JPH05268235A - Transmission line control system for double loop-type communication equipment - Google Patents

Abstract

PURPOSE:To obtain the transmission line control system for a double loop LAN where a communication line is secured even between nodes which lose the communication line with a master node MN by fault occurrence. CONSTITUTION:When a fault occurs in the transmission line 10 between SN1 and SN2, a node device SN2 is permitted to autonomously execute an operation for transmitting fault information which informs of fault occurrence to the adjacent node device SN1 at a side where the fault occurs and a loop back operation. The node device SN1 which receives the fault information is also permitted to autonomously execute the loop back operation. Thereby, the nodes SN1 and SN2 being adjacent to the fault respectively execute the loop back operation so that the ring-shape transmission line which evades the fault is generated. The loop control is completed in a short time, since MN is not made to interpose.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line control system for a loop type communication device used in a local area network (LAN), an exchange, etc. It is configured to be compatible with.

[0002]

2. Description of the Related Art In a conventional loop type LAN, as shown in FIG. 9, a central node device (hereinafter referred to as MN; master node) having a LAN loop control function and a user terminal 91 are connected. Station node device (hereinafter referred to as SN; slave node), and the 0-system transmission line 10 between them.
And the 1-system transmission line 11 are connected by a double loop.
A maintenance terminal 90 is connected to the MN in addition to the normal terminal.

Each node device (common to MN and SN) is shown in FIG.
As shown in 0, a 0-system transmission line interface 50 and a 1-system transmission line interface 51 that interface with each of the double loops, a transmission line system switching circuit 71 that switches the transmission line system to 0 system or 1 system, and a signal. An interface between a terminal, and a multiplexing / demultiplexing circuit 72 for performing multiplexing or demultiplexing, a node control circuit 6 for controlling the switching operation of the transmission path switching circuit 71 and the multiplexing / demultiplexing circuit 72, and a terminal. The 0-system transmission line interface 50 and the 1-system transmission line interface 51 are provided with transmission circuits 52 and 54 and reception circuits 53 and 55 having a failure detection function. Further, in the MN, the maintenance terminal 90 is connected to the node control circuit 6.

In the LAN shown in FIG. 9, a logical communication path 3 for control information is secured on the loop type transmission path between the control circuit 6 of each SN and the control circuit 6 of the MN, and communication is performed. Between the terminal 91 of SN2 and the terminal 91 of SN4,
A logical communication path 2 for transmitting multiple signals is secured on the loop type transmission path. In steady-state communication, the 0-system transmission line 10 in the double loop is used as the operating system, and the other 1-system transmission line 11 is used.
Is used as a standby system to prepare for failure.

Here, as shown in FIG. 11 (a), 0
When a failure occurs in the system transmission line 10 and communication in that section becomes impossible, the system 1 transmission line 11 becomes the active system and the system 0 transmission line
Loop control called "system switching" that changes 10 to the standby system, and "loop" that forms a ring-shaped transmission line by using one system for bypassing the other system in order to bypass the failure point Control of the transmission line called "back" is performed.

This loopback is performed in the following procedure.

The occurrence of a failure is detected by the receiving circuit 53 of the 0-system transmission line interface 50 of SN2, transmitted from this transmission line interface 50 to the node control circuit 6, and transmitted from the node control circuit 6 via the logical communication line 3. Then, the fault information is transmitted to the node control circuit 6 of the MN (FIG. 11).
(B)).

Upon receiving the fault information, the node control circuit 6 of the MN specifies the loopback execution node, and determines the logical communication path 3
The loopback instruction information is sent to the specified node control circuits 6 of SN1 and SN2 via (FIG. 11 (c)).

Upon receiving the loopback instruction information, SN1 and SN2 start loopback, SN1 transmits the signal received by the 0-system transmission line interface 50 from the 1-system transmission line interface 51, and SN2 The signal received by the 1-system transmission line interface 51 is transmitted from the 0-system transmission line interface 50. By doing this, the terminal
A ring-shaped communication path is secured between 91 (Fig. 11
(D)).

When the fault is recovered, SN2 is set to 0.
System transmission line interface 50 detects normality of the transmission line,
Fault recovery information is transmitted from the node control circuit 6 of N2 to the node control circuit 6 of the MN via the logical communication path 3, and the loopback is released from the node control circuit 6 of the MN to the node control circuits 6 of SN1 and SN2. Is sent,
Return to the initial state.

