JPH11252134A - Broadcast communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To utilize a transmission line efficiently by keeping reliability in the case of applying broadcast communication to a plurality of slave stations. SOLUTION: In this broadcast communication system, a master station 1 sends a data packet including a sequence number to the plurality of slave stations 2 through a transmission line 3 by broadcast communication. When the slave station 2 cannot receive a normal data packet from the master station 1, the slave station 2 sends a packet of negative acknowledgement designating a sequence number of the data packet to the master station 1. Furthermore, upon the receipt of the packet of the negative acknowledgement, the master station 1 sends the data packet with the sequence number designated by the negative acknowledgement packet through broadcast communication. Furthermore, the slave station 2 is provided with a function that returns an affirmative acknowledgement packet to designate a sequence number next to that of a finally received data packet within a prescribed time of a degree to receive plural data packets to the master station 1 to allow the master station 1 to confirm the reception.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadcast communication system for simultaneously transmitting data from one master station to a plurality of slave stations in a computer network.

[0002]

2. Description of the Related Art In a computer network, a master station may broadcast a plurality of slave stations connected to the network simultaneously. By the way, in a connectionless type protocol such as UDP, since a master station only broadcasts a data packet unilaterally to a slave station, it is not guaranteed whether or not the data packet has arrived.

On the other hand, when high reliability is required for data transmission, in order to guarantee the arrival of a data packet,
At present, each time a data packet is normally received, an acknowledgment packet is returned from the slave station to the master station.

[0004]

If the technique of returning an acknowledgment packet for each data packet from the slave station to the master station as described above is employed, the reliability of data transmission is improved, but one of the broadcasting methods is used. Since the number of acknowledgment packets corresponding to the number of slave stations to the data packet passes through the transmission path at the same time, the acknowledgment packets collide on the transmission path and the load concentrates on the master station that processes the acknowledgment. The problem arises.

In order to reduce collision of acknowledgment packets and load concentration at the master station, it is conceivable to shift the timing of returning acknowledgment packets for each slave station.
The acknowledgment packet still occupies most of the traffic on the transmission path, which causes a problem that the transmission efficiency is reduced. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for transmitting data to a plurality of slave stations from a master station by broadcast communication while preventing loss of reliability while preventing data loss. It is an object of the present invention to provide a broadcast communication system in which a transmission line is used efficiently by suppressing a large increase in the number of transmission lines.

[0006]

According to the first aspect of the present invention, there is provided a broadcast communication system for transmitting a data packet including a sequence number by broadcast from a master station to a plurality of slave stations in a computer network, When the slave station cannot receive a normal data packet from the master station, the slave station has a function of returning a negative acknowledgment packet specifying the sequence number of the data packet to the master station. A function to retransmit the data packet of the sequence number specified by the packet by broadcast is provided.Furthermore, the next sequence number of the data packet last received at a fixed time interval such that the slave station receives a plurality of data packets is provided. It has a function to return the specified acknowledgment packet and make the main station confirm receipt. A.

According to a second aspect of the present invention, there is provided a broadcast communication system for transmitting a data packet including a sequence number by broadcast from a master station to a plurality of slave stations in a computer network. If a negative data packet cannot be received, a function of returning a negative response packet designating the sequence number of the data packet to the main station is provided, and when the main station receives a negative response packet, the sequence specified by the packet is received. A function to retransmit the data packet of the number by broadcasting is provided.Every time the slave station receives the specified number of normal data packets, it returns an acknowledgment packet specifying the next sequence number of the last received data packet. Then, the main station has a function of confirming reception.

According to a third aspect of the present invention, there is provided a broadcast communication system for transmitting a data packet including a sequence number by broadcast from a master station to a plurality of slave stations in a computer network. If a negative data packet cannot be received, a function of returning a negative response packet designating the sequence number of the data packet to the main station is provided, and when the main station receives a negative response packet, the sequence specified by the packet is received. A function of retransmitting the data packet of the number by broadcasting is provided, and further, the master station has a function of transmitting a data packet requesting the slave station to return an acknowledgment packet. It has a function to return the packet of the acknowledgment in response to the request and to make the master station confirm the reception. It is.

