CN1322713C - Method for enhancing survivability of automatic exchange optical network - Google Patents

Abstract

The present invention relates to a method for intensifying the survivability of automatic light exchanging networks, which belongs to the technical field of light networks. The present invention discloses an ASON survivability intensifying method. In the method, downstream nodes of a damaged link are utilized to coordinate the light network resource allocation of a damaged channel, so the influence of the conflict of light network resources on the survivability of a network during the maintenance of the link is avoided, and the restoring successful rate is enhanced; a grading and parallel restoring process is adopted, so the connection establishing time is shortened.

Description

A method of enhancing the survivability of automatic switching optical network

technical field

The invention belongs to the technical field of optical networks, and in particular relates to the restoration resource coordination based on the control plane of the Automatic Switching Optical Network (ASON) and the fast restoration process with faults.

Background technique

The International Telecommunication Union (ITU-T) positions the Automatically Switched Optical Network (ASON/ASTN) as a global unified transport network. It is expected that thousands of switches and millions of terminal nodes will be connected to this network in the future. middle. At present, the transmission rate of a single fiber has reached the level of Tbps (1012 bit/s). If a single fiber in the ASON optical network fails (such as a fiber break), it will cause a large amount of user data to be lost in a short period of time, resulting in network quality of service (QoS) decline. Carrier-level service quality requires 99.999% reliability, that is, the sum of allowed service interruption time in an average year is only about 5 minutes. Therefore, recovery technology is the key technology of ASON optical network, and occupies an increasingly important position in ASON.

When ASON detects the failure of the optical fiber link, ASON starts the failure recovery process, re-establishes routes for these damaged signals and allocates corresponding optical network resources. In the above process, in order to ensure the recovery time and recovery success rate of the damaged signal, it is necessary to resolve the resource conflict of the damaged signal optical network and reduce the time of the recovery process.

To solve the problem of resource conflict in the damaged signal optical network, the "retry mechanism" is currently used. That is, when ASON re-allocates resources to a damaged signal, if it fails, it will re-allocate network resources until the allocation is successful or the number of allocations exceeds the set threshold. The advantage of this aspect is that the recovery success rate is relatively high, and the disadvantage is that the recovery time is relatively long, thereby reducing the survivability of the network.

The time of the recovery process is mainly limited by the recovery process strategy and the establishment time of new connections during the recovery process. The shorter the recovery process, the stronger the survivability of the optical network.

Contents of the invention

The present invention proposes an ASON survivability enhancement method, uses the downstream nodes of the damaged link to coordinate the optical network resource allocation of the damaged channel, and solves the impact of the optical network resource conflict on the network survivability during the link failure restoration process; adopts a Hierarchical, parallel recovery process reduces connection setup time.

Technical scheme of the present invention is as follows:

1. A method for enhancing the survivability of the Automatic Switching Optical Network, is characterized in that: after a certain optical fiber link of the Automatic Switching Optical Network breaks down, it is divided into two situations and handled:

1) If the fiber fault is in a certain routing domain, then perform the following steps:

1.1) The downstream node connected to the faulty link queries the local link resource database to obtain the entry and exit addresses of all damaged channels in the routing domain;

1.2) The downstream node calculates the recovery route in the routing domain for all damaged channels, and determines the optical network resource allocation principle for these damaged channels;

1.3) The downstream node sends a connection establishment command including a routing message and an optical network resource allocation principle to the starting node of the routing domain restoration route described in step 1.2);

1.4) The initial node described in step 1.3) adopts a parallel method to establish a new connection to the damaged channel:

1.4.1) The starting node receives the connection establishment command, and immediately forwards the command to the downstream node in the route; and allocates local optical network resources according to the resource allocation principle;

1.4.2) The intermediate node restoring the route, after receiving the connection establishment command forwarded from the upstream, immediately forwards the command to the downstream node in the route; and allocates the local optical network resources according to the resource allocation principle;

1.4.3) The last node that restores the route, after receiving the connection establishment command forwarded from the upstream, allocates the local optical network resources according to the resource allocation principle; and sends a message to the upstream node whether the resource allocation is successful or not;

1.4.4) The intermediate node receives the resource allocation success message sent by its downstream node. If the local resource allocation is also successful, it forwards the resource allocation success message to the upstream node; if the local resource allocation is unsuccessful, it forwards the resource allocation success message to its upstream and downstream nodes Send a message that the resource allocation is unsuccessful, and release the local optical network resources;

