CN1126331C - Automatically protected switching method and device in high rate SDH loop - Google Patents

Abstract

A method and device for automatic protection switching on a high-speed SDH loop. The working process is as follows: perform networking configuration, detect multiplex section-level alarm information and extract K bytes, judge whether switching or recovery is required, and execute if necessary The new K bytes are inserted into the overhead bytes and reported at the end; if not needed, just insert the K bytes directly. The present invention uses the APS standard signaling suggested by ITU-T G.841 to respond to the signaling, which is an APS scheme of the double-end protection mechanism; the protection channel that can be used by all nodes on the entire ring is pre-configured to make the allocation of the channel more reasonable; Strictly follow the signaling usage specification, which is compatible; make full use of the original hardware resources, and reduce the cost.

Description

Automatic protection switching method and device on high-speed SDH loop

The present invention relates to SDH (Synchronous Digital Hierarchy synchronous digital system) automatic protection switching (Automatic Protection Switching is called for short APS) method and device of SDH (Synchronous Digital Hierarchy synchronous digital system) optical transmission network, more specifically, is a two-fiber bidirectional multiplexing section on a high-speed SDH loop A shared automatic protection switching method and device.

At present, the SDH optical transmission network has been widely used in the field of communication. With the needs of the society and the advancement of technology, the speed of the SDH optical transmission network is getting higher and higher, especially in the trunk optical cables. Most of the 2.5G bit /s or even higher-speed SDH equipment, which makes the "self-healing function", that is, the automatic protection switching function, which is one of the two advantages of SDH optical transmission network, more and more important. The ITU-T (International Telecommunication Union Telecommunication Standardization Sector International Telecommunication Union's branch on telecommunication standards) Recommendation G.841 "Types and Characteristics of SDH Network Protection Architecture" made specific details on the automatic protection switching function of SDH networks. suggestion. However, this standard only makes logical provisions on the APS algorithm and communication protocol, and does not involve the realization of the device level. The patent application (application number: 96195023.4) "Self-Healing Network" submitted to the Chinese Patent Office by Allison Telephone Co., Ltd. of Sweden on June 18, 1996 proposed its own solution to the automatic protection switching function of SDH optical transmission network. This patent uses the detection function of network nodes to detect faults related to this node (such as the fiber cut between two nodes). , automatically restore the sending service to the original route to achieve the self-healing function. However, through analysis, it is found that it has the following deficiencies: 1. Since no signaling technology specially used for self-healing function is used, this technical solution is only a single-ended protection solution. Signal failures in different light directions cause a chain reaction of switching, which adds additional workload and complex calculations to the protection function control unit. 2. The distribution of protection channel and working channel is unreasonable, and the operability is poor. When an alarm triggers the protection function, the protection channel needs to be reassigned. 3. This solution can only perform switching when the optical fiber signal is completely in failure. When the optical fiber on both sides of the network element node has a signal failure, it cannot be evaluated and optimized according to the quality of the optical signal on both sides. 4. Poor compatibility. Since this solution is a technical solution independently developed by Allison, it will be incompatible with SDH optical transmission equipment produced by other manufacturers due to different protection mechanisms during networking.

An object of the present invention is to propose an automatic protection switching method with strong compatibility, reasonable channel allocation, dual-end protection mechanism and the ability to evaluate and optimize the optical signals on both sides. Another object of the present invention is to propose and realize the above method installation.

An automatic protection switching method on a high-speed SDH loop, its work flow is as follows: first, when the system starts, the APS configuration and maintenance module of the network management layer performs networking configuration; secondly, after entering the normal working state, the line signal alarm extraction module dynamically Detect the multiplex section-level alarm information in the two optical directions and notify the APS core processor module, and at the same time, the APS signaling byte extraction and insertion module dynamically extracts K1 and K2 in the multiplex section overhead bytes in the two optical directions byte and notify the APS core processor module; then, the APS core processor module synthesizes the received information and makes a judgment according to the APS algorithm whether to perform bridge switching or switching recovery. If bridge switching or recovery operation is performed, the bridge switching is commanded The action execution module performs bridge switching operation or switching recovery operation, and then the APS core processor module inserts the K1 and K2 bytes reflecting the current status of the node into the multiplex section in the corresponding optical direction through the APS signaling byte extraction and insertion module In the overhead bytes, the last bridge switching action execution module reports the operation information to the network management layer APS configuration maintenance module; if bridge switching or recovery operations are not required, the APS core processor module only needs to extract and insert the module through the APS signaling byte Just insert the K1 and K2 bytes reflecting the current status of the node into the multiplex section overhead bytes in the corresponding optical direction.

