JPH07115431A - Packet retransmission method - Google Patents

Abstract

PURPOSE:To prevent the degradation of traffic by recording the address of the transmission source in the case of a failure of reception in its own communication controller and requesting the packet retransmission to the transmission source, whose address is stored, at the time when this controller can receive packets. CONSTITUTION:If a packet cannot be received because of the busy sate or the like, the coming packet is not erased, and a transmission source address 21 from a packet analysis part 15 is stored in a transmission source address storage part 18. An address conversion part 17 exchanges the destination address and the transmission source address of the received packet to generate address data by address conversion information 20 from the analysis part 15 and sends this address data to a packet correction part 19. When a packet can be received, a packet generating part 12 generates a dummy packet for packet transmission request by a storage address signal 22 of the transmission source address stored in the storage part 18. This packet is selected and transmitted by the data select signal from a transmission control part 14, and then, the packet is retransmitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a case where bursty discontinuous data communication such as file transfer or emergency communication in an emergency is performed between communication control devices of a loop type network, and the receiving side cannot receive the data. The improvement of the packet retransmission method at the time of.

FIG. 4 is a block diagram of an example loop network. As shown in FIG. 4, the loop-type network includes a supervisory controller 10 that performs transmission path frame construction, network clock supply, network state management, fault detection processing, etc., and communication control apparatuses 1, 2 that perform communication.
3 are connected in a loop by transmission lines 5-8.

When emergency communication is performed from the communication control device 1 to the communication control device 2 in the loop type network,
When the communication control device 2 cannot receive due to some reason such as busy, for the purpose of retransmitting a packet, it is possible to provide a packet retransmission method which does not occupy the transmission paths 6 and 7 until the communication control device 2 becomes receivable. Is desired.

[0004]

2. Description of the Related Art FIG. 5 is a block diagram of a conventional communication control device. In FIG. 5, when predetermined data is accumulated in the transmission buffer unit 11 in FIG. 5, a write completion signal 25 is sent to the transmission control unit 14, a transmission permission signal 26 is given from the transmission control unit 14, and a transmission buffer unit is sent. The data is sent from 11 to the read packet generation unit 12 ', and the packet generation unit 12' shows the control unit area, the destination address area, the source address area, the reception status area, the data area, and the check as shown in FIG. Information is inserted into a packet having a packet format composed of areas and sent to the communication control device on the receiving side.

For example, when a packet is sent from the communication control unit 1 of FIG. 4 to the communication control unit 2, the address of the communication control unit 2 is set in the destination address area and the communication control set is set in the source address area of the packet format. The address of the device 1 is inserted into the data area, the data is inserted into the check area, and the check bit is inserted into the check area. The transmission control unit 14 sends the data select signal 27 to the selector 13 to select the transmission packet. Send to.

When the communication control device 2 receives the packet, the packet analysis unit 15 analyzes the packet, and if the destination is the own device and the state is receivable, the write signal 30 is sent to the reception buffer unit 16. Give and accumulate received data.

The analysis result signal 23 from the packet analysis unit 15 is sent to the packet correction unit 19 'to erase the contents of the received packet and send it to the selector 13 as an empty packet.
It is selected by the data select signal 27 from the transmission control unit 14 and sent to the downstream monitoring control device.

On the other hand, when the arrived packet cannot be received due to some reason such as busy, the address change information 20 from the packet analysis unit 15 is not deleted without deleting the packet.
To the address conversion unit 17, and the address conversion unit 17 replaces the address data 24 in which the destination address and the source address of the received packet are replaced with each other by the packet correction unit 1.
9 ', and the packet modifying unit 19' replaces the address based on the address data 24 in which the destination address and the source address of the received packet are replaced, and
The packet reception state of the packet format is a busy packet with busy "1", and the corrected packet is selected by the data select signal 27 from the transmission control unit 14 and sent to the downstream monitoring control device.

Communication control device 1 that receives a busy packet
In response to the analysis result signal 23 from the packet analysis unit 15, the packet correction unit 19 ′ erases the busy packet to make it an empty packet, and the packet analysis unit 15 sends a packet retransmission signal 28 to the packet generation unit 12 ′. The packet is selected by the data select signal 27 from the transmission control unit 14 and the packet is retransmitted.

This packet is retransmitted until the communication control device 2 becomes receivable, and the data is received as soon as possible.

[0011]

However, until the communication control device 2 receives the data, the transmission lines 6 and 7 in FIG. 4 are occupied for packet retransmission, and there is a problem that the traffic decreases.

It is an object of the present invention to provide a packet resending method capable of preventing a decrease in traffic even when the communication control device on the receiving side cannot receive the packet.

[0013]

FIG. 1 is a flowchart of the principle of the present invention. As shown in FIG. 1, in a loop type network in which a plurality of communication control devices are connected by a transmission line to form a loop and communication is performed between the communication control devices, transmission is performed from another communication control device in step 1. If the received packet can be received by the own communication control device, the process proceeds to step 3 and is received. If the received packet cannot be received in step 1, the address of the communication control device of the transmission source of the arrived packet is stored. , The reception communication control device busy is notified to the communication control device of the transmission source using the packet, and in step 4,
Upon receiving the packet, the communication control device of the transmission source discards the packet and at the same time stops the packet transmission. When the communication control device on the receiving side becomes receivable in step 5, the memory is stored in step 6. The packet transmission request is made using the dummy packet according to the address of the transmission source communication control device, and in step 7, the transmission source communication control device that has received the retransmission request dummy packet discards the dummy packet. , A packet that could not be received by the communication control device on the receiving side is retransmitted.

