JPH0834478B2 - Node device for irregular communication network - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to control of a communication network, and particularly to a node device of an irregular communication network.

2. Description of the Related Art Conventionally, communication networks particularly applicable to multimedia communication such as local area networks (LANs) and public line networks include CSMA baseband LANs such as Ethernet, wideband LANs, and TDMA baseband LANs. There was a combination of digital PBX and. The CSMA baseband LAN is suitable for communication of information that occurs suddenly, such as data information and text information, but is not suitable for multimedia communication such as when the message length is not limited or when data is transmitted. In the case of continuous occurrence, collisions occur frequently, so that high throughput, that is, communication capacity cannot be obtained.
Lack of applicability as multimedia communication.

Broadband LAN has a shortage of capacity for multimedia communication. In addition, there is a difficulty in the scalability and price of the system. The TDMA baseband LAN is the most suitable for multimedia communication among the conventional methods, but generally has difficulty in system expandability and price. Especially when applied to multimedia communication, the price becomes very high.

In view of such a state of the art, the present inventor has already proposed a lattice communication network based on the analogy of living nerve cells. See, for example, JP-A-58-139543.
In this method, a communication network is formed by connecting a communication control element of a multi-input and one-output signal as a node to a multi-coupling structure, and each node has a communication network form in which digital signals are transferred on a first-come-first-served basis.

This grid communication network is particularly excellent in the following points. One is the high degree of freedom of the network topology due to the multi-connection structure. Therefore, even if fault tolerance (survivability) is high, that is, if there is a failure in a part of the network, communication is adaptively secured through another route. Next, the first-come-first-served logic is used to select an optimum communication path.

However, when it takes a long time to fix the communication route and many short packets are transmitted, the efficiency is as low as that of the conventional CSMA baseband LAN. Therefore, full-duplex communication cannot be performed partially, and if the response signal is returned slowly, detection of communication failure is delayed, and backoff such as retransmission control cannot be performed efficiently. Therefore, it is required to efficiently establish full-duplex communication even in the multi-channel system in which a node simultaneously establishes a plurality of connection channels.

By the way, when the contention method is used for link setting, packet collision has been a major obstacle to obtaining high throughput, that is, effective data rate. The probability of occurrence of collision is proportional to the maximum network propagation delay time, that is, the time required for a packet sent by a terminal to reach the terminal farthest away.

The grid communication networks that have been proposed so far use the first-come, first-served logic for link setting. However, due to the multi-coupling structure, the maximum network propagation delay time is essentially short. Further, it has a characteristic that communication is established if a receiving terminal exists inside the boundary even if a collision occurs according to the first-come-first-served logic, by using a communication control element, that is, a node, which has a multi-input single-output signal. . Multiple communications may be established when a collision occurs. However, it is required to further shorten the maximum network propagation delay time in order to sufficiently improve the throughput.

The function of setting the link for the input channel that receives the earliest signal by the first-come-first-served logic is realized at high speed by the wiring logic. However, if the connection link is set after the arrival of a packet is detected, no matter how the circuit is configured by the wiring logic, there is a possibility that the operation will cause a circuit delay and a part of the tip of the packet will be lost. There is. This missing
It accumulates every time it goes through a node, which is one of the causes for increasing the maximum network propagation delay time.

In the case of half-duplex communication with the multi-channel method, the input channels are connected to all output channels in advance in the idle state of the line, and when the input signal arrives at the input channels, the first-arrival input channel is detected and the other input channels are detected. A method of disconnecting the connection has been proposed (Japanese Patent Application No. 60-
170429). As a result, it is possible to prevent the leading edge of the packet from disappearing for the time required for the first-come-first-served logic.

By the way, in the lattice communication networks proposed so far, the transfer of the backward signal is limited before the transfer of the forward signal is completed (for example, Japanese Patent Application No. 60-170427). In other words, although full-duplex communication was possible basically, for example, while the first message packet was being transferred, the response signal (ACK, NAC
K) was not returned. Therefore, full-duplex communication cannot be performed partially, and if the response signal is returned slowly, detection of communication failure is delayed, and backoff such as retransmission control cannot be performed efficiently.

When the fault tolerant property is emphasized in the grid communication network, it is important to reduce the influence of the failure and to detect the failure location quickly. There are three types of serious obstacles. The first is a failure of the node itself, the second transmission transmission path is a failure, and the third is a reception transmission path. However, in the series of grid communication networks previously filed by the present applicant, the probability that communication is hindered by the first and second obstacles is very small, but in the third obstacle, the first one sent by the node is transmitted. A problem arises when the second piece of outgoing information reaches the terminal. This is because the node having a failure in the reception transmission line was able to transmit the forward information, but the recovery information transmitted by the terminal in response thereto could not be received due to the failure in the reception transmission line.

Object In view of such requirements, it is an object of the present invention to provide a node device of an irregular communication network capable of efficiently ensuring complete full-duplex communication.

More specifically, the object of the present invention is to improve the throughput of the entire network by realizing the full-duplex communication of the multi-channel system by preventing the drop of the packet tip and reducing the probability of collision. Is to let. Another object of the present invention is to provide a node device of an irregular communication network capable of accurately identifying a failure and taking appropriate measures such as line blockage.

To achieve the above object, the present invention is a node device connected to a transmission line including a transmission line to a terminal or a node device and a reception line corresponding to the transmission line, and at least the reception lines are connected to each node device. One input means, at least one output means to which each transmission line is connected, connection means for connecting the input means to the output means, and control for controlling the connection means to selectively connect the input means to the output means In the node device of the irregular communication network having the means, the control means is connected to the input means, the first-arrival input detection means for identifying the earliest input means of the input means, and the identification in the first-arrival input detection means. From the first time period means for starting the time period of the second predetermined period after the lapse of the first predetermined period,
Input control means connected to the first timing means and detecting whether or not a signal arrives at the input means from the reception line, and the control means controls the connection means to set the input means already set. For the transmission path not included in the communication, the input means in the idle state is connected to all the output means except at least the output means corresponding to the input means in response to the identification in the first-arrival input detection means. The connection means is controlled, and all the input means except the identified input means among the input means are disconnected from the output means, whereby the identified input means is identified among the output means. The signal is transferred to all the output means other than the one corresponding to the input means, and the input detection means receives the signal from the reception line to the input means corresponding to the output means of the input means that has transferred the signal. Of the input means being monitored, the input means that has not received the signal within the second predetermined period of time is identified, and the control means receives the signal within the second predetermined period of time. If there is an input means that has received a signal after the elapse of the second predetermined period among the input means that did not exist, the connecting means is controlled to control the input means that has received the signal after the elapse of the second predetermined period. The output means corresponding to the input means having the earliest signal arrives, and the input means corresponding to the input means having the earliest signal arrives for the input means receiving the signal after the elapse of the second predetermined period. It is characterized by a node device of an unfixed communication network that is connected to fix the connection between those input / output means and connects all other input means to all output means except output means corresponding to the input means. is there.

