CN108337043B - Fault recovery method with area fault tolerance in multilayer SDN optical network - Google Patents

Fault recovery method with area fault tolerance in multilayer SDN optical network Download PDF

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CN108337043B
CN108337043B CN201711428618.8A CN201711428618A CN108337043B CN 108337043 B CN108337043 B CN 108337043B CN 201711428618 A CN201711428618 A CN 201711428618A CN 108337043 B CN108337043 B CN 108337043B
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path
network
link
paths
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CN108337043A (en
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施展
吴赞红
亢中苗
苏卓
黄宇
汪莹
付佳佳
蔺鹏
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Beijing Vectinfo Technologies Co ltd
Electric Power Dispatch Control Center of Guangdong Power Grid Co Ltd
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Electric Power Dispatch Control Center of Guangdong Power Grid Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/03—Arrangements for fault recovery
    • H04B10/038—Arrangements for fault recovery using bypasses
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
    • H04L41/06—Management of faults, events, alarms or notifications
    • H04L41/0654—Management of faults, events, alarms or notifications using network fault recovery
    • H04L41/0663—Performing the actions predefined by failover planning, e.g. switching to standby network elements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/22—Alternate routing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0005—Switch and router aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062—Network aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062—Network aspects
    • H04Q2011/0073—Provisions for forwarding or routing, e.g. lookup tables
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062—Network aspects
    • H04Q2011/0079—Operation or maintenance aspects
    • H04Q2011/0081—Fault tolerance; Redundancy; Recovery; Reconfigurability

Abstract

The invention relates to the technical field of computer network communication, in particular to a fault recovery method with area fault tolerance in a multilayer SDN optical network. The strategy introduces an SDN unified control platform and an improved routing and spectrum calculation algorithm, considers the concept of path survival degree when finally selecting a standby path, and measures the probability of the standby path having regional failure. The invention can effectively avoid node configuration competition and spectrum competition, greatly shorten the time used in the recovery process, and greatly improve the success rate of fault recovery in consideration of the conditions of area fault and link reuse.

Description

Fault recovery method with area fault tolerance in multilayer SDN optical network
Technical Field
The invention relates to the technical field of computer network communication, in particular to a fault recovery method with area fault tolerance in a multilayer SDN optical network.
Background
As the bandwidth requirements of IP data services increase, the uncertainty and unpredictability of IP services no longer satisfy traditional Wavelength Division Multiplexing (WDM) networks. The conventional WDM network considers that the wavelength has the smallest granularity with a fixed size, and due to the explosive growth of the current internet and video services, the diversity of the internet services is greatly increased, which causes the WDM network to be difficult to adapt to service requests with different granularities, thereby resulting in low frequency spectrum utilization, and the demand for bandwidth allocation becomes more and more urgent, and people need a new optical fiber network architecture to manage the bandwidth capacity provided by the conventional WDM network. A new optical fiber network architecture should be able to reasonably allocate spectrum and also provide different QoS services according to different tenants, in which case an Elastic Optical Network (EON) is evolving from a conventional optical fiber network, and in the transmission section of the current communication network, the EON is different from WDM in that the EON can dynamically allocate spectrum according to service requirements, as a next generation optical fiber transmission network, and network operators would more like to know how to ensure the stability of the network and the recovery strategy. Due to the difference between EON and WDM, the recovery mechanism of WDM cannot be deployed directly to EON. Therefore, a new dynamic recovery strategy is needed.
