Patent Description:
A communication network may include one or multiple layers of network resources, for example, an internet protocol (IP) layer, an optical transport networking layer (OTN) and an optical layer, such as a wavelength division multiplex (WDM) optical layer. The IP layer and the optical layer may also be referred to herein as the client and server layer, respectively. Network resources may include a link, a node, a line card, and an optical fiber, for example. Network services and/or network connections may be defined in the multiple network layers.

<FIG> schematically illustrates a multilayered communication network <NUM> with a vertical topology. Multilayered communication network <NUM> may include an IP layer <NUM>, an optical transport networking (OTN) layers <NUM>, and a wavelength division multiplexing (WDM) <NUM>. IP layer <NUM> may include IP routers <NUM> connected by links <NUM>. The optical signals in IP layer <NUM> may be coupled to OTN layer <NUM> via a vertical communication path <NUM>, and the optical signals in OTN layer <NUM> may be coupled to WDM layer <NUM> via a vertical communication path <NUM>. Furthermore, vertical connection paths may skip a layer and connect, for example IP layer <NUM> directly to WDM layer <NUM>. OTN layer <NUM> may include OTN switches <NUM> connected by links <NUM>. WDM layer <NUM> may include WDM switches <NUM> connected by links <NUM>. IP routers <NUM> and OTN switches <NUM> may typically operate in the electrical domain to route data packets and connections respectively through the network. WDM switches <NUM> may use photonic switching to route light paths along the multiple links <NUM> in WDM layer <NUM>.

The layers, or data planes, in <FIG> may be arranged in a vertical topology whereby the lower layer service provisioning provides capabilities at the higher layers. Stated differently, the links in the upper network layers may be supported by connections in the lower layers. For example, data packets routed through an IP router in San Francisco may appear be connected to an IP router in New York City, but the data packets from San Francisco to New York City may be routed through the OTN or WDM layers.

In the event of a failure in multiple network resources particularly in a lower level, an operator may receive a flood of network resource failure alarms in a central control station without knowledge of which failed resource is most critical for restoring normal network operation. Thus, it may be desirable to have a method and a system to help the operator assessing which of the failed network resources may be most critical.

<CIT> discloses a method for processing shared risk group (SRG) information in communications networks. The method includes receiving network information comprising SRG information from a second domain at a first domain, obtaining at least one SRG identifier by processing the SRG information, and processing the at least one SRG identifier, the processing using processing criteria. The apparatus includes a network interface adapted to receive network information comprising shared risk group information, a processor coupled to the network interface and configured to execute one or more processes, and a memory coupled to the processor and adapted to obtain at least one SRG identifier by processing the SRG information and to process the at least one SRG identifier using processing criteria. <CIT> discloses a method of managing risk in a network including computing a first path between a source and a destination within the network, computing a second path between the source and the destination within the network, comparing a first risk zone of a first network element in the first path to a second risk zone of a second network element in the second path, the first risk zone is based on a first location-based risk identifier assigned to the first network element prior to computation of the first path, the second risk zone is based on a second location-based risk identifier assigned to the second network element prior to computation of the second path, and an overlap of the first risk zone and the second risk zone indicates that the first network element and the second network element have a shared risk.

The invention is defined by the independent claims, with optional features being defined by the dependent claims. There is thus provided, in accordance with the present invention, a method for analyzing failures in network resources in a multilayered communication network using passive shared risk resource groups, which comprises identifying network resources in a plurality of network resources having common risk attributes. The network resources are grouped into one or more passive shared risk resource groups (PSRG) based on the common risk attributes. A first value indicating a first likelihood of a first PSRG failure is assessed and a second value indicating a second likelihood of a second PSRG failure is assessed.

In response to failure of one or more network resources associated with the first PSRG and one or more network resources associated the second PSRG, identifying the one or more failed network resources associated with the first PSRG as the root cause for failure of the one or more network resources associated with the first PSRG and the one or more network resources associated the second PSRG based on determining that the first value is higher than the second value; andrestoring the one or more failed network resources associated with the first PSRG.

Furthermore, in accordance with some embodiments of the present invention, identifying the network resources with the common risk attributes may include limiting a search for the common risk attributes in network resources geographically close to one another.

Furthermore, in accordance with some embodiments of the present invention, the method may include outputting the first value for the first likelihood of the first PSRG failure and the second value for the second likelihood of the second PSRG failure.

Furthermore, in accordance with some embodiments of the present invention, the method may include defining the one or more PSRG based on a predefined mapping of said plurality of network resources in the communication network.

Furthermore, in accordance with some embodiments of the present invention, identifying the network resources in said plurality of network resources having the common risk atributes may include identifying one or more failed network resources from said plurality of network resources having the common risk atributes.

Furthermore, in accordance with some embodiments of the present invention, assessing the first value indicating the first likelihood of the first PSRG failure and the second value indicating the second likelihood of the second PSRG failure may include assigning a higher likelihood when failures of the one or more failed network resources in each of the one or more PSRG meet a predefined criterion.