According to a fourth aspect of the present invention, in the first to third aspects of the present invention, when there is a slave station that does not return an acknowledgment packet to the master station, a packet requesting the slave station to return an acknowledgment packet. Is provided repeatedly up to a specified number of times, and a function is provided in which a response packet of an acknowledgment is returned in response to a packet requesting an acknowledgment to the slave station, and the master station confirms reception.

[0010]

(Embodiment 1) As shown in FIG. 1, a plurality of slave stations 2 are connected to one master station 1 via a transmission line 3. Since the present invention has a feature in broadcast communication, a case where broadcast is performed from the master station 1 to a plurality of slave stations 2 will be described.

In the present embodiment, a data packet to which a sequence number is added is transmitted from the master station 1 to the transmission line 3, and the slave station 2 recognizes the order of the data packets according to the sequence number and restores the original data. Specifically, as shown in FIG. 2, the master station 1 starts transmitting actual data before starting transmission.
A start request packet for notifying the type and size of data to be transmitted is transmitted to the signal line 3 by broadcast communication. As shown in FIG. 3A, the format of the packet of the start request is such that the packet type PT indicating the type of the packet, the data type DT, and the data size DS are connected. On the other hand, the slave station 2 returns an acknowledgment packet with the sequence number being 1 (hereinafter referred to as an ACK packet). In FIG. 2, the names indicating the types of packets (start request, data, ACK, NA
A number in parentheses is shown after K), and this number indicates a sequence number. The format of the ACK packet is such that the packet type PT and the sequence number SN are linked as shown in FIG. The packet type PT will be described later.

As described above, when the master station 1 sends a start request packet and receives an ACK packet from the slave station 2, broadcast of a packet including actual data is started. As shown in FIG. 3B, a data packet (hereinafter, referred to as a data packet) has a format in which a packet type PT, a sequence number SN, an operation code OP, a data length DL, and data DA are concatenated. The operation code OP is assigned a numerical value of 0, 1, or 2 depending on whether it is normal data, requests the slave station 2 to return an ACK packet, or the last data. In the present embodiment, the ACK packet Is not used. In addition, master station 1
The sequence number of the data packet from the base station 2 matches the sequence number of the packet returned from the slave station 2. That is, the data packet with the sequence number 1 is transmitted from the master station 1 in response to the ACK packet with the sequence number 1 from the slave station 2.

In the slave station 2, A having a sequence number of 1
A timer interrupt is generated internally at regular time intervals after the CK packet is returned to the master station 1. This fixed time,
The time is set such that a plurality of packets are transmitted from the master station 1 to the slave station 2. The slave station 2 transmits an ACK packet to the master station 1 every time a timer interrupt occurs. In the present embodiment, instead of returning an ACK packet from the slave station 2 for each data packet from the master station 1,
The fixed time is set so that ACK packets are returned for a plurality of data packets.

On the other hand, when a reception error occurs in the slave station 2,
In other words, if there is an error in the header constituting the data packet, or if the sequence number of the received data packet is not continuous with the sequence number of the data packet received immediately before, the slave station 2 A negative acknowledgment packet (hereinafter, referred to as a NAK packet) specifying a sequence number for requesting retransmission is transmitted. In the example shown in FIG. 2, a reception error has occurred in the slave station 2 with respect to the data packet having the sequence number 2, and the slave station 2 returns a NAK packet having the sequence number 2 to the master station 1. The NAK packet has the same format as the ACK packet, and has a packet type PT as shown in FIG.
And a sequence number SN.

When the master station 1 receives a NAK packet specifying a sequence number from the slave station 2, it retransmits the data packet of the specified sequence number by broadcasting. Here, since the retransmitted data packet is transmitted by broadcasting, it is also transmitted to another slave station 2 in which no reception error has occurred, but the other slave station 2 receives the data packet of the sequence number once normally received. Is received again, the data packet is discarded.

