JPH05292111A - Transmission line changeover method and device therefor - Google Patents

Abstract

PURPOSE:To apply a large capacity transmission line efficiently through multiplexing by adopting a network of a ring structure at a level of a path group and sending/receiving a control signal integrated in a path overhead for each ring between two points having a changeover switch so as to changeover the path groups. CONSTITUTION:Each section described below being a component of each node in a transmission network using an SDH selects a path level by easy control equal to that of a section level. That is, each of transmission line reception sections 3-1-3-4 terminates an SDH signal received from each of transmission lines 1-1-1-4 and gives the signal to a path connection section 9 in the unit of VC-3/4 and detects path group overhead information. Based on this information, a changeover control section 12 discriminates the selection of the path group and controls the control section 9 to select a path group and transmission line transmission sections 4-1-4-4 multiplex the VC-3/4 from the connection section 9 and send the resulting SDH signal to transmission lines 2-1-2-4. Thus, a large capacity transmission line is efficiently applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for switching transmission lines of a transmission network using synchronous multiplex hierarchy.

[0002]

2. Description of the Related Art Conventionally, CCITT Recommendation G.783 "Characteristics of SDH is used as a transmission path switching method of a transmission network using synchronous multiplex hierarchy.
Synchronous Digital Hierarchy (SDH) multiplexing
equipment functional blocks ", Annex A" Multiplex S
ection Protection (MSP) protocol, commands and ope
ration ", CCITT SG XV Report R 41, (August 1990), a backup transmission line is provided at the section level, and a switching control signal provided in the section overhead (SOH) controls the active transmission line. There was a method of switching to and from the backup transmission line.When the section terminating device detects a section level failure such as section AIS or loss of frame synchronization, it is provided in the SOH between the opposite section terminating device. A switching control signal called an MSP byte is exchanged to switch the transmission path.

[0003] A transmission line switching method for a transmission network using asynchronous multiplex hierarchy, as a method for switching the path level, is described by Teranishi and Kitamura, "Designing Transmission Facilities for Digital Networks," Telecommunications Association (1984). There is known a digital transmission line network switching system described on pages 126 to 131 of the above. In this method, a backup path is provided between the path switching devices on a transmission path different from the working path.
The transmission path fault detected by the device near the switching device is sent to the control device placed in the control station, and the control device controls the switching device based on the sent fault information to determine the working path and the backup path. Switch the path between.

[0004]

In the SDH section level switching method using the MSP described above, an optical fiber as a backup transmission line must be installed separately from the working transmission line between opposing section terminators. .. Therefore, many optical fibers are required for the entire network.

On the other hand, in the digital transmission line network switching system,
Since the backup path can be multiplexed with other working paths, the large capacity transmission method can be efficiently applied and the number of optical fibers in the entire network can be reduced. However, in order to perform the planar switching control, the control station must perform centralized control, which complicates the control.

The problem to be solved by the present invention is SDH
In a transmission network using the above, it is possible to realize a transmission line switching method and device capable of efficiently applying a large capacity transmission line by switching the path level with the same easy control as the section level.

[0007]

In order to solve the above problems, according to the present invention, CCITT G.K. On a ring formed by connecting a plurality of nodes in a transmission network using the synchronous multiplex hierarchy of 708 with a plurality of optical transmission lines, the optical container is multiplied by N times the virtual container level 3 (VC-3) (N is a positive integer). A path ring having a capacity smaller than the minimum value of the capacity of the transmission path is defined, and a set of portions in the path ring of VC-3 and VC-4 having the same route in the path ring is defined as a working path group, A path group whose capacity is equal to the start point and the end point in the working path group and the path ring and whose transmission path in the path ring is in the opposite direction of the working path from the working path is defined as a backup path group, and Switching is performed between the working path group and the protection path group by controlling the switching control signal provided in the signal of the working path group and the signal of the protection path group.

The switching control signal is one of V-3 of VC-3 and VC-4 which constitutes the working path group.
Provided in the path overhead (POH) of C-3 or VC-4.

In the switching control signal, the path group A
A flag indicating IS (PG-AIS) is provided, the PG-AIS flag is set to a code other than all marks at the start point of the path group, and when a failure occurs in the transmission path including the path group, the failure detection point The PG-AIS flag is changed to all marks, and the PG-AIS is set at the end point of the path group.
When the flags are all marks, switching is performed between the working path group and the protection path group.