The intermediate node receives the message of unsuccessful resource allocation sent by its downstream node, sends a message of unsuccessful resource allocation to its upstream node, and releases the local optical network resources;

1.4.5) The initial node receives the message of successful resource allocation, and sends a message of successful recovery to the optical network; the initial node receives the message of unsuccessful resource allocation, releases the optical network resources occupied for this recovery, and transfers to Step 2.3), execute the recovery process of higher level routing domain;

2) If the fiber fault is between certain two routing domains, then perform the following steps:

2.1) The downstream node connected to the faulty link queries the local link resource database to obtain the source and sink addresses of all damaged channels and the damaged link information;

2.2) The downstream node determines the optical network resource allocation principle for all damaged channels;

2.3) The downstream node sends to the endorsement node of the superior routing domain the connection containing the source and destination addresses of the damaged channel and the damaged link information described in step 2.1) and the optical network resource allocation principle described in step 2.2) build command;

2.4) The endorsement node of the superior routing domain described in step 2.3) calculates the recovery routes of all damaged channels in the routing domain, and sends a connection establishment command including routing messages and optical network resource allocation principles to the starting node of the recovery route;

2.5) The initial node described in step 2.4) executes steps 1.4.1) to 1.4.4) to determine the connection of the damaged channel in this routing domain;

If the connection is successful, the endorsement node of the upper-level routing domain sends a connection establishment command including the starting node, the last node and the optical network resource allocation principle to its lower-level routing domain; if the connection is unsuccessful, the upper-level routing The endorsement node of the domain sends a connection establishment command including the source and destination addresses of the damaged channel and the damaged link information in step 2.1) and the optical network resource allocation principle described in step 2.2) to its superior routing domain endorsement node; And repeat steps 2.4) and 2.5);

2.6) The entry node of the lower-level routing domain described in step 2.5) executes steps 1.4.1) to 1.4.4) after receiving the connection establishment command, to determine the connection of the damaged channel in the routing domain;

If the connection is established successfully, the entry node of the lower-level routing domain sends a connection success message to the endorsement node of the upper-level routing domain; the endorsement node of the upper-level routing domain generates a recovery success message after receiving the connection success message;

If the connection fails to be established, the entry node of the lower-level routing domain sends a connection failure message to the endorsement node of the upper-level routing domain; the endorsement node of the upper-level routing domain receives the connection failure message, and sends a message containing The source of the damaged channel described in step 2.1), the destination address and the damaged link information and the connection establishment command of the optical network resource allocation principle described in step 2.2); and repeatedly execute steps 2.4) and 2.5);

If the recovery of the highest-level routing domain is still unsuccessful, a recovery failure message is sent to the optical network, and corresponding optical network resources are released at the same time.

The present invention has two prominent features: 1. It coordinates the optical network resources in the recovery channel establishment process, solves the phenomenon that the recovery channels compete for resources with each other in the channel recovery process, improves the success rate of recovery, and reduces the recovery rate accordingly. 2. Using a hierarchical recovery process, the recovery path becomes shorter, the signaling process for recovery, and the number of nodes for recovery design are greatly reduced. This measure also greatly reduces the recovery time of the channel.

Utilizing the present invention, on a simulated network platform composed of 243 nodes, the recovery time of the network is tested, and the average recovery time (15 hops) is 298 milliseconds.

Description of drawings

Figure 1 is a schematic diagram of a network topology.

Figure 2 is a flow chart of the method of the present invention.

Detailed ways

Embodiments of the present invention will be specifically described below in conjunction with the accompanying drawings.

Figure 1 shows an embodiment of a wavelength routed optical network topology. The wavelength routing optical network consists of two stages. Each level consists of a varying number of routing domains. Each routing domain logically consists of a data plane and a control plane, and is physically associated with a certain number of optical node devices (hereinafter referred to as nodes). In this example: the first level of the optical network includes two routing domains, routing domain 1 and routing domain 2, and the second level of the optical network includes routing domain 3. Marks 11, 12, 13, 14 and 15 represent nodes related to routing domain 1; marks 21, 22, 23, 24 and 25 represent nodes related to routing domain 2; marks 31, 32, 33 and 34 represent nodes related to routing domain 3 related nodes. The data plane and control plane of routing domain 1 are realized by nodes 11 , 12 , 13 , 14 and 15 , and the data plane and control plane of routing domain 2 are realized by nodes 21 , 22 , 23 , 24 and 25 . Routing domain 1 and routing domain 2 constitute routing domain 3 . The data plane and control plane of routing domain 3 are implemented by nodes 31 , 32 , 33 and 34 . The nodes are connected by optical fibers, and wavelength division multiplexing optical signals are transmitted in the optical fibers. In this example, 40 channels are transmitted, represented by λ1, λ2, ..., λ40.