Further, as shown in FIG. 12A, when a failure occurs in both the 0-system transmission line 10 and the 1-system transmission line 11, the occurrence of the failure is the 0-system transmission line interface 50 of SN2. And the failure information is detected by the 1-system transmission path interface 51 of SN1 and transmitted from the node control circuits 6 of SN2 and SN1 to the node control circuit 6 of MN via the logical communication path 3 (FIG. 12 (b)). ), And then FIG.
Similar to (c) and (d) of 1, loopback is performed by sending loopback instruction information from the node control circuit 6 of the MN that has received the failure information to the node control circuits 6 of SN1 and SN2.

Further, even when a failure occurs in any of the SNs, the node devices on both sides of the failure detect the abnormality, and the loopback is started by the procedure described above.

[0013]

However, in the conventional transmission line control method of the dual loop type communication device, as shown in FIG. 13, when multiple failures occur at a plurality of points, the control for controlling with the MN is performed. SN2, SN3 and S that lost the logical communication path 3
N4 is removed from the loop control target, and all communication on the transmission path is cut off. Therefore, it has a drawback that communication between terminals connected to those SNs becomes impossible.

Further, in the conventional method, since the loop control is performed via the MN, it takes a long time from the occurrence of the failure to the completion of the loop control, and during that period, all the communication paths are in a communication disabled state for a long time. Get burned.

Further, when a failure occurs in the MN,
It also has the problem of causing a system down.

The present invention solves these problems of the conventional system, and the SN that lost the communication path with the MN.
It is an object of the present invention to provide a transmission path control method for a dual loop communication device that can secure a communication path between terminals connected to each other and can complete loop control in a short time.

[0017]

Therefore, in the transmission line control method of the double loop type communication apparatus of the present invention, when a failure occurs in the communication apparatus, the failure is notified to the node apparatus which has detected the failure. An operation of sending information to the adjacent node device on the faulty side and a loopback operation are autonomously performed, and the node device receiving this failure information is allowed to autonomously perform the loopback operation. There is.

Further, the failure information is continued to be sent to the node device which has detected the failure until the failure is recovered.

SDH is used for transmitting fault information.
(Synchronous Digital Hierarchy) SOH (section overhead) is used.

Further, the node device that has detected the failure has a time interval longer than the time required for transmitting the failure information to the adjacent node device from the detection of the failure to the start of the loopback operation.

[0021]

Therefore, since each of the node devices adjacent to the failure autonomously performs the loopback operation, a ring-shaped transmission path avoiding the failure is formed.

In this loop control, it is not necessary to intervene with the MN one by one, so that the communication path can be secured in a short time.

[0023]

[Embodiment] Regarding the transmission path control system of the embodiment of the present invention,
This will be described using the LAN shown in FIG. This LAN is M
N and SN are connected in a loop by a 0-system transmission line 10 and a 1-system transmission line 11. A terminal device 91 is connected to each of the SN and MN, and a maintenance terminal 90 is further connected to the MN.

The configuration of each node device (common to MN and SN) is, as shown in FIG. 2, a 0-system transmission line interface 50 and a 1-system transmission line interface 51, a loopback circuit 71 for switching to loopback, An interface is provided between a terminal 91 and a multiplexing / demultiplexing circuit 72 that multiplexes or demultiplexes signals, a node control circuit 6 that controls switching operations of the loopback circuit 71 and the multiplexing / demultiplexing circuit 72, and a terminal 91. And a line interface 8.

The 0-system transmission line interfaces 50 and 1
The system transmission line interface 51 is composed of transmission circuits 52 and 54 and reception circuits 53 and 55 having a failure detection function, and there is no communication between the node control circuit 6 and the 0 system transmission line interface 50.
In the system transmission path control bus 30, the node control circuit 6 and the system 1 transmission path interface 51 are connected by the system 1 transmission path control bus 31, respectively.

In this LAN, all the data are formed into SDH (Synchronous Digital Hierarchy) frames shown in FIG. 3A and transmitted on the transmission path. This frame (first frame) is composed of an overhead section (SOH) for transmitting control information between nodes, and a payload section for transmitting information that circulates around the loop in a second frame for 125 μsec. It is transmitted at a cycle of (8 kHz).

The SOH is terminated between the adjacent node devices,
The information in the SOH is updated / regenerated in each node device.

As shown in FIG. 3B, in the payload portion, the header portion, the error check information FCS by the cyclic code in the frame, and the 8-bit (Bch) time slot are collected to form the second portion. Frame is constructed. The first frame and the second frame are frequency-synchronized at 8 kHz.

