JPH05327772A - Computer network system - Google Patents

Abstract

PURPOSE:To lower an error rate with respect to a packet, to avoid retransmission of the packet and to prevent deterioration of the transmission efficiency by varying dynamically transmitting packet length in accordance with the quality of a circuit. CONSTITUTION:In a computer network system, a retransmission processing for securing a transfer of a packet to an upper rank layer application 32 is executed by a retransmission algorithm part 30. By interlocking therewith, whether a packet retransmission request from a lower rank layer network 33 exists or not is decided, and also, whether the quality of a circuit is good or not is decided by counting the continuous number of non-retransmission packets, and in accordance with its quality, packet length is shortened or expanded automatically within the limit. Subsequently, by a packet disassembling/ assembling part 31, a distribution of a packet corresponding to a network is executed, and it is transmitted to the lower rank layer network 33. In such a way, in accordance with a state of the circuit, deterioration of the transmission efficiency of the circuit is prevented, and a communication can be secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a computer network system.

[0002]

2. Description of the Related Art A packet switching system is mainly used in a data communication network for communication between computers and terminals. In this method, information sent from a computer or a terminal is divided into relatively short blocks, and a control code (header section) such as a destination is added to this block and sent to the other side as a packet.

In this packet switching system, in the case of a computer network system which uses a low quality line, it is necessary to take measures against the poor line quality.

As a coping method, (1) the packet transmission speed on the line is reduced.

(2) The transmission packet length is shortened.

There are two methods.

Regarding (1), there are a method of connecting by lowering the packet transmission rate on the line in advance and a method of automatically determining the packet transmission rate by a modem. On the other hand, with respect to (2), a method of determining the transmission packet length in advance by setting or the like is general.

[0008]

When a bit error occurs due to poor quality of a line and a packet is lost, a general communication protocol tries to recover this packet loss by retransmitting the packet. If this retransmission occurs frequently, the transmission efficiency becomes worse.

Further, the method of reducing the transmission rate of the line when the line quality is poor has many operational problems because the transmission rate of the line directly affects the transmission efficiency.

On the other hand, when the line quality is poor, if the transmission efficiency of the line is maintained while maintaining the transmission speed of the line, it is common practice to shorten the transmission packet length in advance and reduce the error rate for the packet. Target. However, when the line state is unstable, if the transmission packet length is kept short, conversely, when the line state is good (high quality), a loss occurs in terms of transmission efficiency.

Therefore, the present invention provides a computer network system capable of communicating in response to fluctuations in the line quality while maintaining the line transmission speed.

[0012]

According to the present invention, there is provided a computer network system for communicating between computers via a line, wherein the quality of the line is judged to be good or bad, and the judgment means determines the line quality. A computer having means for shortening the transmission packet length within a limit when it is determined that the quality is poor, and means for increasing the transmission packet length within a limit when the determination means determines that the line quality is good. A network system is provided.

[0013]

In order to solve this problem, the present invention reduces the error rate for a packet by dynamically changing the transmission packet length, avoids packet retransmission, and reduces transmission efficiency as much as possible. It is a thing.

A means for determining the quality of the line, specifically, determining whether or not there is a packet retransmission request, and counting the number of consecutive non-retransmitted packets, determines that the line quality is poor. If so, the communication packet length is automatically shortened within limits. On the contrary, if it is determined that the line quality is good, the transmission packet length is automatically lengthened within the limit.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a computer network system according to the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram showing a schematic configuration of an embodiment of a computer network system according to the present invention, and FIG. 3 shows an outline of a communication protocol used in the computer network system according to the present invention. It is a thing.

As shown in FIG. 2, the computer 10 is
A processing unit 11 having a CPU (central processing unit) and a CR
A display device 12 such as a T or liquid crystal display device, a program,
A storage device 13 for storing data and the like and an input / output device 14 such as a printer are provided. The computer 10 is connected to another computer 20 via a line 1 such as a telephone line. This is a general computer network system, in which many computers are connected via a line 1 and can communicate with each other in a packet switching system.