Furthermore, in accordance with some embodiments of the present invention, the predefined criterion may be selected from the group consisting of failures of the one or more failed network resources that are geographically close to one another, failures of at least two failed network resources that occur substantially at the same time, and failures of at least two failed network resources that failed together in the past.

In order for the present invention, to be better understood and for its practical applications to be appreciated, the following Figures are provided and referenced hereafter. It should be noted that the Figures are given as examples only and in no way limit the scope of the invention. Fike components are denoted by like reference numerals.

However, it will be understood by those of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, modules, units and/or circuits have not been described in detail so as not to obscure the invention.

Although embodiments of the invention are not limited in this regard, discussions utilizing terms such as, for example, "processing," "computing," "calculating," "determining," "establishing", "analyzing", "checking", or the like, may refer to operation(s) and/or process(es) of a computer, a computing platform, a computing system, or other electronic computing device, that manipulates and/or transforms data represented as physical (e.g., electronic) quantities within the computer's registers and/or memories into other data similarly represented as physical quantities within the computer's registers and/or memories or other information non-transitory storage medium (e.g., a memory) that may store instructions to perform operations and/or processes. Although embodiments of the invention are not limited in this regard, the terms "plurality" and "a plurality" as used herein may include, for example, "multiple", two, or more. The terms "plurality" or "a plurality" may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like. Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed simultaneously, at the same point in time, or concurrently. Unless otherwise indicated, use of the conjunction "or" as used herein is to be understood as inclusive (any or all of the stated options).

While an operator may be monitoring data traffic in multilayer communication network <NUM> at a central control station, for example, the operator may receive multiple network resource failure alarms indicating failures in one or more network resources. Fault isolation, or root cause analysis, may be used to assess the multiple failures. Fault isolation may be used to analyze failures in successively lower network layers in the multilayered communication network, so as to identify a single failed network resource in a lower network layer, which may be used to explain failures in upper network layers. However, in the case where there are multiple failures that may not be explained after having analyzed failed resources on the lowest layer, correlation between failures that have common failure risk attributes may be analyzed to determine if there is a passive shared risk resource group (PSRG).

Embodiments of the present invention describe herein a system and method for analyzing failures in network resources in a multilayered communication network using passive shared risk resource groups.

<FIG> schematically illustrates a system <NUM> for monitoring and analyzing network resource failures in communication network <NUM>, in accordance with some embodiments of the present invention. System <NUM> may include a server <NUM>, which further includes a processor <NUM> coupled to a memory <NUM>, an input device <NUM>, an output device <NUM>, and a communication module and interface <NUM>. Server <NUM> may be part of, or may be in communication <NUM> with multilayered communication network <NUM> through a management/control network <NUM> also communicating <NUM> with network resources such as IP routers <NUM>, OTN switches <NUM>, and WDM switches <NUM>, for example, in the different network layers.

Although the embodiments shown in <FIG> illustrate a communication network with IP and optical links, for example, system <NUM> may also include microwave links and/or free space optical links (not shown in the figure).

Processor <NUM> may include one or more processing units, e.g. of one or more computers. Processor <NUM> may be configured to operate in accordance with programmed instructions stored in memory <NUM>. Processor <NUM> may be capable of executing an application for analyzing failures in network resources in a multilayered communication network using passive shared risk resource groups.

Processor <NUM> may communicate with output device <NUM>. For example, output device <NUM> may include a computer monitor or screen. Processor <NUM> may communicate with a screen <NUM> of output device <NUM> to display an analysis of failure indications in the network resources. In another example, output device <NUM> may include a printer, display panel, speaker, or another device capable of producing visible, audible, or tactile output.

In some embodiments of the present invention, output device <NUM> may include another system capable of analyzing failures in network resources in a multilayered communication network using passive shared risk resource groups. Alternatively or additionally, output device <NUM> may include any system capable of receiving and processing any suitable information regarding the failures in network resources in a multilayered communication network using passive shared risk resource groups.

Processor <NUM> may communicate with input device <NUM>. For example, input device <NUM> may include one or more of a keyboard <NUM>, keypad, or pointing device <NUM> (e.g., a mouse) for enabling a user to inputting data or instructions for operation of processor <NUM>.

Processor <NUM> may communicate with memory <NUM>. Memory <NUM> may include one or more volatile or nonvolatile memory devices. Memory <NUM> may be utilized to store, for example, programmed instructions for operation of processor <NUM>, data or parameters for use by processor <NUM> during operation, or results of operation of processor <NUM>. In operation, processor <NUM> may execute a method for analyzing failures in network resources in a multilayered communication network using passive shared risk resource groups.

Server <NUM> may also be referred to herein as a central controller, a central control station, or a top-level controller. A framework <NUM> may be operating on processor <NUM> of server <NUM>. The term "framework" may refer to a user-written application-specific software stored in memory <NUM> and executed on processor <NUM>. Framework <NUM> may include a fault isolation module <NUM>, a passive shared risk resource group (PSRG) identification module <NUM>, and an orchestration software module <NUM> that further includes a mapping database <NUM> that represents multilayered network <NUM>, its nodes, links and traffic statistics.