The phase relationship between the first frame and the second frame is designated by a pointer inside the SOH, as shown in FIG. 3 (c). Therefore, one time slot enables communication at 64 kbit / sec, that is, communication equivalent to one telephone line.

The first frames on the transmission lines in the adjacent sections are frequency-synchronized at 8 kHz.

The SOH portion of the first frame includes, in addition to the pointer indicating the phase information, A1 / for establishing synchronization.
A2, data communication channels D1 to D12, STM identification C
1, order wire E1 / E2, user channel F1, bit error monitoring B1 / B2, automatic switching signal channel K
1 / K2 and spare Z1 / Z2. The transmission channel fault information is transmitted to the adjacent node by using the user channel F1 among them.

This fault information is displayed in the 1-byte format shown in FIG. The most significant bit indicates the occurrence of a failure, which is 1 when a failure is being detected and 0 when the failure is normal. The lower 7 bits represent the node number of the node device that has detected the failure, and can store the node numbers 0 to 127. When there is no abnormality in the transmission path, the failure information byte transmits 00h. When a failure occurs,
The node device that detects it stores 1 in the most significant bit and its own node number in the lower 7 bits, and sends this fault information to the adjacent node device on the fault side until the fault is recovered. Keep sending.

FIG. 5 shows an algorithm which defines the operation (transmission path control) to be taken by each node device in response to the failure information. In this figure, the failure information is classified into the following two items, and the operation of the node device is defined by the combination of the failure information of each item. (1) Information on whether or not a failure has been detected by the transmission path reception circuits 53 and 55 of the own node This is information on whether or not a failure has occurred on the reception side transmission path of the own node. In, it is displayed as "abnormal" of "transmission line on the receiving side". (2) Information on whether or not a reception failure is detected by the next node device This is information on whether or not an adjacent node has detected a failure in the transmission output of the transmission path of its own node. This indicates that a failure has occurred in the transmission path on the transmission side. In FIG. 5, this state is displayed as “abnormal” in the “transmission line on the transmitting side”.

First, when all transmission lines are normal, the 0-system transmission line 10 is used for operation, and each node device multiplexes / demultiplexes data with respect to the 0-system transmission line 10.

If a failure has occurred at any one of the 0-system transmission path 10 and the 1-system transmission path 11, a loop-shaped transmission path is formed by avoiding the failure by the loop back operation. At this time, data multiplexing / demultiplexing is performed on the 0-system transmission line 10. A node device in which a failure occurs on the receiving side of the 0-system transmission line 10 or the transmitting side of the 1-system transmission line 11
Loop from receiving 1-system transmission line 11 to transmitting 0-system transmission line 10
A node device that is backing up and has a failure on the receiving side of the 1-system transmission line 11 or the transmitting side of the 0-system transmission line 10 loops from receiving the 0-system transmission line 10 to transmitting the 1-system transmission line 11. Make a back.

When a failure occurs on the transmission side of the 0-system and 1-system transmission lines 10 and 11, or the 0-system and 1-system transmission lines 10 and 11
When a failure occurs on the receiving side of, the node device
It is isolated and cannot communicate between nodes.

If the fault occurs on the 0-system transmission line 10 on the transmission side of the own node, this node device
Fault information is received from the downstream adjacent node device through the 1-system transmission line 11. At this time, this node device loops back from the reception of the 0-system transmission line 10 to the transmission of the 1-system transmission line 11.

If a failure occurs in the 1-system transmission line 11 on the transmission side of the own node, this node device will fail from the adjacent node device downstream of the 1-system transmission line 11 through the 0-system transmission line 10. You will receive information. At this time, this node device loops back from the reception of the 1-system transmission line 11 to the transmission of the 0-system transmission line 10.

When the own node detects a failure, the own node always loops back from the normal system to the failure detection system.

Now, assume that the following situations occur in the LAN shown in FIG. (1) A failure occurs at one point on the 0-system transmission line 10 in operation (2) A failure simultaneously occurs at the same one point on the 0-system transmission line 10 and the 1-system transmission line 11 L according to the road control method
The operation of the AN will be described.

[Operation Corresponding to (1)] (FIG. 6) As shown in (a) of FIG. 6, 0 between SN1 and SN2.
When a failure occurs in the system transmission path 10, the 0-system transmission path receiving circuit 53 of SN2 detects the transmission path failure due to an abnormal reception level or the like, and the node control circuit 6 through the 0-system transmission path control bus 30.
To notify. The node control circuit 6 is a system 1 transmission line control bus
Via 1 31, the 1-system transmission line interface 51 is instructed to transmit the transmission line failure information. In addition, the node control circuit 6 of SN2 sends the loopback circuit 71 a 1-system transmission path after a time (protection time) expected to be required for transmitting the fault information to the adjacent node device (SN1) has elapsed. A loop back instruction from 11 to the 0-system transmission line 10 is issued.

