WO2006116896A1

WO2006116896A1 - Rapid restoration method for ason

Info

Publication number: WO2006116896A1
Application number: PCT/CN2005/000609
Authority: WO
Inventors: Desheng Sun
Original assignee: Zte Corporation
Priority date: 2005-04-30
Filing date: 2005-04-30
Publication date: 2006-11-09
Also published as: CN101138197A; CN100550764C

Abstract

The key of the rapid restoration method for ASON of present invention is that the neighbor element of fault link searches the local restoration route to accomplish the restoration process of fault service connection according to the fault of the service layer link. The method comprises that each network element among the network detects the alert condition of all the links of its own realtimely; when the related link fault is detected, the current network element searches the restoration route which isn’t correlate with the fault link on the premise of the fault link capacity with the current network element to be the source and the another neighbor element of the fault link to be the destination; and the current network element starts the restoration operation according to the restoration route. The scheme of the present invention utilizes the mechanism that the link fault triggers the signal of the client layer to restoration automatically, which avoids the disadvantages that the preset route is not flexible enough and the present auto restoration method is too slow and doesn’t have enough reliability, and the scheme of the present invention has the advantages of speed, reliability and flexibility.

Description

Fast recovery method for automatic switched optical network

The present invention relates to the field of optical networks, and in particular, to a fast recovery method for an automatic switched optical network. Background technique

Optical networks, such as optical transmission network (OTTSi), Wavelength-division multiplexing (WDM), Synchronous digital hierarchy (hereinafter referred to as SDH) or Synchronous optical network (Synchronous optical network) (hereinafter referred to as SONET) transmission network, has been widely used in the field of telecommunications.

Automatic switched optical network (hereinafter referred to as ASON) is a research hotspot in the field of optical networks in recent years. ITU's ITU-T G.8080 and G.771X series propose the concept of ASON. By setting up a special Control Plane (hereinafter referred to as CP), the functions of automatic establishment of the service connection and automatic restoration of the connection are completed.

Self-healing ability is an important feature of optical networks. ITU Recommendation ITU-TG.841, “Classification and Characteristics of SDH Network Protection Structures” provides a detailed description of the self-healing function of the SDH/SONET optical transport network. Its recommended protection methods include path-based protection and link-based protection. Path-based protection, the most common are channel protection and subnet connection protection; link-based protection, the most common two-fiber or four-fiber bidirectional multiplex section shared protection ring, 1+1/1: N linear multiplex section links, etc. Channel protection and multiplex section protection have been widely used in traditional optical networks. However, for complex networks such as mesh networks, the above protection methods occupy a large amount of spare resources and are no longer suitable.

In this way, for the mesh network, the recovery method is generally used to realize the self-healing function. At present, there are two methods for recovery that are widely used: preset route recovery methods and automatic rerouting methods.

Pre-route recovery method, such as 1+1 or 1 :N. The main feature of this recovery method is to establish a reserved recovery connection while establishing a working connection for the user service. When the working connection fails, the user service is restored by starting the reserved recovery connection. This recovery method is similar to the protection method recommended by the G.841 recommendation for 1+1/1:N linear multiplex section links.

The automatic rerouting method is recommended by ASON and is an effective method for solving optical network, especially mesh network, automatic recovery problem. The basic principle is as follows: After the service connection fails, the network element base in the rerouting domain In its control plane, source routing, hop-by-hop routing, or hierarchical routing are used to rediscover connections for user services and complete automatic service recovery.

The preset route recovery method described in the U.S. Patent No. 20040190446 has a fast recovery speed. However, for a network with rapid traffic growth, frequent service scheduling, and high dynamic performance requirements, the preset route needs to be updated frequently. Dynamic maintenance, compared to the automatic recovery advocated by the current ASON network, the flexibility is insufficient. As shown in Figure 1, the six-network mesh network, if the preset recovery path of the service between A-B-C is A-F-C, when the A-B link and the F-C link fail simultaneously, A-B-C service recovery failed.