In order to understand the development state of the prior art, the existing papers and patents are searched, compared and analyzed, and the following technical information with high relevance to the invention is screened out:
patent 201010619965.0 entitled network recovery method and device, which is to obtain network state and available resources of network after optical layer of network fails; the available resources comprise idle resources of an optical layer and an IP layer, and intact resources in the failed optical layer LSP and intact resources in an IP link corresponding to the LSP; according to the network state, calculating the path information of the new optical layer LSP, a corresponding IP link and configuration information corresponding to the head node and the tail node of the IP link by using available resources; informing the first node of the new optical layer LSP to establish the optical layer LSP according to the path information of the new optical layer LSP; and when the optical layer LSP is successfully established, informing the head and tail nodes of the IP link corresponding to the optical layer LSP to establish the IP link, and issuing configuration information corresponding to the head and tail nodes. By utilizing available resources to calculate new optical layer LSP and corresponding IP link, the connectivity of IP and optical network is improved. The method establishes the backup path again after the fault occurs through a distributed method, the configuration of the opposite nodes is not in place in one step, although the network interrupted by the fault can be recovered, the problem of node configuration competition is not considered, and the recovery time is not optimized.
Patent No. 201710224247.5, entitled "tree topology network recovery method based on central node master control", mainly solves the problem that the tree topology network in the prior art cannot be quickly recovered due to power failure or restart. The method comprises the following implementation steps: firstly, a central node sends a network recovery command message through local broadcasting; then, after receiving the network recovery command message from the superior node to which each level of slave node belongs, replying a network recovery response message to each level of slave node, and continuously transmitting the network recovery command message to the last-level relay node through local broadcasting; and finally, the final-stage relay node collects and reports the network recovery information step by step until reaching the central node, and the network recovery is completed. The invention actively initiates network recovery by using the central node and performs gradual recovery and summarization on each level of relay nodes, thereby realizing rapid recovery of the network, reducing the time for recovering network communication and being applicable to the field of local area networks and access networks of various communications. The method discusses the recovery problem after the tree topology network is interrupted, the nodes are configured in a layered mode, but the method is basically a distributed recovery scheme and does not optimize the recovery time.
Patent 200810184150.7, "network restoration", which discloses a method for restoring an active path between two nodes of a transport network after a failure, comprising the steps of: determining an alternate path through the network; and establishing a path protection involving the failed active path and the alternate path. If in a layered network, failed paths are restored concurrently at lower and higher layers, restoration actions in higher network layers can be easily reverted. The patent establishes a standby channel for a channel which may fail, and when the channel fails, the standby channel can be used for direct recovery, which greatly reduces the recovery time, but consumes too much resources.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a fault recovery method with regional fault tolerance in a multilayer SDN optical network, which can effectively avoid node configuration competition and spectrum competition and greatly shorten the time used in the recovery process.
In order to solve the problems, the technical scheme provided by the invention is as follows: a fault recovery method with area fault tolerance in a multi-layer SDN optical network comprises the following steps:
s1, performing network architecture modeling on an elastic optical network based on an SDN (software defined network), setting a virtual network resource layer on basic physical equipment, abstracting obtained network resources and providing the abstracted network resources for an upper layer to use; an SDN controller is arranged on the upper layer of the virtual network resource, and a path calculation unit and a flow engineering database are arranged on the SDN controller;
s2, dividing a dynamic recovery process after a network fault occurs into an information transmission stage and a standby path calculation unit, and adding an SDN unified control platform on a traditional network architecture in the information transmission stage; and in the standby path calculation unit, path cascade degree calculation and path survivability calculation are added on the basis of the traditional routing and spectrum allocation algorithm.
