JPH03207138A - Clock path switching system - Google Patents

Abstract

PURPOSE:To secure a communication between nodes by sending out the free- running output of a clock oscillator which oscillates by itself in a normal direction by a subordinate node which is sited between two fault points and receives a clock sent back in the opposite direction from the normal direction. CONSTITUTION:A node B generates a clock signal of the same frequency with a received clock CK1 from a main node A through a clockwise transmission line 1R in subordinate synchronism with the clock CK1 and sends the clock signal out to a next node C through a clockwise transmission line 1S. If a clockwise transmission line to a next node D, however, is faulty and disconnected, the node C sends the received clock CK1 back to a counterclockwise transmission line 2S in the opposite direction from the normal direction and disconnects the faulty point. When the counterclockwise transmission line 2S is faulty and disconnected, the node D at a reception terminal oscillates a signal of the same frequency as the oscillation frequency before the node C disconnects the clockwise transmission line 2S by itself and sends its free-running output to the clockwise transmission line 1S while supplying the clock to its multiplexing device MX to serve as a main node temporarily. Consequently, the communication between the nodes C and D is secured.

Description

[Detailed Description of the Invention] [Summary] A clockwise and counterclockwise duplex transmission line is provided for each multiplexer MX of a plurality of nodes arranged in a ring from a main node A having a clock reference oscillator. It is connected to a ring network that is connected to a plurality of subordinate nodes B, C, and D, and has a function of transmitting a detection signal of the failure to the transmitting side and a function of isolating the failure point when there is a failure in the receiving clock of the transmission line. , In the case of a double failure in which the ring network clock has a failure at one clockwise location and another counterclockwise location, a closed loop of the clock path is created between dependent nodes C and D sandwiched between the 2m failure point. For the purpose of clock path switching method 2 that prevents this from occurring and ensures communication between nodes C and D, the received clock is returned to each dependent node in the opposite direction to the normal direction and the fault is isolated. It is equipped with a clock oscillator PLO that self-oscillates a signal with almost the same frequency as the oscillation frequency before disconnection as the clock of the multiplexer MX, and the clock oscillator PLO is equipped with a clock oscillator PLO that self-oscillates as the clock of the multiplexer MX. In this case, the dependent node D, which received the clock that was sandwiched between two failure points and returned in the opposite direction to the normal direction, sends out the free-running output of the self-oscillated clock oscillator PLO in the normal direction. .

[Industrial application field]

The present invention relates to, for example, an optical communication ring network in which a main node gate and a plurality of subordinate nodes S, -S are arranged in a ring according to the Digital High 7 Rarch. Therefore, if you have a duplex transmission line with the clockwise and counterclockwise sections as the working system and the backup system, the working system clock path and This article relates to a bus switching method with a backup clock path.

[Conventional technology]

As shown in FIG. 4, a conventional ring network has a main node and a plurality of subordinate nodes Sr'-'S. are arranged in a ring shape, and as shown in FIG. 5, the clock of the master OSC of the main node H is supplied to the multiplexer 1iMX, and each subordinate node S
, -S, are sequentially supplied with clockwise (solid line) clock CK and counterclockwise (dotted line) clock CK to each subordinate node St"-h, and each subordinate node is connected to its own node. The lead-in oscillator PLOa is synchronized to the frequency of the reference clock CK or CK from the main node A.

Then, in each dependent node of the ring network, each dependent of the conventional clock path switching method uses, for example, the clockwise clock path CK as the active system, and switches to the counterclockwise protection clock path CK2 when the active system clock path CK fails. As shown in Fig. 6, the node is the receiver OR of the working system.
When the clockwise working clock CK, received by OR. The receiving switch S-8 switches the received counterclockwise backup system clock CK2 to the clockwise clockwise active transmitter OS. If a failure occurs, the counterclockwise standby transmitter O
Transmission switch S++ to switch to the state of sending to S2
, and the clockwise/counterclockwise switching board S1,
Current system clock CK. Path switching between the bus and the standby clock CK was being performed.

[Problem to be solved by the invention]

The conventional clock bus switching method shown in FIG. . becomes a fault between dependent node C and subordinate node B, and counterclockwise clock CK2 becomes a fault between subordinate node D and main node A [2]. Because of this loopback, a closed loop of the clock path occurs between the dependent nodes C and D sandwiched between the failure points [1] and [2], and the clock synchronization between the dependent nodes C and D is lost, resulting in communication failure. The problem of this invention is to have a transmission line arranged in a ring from the main node A and duplicated clockwise and counterclockwise in order to synchronize the clocks of multiple nodes. In a ring network consisting of a plurality of dependent nodes B, CD, which has a function of detecting a fault in the received clock and transferring the detection signal to the transmitting side, and a function of isolating the faulty part using the detection signal when there is a fault in the transmission path, When the clock path of the ring network becomes a failure at one point in the clockwise direction and another point in the counterclockwise direction, a subordinate node C sandwiched between the two failure points
, D, thereby preventing the occurrence of a closed loop on the clock bus between the subordinate nodes C and D, and ensuring communication between the subordinate nodes C and D.