In some embodiments of the present invention, mapping database <NUM> may include mappings of which ports of IP routers <NUM> map into which ports in OTN switches <NUM> and WDM switches <NUM>, for example, and vice versa, or into any other network layers in multilayered communication network <NUM>. Mapping database <NUM> may include the entire general connectivity topology (e.g., cross layer mapping) of multilayered communication network <NUM>. Orchestration module <NUM> may be used for mapping service requests to available network resources in the multilayered environment and optimizing the usage of different types of network resources. The embodiment shown herein may be also applicable to systems not supporting auto-discovery of cross-layer mapping.

Server <NUM> may be located, for example, typically at one location to monitor data traffic in the network resources of multilayered communication network <NUM> by a network operator via communication module and interface <NUM>. Server <NUM> may be implemented within one multilayered communication network <NUM> operated by the network operator. Server <NUM> may monitor the data traffic throughout the network resources in the communication network. Framework <NUM> may be used to control and to monitor all aspects of the data traffic for the network operator in this exemplary embodiment.

<FIG> schematically illustrates communication network <NUM> with multiple network resource failures, in accordance with some embodiments of the present invention. When a failure in one or more network resources <NUM> occurs, an operator monitoring the operation of multilayered communication network <NUM> may receive a failure indication, such as a failure alarm, regarding the one or more failed network resources on display <NUM>, for example. A failure of a network resource is not limited to a catastrophic failure of the network resource in the context of the disclosure herein, but may include a network resource exhibiting a performance degradation such as higher bit error rate, higher noise, and/or higher optical loss, for example.

Furthermore, when a failure in one or more network resources, such as links, occurs in a lower network layer, such as WDM layer <NUM>, for example, the failed links affect communication layers above the communication layer with the one or more failed resources, such as in IP layer <NUM> and in OTN layer <NUM>. As a result, an operator may receive a flood of network resource failure indications related to network resources throughout multilayered communication network <NUM> making it hard for the operator to identify which of failed network resources <NUM> may cause the largest impact on the data traffic and which of failed network resources <NUM> needs to be fixed first.

In some embodiments of the present invention, system <NUM> may identify a set or a minimum set of failed network resources from the one or more failed network resources, which cause a largest impact on the data traffic in the communication network, relative to the impact on the data traffic from the other failed network resources, so as to explain the failures of the one or more failed network resources outside of the set. State differently, system <NUM> may be configured to identify root causes of all the failures in communication network <NUM>.

The failed network resources in the set may also be referred to herein as root cause failures. Fixing the root cause failures first may typically be the fastest way of minimizing the largest impact in the data traffic. For example, a specific failed network resource may cause a bottleneck in data traffic throughout multilayered communication network <NUM> even though other failed resources may be connected to the specific failed network resource, e.g., the root cause failure causing the data traffic bottleneck or network congestion. Manually or automatically rerouting the data traffic around the specific failed network resource may alleviate the network congestion.

Stated differently, identifying the root cause failures may be a fast way for the operator to pinpoint the failed network resources which had the biggest impact in the performance degradation in the communication network. As a result, the operator may use fault isolation techniques such as root cause analysis (RCA), for example, to identify specific network resource failures that caused the flood of alarms. Fault isolation algorithms may be used to find a minimum set of network resources R, the failure of which explains all the network resource failures. At the same time, set R does not imply failures of network resources which are not failed.

<FIG> schematically illustrates failed network resources identified as root cause failures <NUM>, in accordance with some embodiments of the present invention. System <NUM> may apply root cause analysis to multilayered communication network <NUM>, in order to find a minimum set R of failed resources <NUM> (denoted 145A and 145B in <FIG>). Minimum set R may be used to explain all of the failures in the one or more network resources <NUM> resulting in a degradation of the performance metrics (e.g., latency, network congestion, etc.) of data traffic in multilayered communication network <NUM>. Failure of network resource 145A is on top IP layer <NUM> and is a root cause failure since it does not explain the failure of any other failed network resources except for itself. However, the failure of network resource 145B in lower WDM layer <NUM> explains the failure of network resources (e.g., link 140B) on IP layer <NUM> and network resources (e.g., link 140B) on OTN layer <NUM>.

The one or more network resources <NUM> may be distributed over a plurality of network layers in multilayered communication network <NUM>, such as IP layer <NUM>, OTN layer <NUM>, and WDM layer <NUM> as shown throughout the various figures such as <FIG>, for example. Most generally, index N may be used herein to refer to the Nth top network layer and index K may be incremented from K=<NUM>,<NUM>,<NUM>,. , such that network layer N-K may represent any lower layer under top network layer N in multilayered communication network <NUM>, where N and K are integers.