Further, the path cascade degree calculation method comprises the following steps:
s211, utilizing the number of the states which can be adjusted
Figure GDA0002507095480000031
And possibly provide chains of statesBandwidth b of the interfacekCalculating the average bandwidth
Figure GDA0002507095480000032
Figure GDA0002507095480000033
S212, the connection capacity tau of the link of the ith carrier path is as follows:
Figure GDA0002507095480000034
in the formula (I), the compound is shown in the specification,
Figure GDA0002507095480000035
a number of spectrum occupation states changeable for adjacent subcarriers;
s213. frequency spectrum occupation vector e on link llComprises the following steps:
Figure GDA0002507095480000036
wherein, F represents the number of self-carrier waves;
s214, frequency spectrum occupation vector e of whole pathRComprises the following steps:
Figure GDA0002507095480000037
wherein R represents a link;
s215. e on different linkslA vector space Sp may be formed, defining the average vector of the vector space as
Figure GDA0002507095480000038
Figure GDA0002507095480000039
Wherein n islRepresenting the number of different links;
s216. calculatingDegree of path concatenation DR：
Figure GDA00025070954800000310
In the formula, eRA spectral occupancy vector representing the entire path,
Figure GDA0002507095480000041
an average vector of a vector space composed of spectrum occupation vectors on different links, cov (X, Y) is obtained by solving two random variables X, Y covariance, D (X) is the variance of X, and E (X) is the expectation of X, and the formula is as follows:
cov(X,Y)＝E(XY)-E(X)E(Y)，
Figure GDA0002507095480000042
further, the step of calculating the path survivability includes:
s221. defining a link l1And a link l2The distance between
Figure GDA0002507095480000043
Comprises the following steps:
Figure GDA0002507095480000044
in the formula (I), the compound is shown in the specification,
Figure GDA0002507095480000045
representative link l1And l2Middle point m of1And m2The distance between them;
s222. Link L ═ L1,l2…llp.A path ofiAnd any link α
Figure GDA0002507095480000046
Comprises the following steps:
Figure GDA0002507095480000047
in the formula IiTo form a path PlWherein i ∈ [1, l]And l represents a component path PlThe number of links.
S223, when the link α fails for some reason, the parameters
Figure GDA0002507095480000048
The sum constant β may be used to represent the path PlDefined as the fault parameter, β,
Figure GDA0002507095480000049
representative path RlProbability of possible failure:
Figure GDA00025070954800000410
s224. probability that backup path Rl can work normally
Figure GDA00025070954800000411
Comprises the following steps:
Figure GDA00025070954800000412
further, the fault recovery method specifically includes:
s31, a node or a link at a certain position of the network fails;
s32, sending a message overtime to the fault node by the adjacent node of the fault node to obtain node unreachable information at a certain position, and sending the unreachable information and the request calculation standby path information to an SDN control platform;
s33, after the SDN controller receives the relevant information, updating the latest topological structure of the network, submitting a request of the node for calculating the standby path to a path calculating unit, reading the latest network topological structure by the path calculating unit, and calculating the standby path by using the improved routing and spectrum allocation algorithm proposed in the step S2;
s34, the SDN receives a plurality of paths given by the path calculation unit, divides the information flow into a plurality of paths, respectively allocates the paths to different paths, reserves a GB value required by each path when allocating a frequency spectrum, and returns information to a related request node; wherein GB is the guard band width on a link;
and S35, informing the related nodes involved by the new standby path by the SDN control platform, and completing the configuration of the nodes at one time.
Further, the step S33 includes:
s331, a path calculation unit reads a network topology structure, selects the first k paths with the shortest delay and meeting a delay difference DD threshold value, and stores the paths as candidate paths, wherein DD is the delay difference between the same paths;
s332, for the candidate path in the step S331, distributing the service flow needing the standby path to the candidate path, checking whether to follow the continuity and adjacency constraints when distributing the continuous spectrum, if the continuity and adjacency constraints are met, distributing successfully, returning to the standby path information request node, and ending the process;
s333, if the continuity and adjacency constraints cannot be met, namely no available continuous resources exist on the path, the path calculation unit respectively calculates the path cascade degrees of the candidate paths, screens out the paths meeting the threshold constraint and stores the paths as new candidate paths again;
and S334, considering that the standby path needs to have the requirement of regional fault tolerance, the path calculation unit calculates the survivability of the new candidate paths on the basis of the failed link or node, screens out the previous paths with the strongest survivability and returns the paths to the SDN control platform.
