CN115208793A

CN115208793A - Method and apparatus for fault detection using bidirectional forwarding detection

Info

Publication number: CN115208793A
Application number: CN202110330842.3A
Authority: CN
Inventors: 陈迅; 朱永庆; 阮科; 黄晓莹; 陈华南; 龚霞
Original assignee: China Telecom Corp Ltd
Current assignee: China Telecom Corp Ltd
Priority date: 2021-03-26
Filing date: 2021-03-26
Publication date: 2022-10-18
Also published as: WO2022199063A1

Abstract

The present disclosure relates to a method and apparatus for fault detection using bidirectional forwarding detection. A method of fault detection with Bidirectional Forwarding Detection (BFD) is provided, comprising: a BFD module arranged in a first stage of the network detects whether traffic is interrupted at predetermined time intervals; in the event of a detected traffic interruption, sending a status detection request to a BFD module arranged in a second stage of the network; receiving a status detection reply from a BFD module in the second stage, the status detection reply including whether an interrupt is detected by the BFD module in the second stage; and under the condition that the BFD module in the second stage detects the interruption, the BFD module in the first stage initiates the state detection of the first stage so as to judge whether the service is recovered.

Description

Method and apparatus for fault detection using bidirectional forwarding detection

Technical Field

The present disclosure relates to the field of network technology and security (IP), and more particularly, to a method and apparatus for fault detection using bidirectional forwarding detection.

Background

Bidirectional Forwarding Detection (BFD) is a network protocol used to detect failures between two Forwarding points. BFD is a bidirectional forwarding detection mechanism that can provide millisecond detection to achieve fast detection of links. BFD can realize the rapid convergence of the routing by linking with the upper layer routing protocol so as to ensure the continuity of the service.

However, the BFDs of the current stages operate independently and do not communicate messages with each other. This brings a certain risk of switching collision, and because the BFD fault detection of each layer is independent, it is only possible to increase the fault detection interval by the upper layer to prevent path oscillation caused by multiple fault switching.

In the prior art, BFD is utilized to carry out fault detection in a network, the BFD in each layer of the network independently works, and the time interval of the outer layer needs to be set to be larger than that of the inner layer, so that the condition that collision is caused when two layers are switched simultaneously is reduced. In the prior art, each layer of the network may be configured as follows:

1. a routing layer: BFD for IGP/BGP for fault detection, with an interval set to 10ms (by way of example and not limitation). Fast protection in case of timeouts can be achieved by topology independent TI-LFA (loop free backup), IP FRR (fast reroute), etc.

2. A tunnel layer: path BFD is used for fault detection, setting the interval to 50ms (by way of example and not limitation). E2E (end-to-end) tunnel protection is realized through the main backup Candidate Path, and switching to the backup Path can be performed under the condition of time-out.

3. And (4) a service layer: failure detection is performed using BFD for Locator, setting the interval to 100ms (by way of example and not limitation). And the fast service switching can be realized when the EVPN node fails through the FRR protection of the EVPN.

If the handover between the routing layer and the tunnel layer is not effective, the service layer will wait a longer time interval to trigger the handover.

Although the above-described methods can reduce the possibility of collision, they cannot be completely avoided. For example, for the time interval set above, if a failure occurs in 95ms, BFDs of the three layers of routing, tunneling, and traffic will detect the failure at the same time and trigger a switch, and all three layers will switch to the backup path. After the switching, the service layer detects the availability of the main tunnel again and switches back to the main tunnel again. This may increase the risk of packet loss due to handover.

Disclosure of Invention

The following presents a simplified summary of the disclosure in order to provide a basic understanding of some aspects of the disclosure. However, it should be understood that this summary is not an exhaustive overview of the disclosure. It is not intended to identify key or critical elements of the disclosure or to delineate the scope of the disclosure. Its sole purpose is to present some concepts of the disclosure in a simplified form as a prelude to the more detailed description that is presented later.

According to a first aspect of the present disclosure, there is provided a method of fault detection with Bidirectional Forwarding Detection (BFD), comprising: a BFD module arranged in a first stage of a network detects whether a service is interrupted at a predetermined time interval; in the event of a detected traffic interruption, sending a status detection request to a BFD module arranged in a second stage of the network; receiving a status detection reply from a BFD module in the second stage, the status detection reply including whether an interrupt is detected by the BFD module in the second stage; and under the condition that the BFD module in the second stage detects the interruption, the BFD module in the first stage initiates the state detection of the first stage so as to judge whether the service is recovered.

According to a second aspect of the present disclosure, there is provided a method of fault detection with Bidirectional Forwarding Detection (BFD), comprising: in the event that a BFD module disposed in a first level of the network detects a traffic disruption at a predetermined time interval, a BFD module disposed in a second level of the network receives a status detection request from the BFD module in the first level; in response to receiving the status detection request, the BFD module in the second stage detects whether the second stage is interrupted and sends a receive status detection reply to the BFD module in the first stage, the status detection reply including whether the BFD module in the second stage detects an interruption.

According to a third aspect of the present disclosure, there is provided an apparatus for failure detection with Bidirectional Forwarding Detection (BFD), the apparatus comprising BFD modules arranged in a first stage of a network and BFD modules arranged in a second stage of the network, wherein the BFD modules in the first stage are configured to: detecting whether the service is interrupted at a preset time interval; under the condition that service interruption is detected, sending a state detection request to a BFD module in the second level; receiving a status detection reply from a BFD module in the second stage, the status detection reply including whether an interrupt is detected by the BFD module in the second stage; and initiating the state detection of the first level to judge whether the service is recovered or not under the condition that the BFD module in the second level detects the interruption.