The automatic recovery process shown in Figure 2 is characterized by the initiation of service recovery after the completion of the Route Data Base (RDB) update. This latest RDB-based recovery method is highly reliable, but fault broadcast and RDB updates result in A large delay in business recovery time. For large networks, the delay is more pronounced. '

The automatic recovery process shown in Figure 3 is based on accurate link fault location to search for recovery routes that are not related to the fault link to establish a recovery connection for service recovery. Link fault location techniques are relatively familiar, such as using transport plane alarm correlation analysis to locate faults. This recovery method can make full use of the resources of the non-faulty link, and the recovery reliability is high. However, fault location also results in a large delay in service recovery time. If the service connection path is long, the link capacity is large, and the alarm information is large, the delay is more obvious.

The automatic recovery method in the ASON network described in the Chinese patents with the patent numbers 02123980.0 and 03114810.7 basically follows the process shown in Figure 4 to complete the automatic recovery of the service. This recovery method searches for recovery routes by avoiding the original service path as a constraint, and overcomes the recovery delay caused by RDB update or fault location, but the reliability of recovery is small for small and medium-sized networks. For example, in the four-network mesh network shown in FIG. 5, for the service connection of the service path A-B-C-D, any one of the three links A-B, B-C or C-D fails, Recovery will fail.

The optical network structure specified in ITU Recommendation ITU-TG.805 is a layered network with a client/server relationship between the layers. The client layer signal transmission process is as follows: The upper service network element adapts the client layer signal into the service layer link, passes the service layer link between the multiple network elements, and finally reaches the lower service network element, and the lower service network element receives the service. The layer link resolves the client layer signal. Figure 6 depicts the framework structure of the client layer signal S from the network element A to the service element link L2 between the AB, the service layer link L2 between the BC, and the service layer link L3 between the CDs to the network element D. In general, the service layer network fails, that is, the service layer link fails, causing the client layer signal failure. From the perspective of the alarm monitoring mechanism, the network element that terminates and regenerates the layer network signal can detect and determine the alarm of the layer signal. Thus, if the link L2 of Figure 6 fails, the network elements B, C can immediately detect the L2 fault condition. The L2 fault causes the customer layer signal S to fail, but because of any one of the links L1, L2, L3, it can cause an S fault. Therefore, if viewed from the client layer alone, any network element on the client layer signal path cannot determine the specific fault location. Because of this, the implementation of the automatic recovery methods of Figures 2, 3, and 4 is only possible. Summary of the invention

The object of the present invention is to overcome the shortcomings of traditional protection of occupied resources, insufficient flexibility of preset route recovery, slow speed of existing automatic recovery methods, and low reliability, and propose a fast recovery method for optical transmission network capable of balancing speed, reliability and flexibility. . .

The core idea of the present invention is to recover the faulty service connection recovery process by searching for a local recovery route by the neighboring network element of the faulty link based on the service layer link failure. To simplify the description, the links appearing in the following and in the drawings refer to service layer links.

The method for quickly recovering an automatic switched optical network according to the present invention includes at least a Link Resource Manager (hereinafter referred to as LRM), a Connection Controller (hereinafter referred to as CC), and a Routing Controller ( Standard components such as Route Controller (hereinafter referred to as RC) and Protocol Controller (hereinafter referred to as PC) are characterized by service layer link failure, including the following steps:

Step 1: The network element in the network detects the alarm status of all the links of the local network element in real time. If the related link fault is detected, the local network element reports the fault information to another neighboring network element of the faulty link and proceeds to the step. 2. If the link fault notification information is detected, go directly to step 2;

• Step 2: The local NE searches for each service connection carried by the faulty link. If there is a service connection that needs to be restored, go to Step 3. Otherwise, go to Step 1.

In the third step, the local network element is used as the source, and another adjacent network element of the faulty link is used as the purpose, and the related service connection is searched for the recovery route that is not related to the faulty link. According to the recovery route, the local NE initiates the recovery operation and returns to step 2.

The number of recovery connections to be newly created by the method is the number of original service connections that need to be restored; Be sure to create a new recovery connection.