Compared with the prior art, the beneficial effects are: the fault recovery method with regional fault tolerance in the multilayer SDN optical network provided by the invention combines the SDN controller and provides an improved routing selection and spectrum allocation algorithm, so that node configuration competition and spectrum competition can be effectively avoided, the time used in the recovery process is greatly shortened, and the success rate of fault recovery is greatly improved in consideration of the conditions of regional faults and link multiplexing.
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Fig. 1 is a schematic diagram of a simulation topology according to an embodiment of the present invention.
Fig. 2 is a comparison diagram of recovery failure rates according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating the comparison of recovery time according to an embodiment of the present invention
Detailed Description
A fault recovery method with area fault tolerance in a multi-layer SDN optical network comprises the following steps:
s1, performing network architecture modeling on an elastic optical network based on an SDN (software defined network), setting a virtual network resource layer on basic physical equipment, abstracting obtained network resources and providing the abstracted network resources for an upper layer to use; an SDN controller is arranged on the upper layer of the virtual network resource, and a path calculation unit and a flow engineering database are arranged on the SDN controller;
s2, dividing a dynamic recovery process after a network fault occurs into an information transmission stage and a standby path calculation unit, and adding an SDN unified control platform on a traditional network architecture in the information transmission stage; and in the standby path calculation unit, path cascade degree calculation and path survivability calculation are added on the basis of the traditional routing and spectrum allocation algorithm.
In the invention, firstly, an elastic optical network is modeled based on SDN, a virtual network resource layer is arranged on basic physical equipment, network resources which can be obtained are abstracted and provided for an upper layer to use, an SDN controller is arranged on the virtual network resource layer, the virtual network resources provided by the virtual network resource layer can be allocated, and a Path Computation Element (PCE) and a Traffic Engineering Database (TED) are respectively arranged on the SDN controller. In this architecture, the SDN controller may grasp the state of the entire network through a virtual network resource layer, and provide required data for a path computation unit and a traffic engineering database to complete necessary computations.
After the network architecture modeling is completed, in order to discuss the strategy of the scheme more carefully, the dynamic recovery process after the network failure occurs is divided into two stages for discussion, namely an information transmission stage and a standby path calculation stage. The information transmission stage refers to the propagation of fault information on the network and the propagation of backup path information for backup path calculation on the network when a fault just occurs, and the two processes use the same mode, so that the two processes are combined into the same stage for consideration; the standby path calculation stage is a stage in which the SDN controller receives information requesting a standby path, sends the information to the path calculation unit, and calculates the standby path using network information in the path calculation unit.
In the information transmission stage, the SDN unified control platform is added to the traditional network architecture, so that node configuration competition and spectrum competition which may occur in the recovery process can be effectively avoided, and the time for complete fault recovery can be effectively shortened when the standby path calculation time is the same. For example, when a link fails, all traffic carried on the link needs to calculate a backup path to recover the service, assuming that there are two traffic flows of the original path failed link, if a conventional recovery mechanism is adopted at this time, starting points of the two traffic flows need to initiate a request for calculating the backup path, and after the calculation is completed, information is sent along the backup path to establish a new backup route for carrying the service, and if the backup path calculated by the two traffic flows is routed through a same path or a same node, node configuration competition and spectrum competition are easily triggered, for example, if the service 1 calculates the backup path first, the service 2 calculates the backup path, and when the service 2 configures information along the backup path, the link and the node common to the path and the service 1 need to wait for the link node to continue to configure the backup path of the service 2 after the link node completes configuring the backup path of the service 1, this is the node configuration competition and the spectrum competition, and when the node configuration competition and the spectrum competition occur, the time consumption of the whole recovery process will be increased undoubtedly because the standby path configuration of one or several services has a waiting condition. In the scheme, an SDN unified control platform is introduced, service 1 and service 2 send information requesting for calculating a standby path to an SDN controller when detecting path interruption, the SDN controller obtains the overall state of the network through a virtual network resource layer and sends related information to a path calculation unit to request new standby paths for service 1 and service 2, and after the standby path calculation is completed, the information is directly sent to related nodes, and the information contains final node configuration information, namely configuration information of service 1 and service 2 two-day service standby paths is covered, so that node configuration competition and spectrum competition can be effectively avoided.
