JPS6232743A - Packet exchange system - Google Patents

Abstract

PURPOSE:To simplify a program by comparing a packet signal with a packet number of 1 bit transmitted from the transmission side with a packet signal returned from the receiving side and deciding the necessity of retransmission in accordance with the presence or absence of an error. CONSTITUTION:A packet signal with packet No. of 1 bit is transmitted from a transmission side computer 1 through a network 2. A receiving side computer 3 receives the packet signal, and if no error is detected, returns the same packet number to the transmission side. The transmission side compares the return packet number with the transmitted packet number, and when confirms no error, sends the succeeding packet signal. When detecting an error, the receiving computer 3 returns the received packet signal with a packet number different from the received one. Detecting the different packet number, the transmission side retransmits the same packet signal again. Consequently, the program is simplified and both the computers on the transmission and reception sides can be prevented from the reduction of processing capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a packet switching system, and more particularly, to a packet switching system in which when a transmitted packet has an error, the transmitted packet is retransmitted to recover from the transmission error.

BACKGROUND OF THE INVENTION Recently, packet switching systems have become popular as a type of data communication system. In the packet switching method, a sending computer divides a communication message into small units called packets, attaches a destination to each packet, performs store-and-forward operations for each destination, and sends the message. Restore messages.

Conventional data exchange protocols (communication protocols) include DEC's DDCMP (Digital Data Communication Message Protocol), 18M's 5DLC (Synchronous Data Link Control), and CCjTT (International Telecommunications). x, 25, etc. recommended by the Telephone Advisory Committee). In any of the above protocols, each packet is provided with a packet reception number field of several bits and a packet transmission number field of several bits. If there is a packet that cannot be received normally on your side, the sequence number of the packet transmission field 1: of that packet is extracted and stored in the packet reception number field. A packet is generated and sent (i (returned to l111, and the receiving side retransmits the get of the sequence number specified by +lSi) to recover from the transmission error (/).

Problems to be Solved by the Invention In the conventional data communication system described above, each packet is provided with a packet reception number field and a packet transmission number field of several bits, and the sequence number written therein is represented by several bits. For this reason, the processing procedures for bucket i-exchange on the sending and receiving sides are complicated, and when packets are exchanged between small computers such as personal computers, it takes a lot of effort to develop the control program. This requires time and money, and the overhead associated with the packet switching processing of a small computer becomes large, resulting in a reduction in its processing capacity.

Therefore, the present invention provides a method for each sending packet and returning packet.
It is an object of the present invention to provide a packet switching system that solves the above problems by assigning bit packet numbers.

Means for Solving the Problems In the present invention, a 1-bit packet number is attached to a transmitted packet. The receiving-side combicoater determines whether or not there is an error in this transmitted packet, and returns the return bucket 1-, which has a packet number different from the erroneous transmitted packet, to the transmitting computer.If there is no error, the packet number is the same as that of the transmitted packet. The return packet is sent back to the sending computer. At the sending side computer, the packet numbers of the sending packet and the returned packet match, and the value of the replacement packet number in which there is no error in the returning packet is switched to generate a new sending packet and transmitted to the receiving side computer. When the packet numbers of the above-mentioned sent packet and return)<get are different, or when there is an error in the returned packet, the same sent packet as the previous one is sent to the receiving computer.

Operation In the present invention, the packet number of each packet is 1 bit. When the receiving computer detects an error in the transmitted packet, the packet number of the returned packet is set to be different from that of the transmitted packet.

The receiving computer can determine whether the sending packet has been correctly transmitted to the receiving computer based on the presence or absence of an error in the returned packet and the packet number of the returning packet, and retransmits the sending packet if the sending packet has not been correctly transmitted. In this way, it is possible to determine whether retransmission is necessary or not based on the 1-bit packet number.

Embodiment FIG. 2 shows the operating environment of the packet switching system according to the present invention. In the figure, 1 is a sending computer, which is connected to a network (switching network) 2. A receiving computer 3 is also connected to the network 2, and a data link between the sending computer 1 and the receiving computer 3 is established. The sending computer 1 and the receiving computer 3 mutually exchange packets in the format shown in FIG. 3 via the network 2.

In FIG. 3, a start code field is provided at the beginning of the packet in which a start code, which is the same l] signal, is set. This is followed by 1 bit with a value of 0″ or 1″
This is the packet number field where the packet number of is set. The subsequent data field 7 is set with communication data such as divided messages. Data field 7 is followed by CRC (cyclic redundancy).
An error detection code field is provided in which an error detection code such as .code) is set, and an end code field is further provided in which an end code is set.

FIG. 1(A) shows a flowchart of an embodiment of packet exchange processing by the sending computer 1. In FIG.

In the figure, the sending computer 1 sets the packet number field 6 of the first packet to be sent to "1",
This packet is transmitted to the receiving computer 3 (step 11). Thereafter, a return packet sent back by the receiving computer 3 in response to the above transmission packet is received (step 12).

The value of packet number field 6 of this return packet is "
1'' (step 13),
”, the error detection code field 8 of the returned packet
Error detection is performed using the error detection code (step 14). This detection result is determined in step 15,
If there is no error, a new transmission bucket 1~ in which the communication data following the optically transmitted packet and the packet number "1" are respectively set is generated and transmitted (step 1G).
.

If the packet number of the return packet is not "1" in step 13, or if there is an error in the return packet in step 15, the process moves to step 17, where the content is the same as the packet sent in step 11 (packet number "1"). ”) is retransmitted, and the process moves to step 12.