The invention also provides a fast recovery method for an automatic switched optical network, comprising at least standard components such as LRM, CC, RC and PC, characterized in that based on a service layer link failure, the following steps are included:

Step 2: The local network element searches for each service connection carried by the faulty link, and calculates the total capacity of the service to be restored. If the capacity is greater than zero, proceed to step two, otherwise go to step one;

Step 3: The local network element is used as the source, and another adjacent network element of the faulty link is used for the purpose of searching for the recovery route that is not related to the faulty link on the condition that the total capacity of the client signal to be recovered is used. According to the recovery route, the local NE starts the recovery operation and returns to step 2.

The method is based on the capacity of the service to be restored, and only needs to create a new recovery connection; that is, multiple services are merged to create a new connection.

Step 1: The network elements in the network detect the alarm status of all links of the local network element in real time; if the related link fault is detected, go to step 2;

Step 2: The local network element uses the local network element as the source and uses another adjacent network element of the faulty link as the destination to search for the recovered route that is not related to the faulty link based on the faulty link capacity. According to the recovery route, the local NE initiates the recovery operation and returns to step 1.

The method is based on the condition that the link capacity needs to be restored. The recovery process no longer involves the service signal carried by the link layer, and only needs to establish a new connection connection; that is, a new connection connection is newly created without considering the service. Compared with the previous two methods, this method is the most succinct.

In the above methods, the LRM completes the detection and management of the link alarm and the link alarm notification information, and is responsible for notifying the CC of the link failure information _{; the} CC starts the fault according to the link alarm and the protection and recovery attributes of the service connection. The service connection recovers the route query, and starts the PC according to the returned result of the RC; the LRM completes the resource reservation and cancellation according to the signaling interaction result.

The above three methods of the present invention use a mechanism for automatically recovering the signal of the client layer based on the link failure, thereby avoiding the lack of flexibility of the preset route recovery, and the automatic recovery methods of FIG. 2, FIG. 3, and FIG. 4 are slow and reliable. Low profile, with the advantages of speed, reliability and flexibility.

The above and other objects, features and advantages of the present invention will become more <RTIgt; DRAWINGS

1 is a mesh network structure diagram including six network elements;

2 is a flow chart of an automatic recovery method for using an alarm broadcast mechanism;

Figure 3 is a flow chart of an automatic recovery method using a fault location mechanism;

Figure 4 is a flow chart of an automatic recovery method using a constrained routing mechanism;

Figure 5 is a mesh network structure diagram including four network elements;

Figure 6 is a structural diagram of an optical network customer signal transmission;

7 is a functional structural diagram of a technical solution of the present invention;

Figure 8 is a flow chart of the technical solution of the present invention.

Figure 9 is a flow chart of a simplified technical solution of the present invention.

Figure 10 is a flow chart of a further simplified technical solution of the present invention. detailed description

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

1, 2, 3, 4, 5 and 6 have been described in the background art.

7 is a functional structural diagram of a technical solution of the present invention. The technical solution of the present invention adopts standard components of the CP described in ITU-T G.8080, including LRM, CC, RC, and PC. The relationship between the units is shown in Figure 7. The LRM completes the detection and management functions of the link alarm or link alarm notification information, and is responsible for notifying the CC of the link failure information. At the same time, the LRM receives the request from the PC and completes resource reservation or cancellation. The CC is used to manage and control the existing service connection. According to the current link alarm, the recovery route query of the faulty service connection is started according to the protection and recovery attributes of the service connection, and the PC is started according to the return result of the RC. The RC receives the CC query request, starts the route calculation based on the current RDB, and returns the calculation result. The PC receives the recovery connection establishment request of the CC, completes signaling interaction with other network elements on the recovery path, and starts the LRM.

8 is a flow chart of a technical solution of the present invention, and FIG. 9 is a flow chart of a simplified technical solution of the present invention. Figure 10 is a flow chart of a further simplified technical solution of the present invention.

With reference to FIG. 8, the ABHD, the DCB service 1 and the DCB service 2 are transmitted in the SDH network of the network structure diagram of FIG. 1. After the optical fiber failure in the B direction of the BC link, the recovery process of the source routing mode is taken as an example to illustrate the present invention. Specific embodiment. In addition, for detailed explanation, special premise: Service ABCD occupies 1 channel, 5# channel provided by 5# channel and B-C link provided by A-B link, 5# channel provided by C-D link DCB service 1 occupies 1 channel, 6# channel provided by 6# channel and C-B link provided by D-C link; DCB service 2 occupies 1 channel, 7 provided by D-C link # channel, C-B link provides 7# channel transmission; B-F link 3# channel idle, F-C link 4# channel idle, C-E link 5#, 6# channel idle The 5# channel of the EB link is idle, the 5# channel of the E-F link is idle, and the 4# channel of the F-B link is idle.

