also possible to output image information by a facsimile, a photo transmission device, or the like. The essence of the invention remains the same.

FIG. 2 shows the configuration of the transmitting terminal, and also shows a microphone and a keyboard for commanding.

In FIG. 2, reference numeral 11 denotes a packet generation circuit for converting input audio (analog data) into digital data to make a packet, and 12 denotes transmission information for storing the packet generated by the packet generation circuit 11. A storage database 13 is a packet transmission circuit that forms and transmits a frame by adding a required header to the packet output by the packet generation circuit 11. An input / output port 14 that transmits the packet and receives a NAK or ACK , 15
Analyzes the received packet and, if it is a NAK, reports the number of received NAKs to the IP of the receiving terminal that returned the NAK.
A NAK reception counter 17 holds a packet number corresponding to the NAK, and a code conversion circuit 17 converts a code input from the keyboard into an internal source code. A code analysis that analyzes the internal source code that is output by the PID and issues a transmission instruction to the packet transmission circuit 13 if the code is a transmission instruction, and outputs a retransmission processing start instruction if the code is a transmission end code Circuit 19 is a code analysis circuit 1
The retransmission control circuit 20 performs a retransmission process by referring to the NAK reception counter 16 when receiving the instruction of No. 8, and reads a packet to be retransmitted from the transmission information storage database 12 according to the instruction of the retransmission control circuit 19, and performs a packet transmission circuit operation. 13 and decrements the count value of the NAK reception counter 16 and erases the sequence number of the retransmitted packet (in the figure, this is the same as the "storage information reading circuit", although it is labeled "storage information reading circuit"). .)
Thus, a transmitting terminal is configured by the above components.

Reference numeral 21 denotes a microphone for inputting command information by voice, and reference numeral 22 denotes a keyboard for inputting a code for controlling a transmitting terminal by a maintenance person. Although only a microphone is shown in FIG. 2 as a means for inputting command information, image information can be input by a facsimile or a photograph transmission device, and when these image communication terminals are connected. However, the essence of the present invention remains unchanged.

FIG. 3 is a diagram for explaining the technique of the present invention, assuming a logical communication performed between a single transmitting terminal and three receiving terminals. It is not restricted to the form of the communication network accommodating three receiving terminals.

The transmitting terminal sequentially transmits (broadcasts) packets forming information to be transmitted by a multicast method.

FIG. 9 shows the structure of a communication frame. In the case of broadcast communication, the structure shown in FIG. 9A, that is, a frame in which an RTP header, a UDP header and an IP header are added to transmission information is used. .

In the example of FIG. 3, packet # 1 is normally received by receiving terminal # 1 and receiving terminal # 3, and is received by receiving terminal # 2.
Assumes that a checksum error has been detected, and assumes that packet # 2 was successfully received by receiving terminal # 1 and receiving terminal # 2 and could not be received by receiving terminal # 3 due to discard. It is assumed that all the receiving terminals normally receive the packet # 3 and thereafter.

Receiving terminal # 2 detects NAK immediately upon detecting a checksum error in received packet # 1.
Is returned to the transmitting terminal.

Upon detecting that the packet # 2 is missing, the receiving terminal # 3 starts a timer, and when a predetermined time has elapsed, the receiving terminal # 3 discards the packet and sends a NAK to the transmitting terminal. I will send it back.

On the other hand, the transmitting terminal transmits the NAK from the receiving terminal.
Each time the NAK is received, the number of received NAKs is counted and stored for each IP address of the receiving terminal that has returned the NAK, and the packet number corresponding to the NAK is stored.

When the broadcast is completed, the transmitting terminal transfers the packets that have not been transferred normally to each receiving terminal in a single-cast system when the total number of received NAKs is equal to or more than a predetermined value. In the example of FIG. 3, the packet # 1 is transferred to the receiving terminal # 2, and the packet # 2 is transferred to the receiving terminal # 3 by the single cast method.

In this case, the frame shown in FIG. 9B, that is, the RTP header and the TCP header (Tr
Transmission is performed using a frame to which an Ansmission Control Protocol is added.

Then, the receiving terminal receiving the packet which could not be normally received in the broadcast communication by the single-cast system analyzes the received packet again, and returns ACK and returns all ACKs if the packet was successfully received. The communication processing ends. In the example of FIG. 3, receiving terminal # 2 returns an ACK when packet # 1 is normally received, and receiving terminal # 3 returns an ACK when packet # 2 is normally received.

As described above, the receiving terminal analyzes the packet received by the broadcast, returns the NAK to the transmitting terminal only when it detects that the packet is not normally received, and retransmits the packet. In response to the prompt, when it is detected that a packet that has not been normally received in the broadcast communication has been normally received by single-cast retransmission, an ACK is returned to the transmitting terminal.