The relationship between routing domain 3 and routing domain 1 and routing domain 2 satisfies the containment strategy suggested by ITU-T G8080: routing domain 1 and routing domain 2 are completely contained in routing domain 3.

Each node in Figure 1 embeds routing protocols, signaling protocols, and link management protocols. These protocols can be the shortest path first (OSPF) routing protocol based on the generalized multi-protocol label switching protocol cluster, the resource reservation (RSVP-TE) signaling protocol and the LMP link management protocol popular in optical networks. Designated by the optical network management system: node 31 is the endorsement node of the control plane in the second level; nodes 12 and 24 are the endorsement nodes of the control plane in the first-level routing domain 1 and routing domain 2 respectively.

Using the C language under the Linux system, the method according to the present invention is developed into a recovery module program, and the recovery module program is embedded in all optical node devices in the optical network. The process flow of the recovery module program is shown in Figure 2. The following uses an example to illustrate the working principle of the recovery module.

Assuming that the optical fiber connecting node 22 and node 23 in Figure 1 is broken, node 23 detects this failure, generates a failure alarm signal, and triggers the recovery process of the optical network:

1) The recovery module of node 23 first judges whether the faulty optical fiber belongs to an internal fault in the routing domain or a fault between routing domains.

This failure is a case of an internal failure in routing domain 2.

2) The node 23 inquires its link resource database, and obtains the number of optical wavelengths transmitted in the broken optical fiber, and its input and output node addresses in the routing domain 2 .

For example, in this example, it is assumed that two wavelengths are transmitted in the broken fiber, namely λ1 and λ2; these two signals are both from routing domain 1, and their entry nodes in routing domain 2 are node 21 and node 22, and the exit Both are node 25.

3) The recovery module in node 23 starts the route calculation module of the OSPF protocol embedded in the node, recalculates the routes from node 21 to node 25, node 22 to node 25 for the above two channels, and determines the allocation principle of optical wavelength resources .

For example, in this example, assume that the route calculation module in the OSPF routing protocol calculates the route from node 21 to node 25 as: 21 entry 21I3->21 exit 21E1->24 entry 24I4->24 exit 24E1->25 entry 25I3->25 exit 25E1; the route from node 22 to node 25 is: 22 entry 22I3->22 exit 22E1->24 entry 24I3->24 exit 24E1->25 entry 25I3->25 exit 25E1.

The allocation principle of optical wavelength resources depends on different network operation conditions. For example, in this example, the following allocation principle is adopted: the available wavelength of the first channel is λ1; the available wavelength of the second channel is λ2.

4) Node 23 sends a connection establishment command of 21I3->21E1->24I4->24E1->25I3->25E1 to node 21, and stipulates that the available optical wavelength when the connection is established is λ1; sends 22I3->22E1 to node 22 ->24I3->24E1->25I3->25E1 connection establishment command, and stipulate that the available optical wavelength when the connection is established is λ2.

5) The node 21 forwards the connection establishment command and the optical resource allocation principle with an available wavelength of λ1 to the node 24; the node 21 sends a connection instruction based on the wavelength λ1 of establishing 21I3->21E1 to the local;

6) The node 24 forwards the connection establishment command and the optical resource allocation principle that the available wavelength is λ1 to the node 25; the node 24 sends a connection instruction based on the wavelength λ1 to establish 24I4->24E1 locally;

7) The node 25 sends a local connection instruction based on wavelength λ1 to establish 25I3->25E1. Connect successfully and send success message to node 24;

The node 24 locally connects successfully, and sends a success message to the node 21;

Node 21 sends a channel 1 recovery success message.

The following steps 8), 9), and 10) are carried out simultaneously with the above-mentioned steps 5), 6), and 7).