Hereinafter, the present invention will be specifically described based on examples.

An irregular communication network to which the node device according to the present invention is applied,
As illustrated in FIG. 11, the node device 10 is advantageously realized as a grid communication network connected in a two-dimensional or three-dimensional grid pattern by the transmission line 12, but the network configuration is essentially indefinite. is there. For example, other shapes such as linear and loop shapes may be adopted.

The node device 10 is provided with a plurality of, in this example, eight input / output ports, to which other node devices 10 and / or terminals 14 can be connected via a transmission line 12.
There is no limit to the number of input / output ports, and it is sufficient if there is at least one. If the node device 10 is within the capacity of the input / output port, the node device 10 or the terminal connected via the transmission line 12
There is no limit on the number of 14. In addition, the entire network is a single node device
Alternatively, a plurality of node devices 10 may be mounted on a single printed wiring board, for example, and the entire device may be treated as one node device to substantially increase the input / output port capacity. Good.

The terminal 14 is a terminal device capable of asynchronously transmitting and receiving data in this embodiment, and includes a processing system such as a personal computer and a service station such as a file station and a print station. The data is advantageously transferred in the form of message packets. As will be described later, in the case of a full-duplex terminal, the terminal 14 is advantageously of a type that sends a response signal as soon as it receives a packet addressed to the eye station.

The transmission line 12 is, for example, an optical transmission line using an optical fiber or an electric transmission line such as a stranded wire or a coaxial cable. In the present embodiment, data is transmitted in analog or digital. It has a full-duplex configuration. The transmission line 12 between the node device 10 and the terminal 14 may have a half-duplex configuration.
In addition, the transmission path between the node devices 10 depends on the traffic.
A plurality of 12 may be provided.

Referring to FIG. 1, the node device 10 has an input port 20 to which a reception line from the transmission line 12 is connected, and an output port 30 to which a transmission line to the transmission line 12 is connected. They are interconnected via a section 40. The input port 20 is eight receiving or input channels in this embodiment.
i0 to i7 and the output port 30 correspondingly has eight transmission or output channels o0 to o7. As a result, up to eight other node devices 10 and terminals 14 can be connected to the node device 10 via the transmission path 12. Of the output channels o0 to o7, the output channels having the same numbers as the input channels i0 to i7, that is, the "corresponding" output channels are connected to the transmission path 12 of the same route.

The switching gate unit 40 is a gate circuit that selectively interconnects any one of the input channels i0 to i7 and any one of the output channels o0 to o7. The input port 20 is also connected to the start control unit 60 and the end control unit 70 via the control gate unit 50. Control gate unit 50
Is a gate for appropriately controlling connection of signals from the input port 20 to the start control unit 60, and connection of control signals from the start control unit 60, the failure storage unit 210, and the end control unit 70 to the switching gate unit 40 and the end control unit 70. Circuit. The start control unit 60 is a functional unit that identifies the input channel from which the input signal arrives first and detects whether or not there is an input signal in each input channel. The termination control unit 70 is a circuit that detects that there is no input signal in the input channel of the communication path that has already been set, and performs processing for terminating the communication. The switching gate unit 40, the start control unit 60, and the end control unit 70 are connected to each other by a gate set bus 80.

The switching gate unit 40 is also connected to an active signal sending unit 200 for sending an active signal,
This is also connected to the start controller 60. Start control unit 60
The termination control unit 70 is also connected to the fault storage unit 210 that stores the channel in which the fault has occurred. Fault memory 2
10 is also connected to the gate set bus 80.

The switching gate unit 40, the control gate unit 50, the start control unit 60, the end control unit 70, the active signal transmission unit 200, and the failure storage unit 210 are controlled by the sequence control unit 90 that controls the entire apparatus including them.

For the sake of simplicity, a specific configuration of the switching gate section 40 has four 4-input NAND gates 42 corresponding to the number of output channels, that is, in this example, as shown in FIG. A signal line from the active signal output unit 200 is connected to one of these input terminals. The switching gate unit 40 further includes 4x (4-
1) 2 input NAND gates 44, 4x (4-1) / 2 flip-flops 46, AND gates 48 and exclusive OR (E
XOR) gate 49 is connected as shown in the figure.

More specifically, the output 43 of the 2-input AND gate 41 of each of the input channels i0 to i3 is the 4-input NA of all the output channels except for the corresponding one of the output channels o0 to o3.
One input of the ND gate 42 is commonly connected via a NAND gate 44. Further, the NAND gate 44 is provided in the preceding stage with four 2's corresponding to the number of input channels.
An input AND gate 41 is provided, and when one input 45 is energized from the control gate unit 50, the internal circuits of the input port 20 and the switching gate unit 40 are selectively connected.

As shown in the truth table of FIG. 2A, when the input / output channels to be interconnected are designated and the control line of the designated channel of the gate set bus 80 becomes high level, the switching gate unit 40 causes the sequence control unit 90 to Interconnects both channels in response to a negative clock signal from the WRITE 0 input from. The connection between the specified channel and the unspecified channel is disconnected. Further, the connection state at that time is held for the channels not specified at this time. As a result, a multi-channel connection that allows a communication path for a combination of a plurality of input / output channels at the same time in one node device 10 is performed.

In this way, the state of all NAND gates 44 can be set with one control. According to this configuration, the NAND
The number of functional units for maintaining the state of the gate 44, that is, the number of flip-flops 46 can be minimized.

