JPH06152649A - Data communication system - Google Patents

Abstract

PURPOSE:To provide communication service via physical lines uniformly to each data communication processing when plural communication lines different respectively from each other used for plural data communication processing sets are set multiplexed to the physical lines. CONSTITUTION:In the system where one physical line 30 is multiplexed by logical communication lines 41, 42, 43, data communication is implemented by the packet exchange system via each logic communication line. The priority of the line 30 on other communication lines except the logical communication lines to which a packet sent continuously belongs is set sequentially higher to terminal equipments T1, T4 and T5 for each packet transmission. Thus, as a result, the above priority is set higher than that of the logical communication line whose frequency of the use is less and the communication service is served impartially to each data communication processing via the physical line 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication system, and more particularly to data communication between a plurality of terminal devices via one physical line, the physical line being used for a plurality of different data communication. Data communication system that allows the physical line to be equally occupied for each data communication when multiplexed.

[0002]

2. Description of the Related Art In a data communication system in which data communication is carried out between terminal devices such as computers via physical lines such as telephone lines, packet switching is mainly used. In the packet switching method, the information to be sent from the terminal device is divided into blocks (data section) of appropriate length in advance based on the transmission capacity of the physical line, and each block has a control code (header section) indicating a destination or the like. Is added to the physical line and sent to the other side. Further, flow control using windows is generally adopted in the packet switching system.

FIGS. 6 (a) and 6 (b) are flow charts of packet transmission processing in a data communication system by a conventional packet switching system. The processing flow shown in FIG. 6 is executed on the terminal device side. As shown in the processing flow, this processing flow branches the processing by the flag BUSY. The flag BUSY is a flag that is turned on or off on the terminal device side, and the physical line connected to the terminal device is currently in use for transmitting a packet and a new packet cannot be transmitted. , The flag BUSY is set to ON, and in other cases, the flag BUSY is set to OFF.

When a data communication request is generated on the terminal device side, as shown in FIG. 6A, after a packet to be transmitted is generated in step S20 (abbreviated as S20 in the figure), in step S21. Flag BUSY
Based on the above, it is determined whether or not the packet is being transmitted by the physical line. If it is determined that the transmission is in progress, the transmission packet generated in step S22 is set in the transmission waiting queue in order to wait for the transmission processing. In this case, the transmission process for the transmission request is not performed, and the transmission request is set to the waiting state.

In step S21, the flag B is set.
The transmission packet generated when it is determined that the packet is not being transmitted through the physical line based on USY is sent to the physical line after the flag BUSY is set to ON in steps S23 and S24, and is transmitted to the other terminal device. Sent.

When the transmission of the above-mentioned packet is completed, the transmission process for the transmission waiting packet set in the transmission waiting queue shown in FIG. 6B is performed accordingly. First,
In step S25, it is determined whether or not the transmission waiting packet is set in the transmission waiting queue. If the transmission waiting packet is not set in the queue, the flag BUSY is set to OFF in step S26 and the process ends. If the transmission waiting packet is set in the queue, the transmission waiting packets are extracted from the transmission waiting queue in the order in which they are input to the queue and the transmission processing is performed in steps S27 and S28.

In the terminal device which carries out the packet transmission processing as described above, when the flag BUSY is OFF and the transmission requests occur frequently, the transmission capacity of the physical line is exceeded, that is, the flag BUSY is set to OFF. The packets will be transmitted continuously until the end. At this time, this physical line is occupied for packet transmission by the terminal device.

In the packet switching system, one physical line is generally used by being multiplexed by a time division system on a plurality of logical communication paths. This logical communication path is
In order to commonly use one physical line for data communication with a plurality of terminal devices, it means a communication path set via the physical line for each of these different data communication.
When a plurality of logical communication paths are set up on one physical line in this way, it looks as if a plurality of physical lines are virtually connected to the terminal device.

Even when one physical line is multiplexed and used by a plurality of logical communication paths as described above, each terminal device adopts the packet sending procedure as shown in FIG. Therefore, if the transmission request amount of data communication using a specific logical communication path is equal to or exceeds the transmission capacity of the physical line, transmission by data communication using the logical communication path is performed. As a result, the packet occupies the physical line itself, and there is a problem that the responsiveness of data communication using another logical communication path by the same physical line is significantly reduced.