The 1-system transmission line interface 51, which has received the instruction to transmit the fault information, sends an SO to the adjacent node SN1.
The transmission path failure information area in H is used to start sending failure information that notifies the occurrence of a transmission path failure and the detected node number. The transmission of the fault information is continued until the node control circuit 6 gives a cancellation instruction.

The SN1 which has received the transmission line fault information from the 1-system transmission line 11 operates as follows.

The 1-system transmission line interface 51 that has received the transmission line fault information notifies the node control circuit 6 of the fault information.

The node control circuit 6 identifies that the failure detection node is the SN2 downstream of the 0-system transmission line 10, recognizes that a failure has occurred on the transmission side of the 0-system transmission line 10 of its own node, and Based on FIG. 5, the loopback circuit 71 has a 0-system transmission line.
Instructs loopback from 10 to system 1 transmission line 11. The loopback circuit 71 starts loopback based on this instruction (FIG. 6B).

Since the failure information is not transmitted to the other node devices, no change is made and the operation of the 0-system transmission line 10 is continued.

The maximum time required from the detection of a failure to the completion of the loopback is the loopback operation after one node receives the failure information within the transmission delay time (about 125 μsec) for transmitting the failure information to the adjacent node. This is the time obtained by adding the time required for carrying out and the protection time.

[Operation Corresponding to (2)] (FIG. 7) As shown in FIG. 7A, both the 0-system transmission line 10 and the 1-system transmission line 11 have a failure between SN1 and SN2. When the error occurs, the 1-system transmission line receiving circuit 55 of SN1 and the 0-system transmission line receiving circuit 53 of SN2 detect a transmission line failure due to an abnormal reception level or the like, and notify each node control circuit 6 to that effect.

Node control circuit 6 of SN1 which received the notification
Instructs the 0-system transmission line interface 50 to send out failure information of the 1-system transmission line 11, and the node control circuit 6 of SN2.
Instructs the 1-system transmission line interface 51 to send the failure information of the 0-system transmission line 10. Furthermore, after the elapse of the protection time, S
Based on the algorithm of FIG. 5, the node control circuit 6 of N2 tells the loopback circuit 71 from the 1-system transmission lines 11 to 0.
The loopback to the system transmission line 10 is instructed, and the node control circuit 6 of SN1 instructs the loopback circuit 71 to loop back from the system 0 transmission line 10 to the system 1 transmission line 11.

0 of SN1 which received the instruction to send the fault information
The system transmission line interface 50 sends SOH to SN2.
Using the transmission path failure information area in, the transmission of failure information that notifies the occurrence of the transmission path failure and the detected node number is started (however, it is not transmitted to SN2 due to the failure).

Also, the SN2 system 1 transmission line interface
Similarly, 51 starts to send fault information to SN1 informing the occurrence of a transmission line fault and the detected node number (however, it is not transmitted to SN1 due to the fault). The transmission of these pieces of fault information is continued until the node control circuit 6 gives a cancellation instruction.

Also, SN1 which received the loopback instruction
The loopback circuit 71 of SN2 and SN2 starts loopback according to the instruction (FIG. 7B).

The required time from the detection of a failure to the completion of loop back is the same as in the case of "the operation corresponding to (1)".

As described above, the node device that has detected the failure transmits the failure information to the adjacent node device on the side where the failure has occurred, and at the same time, starts the loopback operation by itself. Further, when the node device receives the failure information, the loopback operation is started even if the failure is not detected by itself. Due to these series of operations, the failure
Whether it occurs on one of the transmission lines, on both transmission lines, or when a failure occurs in the node device, loopback is performed and ring-shaped transmission avoids the failure. The road is set.

When the fault that has occurred is recovered,
The transmission line receiving circuit of the node device, which has detected the failure until then, detects the recovery of the transmission path failure by the reception level recovery, synchronization establishment, etc., and notifies the node control circuit 6 to that effect. The node control circuit 6 instructs the transmission path interface to stop transmission of transmission path failure information, and causes the loopback circuit 71 to release the loopback after the protection time has elapsed.