The control gate unit 50 has four OR gates 52, an inverter 54, a three-input NAND gate 56, an EXOR gate 58 and an AND gate as shown in FIG.
The gate 51 is connected and configured as shown. OR
The gate 52 receives the signal 53 from the start control unit 60 and the end control unit 70.
Switching gate unit 40
OR gate for outputting to the four AND gates 41. The inverter 54 and the 3-input NAND gate 56 are circuits that take the logical product of the signal from the input port 20, the signal from the failure storage unit 210, and the signal from the end control unit 70, and output the logical product to the start control unit 60. EXOR gate 58 and AND gate 51
Is to detect the signal from the termination control unit 70 when detecting the end of the communication in which the communication path is set, and to detect the interruption of the first or first forward signal that arrives at the first-arrival input channel. This circuit selectively outputs the output of the start control unit 60 to the end control unit 70.

The node device 10 has an active signal output unit 200,
This is a functional unit that generates an "active signal" indicating that the eye station node and its input / output channel are operating normally, that is, active. The active signal is not limited except for its signal length. The signal length is longer than the minimum time required to operate the flip-flop of the start control unit 60, and is set to such a length that it reaches and finishes within the “active detection time constant” described later.

As shown in FIG. 4, the active signal output unit 200 is
The AND gate 202 for taking the logical product of the signal from the sequence control unit 90 and the signal MODE 0 from the start control unit 60, and the logical product of the output of the gate 202 and the output from the start control unit 60 are obtained. 4 for outputting to the switching gate unit 40
It consists of a NAND gate 204. In this embodiment, the signal MODE 0
Is always set to a high level by the output from the mode changeover switch 67 of the start control unit 60.

The specific configuration of the start control unit 60 is 4 for each input and output for simplification.
As shown in FIG. 5 for the case of channels, it comprises a first-arrival input signal detector 60a and an input signal detector 60b. The first-arrival input signal detection unit 60a is a functional unit that identifies a channel of an input signal that has arrived first among input channels i0 to i3 according to a first-come-first-served logic. This corresponds to the number of input channels,
That is, four flip-flops 62, a group of NAND gates 66, a four-input NAND gate 68 and an inverter 61,
A three-input NAND gate 63, a bus buffer 65, and a mode switch 67 are connected as shown in the figure.

The flip-flop 62 is a circuit that holds the state of the input channel when the input signal arrives. A group of NAND gates 66
Provides a priority among the outputs 64 of the flip-flops 62. The 4-input NAND gate 68 and the inverter 6 have a holding function of fixing the states of all the flip-flops 62 by setting the S terminals to low level in response to the arrival of an input signal to one of the flip-flops 62, and First
This is a circuit for notifying the sequence control unit 90 that the second forward signal has arrived.

The three-input NAND gate 63 calculates the logical sum of the output of the group of NAND gates 66 and the output of the input signal detection unit 60b, and outputs the logical sum to the gate set bus 80 via the bus buffer 65.
Output to The mode changeover switch 67 is always connected in this embodiment.

The input signal detector 60b is a circuit that detects whether or not an input signal arrives at the input port 20. It is configured by connecting flip-flops 69 and 120, four NAND gates 122, and a four-input OR gate 124 as shown. The flip-flop 69 is a two-state circuit for holding the state of the input channel when the input signal arrives. The flip-flop 120 is a circuit for storing the output state of the flip-flop 69 and fixing their states by setting their S inputs to low level. The NAND gate 122 is a gate circuit that controls connection of the output of the flip-flop 69 to the first-arrival input detection unit 60a. The OR gate 124 is a circuit for taking the logical sum of the outputs of the flip-flops 69 and notifying the sequence control unit 90 that the first recovery signal has arrived.

The fault storage unit 210 is a storage circuit for storing a fault or a dormant channel, as shown in FIG. This is set in the flip-flop 212 by ORing the signal from the start control unit 60, the signal from the end control unit 70, and the signal BOOT 0 from the sequence control unit 90 with the flip-flop 212 that performs the storage. 3-input OR gate 214 for
And an OR gate 218 that takes the logical sum of the output of the flip-flop 212 and the setting state of the mode changeover switch 216, and a bus buffer 211 for transferring the logical sum output to the gate set bus 80. The mode switch 216 is
The channel to which the terminal that does not have the function of outputting an active signal is connected is left open.

The termination control unit 70 is composed of a communication termination detection unit 70a and a connection storage unit 70b, as shown in the case of four channels in FIG. The communication end detection unit 70a includes four NOR gates 7
2, a shift register 74, an AND gate 76, and one 4-input OR gate 78 are connected as shown. The NOR gate 72 calculates the logical sum of the signal from the input port 20 and the signal from the output port 30. The shift register 74 is a circuit for detecting the end of communication based on the time according to the communication end detection time constant described later. The AND gate 76 is a circuit that takes the logical product of the output of the shift register 74 and the output of the control gate unit 50. The 4-input OR gate 78 is
This is a circuit that informs the sequence control unit 90 that there is communication that has ended among the communication with the fixed communication path, and that the first outbound signal from the first-arrival input channel has been interrupted. The control gate unit 50 selects which information is to be reported. As can be seen from the above, the termination control unit 70 includes 2 in the communication whose communication path is fixed.
When there is no signal on both input channels,
Identified as the end of communication.

The end of communication is identified by the absence of a signal or the continuation of a predetermined logic state for a period of time according to the communication end detection time constant. The “communication end detection time constant”, that is, the third predetermined period is a time for detecting that the communication has ended because no signal continues after the forward signal or the backward signal. In the case of full-duplex communication, the length is set to the time required to distinguish the end of true communication from the sequence of "0" or "1" which is the information content. Usually, some margin time is added to this. For example, in the case of Manchester coding, a time length of 1 bit is used, and in the case of a coding rule for inserting "0" into "1" of 6 consecutive bits in NRZI, a time length of 7 bits or more is taken. Normally, they are set to twice as long, that is, a time length of 2 bits or 14 bits, respectively. This is the same as the input signal detection time constant.

When half-duplex communication is included together with full-duplex communication, the length of the communication end detection time constant is determined by the propagation delay time for reciprocating the maximum effective network length, and after the terminal 14 has finished receiving the forward signal or the return signal. It is set substantially equal to the sum of the time required to start transmitting the return signal or the forward signal. This is the same as the terminal response monitoring time. Usually, some margin time is added to these.

The connection storage unit 70b includes four flip-flops 71 for storing the channel on which the communication path has been fixed, and an AND gate 73 for controlling writing and erasing of the storage.
And a bus buffer 75 for controlling the connection of the output to the gate set bus 80 are connected as shown in the figure.