Therefore, the receiving terminal returns NAK only when the packet by the broadcast cannot be normally received,
Since the ACK may be returned when the retransmission packet is normally received, the load on the receiving terminal for returning the NAK or the ACK is reduced.

Further, since the number of returned NAKs or ACKs is reduced, the processing load on the transmitting terminal is reduced, and the possibility that a specific link is congested by the returned NAKs or ACKs is also reduced.

On the other hand, when receiving the predetermined number of NAKs, the transmitting terminal retransmits the packet corresponding to the NAK by single-cast only to the receiving terminal that has returned the NAK.

Therefore, generally, the load of the retransmission process at the transmitting terminal is reduced, and the load of the NAK or ACK reception process is also reduced.

The NA returned from the transmitting terminal
The packet corresponding to the NAK is retransmitted when the number of K becomes equal to or more than a predetermined value. In the case of a command by voice, the command content can be understood even if there is some packet loss or checksum error. On the other hand, in the case of a command that includes data, the NAK is always received when a NAK is received because the effect of a packet loss or checksum error is large.
This is because the necessity of retransmission differs depending on the means and contents of a command, such as the need to retransmit a packet corresponding to AK.

Hereinafter, the technique of the present invention will be described in more detail with reference to flowcharts.

FIG. 4 is a flowchart (part 1) of an error detection process and a NAK transmission process in the receiving terminal, mainly showing the error detection process.
The flowchart (No. 2) of the error detection process and the NAK transmission process mainly illustrates the NAK transmission process.

Here, before describing the flowcharts shown in FIGS. 4 and 5, the structure of an area for temporarily storing the sequence number of an unreceived frame will be described.

FIG. 6 shows an example of the structure of an area for temporarily storing the sequence numbers of unreceived frames.

In FIG. 6, Y (0) to Y (6) are seven areas for storing sequence numbers of unreceived frames, and Time (0) to Time (6) are Y (0) to Y (6). ) Is set to a predetermined value when stored, and is an area for storing a timer value that is decremented each time a NAK transmission process is performed after a new frame is received.

That is, the sequence number of the unreceived frame detected for the first time is stored in Y (0), and when the sequence number of the unreceived frame is stored in Y (0), Time
In this example, 7 is stored in (0), and the value of Time (0) is decremented each time the NAK transmission processing is performed. When the value of Time (0) becomes 1, the NAK packet is edited and returned to the transmitting terminal. In other words, when a frame that is not expected to be received next to a frame that has already been received is received seven times and an expected frame is not received, the frame is discarded during transfer. And returns a NAK packet.

In the example shown in FIG. 6, since X is an integer of 0 to 6 and seven areas of Y (X) and Time (X) are secured, the number of possible values of X (in this case, 7) and Y
The number (7 in this case) of the regions of (X) and Time (X) are equal. Note that 7 is merely an example.

That is, the number of possible values of the counter X and Y
(X) and Time (X) have the same number of regions, and
7 is merely an example, and the number of possible values of X and the number of areas of Y (X) and Time (X) are not limited to seven.

Now, the flowchart of FIG. 4 will be described.

S1. Initialize counter X (clear to 0)
I do.

S2. Whether the sequence number of the received frame is the expected sequence number, that is, whether the sequence number of the currently received frame is included in the sequence numbers stored in the area for storing the sequence number of the unreceived frame Determine whether or not.

S3. If it is determined in step S2 that the sequence number of the received frame is the expected sequence number (Yes), it means that an unreceived frame has been received, so that the timer is set to 0 and step S2 is performed.
Jump to 13.

S4. If it is determined in step S2 that the sequence number of the received frame is not the expected sequence number (No), the count value of the counter X is incremented.

This is to wait for reception of a frame having the same sequence number as the sequence number of the unreceived frame.

S5. It is determined whether or not the count value of the counter X has reached a predetermined value (here, it is assumed to be 7).

The reason why the predetermined value is set to 7 is that, as described above, if an unreceived frame has not arrived after waiting for the arrival of a frame seven times, it is determined that the unreceived frame has been discarded. It is.

If it is determined that the count value of the counter X has not reached 7 (No), the process jumps to a receiving process (not shown).

S6. If it is determined in step S5 that the count value of the counter X has reached 7 (Yes), it is determined whether a value obtained by adding 1 to the sequence number Z of the immediately preceding frame is the expected sequence number. Is determined.

This determination is made based on whether or not the sequence number of the currently received frame is not the sequence number of the unreceived frame but a value obtained by adding 1 to the sequence number of the frame received immediately before. This is to determine whether or not the frame is expected to be received next to the frame received immediately before.