The transmission line interface that has received the instruction to stop the transmission of the fault information stops the transmission line fault information that has been transmitted to the adjacent node, and sets 0 in the transmission line fault information area in the SOH.
The SDH frame containing 0h is transmitted. The adjacent node receiving this frame cancels the loopback and returns to the initial state.

Since the loop control is performed as an autonomous operation of the SN, there is no problem in forming a loopback even if the SN has lost communication with the MN due to a failure.

Therefore, as shown in FIG. 8, even when multiple failures occur at a plurality of different locations, the node devices (SN1 and SN2, SN4 and SN5) adjacent to each failure autonomously loop back. Control is performed to secure a plurality of ring-shaped transmission lines. As a result, M
Even in SN2, SN3, and SN4 where the communication path with N is cut off, a communication path connecting them is formed, and communication between these is possible.

In any case, the failure information is transmitted only to the adjacent node, so that it does not require a long time until the loopback is completed.

[0060]

As is apparent from the above description of the embodiments, the transmission line control system of the double loop type communication device of the present invention enables high speed loop control.

Further, a communication path can be secured even between SNs whose communication path with the MN has been interrupted due to the occurrence of a failure.

[Brief description of drawings]

FIG. 1 is an L for implementing a transmission path control system according to an embodiment of the present invention.
AN configuration diagram,

FIG. 2 is a block diagram of a node device that implements the same transmission line control method;

FIG. 3 is a diagram showing an inter-adjacent-node frame (a), a loop revolving frame (b), and a revolving frame mapping (c) in the adjacent frame, which are used in the same transmission path control system;

FIG. 4 is a diagram showing a failure information format used in the same transmission line control method;

FIG. 5 is a diagram showing a loop control algorithm in the transmission path control system;

FIG. 6 is a diagram showing a 0-system failure occurrence state (a) and a loopback control state (b) in the same transmission line control method;

FIG. 7 is a diagram showing a failure occurrence state of both systems (a) and a loopback control state (b) in the same transmission path control system;

FIG. 8 is a diagram showing a loopback control state for occurrence of multiple failures in the transmission path control system;

FIG. 9 is a block diagram of a LAN that implements a conventional transmission path control method;

FIG. 10 is a configuration diagram of a conventional node device,

FIG. 11 is a diagram showing a 0-system fault occurrence state (a), a fault detection state (b), a loopback instruction state (c), and a loopback control state (d) in the conventional transmission path control system. ,

FIG. 12 is a diagram showing a fault occurrence state of both systems (a) and a fault detection state (b) in the conventional transmission line control method;

FIG. 13 is a diagram showing a multiple failure occurrence state in the conventional transmission path control system.

[Explanation of symbols]

 MN Master node device SN1 to SN5 Slave node device 10 0 system transmission line 11 1 system transmission line 2 Logical communication channel for user information 3 Logical communication channel for control information 30 0 system transmission line Control bus 31 1 system transmission line Control bus 4 Multiplexing control bus 50 0 system transmission line interface 51 1 system transmission line interface 52 0 system transmission line transmitting circuit 53 0 system transmission line receiving circuit 54 1 system transmission line transmitting circuit 55 1 system transmission line receiving circuit 6 node control Circuit 71 Loopback circuit 72 Multiplexing / Demultiplexing circuit 8 Line interface 90 Maintenance terminal 91 Terminal

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Ken Tomioka 4-3-1, Tsunashima-higashi, Kohoku-ku, Yokohama-shi, Kanagawa Matsushita Communication Industrial Co., Ltd.

Claims (4)

[Claims] 1. A transmission line control method for a dual loop type communication device in which a plurality of node devices are connected by a dual transmission line for transmitting data in opposite directions, wherein when a failure occurs in the communication device, A node device that has detected a failure causes the node device that has received the failure information to autonomously perform an operation of sending failure information that informs the occurrence of the failure to an adjacent node device on the side where the failure has occurred, and a loopback operation. A transmission path control system for a dual loop communication device, characterized in that the device autonomously performs a loopback operation. 2. The transmission path control method for a dual loop communication device according to claim 1, wherein the node device that has detected the failure continues to send the failure information until the failure is recovered. 3. SDH for transmitting the fault information
2. A (synchronous digital hierarchy) SOH (section overhead) is used.
Alternatively, the transmission line control method of the double loop communication device according to the item 2. 4. The node device that has detected the failure has a time interval longer than the time required for transmitting the failure information to the adjacent node device from the detection of the failure to the start of the loopback operation. The transmission path control method for a double loop communication device according to claim 1,