According to such a configuration, the shift register 74 can always detect the end of communication for all channels.
That is, since the communication end can be detected also for the channel not selected by the control gate unit 50, there is no delay corresponding to the communication end detection time constant in detecting the communication end when switching is performed.

In addition, in the case of full-duplex communication and the case of including both full-duplex communication and half-duplex communication, the communication end detection time constant may be set accordingly. Therefore, it is not necessary to change the hardware of the device itself.

In addition, instead of these four NOR gates 72, four NAND gates are used.
If a gate is provided, the logical product of the input channel and the output channel can be obtained. In this way, the termination control unit 70 identifies the termination of the communication when there is no signal in one of the two input channels included in the communication with the fixed communication path.

The sequence control unit 90, as shown in FIG. 8, includes five shift registers 91 to 95 and a gate group 96 for appropriately combining the output states thereof to generate a necessary control signal.
When the occurrence and end of communication conflict with each other, a flip-flop 97 and an AND gate 220 for prioritizing the end of communication
The mode switch 98 and the boot switch 99 are connected as shown in the figure. The system clock CK1 is connected to the clock input terminals of the shift registers 91 to 95.
Or CK0 is connected. In this embodiment, the flip-flop 95 is not used, and the mode changeover switch is used.
98 is always open. The boot switch 99 is an operation switch that is operated only when the node device 10 is started up and initializes all flip-flops in the node device 10.
The sequence control unit 90 also does not need to change the hardware of the device itself between the case of full-duplex communication and the case of including both full-duplex communication and half-duplex communication. The operation timing of the sequence controller 90 is shown in FIG. The “active detection time constant” and the “input signal detection time constant” are formed by the sequence controller 90.

An outline of communication control in the node device 10 will be described. Here, for convenience, the term “transmission terminal” refers to a terminal that sends a signal to the transmission line 12, and “reception terminal” refers to a signal that is transmitted to the transmission line 12.
It means the terminal on the receiving side from 12. Also, the term "originating terminal" refers to a terminal in which a connection is not set up with another terminal, that is, a terminal that starts transmitting information addressed to a specific terminal from an idle state, and the "receiving terminal" is the terminating terminal. A destination terminal that returns a response to information for the first time.
A signal transmitted from the transmitting terminal is called an "outgoing signal", and a signal transmitted from the receiving terminal, particularly a signal returned in response to the outgoing signal, is called a "return signal".

In a certain node device 10, in an idle state in which a connection is not set between specific input / output channels, the connection gate of the switching gate unit 40 is in an open state, and all input channels exclude output channels corresponding to each. Connected to all output channels.

When an input signal arrives at any of the input channels i0 to i7 in the idle state, the first-arrival input signal detector 60a
Detects the earliest input signal among the input channels i0 to i7, that is, the "first-come-first-served input channel" by the first-come-first-served logic. In response to the detection of the first-arrival input channel, the switching gate unit 40 disconnects all the other input / output channels except the connections of all the output channels other than the output channel corresponding to the first-arrival input channel and the first-arrival input channel. As a result, broadcasting is performed in which a signal received from the first-arrived input channel is transferred to all output channels other than the corresponding output channel.

The sequence control unit 90 is activated by the detection of the first input channel by the first input signal detection unit 60a, and the sequence control unit 90
Starts the timed monitoring with the active detection time constant.

The "active detection time constant", that is, the first predetermined period, receives the first or first forward signal from the same transmission source from an input channel other than the input channel that first detected the input signal. Alternatively, it is the time for receiving another active signal of the first forward signal from another transmission source.

The length of the active detection time constant is set to be substantially equal to the sum of the propagation delay time that travels the maximum allowable distance between the adjacent node devices 10 or the terminals 14 and the time required for the active signal. Usually, some margin time is added to this. Within this period, the first diverted from the same source
The second forward signal, another first forward signal from another transmission source, or the active signal arrives. This makes it possible to detect a faulty or dormant channel.

The channel in which the input signal arrives within the monitoring time limit of the active detection time constant is stored in the flip-flop of the input signal detection unit 60b. When the period defined by the active detection time constant expires, the sequence control unit 90 clocks the failure storage unit 210, and an input signal does not arrive within the active detection time constant period of the input channels i0 to i3. Store the input channel as a failed or dormant channel in flip-flop 212.

Then, the sequence controller 90 monitors the time constant of the input signal detection time constant. The “input signal detection time constant”, that is, the second predetermined period is a time period for detecting whether or not there is a signal after the lapse of the period according to the active detection time constant.
Its length is, for example, 1 bit in the case of Manchester coding, and 7 bits or more in the case of a coding rule for inserting "0" into "1" of 6 consecutive bits in NRZI. Usually, some margin time is added to this, and it is set to twice as long, that is, a time length of 2 bits or 14 bits, respectively. This activates the input channel that receives the first forward signal from the same source or another first forward signal from another source other than the input channel that detected the input signal first. This is the time for detecting the signal separately from the signal.

The channel in which the input signal arrives within the monitoring time limit of the input signal detection time constant is stored in the flip-flop of the input signal detection unit 60b. When this period ends, the switching gate unit 40 receives an input signal from any of the input channels for which there was no input signal within the period of the input signal detection time constant stored in the input signal detection unit 60b. , Connect its input channel to the output channel corresponding to the first-arrival input channel.

When the time defined by the communication end detection time constant has elapsed, the end control unit 70 instructs the sequence control unit 90, and the sequence control unit 90 resets the first-arrival input signal detection unit 60a and the input signal detection unit 60b to the initial state. .

The end of the communication may be detected by monitoring an input signal from the first-arrived input channel, detecting that the input signal has disappeared, and performing a recovery process. The input signal from both of the other input channels may be monitored to detect that either of them has disappeared, and to perform a recovery process. The detection of the disappearance of the input signal is performed when the logic state of the signal is in a predetermined state for the period of the communication end detection time constant.
For example, it is performed by detecting that it is maintained at "0".

In the above-described embodiment, the input signal is received during the period according to the active detection time constant, and the input channel for which the input signal is not received during the period according to the input signal detection time constant is stored in the input signal detection unit 60b even after the passage. , Only the input signals of those input channels can be detected. After the synchronization period elapses,
It may be configured such that an input channel in which such an input signal does not arrive is connected to an output channel corresponding to the first-arrival input channel and all other input channels are disconnected from the output channel.