The specific implementation includes the following steps:

Step 1: The LRMs of the network elements A, B, C, D, E, and F detect the alarm status of each link of the local network element in real time; the network element B monitors the receiving fiber failure of the local network element B-C section B direction. NE B notifies the network element C of the fault.

Step 2: The network element B notifies the fault information of the CC related link through the LRM; the CC searches for the customer service carried in the B-C section, searches for the qualified A-B-C-D service, and occupies the 5# channel section in the B-C section;

Step 3: In the network element B, taking B as the source and C as the destination, the CC sends a routing query request to the RC. The RC queries the RDB of the NE to obtain the route B-F-C, the B-F segment 3# channel, and the F-C segment 4# channel.

Step 4: The CC starts the signal exchange process between the PC and the network element F and the network element C according to the route returned by the RC. At the same time, the PCs of the network elements B, F, and C complete the resource reservation work by calling their respective LRMs. The original A-B-C-D service was restored, and the restored service path was A-B-F-C-D.

Step 5: After the network element B advertises the fault to the network element C in the first step, the network element C receives the alarm notification information transmitted by the B, and then performs the foregoing step 2 and step 3 in the similar manner for the DCB service 1. Step four. Finally, the original D-C-B service 1 is restored, and the restored service path is D-C-E-F-B. The service occupies the 5# channel in the C-E section, the E-F section occupies the 5# channel, and the F-B occupies the 4# channel. The original D-C-B service 2 is restored, and the restored service path is D-C-E-B. The service occupies the 6# channel in the C-E section, and the E-B section occupies the 5# channel. '

If the process described in FIG. 2 is adopted, the service ABCD receives the fiber failure in the direction of the BC segment B. After the network element A receives the fault information broadcast information of the network element B, the recovery can be started. Compared with the method of the present invention, the method needs to wait for the update of the RDB after the failure is detected, and the speed is slow. In addition, the source and destination of the route calculation are still relatively slow for the original A, D, and RC route calculations.

If the process described in Figure 3 is used, after the service A-B-C-D receives the fiber fault in the direction of the B-C segment B, the network element A must first initiate the fault location function. Only after the fault is located can the service be successfully restored. Compared with the method of the present invention, the method needs to wait for the fault location result, and the fault location speed depends on the efficiency result of the traffic path alarm information collection and the correlation analysis algorithm, and the speed is slow. Similarly, the source and destination of the method routing calculation still have a relatively slow convergence rate for the original In, D, and RC routes.

If the process described in FIG. 4 is adopted, after the service ABCD receives the optical fiber failure in the direction of the BC segment B, the network element A searches for the recovery route by taking the original service path ABCD as a constraint, and can obtain the recovery path AFED, but cannot be reused. The resources of the original non-faulty section AB, CD. Similarly, for the D-C-B service, the network element D searches for the recovery route by taking the original service path D-C-B as a constraint, and can obtain the recovery path D-E-F-B, but cannot reuse the resources of the original non-faulty section D-C. Since this recovery method cannot maximize the reuse of resources in the non-faulty zone on the original service path, the reliability of the recovery is greatly reduced. For example, if the A-F, F-E, E-D, and F-B idle resources are insufficient, the recovery method fails, and the method of the present invention can be successfully restored. Similarly, for the network shown in Figure 5, if the service path is A-B-C-D, when the B-C segment fails, this recovery method fails. However, the method of the present invention can find the A-B-A-C-D recovery path.

Compared with the preset route recovery method, the method of the invention adopts a real-time search route method to initiate recovery, and the dynamic performance and reliability are better.

Referring to FIG. 9, the SDH network of the network structure diagram of FIG. 1 adopts the recovery process of the source routing mode as an example to illustrate the simplified detailed implementation of the present invention. In addition, for detailed explanation, the following services are predicated: A transmits two services via network element B, C to D, one service is transmitted by B to C, and two services are transmitted by C to B.