[0014]

According to the present invention, if the packet transmitted from another communication control device can be received by the own communication control device, the packet is received.
If the packet cannot be received due to busy or the like, the address of the communication control device of the transmission source of the arrived packet is stored, the reception communication control device busy is notified to the communication control device of the transmission source using the packet, and the packet is received. The communication control device of the transmission source stops the packet transmission at the same time as discarding the packet, and when the communication control device of its own becomes ready to receive, requests the communication control device of the transmission source that stores the address to retransmit the packet, and transmits the packet. The original communication control device retransmits the packet.

That is, the communication control device on the receiving side makes a packet resend request at the time when reception becomes possible and causes the communication control device on the transmission source to retransmit the packet, so that the communication control device on the receiving side can receive. While there is no packet, the communication control device of the transmission source does not retransmit the packet, so that it is possible to prevent the traffic from decreasing.

[0016]

2 is a block diagram of a communication control apparatus according to an embodiment of the present invention, and FIG. 3 is a packet retransmission sequence diagram in the case of FIG.

2 is different from the conventional example of FIG. 4 in that FIG.
The packet transmission request area is provided in the packet format shown in (A), the transmission source address storage unit 18 is provided in the communication control device, and the processing when a packet cannot be received is different. The subject will be described below.

The destination address of the packet format shown in FIG. 2A is the address of the communication control device 2, the source address is the address of the communication control device 1, the reception status is "0", the packet transmission request is "0". The communication control device 1 transmits a packet in which data is inserted in the data area without requesting "transmission".

Then, as shown in FIG. 3A, when the communication control device 2 cannot receive the packet because the communication control device 2 is busy, the packet analysis unit 15 does not delete the arrived packet. The source address 21 from the packet is stored in the source address storage unit 18, and at the same time, the address translation unit 17 replaces the destination address and the source address of the received packet with the address translation information 20 from the packet analysis unit 15. The generated address data is created and sent to the packet modification unit 19.

In the packet modification unit 19, the destination address and the source address of the packet format shown in FIG. 2A are exchanged based on the address data, the reception state is set to "1" busy, and the packet transmission request is " The data selection signal 27 from the transmission control unit 14 selects a transmission packet without any transmission request of "0" and transmits it to the downstream monitoring control device as shown in FIG.

Communication control device 1 which received this packet
Is analyzed by the packet analysis unit 15, and the analysis result signal 23
As a result, the packet correction unit 19 erases the contents of the packet and determines that the packet is an empty packet by the data select signal 27 from the transmission control unit 14, selects the empty packet, and transmits the packet to the downstream monitoring control device, and at the same time, stops the packet transmission. To do.

When the communication control device 2 becomes receivable, the packet generation unit 12 inputs the source address stored in the source address storage unit 18 by the storage address signal 22, and the packet shown in FIG. The destination address of the format is the address of the communication control device 1, the source address is the address of the communication control device 2, the reception status is "0", the packet transmission request is "1", and the packet transmission request is "1". A packet is generated, selected by the data select signal 27 from the transmission control unit 14, and transmitted to the downstream monitoring control device as shown in FIG.

The communication control device 1, which has received the dummy packet of the packet transmission request, analyzes it in the packet analysis unit 15 and sends the analysis result signal 23 to the packet correction unit 19, which erases the contents of the packet. At the same time as making the packet empty, the packet generator 12 selects the packet previously generated by the data select signal 27 from the transmission controller 14 and sends it to the communication controller 2 as shown in FIG. Resend.

Then, the communication control device 2 receives this packet. That is, if the communication control device on the receiving side cannot receive the signal for some reason, the communication control device on the transmitting side is notified that the packet could not be received in the busy packet, and the transmission is stopped. The communication control device on the receiving side makes a packet retransmission request and retransmits the packet when reception becomes possible.

Therefore, the period for occupying the transmission lines 6 and 7 in FIG. 4 becomes very short, and it is possible to prevent a decrease in traffic.

[0026]

As described in detail above, according to the present invention, if the communication control device on the receiving side cannot receive the packet for some reason, the packet can be retransmitted without degrading the traffic. .

[Brief description of drawings]

FIG. 1 is a flowchart of the principle of the present invention,

FIG. 2 is a block diagram of a communication control device according to an embodiment of the present invention,

FIG. 3 is a packet retransmission sequence diagram in the case of FIG.

FIG. 4 is a configuration diagram of an example loop network,

FIG. 5 is a block diagram of a conventional communication control device.

[Explanation of symbols]

 1, 2 and 3 are communication control devices, 5 to 8 are transmission lines, 10 is a monitoring control device, 11 is a transmission buffer unit, 12 and 12 'are packet generation units, 13 is a selector, 14 is a transmission control unit, and 15 is A packet analysis unit, 16 is a reception buffer unit, 17 is an address conversion unit, 18 is a source address storage unit, and 19 and 19 'are packet correction units.

Claims (1)

[Claims] 1. In a loop type network in which a plurality of communication control devices are connected by a transmission line to form a loop and communication is performed between the communication control devices, a packet transmitted from another communication control device is self-communication. If it can be received by the control device (S1, S3), if not (S1), the address of the communication control device of the transmission source of the arrived packet is stored, and the packet is used by the communication control device of the transmission source. The communication control device of the transmission source, which has notified the reception communication control device busy (S2), discards the packet, and simultaneously stops the packet transmission (S4), and the communication control device of the reception side receives the packet. When it becomes possible (S5), a packet retransmission request is made using a dummy packet in accordance with the stored address of the communication control device of the transmission source (S6), and the dummy packet of the retransmission request is received. The packet retransmission method, wherein the communication control device of the transmission source discards the dummy packet and retransmits a packet that could not be received by the communication control device on the receiving side (S7).