Furthermore, some network layer naming conventions may refer to IP layer <NUM> as layer <NUM>, an Ethernet layer (not shown) as layer <NUM>, OTN layer <NUM> as layer <NUM>, and WDM layer <NUM> as layer <NUM>, for example. Note that sometimes a link connecting a network resource in network layer N to a network resource N-<NUM> without an intermediate network layer N-<NUM> may be implemented, so there may not be consecutive network layer registration at all physical locations of communication network <NUM>.

In some embodiments of the present invention, the fault isolation algorithms described herein may account for scenarios where system <NUM> may not have access to all of the network layers so as to identify and isolate the network resource failures. For example, system <NUM> may have access to IP layer events and not to alarms generated by faults in the optical layers. Furthermore, the algorithms used in fault isolation module <NUM> as described herein may account for situations where not all root causes for the network resource failures may be determined using root cause analysis methods. For example, network resources such as passive elements (e.g., fibers, data cables, etc) on multiple network layers that traverse a fiber duct, for example, where fiber duct may be damaged, thus damaging the passive elements. Root cause analysis, for example, may not be able to localize these failures based on the known connectivity of the failed network resources (e.g., from mapping database <NUM>, for example).

In some embodiments of the present invention, system <NUM> may use an additional algorithm by grouping the failed network resources into passive shared risk resource (PSRG) groups based on common risk attributes. PSRG identification module <NUM> may search for failure risk relationships, or attributes, among the failed network resources such as a common physical location with fibers and/or cables running through the same fiber cabling duct.

In some embodiments of the present invention, PSRG identification module <NUM> may identify and/or group one or more failed network resources possessing common risk attributes into passive shared risk resource groups (PSRG). PSRG group identification module <NUM> may then compute and/or assign a likelihood of a PSRG failure for each of the one or more PSRGs in the communication network.

The fault isolation algorithms with incomplete alarms and the PSRG identification algorithms are now addressed hereinbelow. The term shared risk resource group may generally refer to a shared risk link group (SRLG), a shared risk node group (SRNG), and a shared risk equipment group (SREG) depending on the type of network resource. An SRG failure may result in multiple circuits failing in the communication network.

A passive SRG (PSRG) in the context of this disclosure may typically refer to any passive component associated with other network resources, such that a PSRG failure may cause the other associated resources to fail. For example, a fiber duct is a PSRG, which may include multiple fibers. When this duct is damaged, the fibers in the damaged duct may fail resulting in a degradation in data traffic and/or network performance (e.g., degradation in data rates and/or increased latencies, for example) due to the failed passive components.

In some embodiments of the present invention, a fault isolation algorithm (e.g., in fault isolation module <NUM>) may include analyzing all newly failed network resources. The already-failed network resources (e.g., older network resource failures) may not be taken into account by the algorithm. Fault isolation module <NUM> may arrange the newly-failed network resources by network layer. Fault isolation module <NUM> may examine network resources in the top or highest network layer N, (e.g., IP layer <NUM> in <FIG> where N=<NUM>).

Fault isolation module <NUM> may search for a set of network resources S in top network layer N that depend on a failed network resource X at layer N-K (e.g., a progressively lower layer). The terms progressively lower layers, or progressively lower network layers, may refer to herein as fault isolation module <NUM> analyzing the failures in the network layers moving from the top layer N to a lowest layer in communication network <NUM>. A network layer in the progressively lower network layers is between the highest network layer (e.g., top network layer N) and the lowest network layer (e.g., typically the optical trunk layer). The term progressively lower network layers includes the lowest network layer and does not include the highest or top network layer.

<FIG> schematically illustrates failed network resources with missing failure indications, in accordance with some embodiments of the present invention.

<FIG> schematically illustrates an exemplary embodiment where the analysis of failures in a lower network layer are used to account for failures without alarms in an upper network layer, in accordance with some embodiments of the present invention.

In the exemplary embodiment shown in <FIG>, there are alarmed links on each of the three layers IP layer <NUM>, OTN layer <NUM> and WDM layer <NUM> as shown in <FIG>. Fault isolation module <NUM> may assess that link 145A on WDM layer <NUM> is a root cause failure of links denote 140A on OTN layer <NUM> and on IP layer <NUM>. Similarly, fault isolation module <NUM> may attempt to determine the root cause of the failure alarm indication associated with failed link 140B on IP layer <NUM>. However, there are no alarmed links on OTN layer <NUM> as shown in <FIG>.

In some embodiments of the present invention, when analyzing the failures in progressively lower network layers, fault isolation module <NUM> may be configured to skip the analysis of failures in a specific network layer when no failure indication is received by the specific network layer as shown by arrows <NUM> in <FIG>. In this exemplary case, no failure indication is triggered in system <NUM> for failed network resource <NUM> (e.g., link <NUM>) on OTN layer <NUM>. However, in analyzing the failures in the WDM layer <NUM>, fault isolation module <NUM> may identify and/or deduce that failed link 145B on WDM layer is the root cause failure of link <NUM> with no alarm on OTN layer <NUM> and alarmed link 140B on IP layer <NUM> via the mapping of the network resource connectivity, for example. Fault isolation module <NUM> may assess that link 145B in the lowest layer (e.g., WDM layer <NUM>) is the root cause of the failure that accounts for the failures in link <NUM> and link 140B in the layers above WDM layer <NUM>.