This problem is that data transmission requests for data communication using a specific logical communication path occur at closely spaced intervals in time, while data communication using another logical communication path through the same physical line is used. This is a particularly noticeable problem in a situation in which the transmission requests of 1 occur at coarse intervals in time.

Conventionally, in order to avoid the problem that the data communication using the specific logical communication path occupies the physical line as described above, in general, a measure to secure a sufficient transmission capacity of the physical line in advance. Has been taken. But,
There is a limit to the transmission capacity of the physical line, which is not realistic. In addition, although a dedicated physical line was specially assigned to this specific logical communication path, it may be a fundamental solution because it requires multiple physical lines, resulting in high cost. There wasn't.

Therefore, an object of the present invention is that when a plurality of different communication paths used for a plurality of different data communication processes are set in a physical line in a multiplexed manner, each communication line occupies the physical line. It is an object of the present invention to provide a data communication system capable of uniformly supplying a communication service via a physical line to each data communication process by equalizing the period for performing the data communication.

[0013]

A data communication system according to the present invention includes a physical line and a plurality of terminal devices that perform data communication via the physical line, and a plurality of different data communication processes between these terminal devices. Is a system in which each of a plurality of different communication paths used for each of these is multiplexed and set in this physical line, each of the above-mentioned terminal device, priority setting means, priority lowering means,
The communication means and the priority raising means are provided.

The priority setting means sets, in response to the establishment of the above-mentioned communication path, a priority of occupation of a physical line, which is uniquely determined in advance for the communication path, to the communication path. After that, when a request for data communication by the data communication processing is generated, the priority lowering means lowers the priority of the communication path used for the data communication processing by a predetermined order in response to the request. Further, during the period in which the above-mentioned request for data communication is generated and the data communication is possible through the physical line, the communication means uses the communication path with the highest priority and supports the communication path. While performing the data communication processing, the priority raising means raises the priority of the other communication paths except the communication path corresponding to the data communication processing by a predetermined rank every time the data communication processing is performed.

[0015]

The data communication system according to the present invention is configured as described above, and each of the terminal devices is used in the data communication process in response to the generation of the communication request by the data communication process by the priority decreasing means. While lowering the priority of the communication path by a predetermined order and during the period when this request is generated and data communication is possible via the physical line, the communication path having the highest priority by the communication means is used. While performing the data communication processing corresponding to, each time the data communication processing is performed, the priority increasing means increases the priority of the other communication paths except the communication path corresponding to the data communication processing by a predetermined order. , The priority of communication channels successively used for data communication becomes lower than that of other communication channels. So that the priority of use is assigned higher.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings.

The data communication system according to this embodiment is
This is a computer network system in which one physical line is multiplexed with a plurality of logical communication paths. In this system, a plurality of logical lines are used so that data communication using a specific logical communication path does not occupy the physical line. By adjusting the transmission priority of the transmission packet generated in each communication path between the logical communication paths, it is possible to uniformly supply the data communication service to each of the plurality of logical communication paths. .

1 (a) and 1 (b) are diagrams for explaining the structure of a queue for transmission packets in a data communication system according to an embodiment of the present invention. Figure 2 (a)
6B and 6B are flow charts of packet transmission processing in the data communication system according to the embodiment of the present invention.
FIG. 3 is a schematic configuration diagram of a data communication system according to an embodiment of the present invention.

In FIG. 3, this data communication system is a computer network system in which terminal devices T1 to T6, such as computers, are communicatively connected to each other via a communication line network 1. FIG. 4 shows a block configuration of each terminal device shown in FIG. As shown in FIG. 4, each terminal device has a CPU (central processing unit) 20 so as to have a function as a computer, and an internal memory 21 including a queue buffer 22 accessed by the CPU 20.
Processing unit 10 including an external memory unit 11 for storing programs or data, CRT (cathode ray tube)
Alternatively, the display unit 12 including a liquid crystal display device, the processing unit 1
0 and communication line network 1 for communication connection I / F
(Abbreviation of interface) unit 13 and an input / output unit 14 including a printer, a keyboard, or the like. The communication line network 1 is a telephone line network or the like.

FIG. 5 conceptually shows that one physical line is multiplexed by a plurality of logical communication paths. In FIG. 5, the terminal device T1 includes application software SA, SB and SC including communication processing.
4 includes similar software Sa, and further the terminal device T
5 also includes similar software Sb and Sc. In FIG. 5, the physical line 30 is a logical communication path 41, 42 and 4
3 is used by multiplexing. The communication path 41 is set between the software SA of the terminal device T1 and the software Sa of the terminal device T4, and the communication paths 42 and 43 are respectively software SB and SC of the terminal device T1.
And the software Sb and S of the terminal device T5
It is set between each of c.