As described above, the slave station 2 generates a timer interrupt every time a predetermined time elapses, and transmits an ACK packet to the master station 1. The ACK packet has a sequence number that is the sequence number next to the sequence number of the data packet received from the master station 1. In other words, the ACK packet specifies a sequence number to be received by the slave station 2 next, and notifies that the sequence number immediately before the specified number has been successfully received. In the illustrated example, an ACK packet having a sequence number of 6 is returned to indicate that a data packet having a sequence number of 5 is normally received. On the other hand, the master station 1 has a sequence number of 6
Is transmitted to the slave station 2.

When the last data packet (the operation code OP indicates the last data) is transmitted from the master station 1 to the slave station 2, the slave station 2 returns an ACK packet, at which point the data transmission ends. . The packet type PT described above
Is represented by a numerical value from 0 to 4, where 0 is set for the start request packet, 1 for the data packet, 2 for the ACK packet, 3 for the NAK packet, and 4 for the survival confirmation packet. Here, the survival confirmation packet has a format of only the packet type PT as shown in FIG. 3E, and is used to confirm whether or not the slave station 2 can respond. However, it is irrelevant to the operation of the present embodiment.

In order to realize the above operation, the slave station 2 operates according to the procedure shown in FIG. That is, when a data packet is received or a timer interrupt occurs (S1), it is first determined whether the packet is a data packet or a timer interrupt (S1).
2) If it is a data packet, it is first determined whether there is a normal or a reception error (S3), and if it is a normal data packet, data packets from the main station 1 are sequentially received up to the last packet (S4). When the last packet is received, AC
The K packet is returned to the master station 1 (S5). When a timer interrupt occurs in the process of receiving a data packet (S2), an ACK packet specifying a sequence number to be received next is returned to the master station 1 as described above (S2).
6). Here, if there is a slave station 2 that does not return an ACK packet, the master station 1 determines that the slave station 2 cannot communicate.

On the other hand, if the received data packet is not normal, a NAK packet is returned to the main station 1 (S7).
As described above, a data packet is not normal when there is an error in the header constituting the data packet and when the sequence number of the received data packet is not continuous with the sequence number of the data packet received immediately before. There is. If there is an error in the header of the data packet, the slave station 2 requests the master station 1 to retransmit the packet. If the sequence numbers are discontinuous, the slave station 2 determines that the data packet has been missed and receives it. It requests the main station 1 to retransmit the leaked data packet. When retransmission of a data packet is requested by a NAK packet, the main station 1 retransmits a data packet having a sequence number that matches the sequence number of the NAK packet.

(Embodiment 2) In Embodiment 1, following the start request packet from the master station 1, the slave station 2
After returning the K packet, the slave station 2 generates a timer interrupt at regular intervals and returns an ACK packet to the master station 1. In the present embodiment, a certain number of normal data packets are transmitted from the master station 1 to the slave station 2. The ACK packet is returned from the slave station 2 to the master station 1 each time it is received.

That is, in the example shown in FIG. 5, an example is shown in which the slave station 2 returns an ACK packet when it receives five normal data packets (after the slave station 2 receives a data packet having a sequence number of 5), ACK packets with a sequence number of 6 from 2 are transmitted). Therefore, in the example shown in FIG. 5, an ACK packet is returned each time a normal data packet whose sequence number is a multiple of 5 is received.

The processing procedure in the slave station 2 is as shown in FIG.
That is, when a data packet is received (S1), it is first determined whether or not the packet is a normal data packet (S2). It is determined whether it is less than 5 times in the example of 5) (S3). If the number of received packets is less than the specified number, the number of received packets is incremented (S4), and data packets from the main station 1 are sequentially received up to the last packet (S5). When the final packet is received, an ACK packet is returned to the master station 1 (S6).

On the other hand, if the received data packet is not normal, a NAK packet is returned to the main station 1 (S7).
If the number of received packets is equal to or more than the specified number (S
3) Return an ACK packet to the main station 1 (S8), and return the number of received packets to 0 (S9). Here, if there is a slave station 2 that does not return an ACK packet, the master station 1 determines that the slave station 2 is in a state where communication is impossible.