Fault isolation module <NUM> may start analyzing failures in network layer N-<NUM>. If there are no alarms in network layer N-<NUM>, fault isolation module <NUM> may skip over network layer N-<NUM> and may proceed to analyze failures in networks layers N-<NUM>, N-<NUM>, and so forth until fault isolation module <NUM> finds a failed resource X in a network layer N-K that explains all of the failures in set of network resources S as schematically illustrated in <FIG>. If all of resources in set S failed, then failed resource X is the likely root cause. Root cause failure 145B (e.g., X) explains the failures of link <NUM> with no alarm and link 140B by skipping OTN layer <NUM> with no alarms.

In some embodiments of the present invention, fault isolation module <NUM> may then mark X as the root cause failure of resources in set S and identify that the failures of network resources in S are "explained" by the root cause failure of network resource X.

Fault isolation module <NUM> may identify a minimum set of resources R which explains a set of network resource failures F in communication system <NUM>. Fault isolation module <NUM> may add failed network resources <NUM> to set R in analyzing the failures in the progressively lower layers (N-K), the analysis repeated until reaching the lowest network layer (e.g., WDM layer <NUM> in <FIG>).

<FIG> illustrates failed network resources <NUM> which generated a failure alarm, whereas link <NUM>, for example, failed but did not generate an alarm in this exemplary embodiment. Links 145A and 145B in set R are the root cause failures of network resources <NUM> and explain the failures of network resources <NUM>.

<FIG> schematically illustrates failed network links <NUM> forming a passive shared risk link group (SRLG) <NUM>, in accordance with some embodiments of the present invention. When fault isolation module <NUM> in analyzing the failures in the progressively lower layers N-K reaches the lowest layer, such as WDM layer <NUM>, and multiple root cause failures in failed network resources <NUM> occur at substantially the same time, there may be a common risk attribute between the multiple root cause failures. The common risk attribute may also be referred to herein as a common failure risk attribute, a common hidden risk, or a common failure risk relationship. In this case, PSRG identification module <NUM> may defined a passive shared risk link group, or passive SRLG. More generally, this may be referred to a passive shared risk group (PSRG). The passive SRLG may be added to the fault isolation model.

In some embodiments of the present invention, if upon reaching the lowest network layer in analyzing the failures, fault isolation module <NUM> determines that failed resources with multiple root cause failures have common risk attributes, PSRG identification module <NUM> may group the failed network resources with multiple root cause failures into one or more passive shared risk resource groups (PSRG), each PSRG with a respective common risk attribute (e.g., failure time, failure location). In some embodiments, PSRG identification module <NUM> may assess a likelihood L of a common failure risk for each of the one or more PSRG based on the respective common risk attribute. In some embodiments, L may be between <NUM> and <NUM>.

In some embodiments of the present invention, if two failures of two respective network resources occur at the same time, PSRG identification module <NUM> may assign L some fixed value L<NUM>. However, if the two failures do not occur at exactly the same time, L may be assigned a lower likelihood value of L<NUM> where L<NUM><L<NUM>. Stated differently, there is a higher common failure risk in the two network resources failing substantially at the same time, relative to the case of two failures not occurring at the same time. For example, L may be defined relative to a predefined time interval such as <NUM>% if the failures happen less than one minute apart, and <NUM>% if the failures occur two minutes apart. These are numerical examples just for conceptual clarity, and not by way of limitations of the embodiments of the present invention described herein.

In some embodiments of the present invention, if the failures are in fibers that are geographically close to one another, then L may be set to a higher value. If the fibers traverse a shared route such as in a portion of a fiber cable, the longer the shared route, the higher the likelihood L of common failure risk.

In some embodiments of the present invention, if two failures of two respective network resources occur again, where PSRG identification module <NUM> may assess a failure history of the network resources in communication network <NUM>, which may be stored for example in memory <NUM>, the likelihood of a common failure risk is much higher. L may be increased, for example, by a factor of <NUM>.

In the exemplary embodiment shown in <FIG>, failure alarms on links 140A and 140B on multiple layers (e.g., IP layer <NUM>, OTN layer <NUM>, and WDM layer <NUM>) may alert an operator of system <NUM>, for example, on display <NUM>. To the operator, these network resource may appear to have no common risk attributes. However, as shown by arrows <NUM>, PSRG identification module <NUM> may determine that the root cause failure of links 140A and 140B on such as two fibers on WDM layer <NUM> may be a result of the two fibers traversing the same underground fiber cable that may be damaged. PSRG identification module <NUM> may group and/or define the two fibers (e.g., links 140A and 140B on WDM layer <NUM>) in the common underground fiber cable into passive SRLG <NUM>.