If it is determined that the value obtained by adding 1 to the number Z of the frame received immediately before is the expected sequence number (Yes), the process jumps to step S12.

S7. If it is determined in step S6 that the value obtained by adding 1 to the sequence number Z of the immediately preceding frame is not the expected sequence number (No),
Since a frame having a number obtained by adding 1 to the sequence number Z of the frame received immediately before has not been received, Z + 1 is stored in the area Y (X ′) holding the number of the unreceived frame.

X 'indicates the number of an empty area located next to the area storing the sequence number of the unreceived frame in FIG.

S8. In order to determine whether or not an unreceived frame is received within a predetermined time, a predetermined value (here, as described above) is assigned to Time (X ′) corresponding to Y (X ′) in which Z + 1 is stored. Is assumed to be 7).

S9. The count value of the counter X 'is incremented.

In this method, the first area in which the sequence number of an unreceived frame is not stored is designated, and the sequence number of the unreceived frame is stored in an incremented area when the next unreceived frame is detected. That's why.

S10. The count value of the counter X ′ is a predetermined value (here, 7 is assumed as in the above).
Is determined.

This means that it is determined whether or not the area for storing the sequence number of the unreceived frame is completely filled.

If it is determined that the count value of the counter X 'has not reached the predetermined value (No), the process proceeds to step S1.
Jump to 2.

S11. In step S10, the counter X '
Is determined to have reached the predetermined value (Ye
In s), the sequence number of the unreceived frame is stored in all seven areas. When the next unreceived frame is detected, the count value of the counter X ′ is overwritten to overwrite the area of Y (0). Is initialized.

S12. The expected sequence number is set for Z.

S13. A checksum error is detected for a packet mounted in the received frame, and it is determined whether the checksum is normal.

S14. If it is determined in step S13 that the checksum is not normal (No), NA
The timer is set to 1 in order to perform the K transmission process.

If it is determined in step S13 that the checksum is normal (Yes), a reception process of the received packet is performed.

After the processing of step S14 and the packet reception processing are completed, the processing shifts to NAK transmission processing.

Next, the flowchart of FIG. 5 will be described.

S21. Initialize the counter X.

S22. It is determined whether or not the value of the timer is 1.

S23. If it is determined in step S22 that the value of the timer is not 1 (No), the value of the timer is decremented, and the process jumps to step S27.

S24. If it is determined in step S22 that the timer value is 1 (Yes), the NA
In order to perform K transmission, edit a packet for transmitting NAK, and S25. Request NAK transmission.

S26. I / O port of receiving terminal is NAK
Send

S27. The count value of the counter X is incremented.

S28. It is determined whether or not the count value of the counter X has reached a predetermined value (here, it is assumed to be 7 in the same manner as described above).

If it is determined that the count value of the counter X has not reached 7 (No), the process jumps to step S22 and repeats the processing of steps S23 to S28.

On the other hand, if it is determined that the count value of the counter X has reached 7 (Yes), the process jumps to a receiving process (not shown).

As described above, the receiving terminal performs the error detection processing and the NAK transmission processing, transmits the NAK immediately when the checksum error is detected, and determines the arrival of the unreceived packet for a predetermined time when detecting the non-reception of the packet. Wait and send NAK when timeout occurs. Accordingly, the receiving terminal analyzes the packet received by the broadcast communication, and when detecting that the packet is not normally received, returns the NAK to the transmitting terminal to prompt retransmission of the packet, and In the broadcast communication, when it is detected that a packet that has not been normally received is normally received, a normal reception completion signal (ACK) is returned to the transmitting terminal.

Therefore, the receiving terminal returns NAK only when the packet by the broadcast cannot be normally received,
Since the ACK may be returned when the retransmission packet is normally received, the load on the receiving terminal for returning the NAK or the ACK is reduced.

Further, since the number of returned NAKs or ACKs is reduced, the processing load on the transmitting terminal is reduced, and the possibility that a specific link is congested by the returned NAKs or ACKs is also reduced.

FIG. 7 is a flowchart of the NAK receiving process in the transmitting terminal. Hereinafter, N along the reference numerals in FIG.
The AK receiving process will be described.

S31. It monitors whether there is a received frame.

If there is no received frame (No), the NAK receiving process is temporarily terminated.

S32. In step S31, when there is a received frame (Yes), it is determined whether or not communication information is being transmitted by broadcast communication.

If the communication information is not being transmitted (No), the NAK receiving process is temporarily terminated.

S33. If it is determined in step S32 that the communication information is being transmitted (Yes), the received frame is analyzed to determine whether the received frame is a NAK.