The processing flow for the transmission packet by each terminal device in this embodiment is shown in FIGS. 2 (a) and 2 (b). The difference between the processing flow shown in FIG. 2 and the conventional processing flow shown in FIG. 6 is that a transmission request for a transmission packet to wait for transmission processing is structured according to the priority of transmission. The process includes insertion of a transmission packet into the transmission queue with priority (* 1 in FIG. 2) and extraction of the packet from the transmission queue with priority (* 2 in FIG. 2).

The structure of the transmission queue with priority used in this embodiment is shown in FIGS. 1 (a) and 1 (b). The transmission queue is stored in the queue buffer 22 shown in FIG. The transmission queue includes an LCN (logical channel number) structure 7i (i = 1, 2, 3 ...) And a packet structure 8i provided in association with the transmission packet PAi. The structures 7i and 8i are collectively managed by the priority management table 90 stored in the queue buffer 22 of FIG.

The priority management table 90 is composed of a plurality of records as shown in FIG. 1, and each record determines the priority of transmission of the packet PAi waiting for transmission stored in the transmission queue. Includes Pj and pointer Q1.
The priority Pj is P ₀ , P ₁ ,
P _2, ... P _max contains a pointer Q1 of each record corresponding priority Pj (j = 0,1,2, ... max ) to assign priorities Pj to LCN structure 7i should have The structure 7i is connected to the record.

Each of the LCN structures 7i is created individually for each of a plurality of logical communication paths. Each structure 7i manages a pointer Q2 for connecting another LCN structure having the same priority Pj to itself and a packet structure 8i which manages a packet PAi transmitted via a logical communication path corresponding to the structure 7i. Includes a pointer Q3 for connecting to. Each of the LCN structures 7i starts the application software on the transmission request side at the time when the corresponding logical communication path is established according to the communication protocol of the communication system, that is, as shown in FIG.
0 transitions the software to the ready state)
When the application software on the transmission partner side is also activated and a communication connection is established by the logical communication path via the physical line 30, it is generated by the CPU 20 and uniquely assigned to the logical communication path in advance. The record in the management table 90 corresponding to the priority is connected via the pointer Q1. Thereby, the packet PA in the LCN structure 7i and the packet structure 8i connected to the LCN structure 7i
i will be set in the transmission queue.

At the time point when the above-mentioned established logical communication path is disconnected in accordance with the communication protocol, that is, either one of the application software that has been started as a pair on the transmitting side and the receiving side is stopped (ended) by the control of the CPU 20. When the status is changed, the LC corresponding to the logical communication path
The N structure 7i is removed from the transmission queue. That is, C
The PU 20 sets the value of the pointer (Q1 or Q2) in the preceding stage of the LCN structure 7i to the pointer NULL, so that the structure 7i is removed from the transmission queue.

The packet structure 8i includes a packet PAi to be transmitted and a pointer Q4 for connecting to another packet structure having the packet PAi to be transmitted next.

As described above, the priority management table 90, the LCN
Each of the structure 7i and the packet structure 8i adopts a structure having a pointer, and the transmission queue uses the pointer to establish the priority Pj corresponding to the communication path when the logical communication path is established. Is allocated, and when the logical communication path is disconnected, the data (LCN structure 7
i and the packet structure 8i) are removed from the transmission queue to collectively manage the transmission waiting packets PAi. In this transmission queue, the allocation of the priority Pj to each logical communication path is changed every time a packet PAi is transmitted or a transmission request is generated. Here, this is called dynamic allocation of the priority Pj, which is a feature of the communication system. This dynamic allocation is performed in the process of inserting the transmission packet into the transmission queue (* 1 in FIG. 2) and the process of extracting the transmission packet from the transmission queue (* 2 in FIG. 2). The dynamic allocation will be explained by explaining.

First, the process of inserting a transmission packet into the transmission queue (* 1 in FIG. 2) is realized by the following procedure.

(1) A packet structure 8i corresponding to the transmission packet PAi is generated. (2) Paying attention to the list of packet structures 8i connected from the LCN structure 7i corresponding to the logical communication path used by the transmission packet PAi, the packet structure 8i generated in (1) is added to the list. Connect to the end.

