CN103259590B - A kind of light multicast static P circle segment protection method of jumping section based on 2 - Google Patents

Abstract

The invention relates to a 2-hop-based optical multicast static P circle segment protection method, a method for requesting protection of all nodes and links of static services in an optical multicast switching network. An integer linear programming model with the goal of minimizing wavelength resources is proposed, which solves the problem that traditional static multicast service node protection and link protection cannot be balanced. According to the advantages of saving wavelength resources by P-circle protection, a 2-hop P-circle protection method is proposed. This method calculates the optimal P-circle solution of the link-separation path set by finding the 2-hop section of the link-separation path of the optical multicast network The set realizes the minimum demand allocation of wavelength resources, improves the utilization rate of limited wavelength resources in optical networks, and ensures the survivability of nodes and links in optical multicast networks at the same time.

Description

A 2-hop-based static P-ring protection method for optical multicast

technical field

The invention relates to the technical field of optical fiber communication, in particular to a P circle protection method for 2-hop static services used to solve node link failures in optical network multicast.

technical background

With the development of optical network technology, there are more and more optical multicast applications in the optical network for single-point transmission and multi-point reception, and the consumption and congestion of optical network bandwidth increase rapidly. With the gradual increase of optical fiber transmission capacity, once The failure of a certain node or link may cause multiple destination nodes to fail to receive data, and a large number of services will be lost. Improving the survivability of optical network multicast has become an important issue faced by optical networks. At present, there are mainly two measures to ensure the survivability of the optical network, network protection and network restoration. Protection refers to reserving protection resources for services in advance. When a fault occurs, services can be carried by backup resources. Restoration means not reserving protection resources for services in advance, and then dynamically searching for available resources in the network to carry services affected by the failure after a failure occurs. In comparison, the protection technology has a shorter service recovery time, but consumes more redundant resources; while the recovery technology has better resource utilization, but the fault recovery time is long, and it cannot provide completely reliable protection.

Studies in recent years have shown that P-ring protection uses less wavelength resources in the protection of static services, has the advantages of traditional ring protection, and can also protect cross-connected links, improving the protection range. It is an effective survival guarantee method for multicast networks with increasing transmission capacity. In an optical network, the wavelength itself is a very scarce resource, and the more resources are used, the greater the resource overhead. P-rings are usually ring connections that are pre-calculated and pre-configured in the network with the goal of minimizing the usage of wavelengths. In the traditional P-circle protection, node protection and link protection often cannot be taken into consideration. In traditional section protection, both node protection and link protection can be considered, but the traditional protection method has a high consumption of wavelength resources, which are very scarce resources in optical networks. The invention proposes a static P-circle protection method based on 2 hops to realize the protection of optical network multicast node faults and link faults, and at the same time minimize the wavelength usage of the P-circle.

Contents of the invention

Aiming at the single protection object of existing optical multicast routing, that is: only for the status quo of node failure or link failure, the present invention designs a static P circle segment protection method based on 2 hops, the method comprising: using a The improved depth-first search algorithm finds all the loops in the undirected graph, uses the heuristic algorithm to segment the multicast service, and designs the integer linear programming model to find the optimal solution from the set of all loops. The specific technical scheme is as follows:

A 2-hop-based optical multicast P circle segment protection method, the optical network is abstracted into a graph G(V,E) represented by a node set V and a fiber link set E, and the search graph G(V,E) All the rings, delete the nodes and edges with rings, until there is no cycle in the graph G(V, E), calculate the multicast tree corresponding to the multicast request connection path; for each path from the source node to the destination node Segmentation, every 2 hops is regarded as a segment; the multicast request path is divided into several 2-hop overlapping path segments, and the 2-hop overlapping path segment is used as a unit to protect the intermediate nodes and 2 links of the 2-hop segment. sex.