(Means for Solving the Problem) As shown in Fig. 1, this problem is solved by having each subordinate node B, C, and D synchronize their own clocks with the clock from the main node A of the ringtone network. , like node 8, sequentially sends out the dependent outputs oscillated in slave synchronization with the received clockwise clock CK, to the next node C on the clockwise transmission path. When transmission line ■ has a failure, the data sent to node D is looped back to the next node D via the counterclockwise transmission line opposite to the normal one, isolating the fault, and the next node receives the looped back counterclockwise clock CK. D is a chronograph oscillator (P) that disconnects the counterclockwise transmission line ■ when there is a failure, and self-oscillates with high stability a signal with almost the same frequency as the oscillation frequency before the disconnection.
LO) 1, and in the case of a double failure in which the Cronk transmission line becomes a failure at one point in the clockwise direction of the network [2] and another point in the counterclockwise direction [2], there are two points of failure. [1] [
2], the node C at one end of the node sandwiched between the nodes returns the normal clockwise clock CK to the opposite counterclockwise transmission line 2S, and the dependent node at the other end receives the looped counterclockwise clock CK. This problem is solved by the present invention, in which D sends out the free-running output of a clock oscillator PLO that self-oscillates a signal with almost the same frequency as the oscillation frequency before disconnection of the counterclockwise transmission line 2S to the normal clockwise transmission line. Ru.

In the principle diagram of FIG. 1 showing the basic structure of the clock path switching method of the present invention, 1 is a clock oscillator PL for the multiplexer MX provided at each subordinate node B, C, D of the ring network.
Normally, a node B, such as a node B, generates a clock signal of the same frequency in synchronization with the clock CKI received from the main node A, for example, on a clockwise transmission path IR, and supplies it to the multiplexer MX of its own station. Then, the dependent signals are sent to the next node C on the clockwise transmission path in order. However, when the clockwise transmission path 2 to the next node is disconnected due to a failure, as in the case of node C, the received clock CK. is looped back to the counterclockwise transmission line 2S in the opposite direction to the normal direction, and the faulty point (■) is isolated. The next node D in the counterclockwise direction receives the clock CK, which is returned to the counterclockwise transmission path 2S.
If the counterclockwise transmission line ■ ahead is disconnected due to a failure, node C
is the oscillation frequency CK. of the clockwise transmission line 2S before disconnection. It self-oscillates a signal with almost the same frequency as the multiplexer MX of its own station.
At the same time, it is arranged to supply the signal to the clock as a clock and at the same time send it to the normal clockwise transmission line 1S.

[Effect]

The PLO of the clock oscillator 1 of the present invention is provided at each subordinate node B, C, D of the ring network, and its output becomes the transmission clock of each multiplexer MX. It slave-synchronizes with the clock CK received on the transmission line IR, generates a clock signal of the same frequency, and sends the slave output to the next node C on the clockwise transmission line Is. However, at node C, the transmission line from the same clockwise transmission line 1SO to the next node D is disconnected due to a fault, so the received clock CK is looped back to the counterclockwise transmission line 2S in the opposite direction to the normal direction and is routed to the faulty point. to separate the Then, the node D at the end that receives the clock CK, which is returned to the counterclockwise transmission line 2S, is located at one point in the counterclockwise transmission line 2S beyond that.
Since it is disconnected due to the failure, it is also separated from the failure point ■. Then, node D is connected to clockwise transmission path 2.
Self-oscillates with high stability a signal of almost the same frequency as the frequency normally oscillated in slave synchronization with the reception clock CK of the clockwise transmission line IR from the main node ^ before disconnecting S.
It supplies the multiplexer MX of its own station as a clock, and at the same time sends its free-running output to the clockwise transmission line 1S, temporarily serving as a main node. Therefore, the clock path switching method of the present invention can prevent a double failure in which the clockwise clock CK is a failure at one point in the clockwise direction of the ring network and the counterclockwise clock C) is a failure at another point [2]. In this case, the dependent node D at one end of the dependent nodes C and D sandwiched between the two failure points [1] and [2] clocks the free-running output of its clock oscillator 1 to the multiplexer MX of its own station. At the same time, it serves as the main node that sends data to the clockwise transmission path, so that a closed loop of the clock path is prevented from occurring between the subordinate nodes C and D.
Since communication between D is ensured, the problem is solved.

〔Example〕

FIG. 2 is a block diagram showing the structure of the subordinate node D of the clock bus switching system according to the embodiment of the present invention, and FIG. 3 is a time chart for explaining its operation.