(3) In the priority management table 90, the LCN structure 7i connected to the packet structure 8i corresponding to the transmission packet PAi has the priority Pj + 1 which is one lower than the current priority Pj. Correct the connection to the LCN structure 7i.

Next, the transmission packet P from the transmission queue
The Ai extraction process (* 2 in FIG. 2) is performed by the following procedure.

(4) Pointer Q1 of the priority management table 90
Among all the LCN structures 7j connected by, the LCN structure 7i having the highest priority Pj is searched.

(5) The leading packet structure 8i connected to the retrieved LCN structure 7i is specified, and the transmission packet PAi in the specified structure 8i is designated as a packet for transmission.

(6) Of all the LCN structures 7i stored in the transmission queue, except for the above-mentioned retrieved LCN structure 7i, the current priority Pj is given one higher priority. The value of the pointer Q1 to the LCN structure other than the searched LCN structure is corrected so that the degree becomes Pj-1.

The dynamic allocation of the priority Pj by the process of extracting the transmission packet PAi is shown in FIGS. 1 (a) and 1 (b).
Shown in.

In FIG. 1 (a), LCN is associated with each logical communication path because four different logical communication paths are established.
Structures 71, 72, 7n and 7n + 2 are generated respectively. A priority Pj uniquely assigned in advance is given to each of these four logical communication paths. Specifically, the priority Pj of each LCN structure is P ₁ , P ₂ , P _n , and P.
Each L via the pointer Q1 is initialized to _{n + 2}
The CN structure is linked to the priority management table 90. further,
In the LCN structure 71, packet structures 81, 82, and 83 having transmission packets PA1, PA2, and PA3, respectively, are generated and connected in order, and an LCN structure 72 is formed.
To the NCN structure 7n, packet structures 85, 86 and 87 respectively having transmission packets PA5, PA6 and PA7 are generated and connected, and further LCN. The transmission packet PA8 is included in the structure 7 _{n + 2.}
And packet structures 88 and 89 respectively having and PA9 are generated and connected in sequence. In the initial state in which the priority Pj is assigned in FIG. 1A, the packet PA1 to which the highest priority P ₁ indicated by the slanted line in the figure is assigned is the packet with the highest transmission priority as described above. Becomes This is because the right to occupy the physical line 30 is the LCN structure 7
1 indicates that it is assigned to the corresponding logical communication path.

After the initial state is set as shown in FIG. 1A, the packet PA1 is transmitted using the logical communication path corresponding to the LCN structure 71.
Is transmitted, the operation of modifying the priority Pj according to (6) described above is performed in response to this transmission. Even after this operation is completed, since the occupation right of the physical line 30 is still in the logical communication path corresponding to the LCN structure 71, the packet with the highest transmission priority becomes the transmission packet PA2. A packet PA2 is transmitted in the same manner as the above-mentioned transmission packet PA1, and the priority P according to (6) above is transmitted in response to the transmission of this packet PA2.
The correction operation of j is performed. After that, when two communication requests are made regarding the communication corresponding to the structure 7 _n , the connection state between the LCN structure and the priority management table 90 shows the highest priority logical communication as shown in FIG. LCN structure 7
Since it is a logical communication path corresponding to 2, the packet with the highest transmission priority becomes the packet PA4. That is, even though the packet PA3 to be transmitted to the LCN structure 71 corresponding to the communication path having the highest priority in the above-mentioned initial state is in the transmission waiting state, the logical communication path has a lower priority than that. On the other hand, this indicates that the right to occupy the physical line 30 has been given. Similarly, LCN structures 7 _n and 7
_Also for each logical communication path corresponding to _{n + 2} , the priority Pj is dynamically changed for each transmission of the packets PA1 and PA2 and each time a transmission request is generated.

Through the above processing, the logical communication path in which the packets are continuously transmitted has a relatively lower priority Pj for each transmission than the other logical communication paths. As a result, the lower the frequency of use, the higher the priority Pj is assigned to the logical communication path. Therefore, it becomes possible to evenly distribute the occupation right of the physical line 30 to each of all the logical communication paths, and the uniform supply of the data communication service is realized to each communication path.

Next, with reference to the flow charts of FIGS. 2A and 2B, a processing procedure for sending a packet to be transmitted while dynamically assigning the priority Pj will be described.