<FIG> schematically illustrates a PSRG with network resources in the same geographical vicinity, in accordance with some embodiments of the present invention. A span between two network elements, which share a common site or the same geographic proximity may likely be an SRLG. As shown in <FIG>, optical switches <NUM> may route optical signals in two optical fibers <NUM> and <NUM> respectively via two optical amplifiers <NUM> in a SiteA <NUM>. From the outputs of optical amplifiers <NUM> in SiteA <NUM>, the optical signals are routed in a fiber duct <NUM> spanning from SiteA <NUM> to a SiteB <NUM>. SiteA <NUM> and SiteB <NUM> may be separated by large distances such as <NUM> (e.g., long haul links), for example.

The optical signals in two optical fibers <NUM> and <NUM> upon entering SiteB <NUM> may be amplified by optical amplifiers <NUM>. The amplifier optical signals in two optical fibers <NUM> and <NUM> leaving SiteB <NUM> may then be routed to their next destinations in the communication network by optical switches <NUM>.

In the exemplary embodiment shown in <FIG>, fiber duct <NUM> may be a passive SRLG <NUM> with two optical fibers <NUM> and <NUM> as the two network resources grouped into passive SRLG <NUM> with the common risk attribute as being collocated in fiber duct <NUM> over the distance spanning between SiteA <NUM> to SiteB <NUM>. In this case, passive SRLG <NUM> may be defined even if no failure occurs in the two network resources in this exemplary embodiment.

In some embodiments and in a similar vein, the two optical fiber links shown in <FIG> may be replaced by two free space optical links wherein cloud cover, for example, and the shared failure risk (e.g., SRLG <NUM>) may include a cloud blocking the two free space optical links.

In some embodiments of the present invention, PSRG identification module <NUM> may be configured to search network resources in the communication network, whether they failed or not, for common risk attributes. PSRG identification module <NUM> may group network resources identified with the common risk attributes into one or more PSRG, each PSRG defined by a likelihood of a failure risk based on the common risk attributes associated with each PRSG.

In some embodiments of the present invention, the common risk attribute may be the failures of network resources occurring at substantially the same time and/or located in the same geographical vicinity. A passive SRLG, for example, may include a duct as in <FIG> with many optical fibers connecting different nodes over different layers in the communication network. The passive SRLG may include cables and/or optical fibers passing through a tunnel (such as, the Holland or Lincoln tunnels between New Jersey and New York, for example). The passive SRLG may include underground cabling duct, for example, with optical fibers and/or communication cables on the IP layer placed therein. If the PSRG is damaged, such as by a fire in the tunnel, or by a plow tractor plowing across and damaging the underground cabling duct, all of the optical and IP links in the passive SRLG may fail at substantially the same time. A much higher likelihood of common failure may be assigned to the underground cabling duct or tunnel with the network resources within.

In some embodiments of the present invention, any suitable PSRG and the associated shared risk attributes between the network resources even without failures may be defined based on a mapping of the communication network (e.g., from mapping database <NUM>). The mapping may be based on a predefined knowledge of how the communication cables, lines, or optical fibers are routed between the network elements in the communication network. Thus, defining passive shared risk groups may be useful in implementing route planning diversity in the communication network independent of root cause analysis.

<FIG> schematically illustrates a communication network <NUM> with an IP layer <NUM> and an optical layer <NUM>, in accordance with some embodiments of the present invention. Communication network <NUM> may include IP links <NUM> on IP layer <NUM> connecting IP nodes denoted IP node A, IP node B, IP node C, and IP node D. Communication network <NUM> may include optical links on optical layer <NUM> with optical nodes <NUM> such as an optical connection <NUM> may connect IP node A to IP node C. Similarly, an optical connection <NUM> may connect IP node A to IP node D, and an optical connection <NUM> may connect IP node D to IP node C.

<FIG> schematically illustrates a communication network <NUM> with two IP layer failure alarms on IP alarmed links <NUM> and <NUM>, in accordance with some embodiments of the present invention.

<FIG> schematically illustrates a communication network <NUM> with a suspected optical layer failure <NUM>, in accordance with some embodiments of the present invention.

In the exemplary embodiments shown in <FIG>, there are no failure alarms from network resources on optical layer <NUM>. Two failure alarms on alarmed IP link <NUM> and alarmed IP link <NUM> may be due to a failure in optical layer <NUM> (e.g., cut fibers, failed optical router, etc.) and/or a failure in IP layer <NUM> (e.g., a failed IP router port). A failure in optical connection <NUM> does not explain any of the two failure alarms on alarmed IP link <NUM> and alarmed IP link <NUM>.

In some embodiments of the present invention, fault isolation module <NUM> may be configured to deduce suspected multiple optical failures <NUM> in optical link <NUM> and in optical link <NUM> so as to explain the failures result in alarmed IP link <NUM> and alarmed IP link <NUM> in the exemplary embodiment shown in <FIG>. This approach may be useful deducing a reduced set of suspected failed resources to be further examined making it easier to isolate the failures automatically or manually, such as by sending a set of requests to the set of suspected failed resources to report their failure and/or their operational status, and/or any other attribute indicative of a failure or initiated shutdown.