When the first recovered signal arrives after the lapse of the input signal detection time constant in the input channel in which such an input signal has not arrived, the input channel that has received the first recovered signal becomes the first-arrival input channel. Connect the first-arrival input channel to the corresponding output channel, and connect the first-arrival input channel to the output channel corresponding to the first input signal from which the recovered signal arrives, fix the path between the input and output channels, and input all other input channels to that input. Connect to all output channels except the output channel corresponding to the channel.

In order to explain the present embodiment, a communication procedure in the system of the present embodiment will be described with reference to FIGS. 10A to 10G for a grid communication network in which four node devices 10 are connected in a grid. In the illustrated communication network, four node devices 10a to 10a
0d are connected in a grid pattern by the transmission path 12. Terminals 14a and 14d are connected to the node devices 10a and 10d, respectively. In the figure, the hatched side indicates the transmitting side, and the thick line indicates the flow of information signals.

For full-duplex communication, detection of an input signal and connection control between input / output channels based on the detection are performed in the following seven basic steps.

First, as shown in FIG. 10A, in the first step, a transmitting terminal which wants to transmit data for the first time from an idle state, for example, 14a, transmits the first outbound signal in the form of a packet to the node device 10a through the transmission line 12a. . The first outgoing signal includes a destination address indicating a destination terminal, for example, 14d. The node device 10a detects the first forward signal as the first-arrival input signal. That is, the channel in which the input signal arrives first, that is, the "first-come-first-served input channel" is identified by the first-come-first-served logic. So the first-arrival input channel
All output channels 12ab except the output channel corresponding to 12a
And the first forward signal to 12ac and so on. That is, the first outgoing signal is broadcast to all routes of the node device 10a.

When the node device 10a further receives the first outgoing signal on the first-arrival input channel, the node device 10a disconnects all the other input channels whose communication paths are not fixed to the output channels, and causes the active signal output section 200 to operate. Active signal 230a from output channel corresponding to first-arrival input channel
Is output.

Next, in the second step, as shown in FIG. 10B, the other node devices 10b, 10c, and 10d also
The first outgoing signal is received from b, 12ac, 12bd, and 12cd, and the same broadcast is performed. In this example, the node device 10c recognizes the transmission path 12ac as the first-arrival input channel and broadcasts it to another transmission path such as the transmission path 12cd. Similarly, the node device 10d receives the first forward signal from the transmission line 12bd as well as from the transmission line 12bd.
bd is recognized as the first-arrival input channel, and only the first forward signal from the transmission line 12bd is broadcast to other transmission lines such as the transmission lines 12d and 12cd, and the signal from the transmission line 12cd is not output. In the node devices 10c and 10d, if the arrival time difference between the first-arrival input signal and another input signal that arrives later than that is shorter than the time required for connection control, duplication occurs for a moment. However, since this occurs in the preamble part of the message packet, there is no problem. In this way,
The first forward signal transmitted from the terminal 14a and broadcast from the node 12 is transmitted in the network without duplication. Thus, the first outgoing signal via the shortest path reaches the terminal 14d.

The node devices 10a to 10d monitor all the input channels within the period of the active detection time constant starting from the detection of the first-arrival input channel, and identify the input channel that has not received the input signal within the period. They are stored in the input signal detector 60b. In each node device 10, if the input channel, the output channel, and other node devices or terminals connected to the node device are functioning normally, the active signal or the first signal is sent within the period of the active detection time constant. The outbound signal should arrive. For example, the node device 10
If a signal is not received by the input port 234bx at b for some reason, this is stored in the node device 10b.

The node devices 10a to 10d detect an input channel having no input signal within the period of the input signal detection time constant that starts after the active detection time constant has elapsed. At this time, the active signal has already ended. At this time, the node devices 10a to 10d may be configured to connect the detected input channel to all output channels other than the corresponding output channel. Furthermore, the node devices 10a to 1
0d is an input channel that is not stored in the input signal detection unit 60b among the detected input channels, that is, an input channel in which a signal arrives within the period of the active detection time constant, and all outputs other than the corresponding output channels. It may be configured to connect to a channel.

In the third step, the terminal 14 connected to the node devices 10a to 10d receives the first outgoing signal. At that time, each terminal 14 sends back the active signal 232, and
The destination address included in the th outgoing signal is compared with the address of the target station. In this example, the terminal 14d sends the active signal 232d, and since the destination address matches that of the eye station, the terminal 14d sends the first or first recovery signal to the transmission line 12d. As shown in FIG. 10C, the node device
10d is the input channel corresponding to the output channel that sent the first forward signal, and the input signal does not arrive within the period specified by the input signal detection time constant, and is defined by the input signal detection time constant. The input channel from which the signal arrived after the end of the period. It is connected to the output channel corresponding to the first-arrival input channel.

In this example, as shown in FIG. 10C, the node device 10d
After the period according to the input signal detection time constant elapses, the transmission line 12
When the signal is received from d, the input channel that receives the signal, that is, the first recovered signal is connected to the output channel 12bd corresponding to the first-arrival input channel. Therefore, the first recovered signal received from the transmission line 12d is the node device 1
It is transmitted from 0d to the transmission line 12bd.

Then usually the terminal response monitoring time or full duplex communication,
After the time corresponding to the communication end detection time constant when half-duplex communication is included, all other input channels are connected to all output channels except the output channel corresponding to that input channel. This can prevent the node device 10d from detecting the first forward signal of the transmission line 12cd in FIG. 10C. That is, in this example, this results in transmission line 12
bd and 12d are mutually connected.

In the fourth step, the node devices 10b and 10a also perform the same control as the node device 10d. Therefore, as shown in FIG. 10D, the first backward signal reaches the transmitting terminal 14a by following the path to which the first forward signal was transferred in the reverse direction.
The first forward signal has a certain length, and the terminal 14
Since the terminal device such as d is configured to transmit the first backward signal as soon as the destination address of the first forward signal is identified, the first backward signal is the first forward signal. It is transmitted while overlapping. Therefore, terminal 14a
Even if other terminals than 14d and 14d are connected to this network, they cannot participate in this communication. As a result, confidentiality of communication with other terminals, which is important for the communication system, is maintained, and multi-channel communication is enabled.