In the second stage of the standby path calculation stage, the scheme considers the path cascading degree and the path survivability on the basis of the traditional routing and spectrum allocation algorithm.
Specifically, the path cascade degree calculation method includes the steps of:
s211, utilizing the number of the states which can be adjusted
Figure GDA0002507095480000071
And possibly the link bandwidth b of the offered statekCalculating the average bandwidth
Figure GDA0002507095480000072
Figure GDA0002507095480000073
S212, the connection capacity tau of the link of the ith carrier path is as follows:
Figure GDA0002507095480000074
in the formula (I), the compound is shown in the specification,
Figure GDA0002507095480000075
a number of spectrum occupation states changeable for adjacent subcarriers;
s213. frequency spectrum occupation vector e on link llComprises the following steps:
Figure GDA0002507095480000076
wherein, F represents the number of self-carrier waves;
s214. frequency spectrum occupation direction of whole pathQuantity eRComprises the following steps:
Figure GDA0002507095480000077
wherein R represents a link;
s215. e on different linkslA vector space Sp may be formed, defining the average vector of the vector space as
Figure GDA0002507095480000078
Figure GDA0002507095480000079
Wherein n islRepresenting the number of different links;
s216, calculating the path cascade degree DR：
Figure GDA0002507095480000081
In the formula, eRA spectral occupancy vector representing the entire path,
Figure GDA0002507095480000082
mean vector of vector space composed of spectrum occupation vectors on different links, cov (X, Y) is taken to find two random variables X, Y covariance, d (X) is the variance of X, and e (X) is the expectation of X.
In addition, the step of calculating path survivability includes:
s221. defining a link l1And a link l2The distance between
Figure GDA0002507095480000083
Comprises the following steps:
Figure GDA0002507095480000084
in the formula (I), the compound is shown in the specification,
Figure GDA0002507095480000085
representative link l1And l2Middle point m of1And m2The distance between them;
s222. Link L ═ L1,l2…llp.A path oflAnd any link α
Figure GDA0002507095480000086
Comprises the following steps:
Figure GDA0002507095480000087
in the formula IiTo form a path PlWherein i ∈ [1, l]And l represents a component path PlThe number of links.
S223, when the link α fails for some reason, the parameters
Figure GDA0002507095480000088
And a constant β may be used to indicate the survivability of path P, β is defined as a fault parameter,
Figure GDA0002507095480000089
representative path RlProbability of possible failure:
Figure GDA00025070954800000810
s224. probability that backup path Rl can work normally
Figure GDA00025070954800000811
Comprises the following steps:
Figure GDA00025070954800000812
in some embodiments, the failure recovery method specifically includes:
s31, a node or a link at a certain position of the network fails;
s32, sending a message overtime to the fault node by the adjacent node of the fault node to obtain node unreachable information at a certain position, and sending the unreachable information and the request calculation standby path information to an SDN control platform;
s33, after the SDN controller receives the relevant information, updating the latest topological structure of the network, submitting a request of the node for calculating the standby path to a path calculating unit, reading the latest network topological structure by the path calculating unit, and calculating the standby path by using the improved routing and spectrum allocation algorithm proposed in the step S2;
s34, the SDN receives a plurality of paths given by the path calculation unit, divides the information flow into a plurality of paths, respectively allocates the paths to different paths, reserves a GB value required by each path when allocating a frequency spectrum, and returns information to a related request node; wherein GB is the guard band width on a link;
and S35, informing the related nodes involved by the new standby path by the SDN control platform, and completing the configuration of the nodes at one time.