[0010]

[Operation] A device in which one VC-3 or VC-4 (representative VC) forming the working path group enters the path ring, that is, the start point of the path group is defined in the POH of this VC-3 or VC-4. The PG-AIS flag is set to a code other than all 0s indicating PG-AIS off. When a failure occurs in the transmission path including this path group, the section termination unit of the transmission device that detects this failure converts the multiplexed signal into all ones.
As a result, the PG-AIS flag also becomes all 1, and is detected as PG-AIS at the end point of the path group. At the end of the path group, when PG-AIS is detected, the POH of the representative VC of the backup path
A switching instruction signal is sent to the path group start point by the switching control signal defined in 1. When the switching instruction is received at the path group start point, the path group transmitted from the path group end point to the path group start point is switched from the working path to the protection path, and at the same time, the switching control defined in the POH of the representative VC of the protection path. A switching instruction signal is returned to the end point of the path group by a signal. At the end of the path group, when the returned switching instruction signal is received, the path group transmitted in the direction from the start point of the path group to the end point of the path group is switched from the working path to the protection path.

[0011]

Embodiments of the present invention will be described with reference to FIGS. FIG. 2 is a diagram showing a network configuration in the embodiment of the present invention. This figure shows the network for each level. From the lower level, the section plane 30, VC-3 / 4 path group plane 40, VC-3 / 4 path plane 5
It consists of 0 and. The section surface 30 is a node 32-1.
32-6, and section transmission lines 31-1 to 31-5 connecting these to each other in a ladder shape. On the VC-3 / 4 path group plane 40, path group rings 41-1 to 4-4
1-4 are defined. For example, the path group 41-2
Shows that a part of the band is cut out from the sections 31-1 to 31-4 and set in a ring shape. On the VC-3 / 4 path plane 50, a VC-3 / 4 path is stretched between arbitrary devices and passes through the rings of a plurality of path groups. For example, VC-3 pass 5
1-1 is provided between the node 32-1 and the node 32-6, and passes through the path group rings 41-2 and 41-3.

FIG. 1 shows nodes 32-1 to 32-6 of FIG.
Shows the configuration of. This node is a transmission line 1-
Transmission line receivers 3-1 to 3-4 that terminate SDH signals received from 1-1 to 1-4, path connection unit 9 that connects the terminated SDH signals in VC-3 / 4 units, and transmission line receiver 3 -1 to 3-4, the switching control unit 12 that determines the path group switching based on the path group overhead information and controls the path connection unit 9, and VC-3 / 4 from the path connection unit
And transmission path transmission units 4-1 to 4-4 for multiplexing and transmitting SDH signals to the transmission paths 2-1 to 2-4. The transmission line receiving units 3-1 to 3-4 are section end receiving units 5-1 to 5-4 for terminating the SDH section overhead, and are for terminating the path group and for transmitting the path group information to the control bus 2.
Path group terminal end receiving side 6-1 to 6-4
Consists of. The path connection unit 9 includes a path connection switch 10 that performs cross-connection and switching of paths, and a switch control unit 11 that manages connection information of the path connection switch. The transmission path transmitters 4-1 to 4-4 are the path group termination unit transmitters 7 that write the path group overhead.
-1 to 7-4, and section end section transmission sides 8-1 to 8-4 for writing the section overhead.

FIG. 6 shows the frame structure of STM-N in SDH. The Z3 byte of the path overhead 101 of VC-3 (100) is used as the path group overhead.

FIG. 3 shows a path route during normal operation of this embodiment. The working path group including the VC-3 path 51-1 is set clockwise in the path group ring 41-2, and the backup path group 51-3 is set counterclockwise. On the transmission side of the path group termination unit of the node 32-1,
The path group ring 41 is set by setting the PG-AIS bit provided in the Z3 byte of the path overhead of the VC-3 path 51-1 to 0.
-2. Since the PG-AIS bit is detected as 0 in the node 32-5, the path group ring 41-2
The normality of the working path group in is confirmed.