In the block diagram of FIG. 2, the PLO of the clock oscillator 1 of the dependent node D normally uses the working system clock CK, which the working receiver OR, receives from the clockwise transmission path IR.
After confirming that there is no backup system clock CK2 received from the counterclockwise transmission line 2R by the backup receiver OR, using the gate NAND via the reception switch SW* and the separation device DMUX, the clock CK1 is transferred to the active system clock CK1. Oscillates in slave synchronization. Then, a dependent output of the output of the clock oscillator PLO is sent to the clockwise transmission line 1S from the current transmitter OS via the transmission switch SUS via the multiplexer MUX.

Then, a failure occurs in the clockwise transmission path IR from the previous node C to the active receiver OR, and the input of the active system clock CK is cut off, and the backup system clock CKt is sent from the backup transmitter OS. In the case of a double failure in which a failure (2) occurs in the counterclockwise transmission line 2S and the output of the backup system clock CK, is cut off, the clock CK. is the third
As shown in (1) NG 1 in the time chart in the figure, it is disconnected at time t1, and the information returned to the previous node C is (2) SEND
It is returned at time t2 as shown in I.

Then, the normal backup clock CKt input from the counterclockwise transmission B2R to the backup receiver ORg becomes the working clock CK, which was turned back from the clockwise transmission path IR to the counterclockwise transmission path 2S at the previous node C. t, and the spare receiver OR. As shown in (3)NG2, the output changes from the backup system clock CK2 to the active system clock CL at time t3.

Then, it is output from the spare receiver OR, and is sent to the gate AND via the receiving switch SWII and the isolation device IDMυX.
One of the input information that is input to (4) slave clock 7 is the active system clock CK, and the backup system clock CK. are continuous, but the other input is the output NG of the backup receiver OR, the output NG of the current receiver OR, the output NG L of the return information to the previous node C. } Like (5) NAND output, the NAND output changes from "H" to "L" at the time t when it changes from the backup system clock CKz of N, G 2 to the active system clock CX.
(6) The normal active system clock CK, which is the PLO dependent clock of the AND output, is cut off at time t3, and the clock oscillator PLO, which had been oscillating in dependence on the active system clock CK+, is cut off at time t3. , (7) Like the transmission clock, it self-oscillates from the above-mentioned time point t3 and sends its free-running output from the current transmitter OS to the clockwise transmission line 1S via the multiplexer M[IX and the transmission switch S6. do.

Therefore, the clock path switching method according to the embodiment of the present invention shown in FIG.
The clockwise clock CL becomes a failure at one point ■ of R, and the counterclockwise clock C fails at another point [2] of the counterclockwise transmission line 2S-2H.
In the case of double failure where K, becomes a failure, two failure points [
1] The subordinate node D at one end of the subordinate nodes C and D sandwiched between [2] supplies the free-running output CK of the Cronk oscillator 1 as a clock to the multiplexer MX of its own station, and at the same time performs clockwise transmission. Since it serves as the main node for sending data to the path 1S, the generation of a closed clock path loop between the subordinate nodes C and D is prevented and communication between the nodes C and D is ensured, so there is no problem.

〔Effect of the invention〕

As explained above, according to the present invention, in a ring network in which the transmission path is duplicated in the working system and the protection system, even in the event of a double failure in which both the working system and the protection system fail, the failure point Since communication between nodes sandwiched between nodes is maintained, the reliability of communication in the ring network can be improved.

[Brief explanation of drawings]

FIG. 1 is a principle diagram showing the basic structure of the clock path switching method of the present invention. FIG. 2 is a block diagram showing the structure of node O in the clock path switching method of the embodiment of the present invention. A time chart for explaining the operation of the embodiment of the invention, FIG. 4 is a block diagram of a conventional ring network, FIG. 5 is a block diagram of a conventional Cronk path switching method, and FIG. 6 is a subordinate node of a conventional ring network. FIG. 7 is a block diagram of a conventional clock path switching system. In the figure, 1 is a clock oscillator, Is and IR are clockwise transmission lines, and 2S and 2R are counterclockwise transmission lines. L3 Is it time to make a successful August masterpiece by Shio Shio in August? 1st Figure 3 BiLOo- Zu1△Protect the link of the vagrant, , Pro of the dependent node of the network,,
, Figure 6 Figure 6: Clock path of the control system, front diagram of the Toshin method Figure 7
figure

Claims (1)

[Claims] For each multiplexer (MX) of a plurality of nodes (B, C, D) arranged in a ring on a transmission line from a main node (A) having a reference clock oscillator, the transmission line A plurality of dependent nodes (B, C, D
) In a ring network consisting of It is equipped with a clock oscillator (1) that oscillates, and the clock of the ring network is connected to the clockwise transmission path (1S,
In the case of a double failure in one point [1] of 1R) and another point [2] of the counterclockwise transmission line (2S, 2R), the fault occurs between the two failure points [1] and [2]. The subordinate node (C) at one end of the received node returns the received clock in the opposite direction,
The dependent node (D) at the other end receives the folded clock in the opposite direction to the normal clock and generates a self-oscillated clock oscillator (
A clock path switching method characterized by sending out the free-running output of 1) in the normal direction (1S).