JPS6352829B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention relates to a multi-loop communication system that performs inter-loop communication in a digital communication network composed of a plurality of loop-shaped transmission lines, and particularly relates to a multi-loop communication system that provides excellent serviceability. This invention relates to a multi-loop communication system that enables inter-loop communication.

(b) Background of the technology In recent years, in the field of communications, there has been a demand for improving the serviceability of communication networks. is required to be improved.

(c) Prior art and problems The conventional multi-loop communication system will be explained using FIG.

FIG. 1 is a diagram showing an example of the configuration of a multi-loop communication network. In the figure, SV ₁ to SV ₄ are loop monitoring devices, TN ₁₂ , TN ₁₂ , TN ₂₁ , TN ₂₂ , TN ₃₁ ,
TN ₃₂ , TN ₄₁ , and TN ₄₂ are terminal devices, and LX is a loop coupling device.

Now, when transmitting and receiving communication data between terminals (not shown) connected to terminal equipment TN ₁₁ and terminal equipment TN ₂₂ , first, from terminal equipment TN ₁₁ , which is the terminal equipment on the sending side, Loop coupling device LX sends signaling frames such as addresses indicating the other end station equipment
Send to. As a result, the loop coupling device LX relays the signaling frame to the loop to which the opposite end station device TN ₂₂ is connected, and the communication data is sent to the end station device TN ₂₂ .

However, the conventional multi-loop communication system has the following drawbacks. In other words, when a terminal device in another loop sends a signaling frame to a loop that cannot send or receive frames due to a transmission path failure, etc., the means to know that the terminal device is unable to communicate is to wait for a response. Since there is only a timeout based on a monitoring timer, service quality deteriorates, such as an increase in waiting time until it is known that the connection is not possible, and the reason for the connection is not known. When providing a representative number service in which connection requests are sequentially issued to devices, an increase in waiting time becomes a particularly serious problem.

(d) Purpose of the Invention In order to eliminate such conventional drawbacks, the present invention provides a multi-loop communication system with excellent serviceability by transmitting a response from a loop coupling device to a call request, etc. from a terminal device. The purpose is to provide

(e) Structure of the Invention In a multi-loop communication system that uses signaling frames to connect and disconnect lines in a digital path network configured by interconnecting loops having terminal devices and loop monitoring devices by a loop coupling device, the loop The coupling device includes a means for detecting whether communication is possible in each loop, and when a connection request for a line spanning two loops is received from a calling terminal device, the destination loop of the signaling frame is in a state in which communication is not possible using the above means. The present invention is characterized by being provided with means for generating and transmitting a signaling frame to the effect that connection to the destination loop is impossible in the calling terminal device when this is detected.

(f) Embodiments of the Invention The multi-loop communication system of the present invention will be explained in detail using FIGS. 1 to 4.

FIG. 2 is a diagram showing an example of a signaling frame format. In the figure, CTL is a control code that indicates whether the entire frame is a signaling frame, a data frame, or an empty frame, the DA section is an address that indicates the destination of the frame (hereinafter referred to as address DA), and the OA section is the frame transmission Address indicating the origin (hereinafter referred to as address OA),
LPA is a loop address, NDA is a terminal device address, CHA is a terminal address, CMM is a control code representing a request/response between terminal devices, and DT is data representing additional information related to the control code CMM.

FIG. 3 is a diagram showing the configuration of the loop coupling device LX. In the figure, 1 is a switching circuit, 2 is a control circuit, 3 to 6 are loop coupling circuits, and 7 is a switching bus.

FIG. 4 is a flow chart showing the operation of the control circuit.

Here, we will explain the case where a call is made from a terminal connected to end station TN ₁₁ to a terminal connected to end station TN ₂₁ as inter-loop communication in the multi-loop communication network shown in Fig. 1. do.

First, in the terminal equipment TN ₁₁ , the terminal equipment TN ₁₁
When a call request is detected from a terminal connected to the terminal, the terminal device TN ₁₁ checks the state of the connected loop, etc., and if communication is possible, sends a signaling frame representing the call request, that is, the signaling shown in Fig. 2. Generate a frame and send it to the loop.

Here, the signaling frame sent at that time has the following contents. That is,
The control code CTL shown in Figure 2 is set with a code indicating that the signaling frame is in use, and the address DA is the loop address.
Set the loop address to which the terminal device TN ₂₁ is connected to LPA, the node address of TN ₂₁ to the terminal device address NDA, and the terminal address of the communication destination to the terminal address CHA. Regarding address OA, the own loop address to which terminal equipment N ₁₁ is connected is set to loop address LPA, and the own node (terminal equipment
TN ₁₁ ) Set the caller's terminal address to the terminal address CHA, and enter the control code.
A call request code is set in the CMM. In this case, the contents of the address DT are not particularly set.

When the above signaling frame is transmitted from the terminal device TN ₁₁ , since the destination loop is another loop, the signaling frame is received by the loop coupling device LX. The loop coupling device LX transmits the received signaling frame to the loop connected to the terminal device TN ₂₁ according to the loop address LPA of the address DA. Next, the signaling frame is received by the terminal device TN ₂₁ , and the terminal device TN ₂₁ refers to the control code CMM of the signaling frame and issues a call request to the terminal connected to the terminal device TN ₂₁ . I know what happened.

The terminal device TN ₂₁ checks whether the called terminal can communicate or not, and sends out a response signaling frame as shown below. Address DA is the address OA of the received signaling frame, and address OA is
is the address of the received signaling frame.
Set each DA to the control code CMM,
If the terminal can communicate, a connection possible response code is set; if communication is not possible, a connection failure response code is set.