The processing flow shown in FIG. 2 is executed under the control of the CPU 20, and this processing flow includes the branching of processing by the flag BUSY as in the conventional case. When a data transmission request is generated on the terminal device side as shown in FIG. 2A, a packet to be transmitted is generated in step S1 (abbreviated as S1 in the figure), and then this generated packet is ) To (3) are inserted into the transmission queue according to the procedure of insertion into the transmission queue. Thereafter, in the process of step S3, it is determined whether the packet is being transmitted by the physical line 30 based on the flag BUSY. If it is determined that the packet is being transmitted, the process for this transmission request is not performed and the standby state is set. It On the contrary, if it is determined based on the flag BUSY that the transmission is not in progress, the process of step S5 is executed in step S4, and the above (4) to
According to the processing procedure of (6), the packet with the highest transmission priority is extracted from the transmission queue, the priority operation is processed, and then the packet extracted in the processing is transmitted to step S6.

When the above packet transmission is completed, the process shown in FIG. 2B is performed accordingly. First, in step S7, it is determined whether or not the transmission waiting packet is set in the transmission queue. If the transmission waiting packet is not set, the flag BU is set in step S8.
Although SY is set to OFF and the processing ends, if a packet is set in the transmission waiting queue, step S9 is executed.
In step S10, the packet with the highest transmission priority is extracted from the transmission queue according to the above-mentioned steps (4) to (6), and the priority operation is performed. Then, the extracted packet is transmitted in step S10. To be done.

As described above, the priority Pj of the logical communication path is reallocated every time a packet is transmitted or a transmission request is generated so that the specific logical communication path does not occupy the physical line 30 too much. The occupation period of the physical line 30 is made uniform for each logical communication path.

[0043]

As described above, according to the present invention, each of the terminal devices uses the priority lowering means in response to the generation of the data communication request by the data communication process and the communication path used for the data communication process. While this priority is lowered by a predetermined order, during the period when this request is generated and data communication is possible via the physical line, the communication means uses the communication path with the highest priority, A data communication process corresponding to a route is performed, and each time the priority raising means performs this data communication process, the priority of other communication routes except the communication route corresponding to the data communication process is increased by a predetermined order. . Therefore, the priority of a communication path continuously used for data communication gradually decreases as compared with other communication paths, and as a result, a communication path with a lower frequency of use of the physical line will occupy the physical line. Since the priority of use is assigned to a high level, the period for occupying the physical lines for each of the communication paths is made uniform, so that the communication service via the physical lines is made uniform for each data communication process. Can be supplied.

[Brief description of drawings]

1A and 1B are diagrams for explaining a structure of a queue for transmission packets in a data communication system according to an embodiment of the present invention.

2A and 2B are flow charts of packet transmission processing in the data communication system according to the embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a data communication system according to an embodiment of the present invention.

FIG. 4 is a block diagram of the terminal device of FIG.

FIG. 5 is a diagram conceptually showing that one physical line is multiplexed with a plurality of logical communication paths in the data communication system according to the embodiment of the present invention.

6 (a) and 6 (b) are flow charts of packet transmission processing in a data communication system using a conventional packet switching system.

[Explanation of symbols]

 1 communication line network T1 to T6 terminal device 10 processing unit 20 CPU 22 queue buffer 30 physical lines 41, 42 and 43 logical communication path 7i LCN structure 8i packet structure 90 priority management table PAi transmission packet Pj priority Q1, Q2, Q3 and Q4 pointers In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A physical line and a plurality of terminal devices that perform data communication via the physical line, and each of a plurality of different communication paths used for a plurality of different data communication processes between the terminal devices. A data communication system that is set by being multiplexed on the physical line, wherein each of the terminal devices has a physical line that is uniquely determined in advance with respect to the communication line in accordance with the establishment of the communication line. Priority setting means for setting a priority of private use for the communication path, and a predetermined priority of the communication path used for the data communication processing in response to a data communication request generation by the data communication processing Priority lowering means for lowering only the rank, a period during which the request is generated and data communication is possible via the physical line, and a communication path having the highest priority is used for the communication. A communication unit that performs the data communication process corresponding to a channel, and each time the data communication process is performed by the communication unit, the priority of a communication channel other than the communication channel corresponding to the data communication process is predetermined. A data communication system comprising a priority increasing means for increasing only the rank.