FIG. 4 shows a path route when a failure occurs in this embodiment. FIG. 5 shows the flow of switching control information corresponding to this. When a failure occurs in the transmission path 32-1, a failure in the transmission path is detected at the section end section receiving side of the node 32-2, and all the sections multiplexed in this section are detected.
Convert the contents of VC to all ones. Therefore, the transmission device 32-5
Then, the PG-AIS bit is detected as 1, and it is detected that a failure has occurred in the working path group in the path group ring 41-2. This information is sent to the switching control unit 12 of the node 32-5. In the switching control unit 12 of the node 32-5, Si which is one of the switching control information
Instruct the sender of the path group termination section to send a gnal Failure (SF). On the transmission side of the path group termination unit of the node 32-5, the SF code is assigned to the switching control information transfer area provided in the POH of the VC-3 toward the node 32-4 in the direction in which the backup path group is set up. Write and send. Since the node 32-4 is not the termination point of the path group 41-2, the SF is passed and sent to the node 32-1. The path group termination unit reception unit of the node 32-1 sends the received SF to the switching control unit 12. When the SF is detected, the switching control unit 12 of the node 32-1 instructs the switch control unit 11 to change the connection of the path group, and the switch control unit 11 controls the path connection switch to switch the path group from the working to the protection. At the same time, the switching control unit 12 of the node 32-1 is Re which is one of the switching control information.
Instruct the sender of the path group termination unit to send a vers Request (RR). On the transmission side of the path group termination unit of the node 32-1, toward the node 32-4 in the direction in which the backup path group is set, the RR code is placed in the switching control information transfer area provided in the POH of the VC-3. Write and send. Since the node 32-4 is not the termination point of the path group 41-2, it passes the RR and sends it to the node 32-5. The path group termination unit reception unit of the node 32-5 sends the received RR to the switching control unit 12. When the RR is detected, the switching control unit 12 of the node 32-5 instructs the switch control unit 11 to change the connection of the path group, and the switch control unit 11 controls the path connection switch to switch the path group from the working to the protection. This completes the switching of the bidirectional path group from the backup system to the working system.

[0016]

According to the present invention, a network having a ring structure is formed at the level of a path group, and switching is performed by exchanging a control signal incorporated in the path overhead for each ring between two points having a changeover switch. The transmission path can be switched with easy control. Also, since the backup path is set at the level of the path group of, it is possible to multiplex and transfer the backup path group and other working path groups, and therefore, it is possible to efficiently apply the large capacity transmission path. You can

[Brief description of drawings]

FIG. 1 is a configuration diagram of a transmission device according to an embodiment of the present invention.

FIG. 2 is a network configuration diagram according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a path route during normal operation according to the embodiment of this invention.

FIG. 4 is an explanatory diagram of a path route when a failure occurs in the embodiment of the present invention.

FIG. 5 is an explanatory diagram of a switching flow according to the embodiment of the present invention.

[Figure 6] STM-N frame configuration diagram

[Explanation of symbols]

1-1 to 1-4: transmission line, 3-1 to 3-4: transmission line receiving unit, 9: path connecting unit, 12: switching control unit, 4-1 to 4-1
4-4: transmission line transmission unit, 5-1 to 5-4: section termination unit reception side, 6-1 to 6-4: path group termination unit reception side, 10: path connection switch, 11: switch control unit,
7-1 to 7-4: Path group termination unit transmission side, 8-1 to
8-4: Sending section end section.

Claims (4)

[Claims] 1. CCITT G.M. 708. A transmission path switching method for a transmission network using the synchronous multiplex hierarchy of 708, wherein a virtual container-level 3 (VC-3) is provided on a ring connecting a plurality of nodes in the transmission network with a plurality of optical transmission paths. A path ring having a capacity smaller than the minimum value of the capacity of the optical transmission line by N times (N is a positive integer) Is defined as a working path group, and the starting path and the ending point in the working path group and the path ring have the same capacity, and the transmission path in the path ring is in the opposite direction of the working path from the working path. A certain path group is defined as a protection path group, and the working path group and the protection path are controlled by controlling a switching control signal provided in the signal of the working path group and the signal of the protection path group. Transmission line switching method for switching between the scan group. 2. The switching control signal is a V of one of VC-3 and VC-4 that constitute the working path group.
The transmission line switching method according to claim 1, wherein the transmission control signal is a switching control signal provided in a path overhead (POH) of C-3 or VC-4. 3. The path group A is included in the switching control signal.
A flag indicating IS (PG-AIS) is provided, the PG-AIS flag is set to a code other than all marks at the start point of the path group, and when a failure occurs in the transmission path including the path group, the failure detection point The PG-AIS flag is changed to all marks, and the PG-AIS is set at the end point of the path group.
The transmission line switching method according to claim 2, wherein when the flags are all marks, switching is performed between the working path group and the protection path group. 4. A section terminal section receiving side for terminating SDH section overhead, a path group terminal section receiving side, a path connecting section for connecting a terminated SDH signal in VC-3 / 4 units, and a transmission line receiving section. A switching control unit that determines the path group switching based on the detected path group overhead information and controls the path connection unit, a path group termination unit that writes the path group overhead, a transmission side unit, and a section termination unit that writes the section overhead. A transmission path switching device composed of a transmission side.