Wherein, the step of S33 includes:
s331, a path calculation unit reads a network topology structure, selects the first k paths with the shortest delay and meeting a delay difference DD threshold value, and stores the paths as candidate paths, wherein DD is the delay difference between the same paths;
s332, for the candidate path in the step S331, distributing the service flow needing the standby path to the candidate path, checking whether to follow the continuity and adjacency constraints when distributing the continuous spectrum, if the continuity and adjacency constraints are met, distributing successfully, returning to the standby path information request node, and ending the process;
s333, if the continuity and adjacency constraints cannot be met, namely no available continuous resources exist on the path, the path calculation unit respectively calculates the path cascade degrees of the candidate paths, screens out the paths meeting the threshold constraint and stores the paths as new candidate paths again;
and S334, considering that the standby path needs to have the requirement of regional fault tolerance, the path calculation unit calculates the survivability of the new candidate paths on the basis of the failed link or node, screens out the previous paths with the strongest survivability and returns the paths to the SDN control platform.
Examples
The invention simulates the experimental result on the virtual network topology, and the simulation is carried out on a network with 14 nodes and 21 links, as shown in figure 1. We assume that the link capacity is set to 128 spectrum slots and that the guard bandwidth of one spectrum slot is added between adjacent channels to 12.5 GHz. In the event of a failure in the network, the threshold for the DD constraint is set to 128ms, and the traffic requested by each node is randomly distributed from 2 to 8 subcarriers. Furthermore, the requests to reconstruct the optical path follow a poisson distribution.
The invention analyzes the performance of the proposed recovery mechanism from two aspects, the time for recovering from the fault and the recovery success rate, analyzes the recovery time recovery failure rate of the scheme under the condition of different network loads and compares the recovery time recovery failure rate with the traditional recovery mechanism, and the simulation results are respectively shown in fig. 2 and fig. 3.
In fig. 2, the two curves for SDN/modified RSA-based and GMPLS/RSA-based traditional restoration have the same growth trend in case of increased network load. Both approaches increase recovery failure rates as network load increases. But the failure rate of the proposed scheme is much lower than that of the conventional scheme under the same network load.
In fig. 3, it is shown that the recovery time of the present solution is still low and stable as the network load increases, while the conventional time is much higher. As network load increases, the recovery time of the legacy mode also increases. Thus, the repair solution of the present invention has better performance than the conventional solution.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims (4)

1. A fault recovery method with area fault tolerance in a multi-layer SDN optical network is characterized by comprising the following steps:
s1, performing network architecture modeling on an elastic optical network based on an SDN (software defined network), setting a virtual network resource layer on basic physical equipment, abstracting obtained network resources and providing the abstracted network resources for an upper layer to use; an SDN controller is arranged on the upper layer of the virtual network resource, and a path calculation unit and a flow engineering database are arranged on the SDN controller;
s2, dividing a dynamic recovery process after a network fault occurs into an information transmission stage and a standby path calculation unit, and adding an SDN unified control platform on a traditional network architecture in the information transmission stage; on the basis of a traditional routing and spectrum allocation algorithm, a standby path calculation unit is added with path cascade degree calculation and path survivability calculation; the path cascade degree calculation method comprises the following steps:
s211, utilizing the number of the states which can be adjusted
Figure FDA0002507095470000011
And possibly the link bandwidth b of the offered statekCalculating the average bandwidth
Figure FDA0002507095470000012
Figure FDA0002507095470000013
S212, the connection capacity tau of the link of the ith carrier path is as follows:
Figure FDA0002507095470000014
in the formula (I), the compound is shown in the specification,
Figure FDA0002507095470000015
a number of spectrum occupation states changeable for adjacent subcarriers;
s213. frequency spectrum occupation vector e on link llComprises the following steps:
Figure FDA0002507095470000016
wherein, F represents the number of self-carrier waves;
s214, frequency spectrum occupation vector e of whole pathRComprises the following steps:
Figure FDA0002507095470000017
wherein R represents a link;
s215. e on different linkslA vector space Sp may be formed, defining the average vector of the vector space as
Figure FDA0002507095470000018
Figure FDA0002507095470000019
Wherein n islRepresenting the number of different links;
s216, calculating the path cascade degree DR：
Figure FDA0002507095470000021
In the formula, eRA spectral occupancy vector representing the entire path,
Figure FDA0002507095470000022
mean vector of vector space composed of spectrum occupation vectors on different links, cov (X, Y) is taken to find two random variables X, Y covariance, d (X) is the variance of X, and e (X) is the expectation of X.