Furthermore, in the case of a connection failure response, the reason for connection failure is set in the DT.

The above signaling frame is
When sent from TN ₂₁ , it is sent to the terminal equipment TN ₁₁ by the reverse procedure of the call request signaling frame.
received at The terminal device TN ₁₁ then refers to the control code CMM of the signaling frame to determine whether communication is possible.

In normal cases, the above procedure is used to transfer signaling frames between loops.

Next, the operation of the loop coupling device will be explained in detail.

In FIG. 3, the control circuit 2 is a loop coupling device.
Performs LX state management, acknowledgment processing for received signaling frames, etc. The switching circuit 1 performs switching control such as determining a destination loop and generating a switching timing for a received frame. Loop coupling devices 3 to 6 are provided corresponding to each loop, and receive, exchange, and transmit frames under the control of switching circuit 1 in synchronization with the basic clock on the loop.

Furthermore, the loop coupling circuits 3 to 6 have a function of detecting occurrence/recovery of a loop failure and notifying the control circuit 2 of the occurrence/recovery.

If the loop has a frame addressed to another loop, the loop coupling circuits 3 to 6 receive the frame and issue a frame exchange request to the exchange circuit 1. In the switching circuit 1, if the received frame is a signaling frame, it is transferred to the control circuit 2, and if it is a data frame, it is transferred to the loop coupling device of the destination loop of the frame via the switching bus 7. . The loop coupling circuit to which the frame is transferred via the exchange bus 7 sends the same frame to an empty frame on the loop.

On the other hand, after analyzing the transferred signaling frame, the control circuit 2 normally sends it to the destination loop without manipulating the contents of the received signaling frame. When transmitting a signaling frame from the control circuit 2, the circuit issues a frame exchange request to the switching circuit 1, the switching circuit 1 transfers the signaling frame to the loop coupling circuit, and the loop coupling circuit sends it to the loop.

Here, in the above example, the operation of the loop coupling device LX when communication becomes impossible due to the occurrence of a failure in the loop 2 to which the terminal device TN ₂₁ is connected will be described.

The call request signaling frame received by the loop coupling device LX in the above procedure is transferred to the control circuit 2. The control circuit 2 has previously been connected to the terminal equipment.
It can be seen that the loop coupling circuit 2 of the loop to which the TN ₂₁ is connected has notified that a failure has occurred in that loop, and that the call request cannot be accepted. Therefore, the control circuit 2 generates and transmits a connection failure response signaling frame addressed to the calling source in the following format. Address DA and address OA set the contents of address OA and address DA of the received signaling frame, respectively. The CMM sets a connection failure response code. A code indicating the reason for connection failure is set in the DT section.

The above signaling frame is terminal equipment TN11
When received, the terminal device TN11 knows that the line cannot be connected, and can perform terminal control and internal processing. Therefore, communication control can be performed without spending unnecessary waiting time. Furthermore, since the source address of the connection failure response signaling frame sent from the loop coupler LX is the calling party, the calling terminal station
The TN 11 does not need to be aware of the existence of the loop coupling device LX when processing signaling frames, and the control logic may be the same as that of the conventional system. Also,
This embodiment has means for displaying various messages from the TN, and displays them in accordance with the failure reason code included in the connection failure response signaling frame. For example, in the above example, terminal equipment TN21
If the terminal is in use and the terminal is in use, the connection is not possible. If the terminal is in use, the connection is not possible.
"CLOSE" is displayed. This makes it easier for the user to decide on subsequent measures, further improving serviceability.

Further, FIG. 4 is a diagram showing a flowchart of a control circuit within the loop coupling device. As explained above, the control circuit analyzes the signaling frame after receiving it. Then, it is determined whether or not the destination loop indicated in the signaling frame is in operation, and if it is in operation, the signaling frame is sent to the destination loop, and if it is not in operation,
That is, if there is a failure, etc., a non-response signaling frame is generated, the reason for the non-response is analyzed, and the signaling frame is sent to the source loop.

(g) Effects of the Invention As explained above in detail, according to the multi-loop communication system of the present invention, when the other loop of inter-loop communication cannot communicate, the response waiting time can be extremely shortened, and the cause of communication failure can be extremely shortened. Since the judgment can be easily made, it is possible to obtain the effect that the serviceability of the communication network can be improved.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of the configuration of a multi-loop communication network, Fig. 2 is a diagram showing an example of a signaling frame format, Fig. 3 is a diagram showing the configuration of a loop coupling device, and Fig. 4 is a diagram showing the operation of the control circuit. This is a flowchart showing the following. In the figure, SV to SV ₄ are loop monitoring devices,
TN ₁₁ , TN ₁₂ , TN ₂₁ , TN ₂₂ , TN ₃₁ , TN ₃₂ ,
TN ₄₁ , TN ₄₂ are terminal equipment, LX is loop coupling equipment,
1 is a switching circuit, 2 is a control circuit, 3 to 6 are loop coupling circuits, and 7 is a switching bus.

Claims (1)

[Claims] 1. In a multi-loop communication system that uses signaling frames to connect and disconnect lines in a digital communication network that is constructed by interconnecting loops having end station devices and loop monitoring devices using a loop coupling device, each loop is connected to the loop coupling device. means for detecting whether communication is possible or not; and when a connection request for a line spanning two loops is received from a calling terminal device, the means detects that the destination loop of the signaling frame is in a state in which communication is not possible. A multi-loop communication system, characterized in that the calling terminal device is provided with means for generating and transmitting a signaling frame indicating that connection to the destination loop is impossible.