Among them, along the two services of ABCD, each service occupies one channel, and the 5#, 6# channel, C-D chain provided by the 5#, 6# channel and B-C link provided by the A-B link 5#, 6# channel transmission provided by the road; 1 channel along ABC, 7# wanted by 7# channel and B-C link provided by A-B link; 2 services, each service occupies 1 channel, via D-C 8#, 9# channel transmission provided by 8#, 9# channel, C-B link provided by link; 10~12# channel idle of B-F link, 10~12# channel of F-C link Idle; 10#, 11# channel idle of C-E link, 10#, 11# channel idle of E-B link.

The specific implementation includes the following steps: Step 1: The LRMs of the network elements A, B, C, D, E, and F detect the alarm status of each link of the local network element in real time; the network element B monitors the direction of the local network element BC section B. Receiving fiber failure. NE B notifies the network element C of the fault.

Step 2: The network element B notifies the fault information of the CC-related link through the LRM; the CC searches for the customer service carried in the B-C area, and calculates the total service capacity to be restored into three channels;

Step 3: On the network element B, using B as the source and C as the destination, to find 3 channels, the CC sends a route query request to the RC. The RC queries the RDB of the NE to obtain the route B-F-C, the 10#, 11#, and 12# channels of the B-F link, and the 10#, 11#, and 12# channels of the F-C link.

Step 4: The CC starts the signal exchange process between the PC and the network element F and the network element C according to the route returned by the RC. At the same time, the PCs of the network elements B, F, and C complete the resource reservation work by calling their respective LRMs. The two services transmitted along the A-B-C-D and the one transmitted along the A-B-C are restored. The restored service paths are A-B-F-C-D and A-B-F-C respectively.

Step 5: After the network element B advertises the fault to the network element C, the network element C receives the alarm notification information transmitted by the B, and then performs the foregoing step 2, step 3, and step 4 in a similar manner. Finally, the two services transmitted along the D-C-B are restored, and the restored service path is D-C-E-B. The service occupies the 10# and 11# channels in the C-E segment, and the 10# and 1 fiber channels in the E-B.

Compared with the process shown in Figure 8, the flow of Figure 9 simplifies the search routing and connection establishment, and the implementation and recovery speed is better.

Referring to FIG. 10, after the optical fiber failure of the SDH network in the B-C link B direction of the SDH network of FIG. 1 is taken as an example, the recovery process of the source routing mode is taken as an example to illustrate a further simplified detailed implementation of the present invention. In addition, for detailed explanation, the special premise is: B-C link capacity is N, A service capacity occupied by network element B, C to D is Ml, and service capacity of D transmitted by C to B is M2. And M1+M2 <= N. There is a link with a free capacity of N in the B-F section, and a link with a free capacity of N in the C-F section.

The specific implementation includes the following steps: Step 1: The LRMs of the network elements A, B, C, D, E, and F detect the alarm status of each link of the local network element in real time; the network element B detects the local network element BC link failure.

Step 2: The network element B notifies the fault information of the CC-related link through the LRM. The source B is the source and the C is the destination. The host sends a route query request to the RC to find the link with the idle capacity N. The RC queries the RDB of the NE to obtain the route B-F-C.

Step 3: The CC starts the signal exchange process between the PC and the network element F and the network element C according to the route returned by the RC. At the same time, the PCs of the network elements B, F, and C complete the resource reservation work by calling their respective LRMs.

The services transmitted along the A-B-C-D and the services transmitted along the D-C-B are all restored. The restored service paths are A-B-F-C-D and D-C-F-B.

Compared with the processes shown in FIG. 8 and FIG. 9, the process of FIG. 10 does not need to notify the fault of another network element of the faulty link, and further simplifies the search route and establishes the connection, and has better implementation and recovery speed. Faster.

From the above implementation process and comparative description, it can be further clarified that the three technical solutions of the present invention have the following advantages:

1. The network elements at both ends of the fault link are the recovery start network elements, and no fault location is required. Based on the local original RDB, there is no need to wait for the RDB update.