As shown in FIG. 10E, in the fifth step, the node device 10c does not receive the first backward signal from the transmission line 12cd and the first forward signal received up to that time on the transmission line 12ac. When it disappears, it detects this and connects all input channels to all output channels except the output channel corresponding to that input channel. That is, when it is detected that the input signal is not received during the period of the input signal detection time constant, the first backward signal does not arrive after that time, and the first forward signal is not received. , Connect all input channels to all output channels except the output channel corresponding to that input channel. This means that the communication is not routed through the node device 10 and the route is fixed, or the communication is not established and the transmitting terminal has stopped the transmission of the first forward signal. Therefore, in other cases, the arrival of the first recovered signal is guaranteed within the terminal response monitoring time starting from the detection of the first-arrival input channel. When the transmitting terminal 14a stops transmitting the first outgoing signal halfway because the first outgoing signal does not reach the receiving terminal 14d for some reason and therefore the first returning signal is not returned. The same is true for

When both the full-duplex communication and the half-duplex communication are included, the node device 10c does not receive the first forward signal, and thereafter, even if the period due to the communication end detection time constant elapses, the first return signal is returned. When it detects that no signal arrives, it detects this and connects all input channels to all output channels except the output channel corresponding to that input channel. That is, for any input channel that did not receive the input signal,
If it detects that the first return signal has not been received within the terminal response monitoring time that starts from the end of the first forward signal, all input channels are output except the output channel corresponding to that input channel. Connect to.

By such connection control, the sending terminal 14a and the receiving terminal 1
One communication path is set and fixed for communication with 4d. Each node device 10 can control the setting of communication that newly occurs in a path that is not fixed.

Therefore, in the sixth step, when another first outgoing signal newly transmitted from another terminal arrives at the node device 10d, as shown in FIG. 10F, the first first outgoing signal from the aforementioned transmitting terminal 14a is transmitted to the node device 10d. Like the outgoing signal, the signal is propagated through the network by an unfixed communication path. At that time, the path already used for other communication is not used.

The terminating terminal for this new first forward signal is
In response to this, the first return signal is transmitted. This first
As shown in the seventh step in FIG. 10G, the thirteenth return signal also follows the path opposite to the new first forward signal in the same manner as the first return signal for the receiving terminal 14d. To reach the calling terminal. As a result, a new communication path is fixed.

In this way, each node device 10 detects the presence or absence of an input signal and performs sequential control regarding the active detection time constant, the input signal detection time constant, the terminal response monitoring time, and the communication end detection time constant. The same applies to the control regarding the end of communication. For example, in the case of giving permission to continue and terminate communication to one calling terminal in full-duplex communication, that is,
Normally, the first forward signal is connected at an interval shorter than the signal end detection time, and when the return signal is transmitted intermittently, the first forward signal is used for the pair of input channels with the fixed communication path. Detected that the input signal is missing, or that there is no input signal on any of its input channel pairs, then all input channels are switched to all output channels except the output channel corresponding to that input channel. Connecting. Of course, at this time, the return signal is not transmitted.

In the case of half-duplex communication, or in the case of full-duplex communication where there is no need to set the priority for the transmitting station and the receiving station, there is no input signal on both of the pair of input channels that have the fixed path. Then, all input channels are connected to all output channels except the output channel corresponding to the input channel.

Alternatively, instead of using the condition of termination detection that the input signal is lost in both of the pair of input channels, the communication is performed by detecting the loss of the input signal in either the input channel or the corresponding output channel. It may be configured to end. These mean exactly the same, because when one of the input channel pairs with a fixed communication path has no input signal, naturally, there is also no output signal of the output channel corresponding to the other input channel.

Alternatively, instead of using the interruption of the input signal on both of the pair of input channels as the condition for detecting the termination, the termination of the communication is detected by detecting the absence of the input signal on both the input channel and the corresponding output channel. May be configured as follows. If there are no input signals in both input channel pairs having a fixed communication path, there is naturally no output signal in the corresponding output channel, which means the same.

In the present embodiment, in principle, the node device 10 does not distinguish between the connection between the node devices 10 and the connection between the node device 10 and the terminal 14. Therefore, the node device 10
It does not care whether another node device 10 or a terminal 14 is connected to the transmission path 12 connected to it. Therefore, the terminal 14 must behave as if it were the same as the other node devices 10 from the node device 10 to which the terminal 14 is connected. Therefore, it is required to output an active signal if there is an input signal. This can be a single pulse. However, it can also be used in a terminal that does not have an active signal sending function. In that case, in the embodiment of FIG. 2, the output of the failure storage unit 210 may be ignored, that is, the display of the failure monitor may be ignored. Alternatively, it may be preset by the mode changeover switch 216 (FIG. 6) that a terminal without the same function is connected.

The basic restrictions on the communication procedure required for the terminal 14 in the present embodiment are as follows. Advantageously, the terminal 14 is capable of transmitting and receiving data in the form of a packet, but is not necessarily limited thereto.

As shown in FIG. 12, the message packet 100 as the first forward signal includes at least the preamble P and the destination address D prior to the message M. The preamble P needs to last at least a predetermined length. This is for synchronizing the terminals 14. There are no other restrictions on the packet 100, but the packet 100 normally has the address of the transmitting terminal 14, that is, the source address S. The message M is followed by a check code area such as CRC and a packet end code E,
This may be followed by a postamble to keep the terminals synchronized.

Upon detecting the reception of the first forward signal, the terminal 14 immediately outputs an active signal.

When the first outbound signal is received and it is determined that the destination address of the packet is addressed to the eye station, the terminal 14
Is the response signal immediately after the determination in the case of a full-duplex communication terminal (Fig. 12) and immediately after the end of the first forward signal in the case of a half-duplex communication terminal (Fig. 14). , The first recovery signal is transmitted. There is no restriction on the first recovery signal, but the response packet as the first recovery signal 10
2 usually takes the same format as the first forward signal as shown in FIG. 12 or FIG. 14, and has a preamble P,
It has a destination address D and the address of the terminating terminal 14, ie the source address S, followed by a code indicating an acknowledgment ACK or a negative acknowledgment NACK. This may be followed by message M. When full full-duplex communication function such as voice communication and video communication such as videophone is required, response packet 10
2, a message M is also added. As mentioned above, the first
It is assured that the second recovery signal is preferentially transmitted to the calling terminal.

The transmitting terminal 14 monitors the reception of the first recovery signal transmitted from the receiving terminal within the "terminal response monitoring time" of a predetermined length. If the reception of the first return signal is detected within the terminal response monitoring time, it is determined that the receiving terminal is in a state where it can respond normally, and communication can be continued.

