JPH09130422A - Data communication system for public network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data communication system for a public network at a low cost with a small transmission delay by installing a filter passing only a data frame whose incoming or outgoing address uses a user identifier to an exchange accommodating users. SOLUTION: An exchange 1 is made up of a bus 2, a router 9, a subscriber line controller 3-i, a line exchange switch 10 and a changeover control device section 8. Lots of unspecified user terminal equipments 22-i are connected to the subscriber line controller 3-i via control links 20-i and main information links 21-i. The subscriber line controller 3-i is equipped with filters 6-j and identification devices 7-j. The filter monitors the data bus 2 and when the filter recognizes a data frame on the bus 2, the filter compares an identifier itself with an identifier of a transfer destination field. When they are coincident, the filter copies the data frame to the main information link. The terminal equipment 22-i receives the copied data frame.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a public network data communication system using an electronic exchange.

[0002]

2. Description of the Related Art Conventionally, the connection form between a terminal and a network has been
There are a data frame multiplex connection using a bus type network or a ring type network used in a LAN, and a connection form by circuit exchange or data exchange used in a public network. In the former data frame multiple connection, all the data frames on the transmission path are delivered to all terminals or communication devices directly connected to the transmission path, and each terminal or communication device selects its own terminal from the data frames. Communication is performed between the terminals by selecting only the data frame addressed to the terminal. Therefore, when performing communication between terminals connected to the same bus, no exchange process is required, and efficient low-cost data communication can be performed. On the other hand, in the latter connection mode, in circuit switching, a communication link is established in advance and data communication is performed one-to-one before data communication. In addition, data exchange can be classified into packets, frame relays, and cell relays, and like the above-mentioned circuit exchange, a communication link is established in advance prior to data communication, but this communication link is a logical link. So
Many-to-many communication is possible. For these,
For example, "TCP / IP Bible" (Publishing Division, SoftBank Corp., 1994), "Internetworking Technology" (Soft Research Center, Ltd., 1995)
Can be referred to.

[0003]

However, when the above-mentioned data frame multiple connection is applied to a public communication network to which terminals of an unspecified number of users are connected, all data frames on the transmission line are connected to the transmission line. Since it is delivered to all the terminals or communication devices that are used, there is a problem that communication contents are leaked and sufficient security cannot be ensured. Further, in the data frame multiplex connection, the transmission delay is large, so that it is not suitable for communication such as a telephone in which real-time performance is important. On the other hand, circuit switching is unsuitable for communication between computers at multiple points as represented by an internetwork because a communication link is established at the end. Further, in the packet and frame relays of the data exchange, since the exchange process is performed by the exchange program, the transmission cost per unit amount of information becomes high, and further, the cell relay requires expensive communication equipment. However, in the data communication at a medium speed or lower, there is a problem that the transmission cost is high like the packet and the frame relay. The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the above-mentioned problems in the conventional technology, to ensure sufficient security at low cost, and to prevent transmission delay. Is to provide a data communication system for public networks that is small.

[0004]

SUMMARY OF THE INVENTION The above objects of the present invention are as follows.
In a public communication network to which terminals of an unspecified number of users are connected and data communication is performed by the terminals, a filter means for transmitting only a data frame whose destination address is an identifier of the user A bus-type network or ring characterized in that each terminal is installed in an exchange that accommodates the terminal, the terminal is connected to the filter means, and the filter means is connected to the public communication network in a bus-type or ring-type. This is achieved by a data communication system for public networks using a pattern network.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In a public network data communication system according to the present invention, a terminal and a network are connected via a filter means and a switch on the basis of a cost-effective data frame multiplex connection. One filter means is installed for each subscriber line to which the above-mentioned terminal is connected, and this filter means internally holds the identifier of the user of the above-mentioned subscriber line. This identifier may be a serial number given to the filter means or a number determined at the time of contract such as a telephone number. When the data frame is transmitted from the terminal to the network, the filter means collates the above-mentioned internally held identifier of the user with the calling address included in the data frame, and if they match. Only, the data frame is passed and sent to the network. Further, when the data frame is received from the network to the terminal, the filter means collates the above-mentioned internally held identifier of the user with the destination address contained in the data frame, and matches them. If the data frame is present, the data frame is passed and delivered to the terminal. Incidentally, the above-mentioned switch connects the subscriber line and the circuit-switched switch when using the circuit-switched telephone service or the like,
When using data communication, the subscriber line is connected to the filter means. Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram of a mode for realizing data communication by a bus type network according to an embodiment of the present invention. In the figure, reference numeral 1 denotes an exchange, and a bus 2 for performing bus type communication and a router 9 for transmitting / receiving a data frame between the bus 2 and another exchange via a data communication relay line 12. The subscriber line control device 3-i (i = 1, 2, ..., The same applies hereinafter), the line switching switch 10, and the switching control mechanism unit 8. 22-i indicates a terminal of the user, and the terminal 22-i is connected to the subscriber line control device 3-through the control signal link 20-i and the main information link 21-i.
accommodated in i.