Find all the loops in the graph G(V,E), including: (1) Read in the network topology G(V,E), and number the nodes in it, which are 1,2,...,i,..., m; (2) Do a depth-first search for node m, reach a point W and push it into the stack; (3) Traverse all outgoing edges of W, and the other endpoints corresponding to the outgoing edges are v1, v2, ..., vJ; ( 4) Determine whether the point vj corresponding to the outgoing edge of W is in the stack, and turn to (5) if it is in the stack, otherwise turn to (6); (5) vj is in the stack and vj is equal to m, then it is a cycle from m to vj , output this cycle, if it is in the stack and vj is not equal to m, then i=i+1 turns to (4); (6) Continue depth-first search until there is no cycle in the graph. Said every 2 hops as a section is specifically: for a path from the source node to the destination node, every 2 hops of the path are stored as a 2-hop section, and continue to find a section from the next node to the destination node until no 2-hop section is found So far, those with less than 2 hops are stored in the form of links.

The present invention protects all nodes and links that need to be protected in the network with the lowest wavelength resource through the P-circle protection of 2 hops. Realize the protection of optical network multicast node failure and link failure, and at the same time minimize the wavelength usage of the P circle.

Description of drawings

Fig. 1 calculates the flow chart of all loop algorithms;

Fig. 2 multicast service segmentation algorithm flow chart;

Fig. 3 schematic diagram of multicast tree segmentation;

Figure 42 Schematic diagram of segment jump P circle protection.

Detailed ways

The present invention uses an improved depth-first-search (Deep-First-Search, DFS) algorithm to find all the loops of the directed graph, uses a heuristic algorithm to segment the multicast service and designs an integer linear programming model from A method to find the optimal solution in the set of all cycles. For the optical multicast request arriving at the input node of the optical network, firstly, according to the available wavelength bandwidth resource and topology relationship in the optical network, use the improved DFS algorithm to find all the loops of the network topology; then from the source node to each destination node The path is segmented, and the segmented path is subjected to link separation processing; finally, the optimal P circle is obtained through an integer linear programming model for each link separation segment.

The technical solution of the present invention will be further described below in conjunction with the accompanying drawings.

The difference between the improved depth-first search algorithm and the traditional depth-first search algorithm is: the traditional algorithm has to search all the paths and vertices connected with the starting point, but the improved depth-first search algorithm proposed by the present invention starts to search from a certain vertex , if it can form a ring, it will output and return the vertices of the previous layer. For each vertex, it is necessary to search all its paths and vertices, not just all the path vertices of the starting point.

Compute all loops. First, the nodes in the network topology G(V, E) are numbered, where G is a directed graph abstracted from the network topology, V is a node set, and E is an edge set. Then perform an improved depth-first search on node 1 in order. If the search is the same as the node, it means that there is a loop, then output the loop, and return to the searched node in the upper layer to continue searching until the search is completed. At this time, node 1 is included. loops are found. Finally, delete the node and all the edges connected to the node, and continue the search for the next node 2 until no loop is found in the graph.

Specifically, it can be as follows: the optical network is abstracted into an undirected graph G(V, E), V represents the node set in the optical network, E represents the fiber link set between node pairs, and the nodes in the network are represented by numbers 1, 2 , 3, ..., m labels represent. Set the variable u=1, corresponding to u represents node 1 in graph G, establish a network loop queue {u} represented by the node serial number, and use the depth-first search algorithm to find the downstream neighbor node w of node u, if there is node w in graph G , w∈[1,m] and w≠u, add node w to the ring queue to get {u, w}, and then traverse all outgoing links of node w in the node ring queue, if a link points to The next node v is not in the loop queue and v≠u, expand the loop queue to get {u, w, v}, and so on, enter the next layer of depth-first search; if node v=u, the current loop queue Indicates that from node u to v is a loop, output the loop, then backtrack and delete node w in the loop queue above, return to the upper layer to find other nodes adjacent to upstream node u, and then perform depth-first search. After a round of the above depth-first search algorithm is completed, all the rings containing the point u have been found, the ring queue is cleared, the node number u is increased by 1, and the above-mentioned backtracking depth-first search process is repeated to find all the rings including the new node u. Then clear the queue. By analogy, until u=m, all cycles of all nodes are found.