In the above workflow, when the system is started, the APS configuration and maintenance module of the network management layer performs networking configuration, which means that the APS configuration and maintenance module of the network management layer provides the required initial data information to the APS core processor module, and completes the time slot crossover configuration under normal conditions. And the allocation of working channel and protection channel. The initial data information includes the identification ID of the current network element node and the identification IDs of two network element nodes adjacent to the current network element.

The multiplex section level alarm information in the above workflow includes multiplex section level frame loss, multiplex section level signal loss, multiplex section alarm indication signal and multiplex section level signal degradation.

The bridging and switching operation refers to sending the services multiplexed from the optical branch to the optical group of the node and the direct service from the node to the protection channel at the same time as the working channel, and splitting from the optical group to the optical branch of the node Outgoing services are transferred from working channel reception to protection channel reception.

An automatic protection switching device on a high-speed SDH loop, including a network management layer automatic protection switching configuration maintenance module responsible for networking configuration, maintenance and debugging, and the network management layer automatic protection switching configuration maintenance module sends network management maintenance and debugging commands to the automatic Protect and switch the core processor module and receive the processing information reported from this module; the line signal alarm extraction module responsible for extracting the multiplex section level alarm information on the optical lines on both sides, the line signal alarm extraction module extracts the multiplex section level alarm information out and send it to the automatic protection switching core processor module; the automatic protection switching signaling byte extraction and insertion module responsible for the extraction and insertion of the K1 and K2 bytes in the multiplexing section overhead bytes on both sides of the optical line, the automatic protection switching The protection switching signaling byte extraction and insertion module sends the extracted K bytes to the automatic protection switching core processor module and receives the insertion K bytes from this module; the bridging switching action execution module responsible for the allocation of working channels and protection channels, so The bridging switching action execution module is responsible for executing bridging switching or switching recovery commands from the automatic protection switching core processor module; and the automatic protection switching core processor module that integrates various information and makes decisions and controls according to the automatic protection switching algorithm.

In the above device, the network management layer APS configuration maintenance module is located in the subnet management control center; the line signal alarm extraction module is located on the optical interface board; the APS signaling byte extraction insertion module and the APS core processor module are located on the optical line overhead processing board; The switching action execution module is located on the time slot cross board.

The communication between the APS core processor module and the network management layer APS configuration maintenance module in the above device is forwarded through the network element control board.

The interface between the APS core processor module and the network element control board is a dual-port RAM.

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Figure 1-A is a schematic diagram of an SDH ring network in a normal state, and Figure 1-B is a schematic diagram of an SDH ring network after bridging and switching;

Fig. 2 is the principle structural representation of device of the present invention;

Fig. 3 is a schematic diagram of the hardware structure of SDH optical transmission equipment;

Fig. 4 is a flow chart of the automatic protection switching method of the present invention;

Fig. 5 is a structural representation of a specific embodiment of the present invention;

Fig. 6 is a flowchart of the APS algorithm in the APS core processor module.

As shown in the figure, Figure 1-A is a schematic diagram of an SDH ring network in a normal state. The service route between nodes A to C is A→B→C. If the transmission optical cable between node B and node C fails, automatic The protection switching scheme will enable node B and node C to perform protection switching at the same time, as shown in Figure 1-B. At this time, the service route between node A and node C becomes A→B→A→D→C, and between AC The service is not interrupted because of the transmission failure between node B and node C, which greatly enhances the survivability of the SDH transmission network, which is the significance of the automatic protection switching scheme.