8) The node 22 forwards the connection establishment command and the optical resource allocation principle that the available wavelength is λ2 to the node 24; the node 22 sends a connection instruction based on the wavelength λ2 to establish 22I3->22E1 locally;

9) The node 24 forwards the connection establishment command and the optical resource allocation principle that the available wavelength is λ2 to the node 25; the node 24 sends a connection instruction based on the wavelength λ2 to establish 24I3->24E1 locally;

10) The node 25 sends a local connection instruction based on wavelength λ2 to establish 25I3->25E1. Connect successfully and send success message to node 24;

The node 24 locally connects successfully, and sends a success message to the node 22;

Node 22 sends a channel 2 recovery success message.

The recovery process is over.

If recovery fails, assuming that channel recovery based on wavelength λ1 fails, node 21 notifies node 23 of this message, and at the same time sends an optical resource release message to all nodes on the recovery path to release the optical network resources occupied for this recovery.

The node 23 notifies the source and destination addresses of the damaged channel and the identification of the broken optical fiber in the routing domain 2 to the endorsement node 31 of the routing domain 3, and requests the restoration of the channel based on the wavelength λ1. The response of node 31 and the specific recovery process are similar to the situation after a fiber break occurs between routing domains, see the relevant part below.

Assuming that the optical fiber connecting node 15 and node 22 in Figure 1 is broken, node 22 detects this failure, generates a failure alarm signal, and triggers the recovery process of the optical network:

1) The restoration module of the node 22 first judges whether the faulty fiber belongs to an internal fault in the routing domain or a fault between routing domains.

This failure is a case of a failure between Routing Domain 1 and Routing Domain 2.

2) The node 22 queries its link resource database to know the optical wavelengths transmitted in the broken optical fiber, the addresses of the source and sink nodes to which these optical wavelengths are connected, and the identifier of the broken optical fiber.

For example, in this example, it is assumed that two wavelengths are transmitted in the broken fiber, namely λ1 and λ2; the source addresses of these two signals are respectively 11 entry 11I3 and 12 entry 12I3; the sink addresses are 23 exit 23E1 and 24 Exit 24E1; the mark of the broken optical fiber is 15 entrances and exits 15IE1-22 entrances and exits 22IE3.

3) The node 22 determines the optical wavelength resource allocation principle of the recovery channel of the above two damaged channels.

The allocation principle of optical wavelength resources depends on different network operation conditions. For example, in this example, the following allocation principle is adopted: the available wavelength of the first channel is λ1; the available wavelength of the second channel is λ2.

4) Node 22 sends the following connection request to the endorsement node of routing domain 3, that is, node 31: wavelength λ1, connect 11I3->23E1; wavelength λ2, connect 12I3->24E1; route establishment avoids the optical fiber connecting 15IE1-22IE3.

5) The node 31 calculates corresponding routes in the routing domain 3 and assigns corresponding wavelengths to each route.

For example, assume that the routes calculated by node 31 for the two channels in this example are the same, 31E1->34I2; the wavelength assignment is successful.

6) Node 31 sends a connection establishment request to the endorsement node 12 of routing domain 1: wavelength λ1, connects 11I3->13E1; wavelength λ2, connects 12I3->13E1; sends a connection establishment request to the endorsement node 24 of routing domain 2: wavelength λ1, Connect 21I3->13E1; wavelength λ2, connect 21I3->13E1.

7) The endorsement nodes of routing domain 1 and routing domain 2 initiate a corresponding connection establishment process in the routing domain. Assuming that the connection is successfully established, a network restoration success message is sent.

The recovery process is complete.

If the connection fails, this example assumes that in routing domain 1, the connection based on wavelength λ1 fails to be established, then the endorsement node 12 sends a message of recovery failure based on wavelength λ1 to the endorsement node 31 in routing domain 3, and releases the routing domain for use by this connection at the same time network resources;

In this example, since it is a two-level network, node 31 is at the uppermost level of the network, so node 31 sends a message to the network that the recovery of the damaged channel based on λ1 fails, and at the same time sends a message to the routing domain 2 to release the recovery resource based on λ1; If the network has more than two levels, the node 31 will continue to request the establishment of the recovery connection to the upper level network.