Accompanying drawing 1 is to seek all loop algorithm flow diagrams of directed graph, and its improved depth-first search algorithm step is described as follows:

Step1 reads in the network topology G (V, E), and numbers the nodes in it, which are 1, 2...i...m respectively.

Step2 conducts a depth-first search for node m, reaches a point W and pushes it into the stack.

Step3 traverses all outgoing edges of W, and the other endpoints corresponding to the outgoing edges are v1v2...vJ.

Step4 judges whether the point vj corresponding to the outgoing edge of W is in the stack, and if it is in the stack, turn to Step5, otherwise turn to Step6.

Step5vj is in the stack and vj is equal to m, then it is a ring from m to vj, output this ring, if it is in the stack and vj is not equal to m, then i=i+1 turns to Step4.

Step6 continues the depth-first search, if the search is completed, the algorithm ends, otherwise turn to Step3.

The method of segmenting the multicast service with a heuristic algorithm solves the problem of node protection and link protection in the multicast service, where Ci is the set of storage link separation segments, and each element in Ci is a mutual link road separated. S is a collection of all segments stored after segmenting the multicast service, and i is a counter of a set of link separation segments. Dividing the multicast service into several 2-hop overlapping path segments, and taking the 2-hop path segment as the unit to protect can realize the survivability of the intermediate node and the 2 links of the 2-hop segment. First, the multicast service is abstracted into a multicast tree, and then each path from the source node to the destination node is segmented, and every 2 hops is counted as a segment. Finally, link separation processing is performed on the divided segments, because the condition that the same P circle can be used for protection is that the two path segments are link separation.

In the optical network multicast, the tree abstracted by the business is segmented, because the failure of a link or node means the failure of all segments including the link or node, so the two path segments can use the same P circle The condition for protection is that they are link disjoint. A 2-hop section includes 2 links and their intermediate nodes, and the protection of each 2-hop section can achieve the node link protection of the entire multicast service. The process is:

Step 1: In optical multicast service transmission, build a multicast tree with minimum link cost according to network topology and multicast requests from source to all destination nodes. In this multicast tree, in the path from each source node to the destination node, except the source node and the destination node, other intermediate nodes and their associated two links on the path are called a 2-hop segment. Sow all such 2-hop segments on each source-to-destination node path in the tree graph, and store them in a set; and store the links associated with the source node and the destination in another 1-hop link set. Compare the 2-hop segments in the above set, and merge the same 2-hop segments in the set. Define a set of path segments to store all 2-hop segments and 1-hop segments.

Step 2: Set a variable i, initialize i=1, define a set cluster Ci to be used in the segment of the path segment set obtained in step 1 where the links are separated from each other, initialize the set cluster Ci, in the path segment set obtained in step 1 , randomly select a path segment X, if the path segment is separated from the path segment links in the Ci set, store the path segment X in the set Ci, and delete the path segment from the path segment set; Randomly select another path segment in the set, compare it with the set Ci according to the above method to see if the link is separated, if so, store the path segment in the Ci set and delete the path segment in the path segment set; otherwise, mark it in the path segment set For this path segment, for the unmarked path segment in the path segment set, continue to compare whether it is separated from the path segment link in the set Ci, until all the path segments in the path segment set are marked or are an empty set, if the path segment set is an empty set, The algorithm ends; if the set of path segments is not empty, add 1 to the variable i, and cancel the marking symbols of the marked path segments in the path segment, repeat the above steps, and store the separated paths in the path segment in the new set Ci; and so on , until the collection of path segments is empty.