When the received frame is not NAK (N
In o), the NAK receiving process is temporarily ended.

S34. The IP address of the receiving terminal that has returned the NAK is read.

S35. If it is determined in step S33 that the received frame is a NAK (Yes), the N
It is determined whether or not the IP address of the receiving terminal that has returned the AK is the IP address of the destination receiving terminal of the broadcast communication.

If it is determined that the IP address of the receiving terminal that has returned the NAK is not the IP address of the destination receiving terminal of the broadcast communication (No), the NAK receiving process ends once.

S36. When it is determined in step S35 that the IP address of the receiving terminal that has returned the NAK is the IP address of the destination receiving terminal of the broadcast communication (Yes)
, The NAK reception number is incremented for each return source IP address, and the return source IP address is stored.
The NAK receiving process ends.

FIG. 8 is a flowchart of the retransmission processing in the transmitting terminal. Hereinafter, the retransmission processing will be described along the reference numerals in FIG.

S41. It is determined whether the key code input from the keyboard is a transmission completion code.

When it is determined that the received code is not the transmission completion code (No), the retransmission processing is temporarily terminated.

S42. If it is determined in step S41 that the key code input from the keyboard is the transmission completion code (Yes), it is determined whether the number of NAKs received is equal to or greater than a predetermined threshold.

Not whether or not NAK was received, but N
The determination of whether or not the number of received AKs is equal to or greater than a predetermined threshold value is based on the fact that the influence of the packet loss or the checksum error differs depending on the command means, as described above. If the NAK is received even once, the NA
If it is necessary to retransmit the packet corresponding to K, the threshold may be set to 1.

When the number of received NAKs is less than a predetermined threshold (N
In o), the retransmission processing is once ended.

S43. If it is determined in step S42 that the number of received NAKs is equal to or greater than the predetermined threshold (Yes), the IP address of the receiving terminal that has returned the NAK is read.

S44. IP of receiving terminal that returned NAK
It is determined whether or not the address is the IP address of the destination receiving terminal of the broadcast communication.

When it is determined that the received IP address is not the IP address of the receiving terminal of the broadcast communication (No), the retransmission processing is temporarily ended.

S45. If it is determined in step S44 that the IP address of the receiving terminal that has returned the NAK is the IP address of the destination receiving terminal of the broadcast communication (Yes), a packet of the transmission information to be retransmitted is transmitted from the transmission information storage database. read out.

S46. It requests the packet transmission circuit to transmit the packet, and ends the retransmission processing.

Although not shown in FIG. 8, after step S46, it is determined whether or not the packet has been transmitted to all the receiving terminals that have returned the NAKs. On the other hand, if the transmission of the packet to be retransmitted has not been completed, steps S43 to S46 are performed.
Will be repeated.

As described above, the transmitting terminal performs NAK receiving processing and retransmission processing. Accordingly, when the transmitting terminal receives a predetermined number of NAKs, the transmitting terminal retransmits the packet corresponding to the NAK only to the receiving terminal that has returned the NAK.

Therefore, in general, the load of retransmission processing at the transmitting terminal is reduced, and the load of NAK or ACK reception processing is also reduced.

In the communication system constituted by the transmitting terminal and the receiving terminal, the receiving terminal analyzes the packet received by the broadcast communication, and detects that the packet is not normally received. , Returns a NAK to the transmitting terminal to urge retransmission of the packet, and returns a normal reception completion signal ACK to the transmitting terminal when detecting that a packet that has not been received normally in broadcast is received normally. When the transmitting terminal receives a predetermined number of NAKs, the transmitting terminal transmits the NAK to only the receiving terminal that has returned the NAK.
Is retransmitted.

Therefore, the receiving terminal returns NAK only when the packet by the broadcast cannot be normally received,
Since the ACK may be returned when the retransmission packet is normally received, the load on the receiving terminal for returning the NAK or the ACK is reduced.

Further, since the number of returned NAKs or ACKs is reduced, the processing load on the transmitting terminal is reduced, and the possibility that a specific link is congested by the returned NAKs or ACKs is reduced.

Further, the load of the retransmission processing on the transmitting terminal is generally reduced.

[0130]

As described above in detail, according to the present invention, the IP
If the correct information cannot be received by some receiving terminals in the compliant broadcast communication, the information can be retransmitted only to the receiving terminal that could not receive the information correctly. Everything can be solved.

That is, according to the first invention, the receiving terminal:
The packet received by the broadcast is analyzed, and when it is detected that the packet is not normally received, the NAK is returned to the transmitting terminal to prompt retransmission of the packet, and the packet is normally received by the broadcast. When it is detected that the unsuccessfully received packet has been received normally, a normal reception completion signal (ACK) is returned to the transmitting terminal.