Fig. 2 shows a schematic diagram of the principle structure of the device of the present invention. As shown in Figure 2, the present invention includes following modules: network management layer APS configuration maintenance module, line signal alarm extraction module, APS signaling byte extraction insertion module, bridging switching action execution module and APS core processor module, respectively below these The functions of the modules and their interconnections are introduced in detail.

The APS configuration and maintenance module at the network management layer is responsible for network configuration, maintenance and debugging. When the system is started, the APS configuration and maintenance module of the network management layer needs to perform initialization operations, including: 1. Assignment of network element identifiers. In the MS-SPRING (two-fiber bidirectional multiplex section shared protection ring) single ring, the number of nodes cannot exceed 16, and each network element must be assigned a unique ID (Identifier), which ranges from 0 to 15. The network element identification ID is the first element to start the APS function of this node normally. It must be downloaded to the APS core processor along with the basic network element database when the node is powered on and started. At the same time, the two adjacent network elements must be The ID of each network element should also be notified to the APS core processor. 2. Allocation of working time slots and protection time slots. According to the design scheme of MS-SPRING APS, half of the AU4 (Administrative Unit level 4 management unit) time slot capacity on each optical line needs to be allocated as a working time slot for transmitting normal working services, and the other half is used as an optical line. The protection time slot for transmitting the failed cross-segment working service in case of failure. In the normal working state, the APS configuration maintenance module of the network management layer is also responsible for maintenance work, and the APS external commands for maintenance operations include:

1. Protection lock LP-R; this command is to prevent the working channel from accessing the protection channel of a certain ring switching on the specified span, and it can be realized by making the node lose the ability to request any ring protection switching. Since this command cannot be transmitted in K bytes, it must be issued by the APS configuration maintenance module of the network management layer at the two end nodes on the protection-locked span at the same time. direction parameter.

2. Forced switching of FS-R; this command executes the ring switching from the working channel to the protection channel. Unless there is a higher-level bridging request, the bridging switching must be performed regardless of the state of the protection channel. Since FS-R can be transmitted in K bytes, it can be stipulated that the network management layer only sends it to the node that starts the forced switching, and attaches the direction parameter.

3. Manually switch MS-R; this command is the same as the forced switching command, except that the bridging request level is lower.

4. Clear CLR; this command clears the external commands issued by the original network management layer, and also adds direction parameters. When clearing the protection lock command, it needs to be issued at the two nodes of the corresponding span at the same time, and the direction parameter is added, while when clearing other external commands, it is only necessary to issue the clear command at the node where the external command was originally issued, and attach the same direction parameter.

The APS configuration and maintenance module at the network management layer is also responsible for debugging, mainly performing ring exercises. The ring exercise command is EXER-R; this command is only to exercise the protection switching of the requested channel, but not to implement bridging and switching actions. Since the ring exercise can be transmitted by K bytes, it can also be agreed that the command will be issued by the network management layer of the starting node, and can be Agreed direction. The network management layer only issues this command on the node that starts the forced switching, and attaches the direction parameter.

The line signal alarm extraction module is responsible for extracting multiplex section-level alarm information on the optical lines on both sides, including signal failure (that is, LOF (Loss Of Frame frame loss) at the multiplex section level, LOS (Loss Of Signal signal loss) and MS- AIS (Multiplex Section Alarm Indication Signal Multiplex Section Alarm Indication Signal)) and signal degradation. The line signal alarm extraction module provides trigger conditions for automatic protection switching to the APS core processor.

The APS signaling byte extraction and insertion module is responsible for extracting and inserting K1 and K2 bytes in the overhead bytes of the multiplex section. In the two-fiber bidirectional multiplex section shared automatic protection switching scheme, two APS signaling bytes are used: K1 and K2. K1 and K2 are transmitted in the multiplex section overhead bytes of the STM-N (Synchronous Transport Module level N) carrying the protection channel. The 1-4 bits of K1 are the bridge request codes, which are listed in the following table in descending order of priority; the 5-8 bits of K1 are the destination node IDs of the bridge request codes indicated by the 1-4 bits of K1. Bits 1 to 4 of byte K2 are the ID of the source node sending the bridge request, the fifth bit is the long/short path flag (where 0 represents the short path and 1 represents the long path), and bits 6 to 8 are the source node sending the bridge request The current bridge request status code.