Find the optimal solution from the set of all cycles. Take all the ring sets as the solution set, compare each link separation section set, and obtain the optimal solution for each link separation section set through the integer linear programming model, so as to minimize the wavelength used by the P circle.

Accompanying drawing 2 is the flow diagram of the algorithm for segmenting the multicast service with the heuristic algorithm.

Step 1 is initialized, i=1, the link separation segment set Ci is empty, and the path segment set is S.

Step2 randomly selects a path segment s from S and marks it, and compares it with Ci. If all elements in Ci are link-separated, then turn to Step3; otherwise, turn to Step4.

Step3 updates Ci and S, Ci=Ci∪s, S=S-s, turn to Step2.

Whether Step4S is empty, if it is an empty set, then i=i+1 turns to Step2; otherwise, the algorithm ends.

Accompanying drawing 3 is the example diagram of the segmentation of the multicast tree abstracted by the multicast service.

As shown in Figure 3, S is the source node, d is the destination node, and the others are intermediate nodes. Each path from source node S to destination node d is segmented by 2 hops, and the path less than 2 hops is treated as a single link . It can be seen that if the multicast service is segmented in this way, the segment is used as the unit. As long as these segments are protected, then all nodes and links in the network except the source node and the destination node can be guaranteed to be protected. Attached Figure 4 is a schematic diagram of P circle protection for 2 jumps, (a) is a schematic diagram of P circle protection, and the black thick solid line is P circle. (b) The picture is a schematic diagram of the protection of the crossover link. The dotted line is the faulty section, and the black thick solid line with arrows is the protection path. It can be seen that the P ring can provide two protection paths for the crossover link, and the service will be switched after a fault occurs. Retransmit on any protection path. (c) The figure is a schematic diagram of protection in the upper section of the circle. The dotted line is the faulty section, and the black thick solid line with arrows is the protection path. After a fault occurs, the service will be switched to the protection path to complete the protection. It can be seen that the P ring can provide a protection path for the upper section of the ring.

Claims (3)

1. the static P of light multicast jumping section based on 2 encloses a segment protection method, it is characterized in that, by abstract for optical-fiber network for using node set v,optical fiber link set ethe figure represented g( v, e), set up the multicast tree of minimum cost route according to multicast request, at figure g( v, e) in other limit ring that can form on search taboo multicast tree limit, delete node and the limit of all rings, then look for loop, until scheme g( v, e) in there is no loop; From source node, carry out segmentation to bar every in the loop found to the path of destination node, every 2 jump as one section; Multicast tree protection is divided into several 2 jumping crossover route segments, jumps in units of crossover route segments by 2 and carry out protecting the survivability realizing this 2 intermediate node and 2 links of jumping section to protect; Finally jump crossover road to be divided into 2 and carry out link disjoint process, occur simultaneously and just form P circle;

Search graph g( v, e) in all rings, delete and have node and the limit of ring, until figure g( v, e) in there is no loop, specifically comprise: (1) reads in network topology G(V, E), being numbered node wherein, is 1 respectively, 2 ... i ... m; (2) depth-first search is carried out for node m, arrive a some W it is stacked; (3) travel through W all go out limit, another end points going out limit corresponding is respectively v1, v2 ... vJ; (4) judge that W's goes out some vj corresponding to limit whether in stack, then turn in stack (5), otherwise turn to (6); (5) vj is in stack and vj equals m is then a ring from m to vj, and export this ring, if vj is not equal to m in stack, i=i+1 turns to (4); (6) depth-first search is continued, until do not have ring in figure.

2. method according to claim 1, it is characterized in that, described every 2 jumpings are specially as one section: for a paths from source node to destination node, every 2 jump path jumps section as one 2 and stores, continue next node to the destination node section of looking for, until can not find 2 jumping sections, the link form of pressing of jumping less than 2 stores.

3. method according to claim 1, is characterized in that, depth-first search is searched for from some summits, searches and can form a ring and then export and return to the summit of last layer.