After executing step 16, the return bucket 1- is received from the receiving computer 3 (step 18), and it is determined whether the packet number of this return packet is "0" (step 19). If it is "0", error detection is performed on the returned packet (step 20), and if it is determined in step 21 that there is no error, the process moves to step 11 and the next packet is transmitted.Step 19
If the packet number is not "'o" and step 21
If there is an error in the returned packet, the process moves to step 22, where a packet with the same content (packet number "O") as the transmitted packet in step 16 is retransmitted.
Proceed to step 18. The above process is repeated until all communication messages are sent.

FIG. 1(B) shows a flowchart of one embodiment of the packet exchange process of the receiving computer 3.

In the figure, the receiving computer 3 receives the first transmission packet from the transmitting computer 1 (step 22).
). After this, it is determined whether the value of the packet number field 6 of the received transmission packet is 1'' (step 23), and if it is "1", the error detection code of the error detection code field 8 of the transmission packet is used. Error detection is performed (step 24). Thereafter, it is determined whether there is an error (step 25), and if there is no error, a return bucket l- with packet number "1" set is generated and sent back to the sending computer 1 (step 26).Step 23 If the packet number of the transmitted packet is not "1" or if there is an error in step 25, a return packet with packet number 110 II is generated and sent back to the sending computer 1 (step 27), and the process proceeds to step 22. Transition.

After executing step 26, a transmission packet from the sending computer 1 is received (step 28), and it is determined whether the packet number of this transmission packet is "O" (step 29). If the packet number is "0", error detection is performed on the transmitted packet (step 30), and if it is determined in step 21 that there is no error, the process moves to step 32, where a return packet with packet number 110 II is generated and sent to the sending side. It is sent back to computer 1. After this, the process moves to step 22. Furthermore, if the packet number is not "0" in step 29 and if there is an error in the transmitted packet in step 31, a return packet with packet number "1" is generated and returned (step 33). After this, the process moves to step 28. The above process is repeated as long as the transmission packet is being transmitted.

As a result, as shown in FIG. 4, the sending computer 1 sends out a packet with packet number "1" in the first step 1, and if this sending packet is transmitted to the receiving computer 3 without error, the receiving computer 1 returns a return packet with the same packet number as the sent packet to the sending computer 1.If this return packet is transmitted to the sending computer 1 without error, the sending computer 1 executes step 2.In step 2, The packet number of the transmitted packet is switched to "0". In this way, the packet numbers are switched one after another in steps 21, 3, and 4 to perform packet exchange. In step 5, if the sending packet with packet number "1°" is sent by mistake, the receiving computer 3 sends packet number II OI.
The return packet of I is sent back to the sending computer 1.

As a result, in step 6, the sending computer 1
The same transmission packet as that in is retransmitted, and if it is transmitted to the receiving computer 3 without error, the receiving computer 3 sends back a return packet with the packet number "'1゛°".This causes the transmission error to be recovered. It will be done.

After this, in step 7, if the return packet with packet number "0" corresponding to the sent packet with packet number "OII" is erroneously transmitted, the sending computer 1
At step 7, the same send bucket as in step 7] is retransmitted. After the return packet with packet number "0" corresponding to this transmission packet is transmitted to the sending computer 1 without error, the sending computer 1 executes the following procedure.

In this way, by attaching a 1-bit packet number to a packet, it is possible to determine whether or not a transmitted packet needs to be retransmitted.Since the packet number is 1-bit, the transmitting computer 1. The processing procedure of each receiving computer 3 is extremely simple as shown in FIG. This allows sending computer 1. The time and cost required to develop a control program for each of the receiving-side combination coaters 3 is reduced, and the processing capabilities of these computers 1 and 3 are not reduced.

Note that steps 23 and 2 in FIG. 1(B) do not necessarily need to be provided, and are not limited to the above embodiment.

Effects of the Invention As described above, the packet switching system according to the present invention can determine whether or not there is a need to retransmit a transmitted packet simply by attaching a 1-bit packet number to the packet.
The control program for each computer on the receiving side is simplified, requiring less development time and effort. It has features such as no reduction in performance.

[Brief explanation of drawings]

FIG. 1 is a flowchart of an embodiment of processing executed by computers on the sending and receiving sides in the method of the present invention, and FIG. 2 is a diagram showing an embodiment of the operating environment of the method of the present invention.
FIG. 3 is a diagram showing the format of an embodiment of a packet according to the present invention, and FIG. 4 is a diagram for explaining the operation of an embodiment of the present invention. 1... Sending computer, 2... Network (
3. Receiving side computer, 6. Backcut number field, 8. Error detection code field, 11-33. Steps.

Claims (1)

[Claims] In a packet switching method that transmits data in packet units from a sending computer to a receiving computer via a switching network, the sending computer generates a transmission packet with a 1-bit packet number and sends it to the receiving side, Compare the packet number of the return packet returned from the receiving computer in response to the send packet with the packet number of the send packet, and determine whether there is an error in the return packet, and determine if the two packet numbers do not match or there is an error in the return packet. If there is a problem, the above sending packet is retransmitted to the receiving computer, and when both packet numbers match and there is no error in the returned packet, the value of the packet number is switched, a new sending packet is generated, and the packet is sent to the receiving computer, and the packet is received. The side computer determines whether or not there is an error in the transmitted packet, and if there is an error in the transmitted packet, generates a return packet with a different packet number from the transmitted packet and sends it back to the transmitting side computer. A packet switching system characterized in that when there is no error, a return packet having the same packet number as the transmitted packet is generated and sent back to the transmitting computer.