Therefore, the receiving terminal returns NAK only when the packet by the broadcast cannot be normally received,
Since the ACK may be returned when the retransmission packet is normally received, the load on the receiving terminal for returning the NAK or the ACK is reduced.

Further, since the number of returned NAKs or ACKs is reduced, the processing load on the transmitting terminal is reduced, and the possibility that a specific link is congested by the returned NAKs or ACKs is reduced.

According to the second aspect, when the transmitting terminal receives a predetermined number of NAKs, the transmitting terminal retransmits the packet corresponding to the NAK only to the receiving terminal that has returned the NAK.

Therefore, generally, the load of the retransmission process at the transmitting terminal is reduced, and the load of the NAK or ACK reception process is also reduced.

Further, according to the third invention, the receiving terminal comprises:
The packet received by the broadcast is analyzed, and when it is detected that the packet is not normally received, the NAK is returned to the transmitting terminal to prompt retransmission of the packet, and the packet is normally received by the broadcast. When it is detected that the unsuccessfully received packet has been received normally, a normal reception completion signal ACK is returned to the transmitting terminal. When the transmitting terminal receives a predetermined number of NAKs, The N
Retransmit the packet corresponding to AK.

Therefore, the receiving terminal returns NAK only when the packet by the broadcast cannot be normally received,
Since the ACK may be returned when the retransmission packet is normally received, the load on the receiving terminal for returning the NAK or the ACK is reduced.

Also, since the number of returned NAKs or ACKs is reduced, the processing load on the transmitting terminal is reduced, and the possibility that a specific link is congested by the returned NAKs or ACKs is also reduced.

Further, the load of the retransmission processing on the transmitting terminal is generally reduced.

[Brief description of the drawings]

FIG. 1 shows the configuration of a receiving terminal.

FIG. 2 is a configuration of a transmission terminal.

FIG. 3 is a diagram illustrating a technique of the present invention.

FIG. 4 is a flowchart (part 1) of an error detection process and a NAK transmission process.

FIG. 5 is a flowchart (part 2) of an error detection process and a NAK transmission process.

FIG. 6 shows the structure of an area for temporarily storing a sequence number of an unreceived frame.

FIG. 7 is a flowchart of a NAK reception process.

FIG. 8 is a flowchart of a retransmission process.

FIG. 9 is a configuration of a communication frame.

FIG. 10 is a diagram (part 1) for explaining a problem of the conventional technique.

FIG. 11 is a view for explaining a problem of the conventional technique (part 2).

[Explanation of symbols]

Reference Signs List 1 input / output port 2 reception information storage database (reception information storage DB) 3 packet error detection circuit (packet error detection circuit) 4 packet reception processing circuit 5 timer 6 NAK transmission circuit 7 speaker 11 packet generation circuit 12 transmission information storage database ( 13 (transmission information storage DB) 13 packet transmission circuit 14 input / output port 15 received packet preparation circuit 16 NAK reception counter 17 code conversion circuit 18 code analysis circuit 19 retransmission control circuit 20 stored information reading circuit 21 microphone (Mic) 22 key board

Continued on the front page (72) Inventor Akira Karasawa 3-9-1-18 Shin-Yokohama, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture Inside Fujitsu Communication Systems Limited (72) Inventor Yukimasa Yoshida 3-9-1 Shin-Yokohama, Kohoku-ku, Yokohama-shi, Kanagawa No. 18 F-term in Fujitsu Communication Systems Limited (reference) 5K030 GA03 GA12 HA08 HC01 JA05 KA13 LA02 LC08 LD04 LD06

Claims (3)

[Claims] When a packet received by a broadcast is analyzed and it is detected that the packet is not normally received, an abnormal reception signal (NAK) is returned to a transmitting terminal to retransmit the packet. When a normal reception completion signal (AC) is detected when it is detected that a packet that has not been
K) is returned to the transmitting terminal. 2. A transmitting terminal which, when receiving a predetermined number of NAKs, retransmits a packet corresponding to the NAK only to the receiving terminal which has returned the NAK. 3. When the packet received by the broadcast is analyzed and it is detected that the packet is not normally received, the NAK is returned to the transmitting terminal to prompt retransmission of the packet, and the broadcast is transmitted. Then, only when the receiving terminal returns an ACK to the transmitting terminal when it detects that a packet that has not been received normally is received, and only when the receiving terminal has returned a predetermined number of NAKs, An information retransmission method comprising: a transmission terminal that retransmits a packet corresponding to the NAK.