This embodiment is different from the first embodiment in that A
It is not necessary to have a timer function for managing the transmission timing of the CK packet, and it is only necessary to determine whether or not to return the ACK packet by referring only to the sequence number of the packet. Can be. Other configurations and operations are the same as those of the first embodiment. (Embodiment 3) In the present embodiment, the master station 1 requests the slave station 2 to return an ACK packet. This request indicates the operation code OP of the data packet to the slave station 2 as an ACK request (having a numerical value of 1). That is, as shown in FIG. 7, if the operation code OP is an ACK request in a data packet with a sequence number of 5, an ACK packet with a sequence number of 6 is returned from the slave station 2 to the master station 1 and responds to this. The master station 1 transmits a data packet having the sequence number 6 to the slave station 2.

The processing procedure in the slave station 2 is as shown in FIG.
That is, when a data packet is received (S1), it is first determined whether or not the packet is a normal data packet (S2). If the packet is a normal data packet, it is determined whether or not the operation code OP is an ACK request (S3). ). If it is not an ACK request, data packets from the master station 1 are sequentially received up to the last packet (S4). When the last packet is received, AC
The K packet is returned to the master station 1 (S5).

On the other hand, if the received data packet is not normal, a NAK packet is returned to the main station 1 (S6).
If the data packet is an ACK request (S3),
An ACK packet is returned to the master station 1 (S7). In the present embodiment, since it is not necessary to have a timer function for managing the transmission timing of the ACK packet as in the first embodiment, the present embodiment can be applied even when the slave station 2 has a low function.
Since the timing at which a packet is returned can be controlled by the main station 1, the application at the main station 1 can be flexibly created.

In each of the above-described embodiments, if there is a slave station 2 that does not return an ACK packet at a timing at which the slave station 2 should return an ACK packet to the master station 1, the existence check packet (FIG. 3 (e) ) May be transmitted.
The survival confirmation packet confirms from the master station 1 whether or not the slave station 2 can respond.
Return K packet. Therefore, if there is no response to the survival confirmation packet and the survival confirmation packet is repeatedly transmitted a specified number of times (the number of retries), the reliability of the reception confirmation can be improved.

[0028]

According to the first aspect of the present invention, there is provided a broadcast communication system for transmitting a data packet including a sequence number by broadcast from a master station to a plurality of slave stations in a computer network. A function to return a negative acknowledgment packet designating the sequence number of the data packet to the master station when a normal data packet cannot be received from the master station is provided. Acknowledgment that specifies the next sequence number of the last received data packet at regular intervals such that the slave station receives a plurality of data packets, and a function of retransmitting the data packet of the received sequence number by broadcast. Has the function of returning the packet of When transmitting multiple data packets simultaneously to the station, the acknowledgment packet is transmitted through the transmission line when multiple data packets are transmitted. Then, there is an advantage that the traffic on the transmission path can be reduced and the transmission efficiency can be increased. Moreover, if the data packet is not normal, it is possible to recover the reception error by retransmitting the data packet,
Since an acknowledgment packet is generated for a plurality of data packets, reception confirmation can be performed, and as a result, communication reliability is not impaired.

According to a second aspect of the present invention, there is provided a broadcast communication system for transmitting a data packet including a sequence number from a master station in a computer network to a plurality of slave stations by broadcast communication. If a negative data packet cannot be received, a function of returning a negative response packet designating the sequence number of the data packet to the main station is provided, and when the main station receives a negative response packet, the sequence specified by the packet is received. A function to retransmit the data packet of the number by broadcasting is provided.Every time the slave station receives the specified number of normal data packets, it returns an acknowledgment packet specifying the next sequence number of the last received data packet. And has the function of causing the master station to perform reception confirmation. It is possible to obtain the same effect as when compared to the invention of claim 1 because the timer function is not necessary, the processing of the slave station is simplified.