The transmitting terminal stops transmission when there is no input signal within the period of the active detection time constant after starting the transmission of the first forward signal or when there is an input signal within the period of the input signal detection time constant. To do. In the former case, it means that there is a failure in the transmission line or node device to which the terminal is connected, and the repair is necessary. In the latter case, it means that a collision has occurred with the node device to which the terminal is connected, and the transmitting terminal shifts to the retransmission processing of the first forward signal.

When the reception of the first backward signal is not detected within the terminal response monitoring time, it is judged that the first forward signal did not reach the called terminal or the called terminal was not in a state where it can respond normally. Then, the calling terminal stops the communication as shown in FIG. The originating terminal 14 can then retransmit the first forward signal. This may be the same control as in the CSMA system, for example. With these functions, the path between the originating and terminating terminals is fixed, and the communication channel can be occupied for communication.

In the case of the terminal of full-duplex communication, the “terminal response monitoring time”, that is, the fourth predetermined period is the time starting from the time when the calling terminal starts transmitting the first forward signal. The length is substantially equal to the sum of the propagation delay time to and from the maximum effective network length and the time required for the receiving terminal to start transmitting the first backward signal after receiving the first forward signal. Are set equal to each other. Usually, some margin time is added to this.

In the case of a system that includes both full-duplex communication and half-duplex communication, the “terminal response monitoring time” is a time that starts from when the transmitting terminal has finished transmitting the first outgoing signal. The length is the sum of the propagation delay time for reciprocating the maximum effective network length and the time required for the called terminal to start transmitting the first return signal after finishing receiving the first outgoing signal. Is set substantially equal to Usually, some margin time is also added to this. Node device within terminal response monitoring time
It is guaranteed that the input signal reaches 10.

The receiving terminal may notify the transmitting terminal of the completion after receiving the first outgoing signal correctly. That is, this is realized by transmitting the first return signal immediately after the reception of the first forward signal is completed. This includes an acknowledgment ACK or a negative acknowledgment NACK.

In this embodiment, since the transmission line 12 is a full-duplex transmission line,
Even if the terminal is a half-duplex device, if the following functions are added to the network interface section, the time for determining whether the terminal is in the receivable state is equivalent to that for a full-duplex terminal. Can be shortened. That is, the network interface unit receives the first outbound signal, reads the destination address of the packet, determines whether or not it is addressed to the own station, and when it determines that it is addressed to the own station, the determination is made. Immediately afterwards,
It is configured to send an active signal as its response signal. "Active signal" has no restrictions,
For example, it may take the form of a single pulse. This corresponds to the first return signal, and is transmitted preferentially in each node device 10. Such an additional function is advantageously realized by slightly modifying the network controller of the half-duplex terminal.

When transmitting the forward signal or the backward signal following the first forward signal or the first backward signal, that is, when transmitting a plurality of packets continuously, the terminal 14 determines the communication interval between the packets. It is sufficient that the time does not exceed the time specified by the end detection time constant. In other words, when communication is continued, that is, when the set communication path is used in a fixed manner, the next time the packet specified by the communication end detection time constant elapses after the end of the packet being transmitted. May be transmitted.

For example, in the case of full-duplex communication, a dummy signal such as a postamble is inserted between successive packets, that is, between the Nth packet and the (N + 1) th packet so that the communication end detection time constant does not time up. To If half-duplex communication is involved, when the packet being received ends,
The transmission packet is transmitted before the communication end detection time elapses. In other words, when the receiving terminal finishes receiving the N-th outgoing signal, within a time period defined by the communication end detection time constant,
Preferably, immediately after transmitting the N-th return signal, the transmitting terminal, upon ending the reception of the N-th return signal, also within the time defined by the communication end detection time constant, preferably immediately immediately after the (N + 1) -th return signal The outgoing signal of is transmitted. For example, if the packet format is not used for audio or video communication,
It is sufficient that the no-signal state is shorter than the communication end detection time constant.

 To end the communication, the terminal may stop transmission.

As long as the restrictions on these communication procedures are followed, the degree of freedom with respect to other points is high, and the following effects can be obtained. First, there is no limit on the maximum and minimum packet lengths, and the packet format does not have to be taken. Next, the number of continuous repetitions of the forward information and the return information is not limited, and the communication channel may be occupied. In addition, if the data rate is less than the maximum data rate determined by the hardware configuring the network, the data rate can be freely determined between the transmitting and receiving terminals. Fourth, full-duplex communication and half-duplex communication can be freely selected and may be mixed.

In summary, in the present embodiment, the node device is configured to transfer the first return signal overlapping with the first outgoing signal.
10 performs two controls. One is to detect the first-arrival input channel, and the other input channel from which the signal arrives, ie the same first outbound signal on another path or another first signal sent from another source. It is to identify the input channel on which the outgoing signal arrived. This identification is performed by the time defined by the input signal detection time constant.
The other one is to detect the presence / absence of an input signal only in the input channels other than the input channels thus detected, and exclude the other input channels. Alternatively, by disconnecting the detected input channel from the output channel, it is possible to transfer only the first incoming signal other than the first incoming signal that arrives first. Good.

As a result, it becomes possible to transfer the first backward signal overlapping with the first forward signal. Therefore, the terminal 14
Upon detecting the reception of the first forward signal addressed to the eye station, the first backward signal may be transmitted immediately, and the first forward signal may be transmitted immediately after the first forward signal is received. It is not necessary to perform control such as transmitting a return signal of.

Further, in the idle state, the connection of the input channel to each output channel is maintained in the conductive state, and the connection of each of the other input channels to each output channel is disconnected upon detection of the first-arrival input channel. It can be broadcast without missing the beginning of the second out signal.

Further, in the present embodiment, when the first forward signal is received, the faulty or dormant input channel is identified by detecting the active signal which should be returned from the node device or the terminal, and its storage, fault indication, and line are identified. Appropriate measures such as occlusion can be taken.

In this way, in this embodiment, one node device 10 realizes multi-channel communication that allows a plurality of communications at the same time. The high fault tolerance of the grid communication network that forms links by first-come-first-served logic while avoiding failed nodes and failed lines is maintained.

In the previous application by the applicant, Japanese Patent Application No. 60-170427, the first forward signal and the first backward signal transmitted after the completion of the full-duplex communication are transferred to transfer the communication path. Has been fixed and allowed full-duplex communication. However, in this embodiment, full-duplex communication is enabled from the time when the first forward signal is transmitted.