<FIG> is a flowchart depicting a method <NUM> for assessing failures in network resources in a multilayered communication network, in accordance with some embodiments of the present invention. Method <NUM> may be executed by processor <NUM> of system <NUM> for monitoring and identifying network resource failures in communication network <NUM>.

Method <NUM> may include receiving <NUM> indications of failures in one or more network resources from a plurality of network resources in a communication network including a plurality of network layers.

Method <NUM> may include assessing <NUM> the failures in the one or more failed network resources in each of progressively lower network layers from a highest network layer to a lowest network layer in said plurality of network layers.

Method <NUM> may include identifying <NUM> a set of failed network resources from the one or more failed network resources in the progressively lower network layers causing failures in network layers above the progressively lower network layers.

In some embodiments of the present invention, method <NUM> may include assessing <NUM> the failures in the one or more failed network resources in each of progressively higher network layers from the lowest network layer to the highest network layer in said plurality of network layers. Accordingly, method <NUM> may include identifying <NUM> a set of failed network resources from the one or more failed network resources in the progressively higher network layers causing failures in network layers below the progressively higher network layers.

In some embodiments, method <NUM> may include assessing <NUM> the failures in the one or more failed network resources in each of progressively lower network layers from a highest network layer to a lowest network layer, or in said plurality of network layers in each of progressively higher network layers from the lowest network layer to the highest network layer in said plurality of network layers. Accordingly, method <NUM> may include identifying <NUM> a set of failed network resources from the one or more failed network resources in the progressively lower network layers causing failures in network layers above the progressively lower network layer, or in the progressively higher network layers causing failures in network layers below the progressively higher network layers.

In some embodiments of the present invention, method <NUM> may include assessing <NUM> the failures in the one or more failed network resources in each of progressively lower network layers from a network layer under a highest network layer to a lowest network layer, or in said plurality of network layers in each of progressively higher network layers from a network layer above the lowest network layer to the highest network layer in said plurality of network layers, or any combination thereof. Accordingly, method <NUM> may include identifying <NUM> a set of failed network resources from the one or more failed network resources in the progressively lower network layers causing failures in network layers above the progressively lower network layer, or in the progressively higher network layers causing failures in network layers below the progressively higher network layers.

In some embodiments of the present invention, network resources in any network layer in the communication network may be polled. Thus, when a network resource in a network layer L fails, processor <NUM> may selectively poll network resources in layers below network layer L and network resource above network layer L so as to identify if these polled network resources failed as well. An exemplary embodiment illustrating this, would be services running in a service layer over the IP layer that may fail if an IP link fails in the IP layer, for example. System <NUM> may not know about service layer failures since system <NUM> may not receive real time updates from services running in the service layer. For visual clarity, consider <FIG> with another (service) layer on top of IP layer <NUM> with arrows going upward from IP layer <NUM> and not only downward to OTN layer <NUM>.

In some embodiments of the present invention, a database, such as mapping data base <NUM>, or a separate database, may store the operational status of the plurality of network resources. Processor <NUM> may dynamically update the database as to whether any of the plurality of network resources failed (e.g., when new up or down operational status reports from the polled network resources become available).

In some embodiments of the present invention, identifying <NUM> the set may include identifying root causes of the failures in the communication network.

In some embodiments of the present invention, receiving <NUM> the indications of failures may include receiving the failure indications in response to polling at least one of said plurality of network resources.

In some embodiments of the present invention, identifying <NUM> the set of failed network resources may include identifying a minimal set of failed network resources causing all the failures in the communication network.

In some embodiments of the present invention, the highest network layer and the lowest network layer may include an internet protocol (IP) layer and a wavelength division multiplexing (WDM) layer respectively.

In some embodiments of the present invention, method <NUM> may include arranging the failures according to each network layer in said plurality of network layers.

In some embodiments of the present invention, assessing the failures may include skipping network layers from which no failure indications are received.

In some embodiments of the present invention, method <NUM> may include, if upon receiving no failure indications from said plurality of network layers in the communication network, deducing a suspected set of network resources from said plurality of network resources in said plurality of network layers that cause the failures in the communication network.

In some embodiments of the present invention, method <NUM> may include sending requests to the network resources in the suspected set to report their failure.

In some embodiments of the present invention, method <NUM> may include updating a database with the reported failures of the network resources in the suspected set.

In some embodiments of the present invention, method <NUM> may include automatically rerouting data traffic around the network resources in the suspected set.

In some embodiments of the present invention, method <NUM> may include if upon assessing that the failed network resources in the identified set do not account for all of the failures in the one or more failed network resources from the highest network layer to the lowest network layer:.