2. The method of claim 1, wherein the step of calculating the path survivability comprises:
s221. defining a link l1And a link l2The distance between
Figure FDA0002507095470000023
Comprises the following steps:
Figure FDA0002507095470000024
in the formula (I), the compound is shown in the specification,
Figure FDA0002507095470000025
representative link l1And l2Middle point m of1And m2The distance between them;
s222. Link L ═ L1,l2…llp.A path ofLAnd any link α
Figure FDA0002507095470000026
Comprises the following steps:
Figure FDA0002507095470000027
in the formula IiTo form a path PlWherein i ∈ [1, l]And l represents a component path PlThe number of links of (c);
s223, when the link α fails for some reason, the parameters
Figure FDA0002507095470000028
The sum constant β may be used to represent the path PlDefined as the fault parameter, β,
Figure FDA0002507095470000029
representative path RlProbability of possible failure:
Figure FDA00025070954700000210
s224. backup route RlProbability of working normally
Figure FDA00025070954700000211
Comprises the following steps:
Figure FDA00025070954700000212
3. the method for fault recovery with zone fault tolerance in a multi-layer SDN optical network according to claim 2, wherein the method for fault recovery specifically comprises:
s31, a node or a link at a certain position of the network fails;
s32, sending a message overtime to the fault node by the adjacent node of the fault node to obtain node unreachable information at a certain position, and sending the unreachable information and the request calculation standby path information to an SDN control platform;
s33, after the SDN controller receives the relevant information, updating the latest topological structure of the network, submitting a request of the node for calculating the standby path to a path calculating unit, reading the latest network topological structure by the path calculating unit, and calculating the standby path by using the improved routing and spectrum allocation algorithm proposed in the step S2;
s34, the SDN receives a plurality of paths given by the path calculation unit, divides the information flow into a plurality of paths, respectively allocates the paths to different paths, reserves a GB value required by each path when allocating a frequency spectrum, and returns information to a related request node; wherein GB is the guard band width on a link;
and S35, informing the related nodes involved by the new standby path by the SDN control platform, and completing the configuration of the nodes at one time.
4. The method for fault recovery with zone fault tolerance in a multi-layer SDN optical network according to claim 3, wherein the step S33 includes:
s331, a path calculation unit reads a network topology structure, selects the first k paths with the shortest delay and meeting a delay difference DD threshold value, and stores the paths as candidate paths, wherein DD is the delay difference between the same paths;
s332, for the candidate path in the step S331, distributing the service flow needing the standby path to the candidate path, checking whether to follow the continuity and adjacency constraints when distributing the continuous spectrum, if the continuity and adjacency constraints are met, distributing successfully, returning to the standby path information request node, and ending the process;
s333, if the continuity and adjacency constraints cannot be met, namely no available continuous resources exist on the path, the path calculation unit respectively calculates the path cascade degrees of the candidate paths, screens out the paths meeting the threshold constraint and stores the paths as new candidate paths again;
and S334, considering that the standby path needs to have the requirement of regional fault tolerance, the path calculation unit calculates the survivability of the new candidate paths on the basis of the failed link or node, screens out the previous paths with the strongest survivability and returns the paths to the SDN control platform.
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