The subscriber line control device 3-i comprises a control signal communication device 4-i, a small switch 5-i and a filter device 6-i. The control signal communication device 4-i is a device for performing communication between the terminal 22-i and the switching control mechanism unit 8 via the control signal link 20-i. The small switch 5-i is a device for connecting the main information link 21-i to the bus 2 when performing data communication and to the circuit switching switch 10 when performing normal circuit switching or the like. ,
It is controlled by the switching control mechanism unit 8.

The small switch 5-i described above is a facility for carrying out a conventional public exchange service. The above-described filter device 6-i and the like may be provided in an accessory device connected to the outside of the exchange 1. Hereinafter, in the present embodiment configured as described above, a method of switching the small switch 5-1 when the terminal 22-1 performs data communication will be described with reference to the flowchart shown in FIG.

The terminal 22-1 is connected to the control signal link 20-1.
A request for data communication connection is made to the exchange 1 via the (step 61). In the exchange 1, the control signal communication device 4-1 receives the data communication connection, and the switching control mechanism unit 8 receives the request.
(Step 62). The switching control mechanism unit 8 inquires about the state of the main information link 21-1 (step 63). If the main information link 21-1 is in use, the control link 20-
The terminal 22-1 is notified that the connection is impossible via 1 (step 66), and the process is terminated.

If the main information link 21-1 is not in use, the switching control mechanism section 8 connects the main information link 21-1 and the filter device 6-1 so as to connect the small switch 5-.
1 (step 64) and notifies the terminal 22-1 of the completion of connection via the control link 20-1 (step 65),
The process ends. In the case where the main information link 21-i in FIG. 1 is connected to the filter device 6-i by the small switch 5-i, the main information link 21-n (n = 1, 2,
.., i, j, k, ..., And so on) and the state of the data bus 2 are shown in FIG.

Data frame 50-m (m = 1, 2, ...,
i, j, k, ...
m, a transfer source field 55-m, and a content 52-m. In the example of FIG. 3, the terminal 22-i sends the data frame 50-1 toward the identifier 7-j to the main information link 21-i. At this time, in the transfer destination field 54-1 of the data frame 50-1, the identifier 7-
j is the transfer source identifier 7 in the transfer source field 55-1.
-I is set.

Next, the flow of data frame transmission processing will be described with reference to FIG. 4 by taking the data frame 50-1 of FIG. 3 as an example.
This will be described with reference to FIG. First, the terminal 22-i sets the transfer destination field 54-1 of the data frame 50-1 to the transfer destination identifier 7-j, the transfer source field 55-1 to the transfer source identifier 7-i, and the content 52-1. Information to be transmitted to the main information link 21-i to which the terminal is directly connected (step 7).
1).

The filter device 6-i connected to the main information link 21-i reads the transfer source field 55-1 of the data frame, and reads the contract information 7-i set in the filter device 6-i. After comparison (step 72), if they do not match, the data frame is discarded (step 77) and the process ends, and if they match, the state of the data bus 2 is checked (step 74). If is empty, the data frame 50-1 is copied to the data bus 2 as it is (step 76). If the data bus 2 is in use at step 74, it waits for a certain time until it becomes empty (step 75).

Next, the flow of data frame reception processing will be described with reference to FIG. 5 by taking the data frame 50-2 of FIG. 3 as an example.
This will be described with reference to FIG. The filter device 6-j is the data bus 2
(Step 81), and when the data frame 50-2 is recognized on the data bus 2 (step 82), the identifier 7-j held in the filter device 6-j and the data frame 50-2 are detected. The identifiers of the transfer destination fields 54-2 are compared (step 83). If they do not match as a result of the comparison (step 84), the process returns to step 81.

If the result of the comparison in step 83 is that they match (step 84), the filter device 6
-J indicates the data frame 50-2 by the filter device 6
-J is copied to the connected main information link 21-j (step 85). The terminal 22-j, in step 85,
Data frame 5 copied to main information link 21-j
0-3 is received (step 86). According to the above-described embodiment, it is possible to realize a public network data communication system which can secure sufficient security at low cost and has a small transmission delay.

Next, an embodiment in which the small switch in the embodiment shown in FIG. 1 is replaced by a circuit switch will be described with reference to FIG. The terminal 22-i, the main information link 21-i, the control signal link 20-i, the control signal communication device 4-i, the circuit switching relay line 11, the data bus 2, the router 9 and the data communication relay line shown in FIG. 12 is the same component as that shown in FIG. 1, and in that the filter device 6-i is connected to the main information link 21-i via the circuit switching switch 10, it differs from the embodiment shown in FIG. Is the difference.