In some embodiments of the present invention, method <NUM> may include outputting the set of failed network resources from the one or more failed network or the likelihood of the PSRG failure for each of the one or more PSRGs.

<FIG> is a flowchart depicting a method <NUM> for analyzing failures in network resources in a multilayered communication network using passive shared risk resource groups, in accordance with some embodiments of the present invention. Method <NUM> may be executed by processor <NUM> of system <NUM>.

Method <NUM> may include identifying <NUM> network resources in a plurality of network resources having common risk attributes.

Method <NUM> may include grouping <NUM> the network resources into one or more passive shared risk resource groups (PSRG) based on the common risk attributes.

Method <NUM> may include assessing <NUM> a likelihood of a PSRG failure for each of the one or more PSRGs.

In some embodiments of the present invention, identifying <NUM> the network resources with the common risk attributes may include limiting a search for the common risk attributes in network resources geographically close to one another.

In some embodiments of the present invention, method <NUM> may include outputting the likelihood of the PSRG failure for each of the one or more PSRG.

In some embodiments of the present invention, method <NUM> may include defining the one or more PSRG based on a predefined mapping of said plurality of network resources in the communication network.

In some embodiments of the present invention, identifying <NUM> the network resources in said plurality of network resources having the common risk attributes may include identifying one or more failed network resources from said plurality of network resources having the common risk attributes.

In some embodiments of the present invention, assessing <NUM> the likelihood of the PSRG failure may include assigning a higher likelihood when failures of the one or more failed network resources in each of the one or more PSRG meet a predefined criterion.

In some embodiments of the present invention, the predefined criterion is selected from the group consisting of failures of the one or more failed network resources that are geographically close to one another, failures of at least two failed network resources that occur substantially at the same time, and failures of at least two failed network resources that failed together in the past.

In some embodiments of the present invention, method <NUM> may include automatically restoring the one or more failed network resources associated with each of the one or more PSRG in accordance with the likelihood of the PSRG failure.

<FIG> schematically illustrates a graphic user interface (GUI) <NUM> for outputting the analysis of network resource failures, in accordance with some embodiments of the present invention. The output of the failure analyses from fault isolation module <NUM> may be outputted on display <NUM>. GUI <NUM> may include a plurality of indicators <NUM> such as a time stamp <NUM> (e.g., time/date of failure), a severity type <NUM>, a failure type <NUM>, an alarm description <NUM>, a failure impact <NUM>, remedial actions <NUM>, and a fix indicator <NUM> for indicating to the operator to fix the designated failed resource in GUI <NUM>.

Failure type <NUM> may indicate which type of network resource failed (e.g., link, node, linecard). Alarm description <NUM> may indicate involving which network resources failed, the location of the failure, and what network layer that the failures occurred. Failure impact <NUM> may indicate the name of the customer impacted and/or the service level agreements (SLA), which may result in large penalties for the network operator due to a service outage for the customer, for example. Remedial actions <NUM> may indicate to the operator of system <NUM> as to what measures to take to remedy the failure, such as to check particular failed network resources, to restart a network resource, or to turn in and off a particular network resource, for example. Fix indicator <NUM> may also indicate which failed network resources to fix first.

In some embodiments, GUI <NUM> may output severity level <NUM>, which may be assigned to each of the one or more failure indications or alarms. The severity may assist the operator in for identifying which of the failed network resources are the biggest contributors to the degradation in the data traffic in communication network <NUM>. The severity of the failure indications may include various levels of severity <NUM>, such as a severe failure <NUM>, a major failure <NUM>, a minor failure <NUM>, or a warning. Severity level <NUM> may also indicate if the alarm is a dependent alarm <NUM>.

In some embodiments of the present invention, GUI <NUM> may include an output with the defined PSRGs with the associated likelihoods of the common failure risk for the defined PSRGs.

It should be understood with respect to any flowchart referenced herein that the division of the illustrated method into discrete operations represented by blocks of the flowchart has been selected for convenience and clarity only. Alternative division of the illustrated method into discrete operations is possible with equivalent results. Such alternative division of the illustrated method into discrete operations should be understood as representing other embodiments of the illustrated method.

Claim 1:
A method for analyzing failures in network resources in a multilayered communication network using passive shared risk resource groups, the method comprising:
identifying (<NUM>) network resources in a plurality of network resources having common risk attributes;
grouping (<NUM>) the network resources into one or more passive shared risk resource groups, PSRG, based on the common risk attributes;
assessing (<NUM>) a first value indicating a first likelihood of a PSRG failure for a first PSRG of the one or more PSRGs;
assessing (<NUM>) a second value indicating a second likelihood of a PSRG failure for a second PSRG of the one or more PSRGs;
in response to failure of one or more network resources associated with the first PSRG and one or more network resources associated the second PSRG, identifying the one or more failed network resources associated with the first PSRG as the root cause for failure of the one or more network resources associated with the first PSRG and the one or more network resources associated the second PSRG based on determining that the first value is higher than the second value; and
restoring the one or more failed network resources associated with the first PSRG.