By providing such full-duplex communication, the following effects can be obtained. First, since the first backward signal can be transferred overlapping with the first forward signal, it is possible to detect whether or not communication is established by detecting the first backward signal, and it is possible to quickly control the continuation of transmission and the retransmission. Can be done

Next, active reception control is realized. More specifically, only the terminal that transmitted the first backward signal, that is, the receiving terminal can normally receive the first forward signal. Other terminals cannot intercept those signals.

In addition, half-duplex communication is possible with the same node device, that is, the same algorithm, and mixed with full-duplex communication is allowed.

Furthermore, the communication procedure required for the terminal is simple, and the network interface section of the terminal can be made small and inexpensive.
Therefore, a versatile and highly efficient communication method is established. Especially, it is effectively applied to full-duplex communication.

Effect According to the present invention, as described above, by enabling the transfer of the first backward signal overlapping with the first forward signal, the time until the communication path is fixed is shortened, and the completeness in multi-channel is achieved. Full duplex communication is provided. That is,
In the idle state, the connection of the input channel to each output channel is maintained in the conductive state, and the detection of the first-arrival input channel disconnects the connection of each of the other input channels to each output channel. The leading part of the outgoing signal is not lost.

By allowing the simultaneity of the round-trip signals, the failure of communication can be detected at an early stage, so that the back-off such as retransmission control can be efficiently performed and the throughput of the entire network is improved.

In addition, by detecting the return of the active signal from the node device or the terminal, the faulty line can be identified, and appropriate measures such as blocking of the faulty line can be taken. further,
Half-duplex communication is also possible with the same algorithm, and mixed use with full-duplex communication is realized. High fault tolerance is achieved when the network is configured in a grid.

The present invention thus efficiently ensures full duplex communication. Especially, it is effectively applied to the grid communication network.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an embodiment of a node device of an irregular communication network according to the present invention, FIG. 2 is a circuit diagram showing a specific circuit configuration example of a switching gate unit in the node device, and FIG. 2A is the same. FIGS. 3 to 8 are diagrams showing a truth table of the switching gate section, and FIGS. 3 to 8 show a control gate section, an active signal sending section, a start control section, a failure storage section, an end control section and a sequence control section in the node device, respectively. A circuit diagram similar to FIG. 2 showing a specific circuit configuration example, FIG. 9 is a timing diagram showing the operation timing of the sequence controller shown in FIG. 8, and FIGS. 10A to 10G show the present invention. A state diagram showing states at respective stages of communication control in an example applied to a grid communication network of four nodes, and FIG. 11 is a relay system diagram showing an example of a communication network configuration in which the present invention is applied to the grid communication network. , Fig. 12 FIG. 13 is a diagram showing a packet flow when the first backward signal is normally returned in response to the first forward signal in full-duplex communication. FIG. 13 shows the first packet in full-duplex communication. FIG. 14 is a diagram showing a packet flow in the case where the first return signal responding to the th forward signal is not normally returned, and FIG. 14 is a diagram showing a normal response in response to the first forward signal in half-duplex communication. FIG. 13 is a view similar to FIG. 12, showing the flow of packets when the first return signal is returned to FIG. Explanation of symbols of main parts 10 ...... Node device 40 ...... Switching gate unit 50 ...... Control gate unit 60 …… Start control unit 60a …… First arrival input signal detection unit 60b …… Input signal detection unit 70 …… End control unit 80 …… Gate set bus 90 …… Sequence control unit 200 …… Active signal output unit 210 …… Fault storage unit i0 to i7 …… Input channel o0 to o7 …… Output channel

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H04Q 3/545 9466-5K H04L 11/20 102 D

Claims (3)

[Claims] 1. A node device connected to a transmission line including a transmission line to a terminal or a node device and a reception line corresponding to the transmission line, and at least one input means to which the reception line is connected, respectively. At least one output means to which the transmission line is respectively connected, a connecting means for connecting the input means and the output means, and a connection means for controlling the connecting means to selectively connect the input means to the output means. In a node device of an irregular communication network having a control means for controlling the control means, the control means is connected to the input means, and first-come-first-input detection means for identifying the input means to which a signal has arrived first among the input means, A first time limit means for starting a time limit of a second predetermined period after a lapse of a first predetermined period from the identification by the first-arrival input detecting means; and the receiving means connected to the first time limit means. From the line Input detection means for detecting whether or not a signal has arrived, wherein the control means controls the connection means prior to performing predetermined communication, and outputs all the input means in an idle state as the output means. Of all the input means in the idle state except for the output means corresponding to the input means, and when any of the input means in the idle state has an input signal, the input having the input signal is input. The input signal is unconditionally output from the output means connected to the means, and the first-arrival input detecting means detects the input signal from any one of the input means in the idle state, and the input signal is present. When the input means is identified, the connection means is controlled to disconnect the output means of all the input means except the input means having the input signal among the input means in the idle state, and thereby the identified Is it an input method? From the output means to all output means other than the one corresponding to the identified input means, and the input detection means corresponds to the output means of the input means that has transferred the signal. Monitoring whether or not a signal arrives at the input means from the reception line, and identifies the input means that has not received the signal within the second predetermined period from the monitored input means, and the control means If there is an input means that has received a signal after the elapse of the second predetermined period among the input means that has not received the signal within the second predetermined period, the connecting means is controlled to control the second predetermined period. After the elapse of the period of time, the input means receiving the signal is changed to the output means corresponding to the input means having the earliest signal, and the input means having the earliest signal is passed to the second predetermined period. Connect it to the output means corresponding to the input means that received the after signal Fixing the connection between these input and output means, and all other input means node device irregular communication network characterized by connecting all output means excluding the output unit corresponding to at least the input means. 2. The device according to claim 1, wherein the control means outputs at least the output when the first-arrival input detection means identifies the first input means among the input means. Signal output means for outputting a predetermined signal from the output means corresponding to the identified input means, and storage means for storing the input means that has not received a signal within the first predetermined period, The input detection means identifies the input means that has not received a signal within the first predetermined period of the monitored input means for the transmission path that is not included in the already set communication, and the identified. A node device characterized in that input means is stored in the storage means. 3. The apparatus according to claim 2, wherein the control means controls the connection means in response to the storage means with respect to a transmission line which is not included in already set communication. And prohibiting the connection of the input means stored in the storage means to the output means.