In the computer network system according to this embodiment, the process of disassembling / assembling packets within the communication protocol includes a process of changing the transmission packet length in conjunction with the resending process within the communication protocol.

An outline of the communication protocol assumed by the computer network system according to this embodiment is shown in FIG.

The communication protocols are layered and are shown in FIG.
, A part 30 relating to a retransmission algorithm for performing a retransmission process for guaranteeing the transmission of the packet to the upper layer application 32, and the decomposition of the packet passed (passed to) from the retransmission algorithm part 30 according to the medium of the lower layer network 33. And a part 31 relating to packet disassembly / assembly for performing (assembly).

FIG. 1 shows the flow of processing for changing the transmission packet length in the computer network system according to this embodiment.

The process for changing the transmission packet length in FIG. 1 is a process executed as a pre-process for the portion 31 shown in FIG.

First, it is determined whether or not the packet currently being transmitted is due to retransmission (step S1).
0). This can be easily identified by the information from the retransmission algorithm part 30 of the communication protocol shown in FIG. If the line quality is poor and the transmitted packet is not properly transmitted to the other party, there is a request for retransmission by the other party. If it is a retransmission packet, the current transmission packet length (the transmission packet length is initially set to the maximum transmittable packet length) is set to a value one rank smaller according to the packet length change table shown in Table 1 (step S11). Next, the number of consecutive non-retransmitted packets (xmt) is reset (step S12), and the process of the packet disassembly / assembly part 31 of the communication protocol is started. However, if the minimum packet length is currently set, the packet length cannot be further shortened.

[0024]

[Table 1]

If the answer to step S10 is no,
That is, when the packet is not a retransmission packet, the non-retransmission packet continuous value (xmt) is incremented by 1 to determine how many packets that are not retransmission packets have been transmitted in the past,
That is, it is determined whether or not xmt exceeds the specified value (max_xmt) (step S14), and if it exceeds the specified value max_xmt, the value of the transmission packet length is increased by one rank according to the packet length change table in Table 1. Set to (Step S
15) The number of consecutive non-retransmitted packets (xmt) is reset, and the process of the packet disassembling / assembling portion 31 is started.
However, if the maximum packet length is currently set, the packet length cannot be increased further.

What has been shown above can occur when the line reaches a good state, so that the transmission efficiency is increased.

Incidentally, step S10 concerning the judgment of the retransmission packet and S12, S13, S14 and S16 concerning the setting and judgment of the non-retransmission packet continuous value (xmt) correspond to the means for judging the quality of the line. , Step S1 is a means for shortening or lengthening the packet length within the limit.
1 and S15.

Thus, even if the line is unstable, the transmission packet length can be changed according to the state of the line, and communication can be secured without reducing the transmission efficiency of the line as much as possible. A computer network system can be provided.

[0029]

As described above in detail, in the computer network system according to the present invention, the means for judging the quality of the line and the transmission packet length when the judging means judges that the line quality is poor. Is provided within the limit, and means for increasing the transmission packet length within the limit when the determining means determines that the quality of the line is good, even if the line is unstable, The transmission packet length can be changed according to the state of the line, and communication can be secured without reducing the transmission efficiency of the line as much as possible.

[Brief description of drawings]

FIG. 1 is a flowchart showing an outline of processing for changing a transmission packet length in a computer network system according to the present invention.

FIG. 2 is a block diagram showing the configuration of a computer network system according to the present invention.

FIG. 3 is a block diagram showing an outline of a communication protocol in the computer network system according to the present invention.

[Explanation of symbols]

 10, 20 Computer 11, 21 Processing device 12, 22 Display device 13, 23 Storage device 14, 24 Input / output device

Claims (1)

[Claims] 1. A computer network system for communicating between computers via a line, comprising means for judging quality of the line, and the judgment means for judging that the quality of the line is poor. A computer network system comprising: a transmission packet length shortened within a limit; and a means for increasing the transmission packet length within a limit when the determination unit determines that the line quality is good. ..