According to a third aspect of the present invention, there is provided a broadcast communication system for transmitting a data packet including a sequence number from a master station in a computer network to a plurality of slave stations by broadcast communication. If a negative data packet cannot be received, a function of returning a negative response packet designating the sequence number of the data packet to the main station is provided, and when the main station receives a negative response packet, the sequence specified by the packet is received. A function of retransmitting the data packet of the number by broadcasting is provided, and further, the master station has a function of transmitting a data packet requesting the slave station to return an acknowledgment packet. It has a function to return the packet of the acknowledgment in response to the request and to make the master station confirm the reception. When transmitting data to a plurality of slave stations simultaneously, an acknowledgment packet is returned from the slave station only when the master station requests the slave station. As compared with the above, there is an advantage that the traffic on the transmission path can be reduced and the transmission efficiency can be increased. In addition, if the data packet is not normal, it is possible to recover the reception error by retransmitting the data packet and, if necessary, confirm the reception because an acknowledgment packet is generated. Does not impair. In addition, since an acknowledgment packet is returned from the slave station at the timing determined by the master station, an acknowledgment packet can be requested according to the operation of the master station, and the flexibility of the application program in the master station increases. .

According to the present invention, when there is a slave station that does not return an acknowledgment packet to the master station, a function of repeatedly requesting the slave station to return an acknowledgment packet to the slave station up to a specified number of times. And a function of responding to a packet requesting an acknowledgment to the slave station and returning a packet of the acknowledgment to allow the master station to confirm receipt of the packet will surely detect whether the slave station can communicate. It becomes possible.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of the present invention.

FIG. 2 is an operation explanatory diagram showing a data flow according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a format of a packet used in the embodiment.

FIG. 4 is an operation explanatory diagram showing a processing procedure of a slave station according to the first embodiment.

FIG. 5 is an operation explanatory diagram showing a data flow according to the second embodiment of the present invention.

FIG. 6 is an operation explanatory diagram showing a processing procedure of the slave station according to the first embodiment;

FIG. 7 is an operation explanatory diagram showing a data flow according to the third embodiment of the present invention.

FIG. 8 is an operation explanatory diagram showing a processing procedure of the slave station according to the first embodiment;

[Explanation of symbols]

 1 master station 2 slave station 3 transmission line

Claims (4)

[Claims] 1. A broadcast communication system for transmitting a data packet including a sequence number by broadcast from a master station to a plurality of slave stations in a computer network, wherein the slave station receives a normal data packet from the master station. When the master station receives the negative acknowledgment packet, it has a function to return a negative acknowledgment packet specifying the sequence number of the data packet to the master station. Has a function of retransmitting the data packet by broadcasting, and further, the slave station returns an acknowledgment packet designating the next sequence number of the last received data packet at regular intervals of a plurality of data packets. A broadcast communication system having a function of causing the master station to perform reception confirmation. 2. A broadcast communication system for transmitting a data packet including a sequence number by broadcast from a master station to a plurality of slave stations in a computer network, wherein the slave station receives a normal data packet from the master station. When the master station receives the negative acknowledgment packet, it has a function to return a negative acknowledgment packet specifying the sequence number of the data packet to the master station. The slave station returns a positive response packet specifying the next sequence number of the last received data packet each time it receives a specified number of normal data packets. A broadcast communication system having a function of making a station confirm reception. 3. A broadcast communication system for transmitting a data packet including a sequence number by broadcast from a master station to a plurality of slave stations in a computer network, wherein the slave station receives a normal data packet from the master station. When the master station receives the negative acknowledgment packet, it has a function to return a negative acknowledgment packet specifying the sequence number of the data packet to the master station. The master station has a function of transmitting a data packet requesting the slave station to return an acknowledgment packet, and the slave station responds to the acknowledgment packet return request. Characterized by having a function of returning an acknowledgment packet and allowing the master station to confirm reception. Communications system. 4. The master station has a function of repeatedly requesting a slave station to return a packet of an acknowledgment packet up to a specified number of times when there is a slave station that does not return an acknowledgment packet. 4. A broadcast as claimed in claim 1, wherein said broadcast receiver has a function of responding to a packet requesting an acknowledgment and returning a packet of the acknowledgment to allow the master station to confirm reception. Communications system.