In the embodiment shown in FIG. 6, the terminal 22-
When the switch 1 performs data communication, the switch switching procedure may be read by replacing the small switch 5-1 in the flowchart shown in FIG. 2 with the circuit switching switch 10. The procedure of transmitting and receiving the data frame is the same as that shown in FIGS.
According to the above-described embodiment, similar to the above-described embodiment, it is possible to realize a public network data communication system that can secure sufficient security at low cost and has a small transmission delay. There is also an advantage that the number of parts can be reduced as compared with the embodiment shown.

FIG. 7 is a diagram for explaining an implementation example of the above-described filter device. Generally, in data communication, procedures for data transmission / reception are hierarchically defined. In the example of FIG. 7, in the terminal 22-1, the functional units that perform the processes of the respective layers are arranged from the lower layer to the physical layer processing unit 40-1, the data link layer processing unit 41-1 and the upper layer processing unit 42-. It is represented as 1. The interconnection device 50 is the physical layer processing unit 4 of the terminal.
A physical layer processing unit 40-2 similar to 0-1 and a data bus 2
Has a physical layer processing unit 40-3 and a data link layer processing unit 42-1 connected to each other, and realizes the function of the filter device.

That is, from the data bus 2 to the terminal 22-1
The data frame delivered to the first pass through the physical layer processing unit 40-3 and is delivered to the data link layer processing unit 42-1. The data link layer processing unit 42-1 performs the above-described filtering processing. Then, the physical layer processing unit 40-2
Via the main information link 21-1. The same processing is performed when sending a data frame from the terminal 22-1 to the data bus 2.

According to the method as described above, the interconnection device 5
Since the physical layer can be converted by 0, even if the physical layers of the main information link 21-1 and the data bus 2 are different, the data frame can be transmitted / received. In addition, since existing protocols can be used, there is little effect on terminals, and filter devices can be used with existing interconnection devices.
(So-called router) can be applied. FIG. 8 is a diagram for explaining an example of implementation of the filter device by simple processing. Although the configuration of the terminal 22-1 is the same as the example shown in FIG. 7, the filter device 6-1 does not have a data link processing unit, and has a physical layer processing unit 40-2 and a physical layer processing unit 40-3. In between, the filtering processing unit 43 that performs the above-described filtering processing is provided.

Since the filter device 6-1 does not perform the physical layer conversion like the interconnection device 50 shown in FIG. 7, the physical layer of the data bus 2 and the physical layer of the main information link 21-1 are combined. Are the same. In this embodiment, the existing protocol cannot be used as in the embodiment shown in FIG. 7, but since such a filter device is simpler than the interconnection device 50 of FIG. 7, a lower communication cost is required. Can be expected to be realized. It should be noted that the above embodiment is an example of the present invention, and it is needless to say that the present invention is not limited to this.

[0022]

As described above in detail, according to the present invention, it is possible to realize a public network data communication system which can secure sufficient security at low cost and has a small transmission delay. It has a great effect.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a mode in which data communication is realized by a bus type network according to an embodiment of the present invention.

FIG. 2 is a flowchart of a process of switching from circuit switching to data communication when performing data communication.

FIG. 3 is a diagram for explaining a state of a main information link and a data frame on a bus during data communication.

FIG. 4 is a flow chart of processing when a data frame is transmitted from a terminal to an exchange.

FIG. 5 is a flow chart of processing when the terminal receives a data frame from the exchange.

FIG. 6 is a diagram for explaining a switch configuration for performing switching between data communication and circuit switching with a circuit switching switch.

FIG. 7 is a diagram for explaining internal processing of a terminal or the like when the filter device is realized by a general interconnection device.

FIG. 8 is a diagram for explaining internal processing of a terminal or the like when the filter device is realized by a simple device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 exchange 2 bus 3-i subscriber line control device 4-i control signal communication device 5-i small switch 6-i filter device 7-i identifier 8 switching control mechanism unit 9 router 10 circuit switching switch 11 circuit switching relay line 12 Data communication relay line 20-i Control signal link 21-i Main information link 22-i Terminal

Claims (2)

[Claims] 1. Terminals of unspecified number of users are connected,
In a public communication network that performs data communication with the terminal,
Filter means for transmitting only a data frame having a destination address or a source address as the user's identifier is installed in an exchange that accommodates the terminal for each user, and the terminal is connected to the filter means, A data communication system for a public network using a bus-type network or a ring-type network, characterized in that the filter means is connected to the public communication network in a bus-type or ring-type. 2. A switch is installed between the filter means and the user terminal, and an operation is performed from the user terminal,
2. The public network data communication system according to claim 1, wherein the switch is used to switch between a data communication network and a circuit switching network.