The external commands transmitted in APS signaling include forced ring switching FS-R, manual ring switching MS-R, and practice ring switching EXER-R; automatic switching commands include ring signal failure SF-R, ring signal degradation SD-R, ring Reverse request RR-R, wait for recovery WTR and no request NR, these commands are transmitted in K1 byte. The signaling encoding of each instruction in the APS signaling byte is shown in the following table:

Request command code table (K1 byte 1~4bit) Order coding Order coding FS-R 1101 SF-R 1011 SD-R 1000 MS-R 0110 TR 0101 EXER-R 0011 RR-R 0001 NR 0000

The request status code transmitted in the K2 byte includes the multiplex section alarm indicator signal MS-AIS, the multiplex section remote detection failure MS-RDI, the transmission of extra traffic on protection channels, and the bridged switching state Bridged and Switched , Bridged idle state Idle has been bridged.

Request status instruction code table (K2 byte 6~8bit) state coding MS-AIS 111 MS-RDI 110 Reserved 101 Reserved 100 Extra traffic on protection channels 011 Bridged and Switched 010 Bridged 001 Idle 000

The bridge switching action execution module is responsible for the deployment of the working channel and the protection channel according to the command of the APS core processor. According to the needs of instruction coding, four control signal lines are required between the APS core processor and the bridge switching action execution module, which are respectively used as the east side bridge control signal line, the east side switching control signal line, the west side bridge control signal line, and the west side bridge control signal line. Side switching control signal line. High level indicates that the command is valid, and low level indicates that the command is cancelled. The command code table is as follows: command name APS3 APS2 APS1 APS0 describe East Side Bridging/Switching 0 0 1 1 Bridge the working time slots sent by the outer ring fiber to the east side to the protection time slots sent by the inner ring fiber to the west side, and switch the original working time slots of the inner ring fiber to receive the east side to the outer ring fiber to receive the west side guard slot up West Side Bridging/Switching 1 1 0 0 The original working time slot sent by the inner ring fiber to the west is bridged to the protection time slot sent by the outer ring fiber to the east, and the original outer ring fiber used to receive the working time slot from the west side is switched to the inner ring fiber to receive the east side guard slot up Removing the East Side Switch 0 0 0 1 Restore the receiving signal of the protection time slot from the west side on the outer ring fiber to the receiving signal of the working time slot from the east side of the inner ring fiber. Remove the West Side Switch 0 1 0 0 Restore the signal received from the guard time slot from the east on the inner ring fiber to the received signal from the working time slot from the west side of the outer ring fiber. Removing the East Bridge Switching 0 0 0 0 Restore the signal sent from the inner ring fiber to the west protection time slot to the working time slot sent on the outer ring fiber to the east; restore the received signal from the west protection time slot on the outer ring fiber to Receive signals from the working time slot from the east side of the inner ring fiber. i.e. all back to normal Removing the West Bridge Switching 0 0 0 0 Restore the signal sent from the outer ring fiber to the east protection time slot to the working time slot sent by the inner ring fiber to the west; restore the received signal from the east guard time slot on the inner ring fiber to The signal is received from the working time slot from the west side of the outer ring fiber. i.e. all back to normal

The APS core processor module is the core part of the whole APS solution, it synthesizes all aspects of information, makes analysis decisions based on the APS algorithm and sends out control instructions. The most important part of the APS core processor is the APS algorithm. ITU-T G.841 Recommendation "Types and Characteristics of SDH Network Protection Architecture" makes logical provisions on the APS algorithm. Figure 6 shows the flow of the APS algorithm picture. As shown in Figure 6, in the APS algorithm, first detect whether there is an APS external command from the network management layer, if there is, then process it through a special network management layer command processing sub-module; then detect the complex signal reported by the line signal alarm extraction module Using segment-level fault alarm information, if a new fault is found, which is different from the original fault, it will be handed over to the local fault handling sub-module for fault processing; finally, the APS signaling byte extraction and insertion module extracts the APS signaling byte K1, K2 makes a judgment, decides whether to perform a bridging switching operation or a switching recovery operation, and issues a control command if necessary.