2. The neighboring network element of the faulty link is used as the source and destination, and the route calculation convergence speed is fast;

3. The method of the present invention can meet the recovery requirements of any complex network. Moreover, the more complex the network, the shorter the recovery path of the method of the present invention and the higher the recovery efficiency.

In short, the method of the present invention has the advantages of speed, reliability, flexibility, and the like as compared with the existing recovery method.

The above is a detailed description of the working principle of the present invention, and several typical network structure flows are given, but this is only a visual example for the sake of understanding, and should not be construed as limiting the scope of the present invention. Also, various possible equivalents and modifications may be made in accordance with the teachings of the present invention and the preferred embodiments thereof, and all such changes or substitutions should fall within the scope of the appended claims.

Claims

Rights request

A fast recovery method for an automatically switched optical network, comprising at least a link resource manager (LRM), a connection controller (CC), a routing controller (RC), and a protocol controller (PC) standard component, characterized in that Based on the service layer link failure, the following steps are included: Step 1: Each network element in the network detects the alarm status of all links of the local network element in real time; if the related link fault is detected, the local network element goes to another faulty link. The neighboring NEs notify the fault information and go to step 2; if the link fault notification information is detected, go directly to step 2;

Step 2: The local network element searches for each service connection carried by the faulty link. If there is a service connection that needs to be restored, go to step 3, otherwise go to step 1.

The method according to claim 1, wherein the link resource manager (LRM) completes detection and management of link alarm and link alarm notification information, and is responsible for notifying the connection controller of the link failure information ( CC); The connection controller (CC) initiates a recovery route query for the faulty service connection according to the link alarm, according to the protection and recovery attributes of the service connection, and starts the protocol controller (PC according to the return result of the route controller (RC) The link resource manager (LRM) completes resource reservation and revocation according to the signaling interaction result.

The method of claim 1, wherein the number of newly established recovery connections is the number of original service connections that need to be restored, that is, each service needs to newly establish a recovery connection.

4. A fast recovery method for an automatic switched optical network, comprising at least a link resource manager (LRM), a connection controller (CC), a routing controller (RC), and a protocol controller (PC) standard component, characterized in that Based on the service layer link failure, the following steps are included:

Step 2: The local network element searches for each service connection carried by the faulty link, and calculates the total capacity of the service to be restored. If the capacity is greater than zero, proceed to step two, otherwise go to step one; Step 3: The local network element is used as the source, and another adjacent network element of the faulty link is used for the purpose of searching for the recovery route that is not related to the faulty link on the condition that the total capacity of the client signal to be recovered is used. According to the recovery route, the local NE initiates the recovery operation and returns to step 2.

The method according to claim 4, wherein the link resource manager (LRM) completes detection and management of link alarm and link alarm notification information, and is responsible for notifying the connection controller of the link failure information ( CC); The connection controller (CC) starts the recovery route query of the faulty service connection according to the link alarm, according to the protection and recovery attributes of the service connection, and starts the protocol controller (PC) according to the return result of the route controller (RC) The link resource manager (LRM) completes resource reservation and revocation according to the signaling interaction result.

6. The method according to claim 4, characterized in that the method is based on the capacity of the service to be restored, and only one recovery connection is newly created, that is, a plurality of services are combined to create a new restoration connection.

7. A fast recovery method for an automatically switched optical network, comprising at least a link resource manager (LRM), a connection controller (CC), a routing controller (RC), and a protocol controller (PC) standard component, characterized in that Based on the service layer link failure, the following steps are included:

The method according to claim 7, wherein the link resource manager (LRM) completes detection and management of link alarm and link alarm notification information, and is responsible for notifying the connection controller of the link failure information ( CC); The connection controller (CC) starts the recovery route query of the faulty service connection according to the link alarm, according to the protection and recovery attribute of the service connection, and starts the protocol controller according to the return result of the route controller (RC) ( PC); The Link Resource Manager (LRM) completes resource reservation and revocation according to the signaling interaction result.

The method according to claim 7, wherein the method is based on the condition that the link capacity needs to be restored, and the recovery process no longer involves the service signal carried by the link layer, and only needs to establish a new connection, that is, the service is no longer considered. And directly create a new connection.