Claims (1)

1. A method for enhancing the survivability of the Automatic Switching Optical Network, is characterized in that: after a certain optical fiber link of the Automatic Switching Optical Network breaks down, it is divided into two situations and handled: 1) If the fiber fault is in a certain routing domain, then perform the following steps: 1.1) The downstream node connected to the faulty link queries the local link resource database to obtain the entry and exit addresses of all damaged channels in the routing domain; 1.2) The downstream node calculates the recovery route in the routing domain for all damaged channels, and determines the optical network resource allocation principle for these damaged channels; 1.3) The downstream node sends a connection establishment command including a routing message and an optical network resource allocation principle to the starting node of the routing domain restoration route described in step 1.2); 1.4) The initial node described in step 1.3) adopts a parallel method to establish a new connection to the damaged channel: 1.4.1) The starting node receives the connection establishment command, and immediately forwards the command to the downstream node in the route; and allocates local optical network resources according to the resource allocation principle; 1.4.2) The intermediate node restoring the route, after receiving the connection establishment command forwarded from the upstream, immediately forwards the command to the downstream node in the route; and allocates the local optical network resources according to the resource allocation principle; 1.4.3) The last node that restores the route, after receiving the connection establishment command forwarded from the upstream, allocates the local optical network resources according to the resource allocation principle; and sends a message to the upstream node whether the resource allocation is successful or not; 1.4.4) The intermediate node receives the resource allocation success message sent by its downstream node. If the local resource allocation is also successful, it forwards the resource allocation success message to the upstream node; if the local resource allocation is unsuccessful, it forwards the resource allocation success message to its upstream and downstream nodes Send a message that the resource allocation is unsuccessful, and release the local optical network resources; The intermediate node receives the message of unsuccessful resource allocation sent by its downstream node, sends a message of unsuccessful resource allocation to its upstream node, and releases the local optical network resources; 1.4.5) The initial node receives the message of successful resource allocation, and sends a message of successful recovery to the optical network; the initial node receives the message of unsuccessful resource allocation, releases the optical network resources occupied for this recovery, and transfers to Step 2.3), execute the recovery process of higher level routing domain; 2) If the fiber fault is between certain two routing domains, then perform the following steps: 2.1) The downstream node connected to the faulty link queries the local link resource database to obtain the source and sink addresses of all damaged channels and the damaged link information; 2.2) The downstream node determines the optical network resource allocation principle for all damaged channels; 2.3) The downstream node sends to the endorsement node of the superior routing domain the connection containing the source and destination addresses of the damaged channel and the damaged link information described in step 2.1) and the optical network resource allocation principle described in step 2.2) build command; 2.4) The endorsement node of the superior routing domain described in step 2.3) calculates the recovery routes of all damaged channels in the routing domain, and sends a connection establishment command including routing messages and optical network resource allocation principles to the starting node of the recovery route; 2.5) The initial node described in step 2.4) executes steps 1.4.1) to 1.4.4) to determine the connection of the damaged channel in this routing domain; If the connection is successful, the endorsement node of the upper-level routing domain sends a connection establishment command including the starting node, the last node and the optical network resource allocation principle to its lower-level routing domain; if the connection is unsuccessful, the upper-level routing The endorsement node of the domain sends a connection establishment command including the source and destination addresses of the damaged channel and the damaged link information in step 2.1) and the optical network resource allocation principle described in step 2.2) to its superior routing domain endorsement node; And repeat steps 2.4) and 2.5); 2.6) The entry node of the lower-level routing domain described in step 2.5) executes steps 1.4.1) to 1.4.4) after receiving the connection establishment command, to determine the connection of the damaged channel in the routing domain; If the connection is established successfully, the entry node of the lower-level routing domain sends a connection success message to the endorsement node of the upper-level routing domain; the endorsement node of the upper-level routing domain generates a recovery success message after receiving the connection success message; If the connection fails to be established, the entry node of the lower-level routing domain sends a connection failure message to the endorsement node of the upper-level routing domain; the endorsement node of the upper-level routing domain receives the connection failure message, and sends a message containing The source of the damaged channel described in step 2.1), the destination address and the damaged link information and the connection establishment command of the optical network resource allocation principle described in step 2.2); and repeatedly execute steps 2.4) and 2.5); If the recovery of the highest-level routing domain is still unsuccessful, a recovery failure message is sent to the optical network, and corresponding optical network resources are released at the same time.

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