FIG. 3 is a schematic diagram of the hardware structure of SDH optical transmission equipment, and FIG. 5 is a schematic diagram of the structure of a specific embodiment of the present invention. As can be seen from Fig. 3 and Fig. 5, in the embodiment, the APS configuration maintenance module of the network management layer is placed on the subnet management control center, the line signal alarm extraction module is placed on the optical interface board, and the APS signaling byte is extracted The insertion module and the APS core processor module are placed on the optical line overhead processing board, and the bridge switching action execution module is arranged on the time slot cross board. In this way, the hardware structure of the original equipment is fully utilized without adding a special APS processing board, which effectively reduces the cost. The communication interface between the APS core processor and the network element control board adopts a dual-port RAM, and the interfaces of other parts use the interfaces of the original hardware equipment as much as possible, but a few backplane wirings should be appropriately added to connect the opposite side The signal is connected.

Fig. 4 is a flow chart of the automatic protection switching method of the present invention. When the system starts, the APS configuration and maintenance module of the network management layer performs networking configuration: provide the required initial data information to the APS core processor module, including the IDs of the current network element and two adjacent network elements, and complete the normal state The time slot crossover configuration and the assignment of working channel and protection channel. After entering the normal working state, the line signal alarm extraction module on the optical interface board dynamically detects the alarm information at the multiplex section level and reports it to the APS core processor module, and at the same time, the APS signaling byte extraction and insertion module on the optical line overhead board dynamically extracts The K1 and K2 bytes in the overhead bytes of the multiplexing section are reported to the APS core processor module; then, the APS core processor module synthesizes the received information and makes a judgment according to the APS algorithm whether to perform bridging switching or switching recovery, if To perform bridge switching or recovery operation, order the bridge switching action execution module on the time slot cross board to perform bridge switching operation or switching recovery operation, and then the APS signaling byte extraction and insertion module will reflect the K1 and K2 words of the current status of the node section into the overhead bytes of the multiplex section, and finally the bridge switching action execution module reports the operation information to the APS configuration maintenance module of the network management layer; if there is no need to perform bridge switching or recovery operations, it only needs to be extracted and inserted into the module by the APS signaling byte Just insert K1 and K2 bytes reflecting the current status of the node into the multiplex section overhead bytes.

The automatic protection solution proposed by the present invention uses the internationally accepted APS signaling provided by ITU-T G.841 for signaling response, and is an APS solution with a dual-terminal protection mechanism; The protection channels used by all nodes on the ring make the distribution of channels more reasonable; due to strict compliance with the signaling usage specification stipulated in the ITU-T G.841 recommendation, it has good compatibility; in addition, the automatic protection solution proposed by the present invention, The hardware resources of the original transmission equipment are fully utilized, and the cost is effectively reduced.

Claims (12)

1. the automatic protection switching method on the high rate SDH loop is characterized in that:

Carry out the networking configuration by webmaster layer APS configuring maintenance module when (1) at first, starting in system;

(2) secondly, after entering normal operating conditions, the warning information of the multiplex section level on two light directions of line signal alarm extraction module detection of dynamic is also notified APS core processor module, and K1, the K2 byte in the MSOH byte on two light directions of while APS signaling byte-extraction insert module Dynamic Extraction also notified APS core processor module;

(3) then, the information that APS core processor module synthesis is received judges according to the APS algorithm and whether to carry out bridge joint and switch or switch recovery;

(4) bridge joint is switched or recovery operation if carry out, then order bridge joint switching action Executive Module execution bridge joint switching operation or switch recovery operation, then APS core processor module will reflect that by APS signaling byte-extraction insert module K1, the K2 byte of this node the present situation are inserted in the MSOH byte on the corresponding light direction, and last bridge joint switching action Executive Module reports webmaster layer APS configuring maintenance module with operation information;

(5) bridge joint is switched or recovery operation if need not carry out, and then only needs will to reflect by APS signaling byte-extraction insert module that K1, the K2 byte of this node the present situation are inserted in the MSOH byte on the corresponding light direction by APS core processor module and gets final product.

2. the automatic protection switching method on a kind of high rate SDH loop as claimed in claim 1; it is characterized in that: carry out the networking configuration by webmaster layer APS configuring maintenance module when described system starts and refer to that webmaster layer APS configuring maintenance module provides needed primary data information to APS core processor module, and finish time-slot cross configuration under the normal condition and the distribution of working channel and guard channel.

3. the automatic protection switching method on a kind of high rate SDH loop as claimed in claim 2 is characterized in that: described primary data information comprises the sign ID of Home Network unit node and the sign ID of two network element nodes adjacent with this network element.

4. the automatic protection switching method on a kind of high rate SDH loop as claimed in claim 1; it is characterized in that: described multiplex section level warning information comprises the LOF of multiplex section level; the dropout of multiplex section level, the Signal Degrade of Multiplex Section AIS and multiplex section level.

5. the automatic protection switching method on a kind of high rate SDH loop as claimed in claim 1; it is characterized in that: described bridge joint switching operation refers to this node multiplexing professional and sending to guard channel when sending to working channel from the straight-through business of this node from the light Zhi Luxiang light group road, and the business of will be from the light group road telling to this node optical branch road receives from working channel and forwards guard channel to and receive.

6. the automatic-protecting switching device on the high rate SDH loop, it is characterized in that: comprise and be responsible for the networking configuration, safeguard and the webmaster layer APS configuring maintenance module of debugging that described webmaster layer APS configuring maintenance module sends to APS core processor module with the Network Management and Maintenance debug command and the process information that receives from this module reports; Be responsible for the line signal alarm extraction module that multiplex section level warning information extracts on the optical link of both sides, described line signal alarm extraction module extracts multiplex section level warning information and it is sent to APS core processor module; Be responsible on the optical link of both sides K1, the extraction of K2 byte and the APS signaling byte-extraction insert module of insertion in the MSOH byte, described APS signaling byte-extraction insert module sends to APS core processor module with the K byte of extracting and receives insertion K byte from this module; Be responsible for the bridge joint switching action Executive Module of working channel and guard channel allotment, described bridge joint switching action Executive Module is responsible for carrying out from the bridge joint of APS core processor module and is switched or switch the recovery order; And synthesise various information, the APS core processor module that makes a policy and control according to the APS algorithm.

7. the automatic-protecting switching device on a kind of high rate SDH loop as claimed in claim 6, it is characterized in that: described webmaster layer APS configuring maintenance module is in subnet management control centre.

8. the automatic-protecting switching device on a kind of high rate SDH loop as claimed in claim 6, it is characterized in that: described line signal alarm extraction module is positioned on the Optical Fiber Interface Board.

9. the automatic-protecting switching device on a kind of high rate SDH loop as claimed in claim 6, it is characterized in that: described APS signaling byte-extraction insert module and APS core processor module are positioned on the optical link Overhead Processing Board.

10. the automatic-protecting switching device on a kind of high rate SDH loop as claimed in claim 6, it is characterized in that: described bridge joint switching action Executive Module is positioned on the time-slot cross plate.

11. the automatic-protecting switching device on a kind of high rate SDH loop as claimed in claim 6 is characterized in that: the communication between described APS core processor module and the webmaster layer APS configuring maintenance module is transmitted by the network element control plate.

12. the automatic-protecting switching device on a kind of high rate SDH loop as claimed in claim 11 is characterized in that: the interface between described APS core processor module and the network element control plate is dual port RAM.

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