According to a fourth aspect of the present disclosure, there is provided an apparatus for failure detection with Bidirectional Forwarding Detection (BFD), the apparatus comprising BFD modules arranged in a first stage of a network and BFD modules arranged in a second stage of the network, wherein the BFD modules in the second stage are configured to: receiving, by the BFD module in the second stage, a status detection request from the BFD module in the first stage in the event that the BFD module in the first stage detects a service interruption at a predetermined time interval; in response to receiving the status detection request, the BFD module in the second stage detects whether the second stage is interrupted and sends a receive status detection reply to the BFD module in the first stage, the status detection reply including whether the BFD module in the second stage detects an interruption.

According to a fifth aspect of the present disclosure, there is provided a non-transitory computer readable storage medium having a program stored thereon, characterized in that, when the program is executed by a computer, the computer is caused to execute the method according to the first aspect of the present disclosure.

According to a sixth aspect of the present disclosure, there is provided a non-transitory computer readable storage medium having a program stored thereon, wherein the program, when executed by a computer, causes the computer to perform the method according to the second aspect of the present disclosure.

According to a seventh aspect of the present disclosure, there is provided an apparatus for fault detection, comprising a memory and a processor, the memory being communicatively coupled with the processor, the memory having stored therein a program, which when executed by the processor, causes the processor to perform the method according to the first aspect of the present disclosure.

According to an eighth aspect of the present disclosure, there is provided an apparatus for fault detection, comprising a memory and a processor, the memory communicatively coupled with the processor, the memory having stored therein a program which, when executed by the processor, causes the processor to perform the method according to the second aspect of the present disclosure.

According to a ninth aspect of the present disclosure, there is provided a computer program product comprising a computer program which, when executed by a processor, implements the method according to the first aspect of the present disclosure.

According to a tenth aspect of the present disclosure, there is provided a computer program product comprising a computer program which, when executed by a processor, implements the method according to the second aspect of the present disclosure.

By utilizing the method and the device provided by the disclosure, the situation of the fault switching conflict can be effectively reduced, and meanwhile, the upper layer can keep selecting smaller fault detection intervals, thereby reducing the fault switching time and improving the user experience.

Other features of the present disclosure and advantages thereof will become more apparent from the following detailed description of exemplary embodiments thereof, which proceeds with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description, serve to explain the principles of the disclosure.

The present disclosure may be more clearly understood from the following detailed description with reference to the accompanying drawings, in which:

fig. 1 shows a schematic diagram of a network according to an embodiment of the present disclosure;

FIG. 2 shows a schematic diagram of a scenario of fault detection according to an embodiment of the present disclosure;

FIG. 3 shows a schematic diagram of a scenario of fault detection according to an embodiment of the present disclosure;

FIG. 4 shows a schematic diagram of a scenario of fault detection according to an embodiment of the present disclosure;

FIG. 5 shows a flow diagram of a method of fault detection according to an embodiment of the present disclosure;

FIG. 6 illustrates an exemplary configuration of a computing device in which embodiments in accordance with the present disclosure may be implemented.

Detailed Description

The following detailed description is made with reference to the accompanying drawings and is provided to assist in a comprehensive understanding of various exemplary embodiments of the disclosure. The following description includes various details to aid understanding, but these details are to be regarded as examples only and are not intended to limit the disclosure, which is defined by the appended claims and their equivalents. The words and phrases used in the following description are intended only to provide a clear and consistent understanding of the disclosure. In addition, descriptions of well-known structures, functions, and configurations may be omitted for clarity and conciseness. Those of ordinary skill in the art will recognize that various changes and modifications of the examples described herein can be made without departing from the spirit and scope of the disclosure.

Fig. 1 shows a schematic diagram of a network according to an embodiment of the present disclosure. As shown in fig. 1, the network may include a routing layer, a tunneling layer, and a traffic layer. The routing layer can adopt BFD for IGP/BGP to carry out fault detection, the tunnel layer can adopt path BFD to carry out fault detection, and the service layer can adopt BFD for Locator to carry out fault detection. The BFDs of the various layers may cooperate to perform fault detection. When a failure occurs, a switchover from a primary PW (Pseudo Wire) to a standby PW may be performed.

In the fault detection method according to the present disclosure, each layer of BFD may work cooperatively, and the upper and lower BFDs perform association and message interaction, and may use the same time interval. The upper level and the lower level may be associated in a one-to-many manner.

At the traffic layer, BFD for Locator may be employed, setting the interval for failure detection to 50ms (by way of example and not limitation), while the tunnel layer BFD is set to the subordinate BFD, setting the handshake time to 5ms (by way of example and not limitation).

At the tunnel layer, BFD for tunnel may be employed, BFC for Locator of the traffic layer is set to the upper BFD, and handshake time is set to 5ms (by way of example and not limitation). Meanwhile, the routing layer BFD can be set to be the lower-level BFD, and the handshake time is set to be 5ms.

At the routing layer, BFD for IGP/BGP may be employed, with the tunneling layer BFD for tunnel set to the upper level BFD, and the handshake time set to 5ms (by way of example and not limitation).

Every 5ms (by way of example and not limitation), two adjacent layers may confirm each other whether they are in an active state through BFD handshake messages. And initiating state detection by the upper BFD, initiating a detection requirement to the lower BFD after detecting the service interruption, initiating the state detection of the current layer by the lower BFD, and simultaneously replying the upper BFD.

Fig. 2 shows a schematic diagram of a scenario of failure detection in which a switchover is triggered by a lower level BFD, according to an embodiment of the present disclosure.

As shown in fig. 2, the upper BFD and the lower BFD may perform a status confirmation request and a status confirmation reply at regular time intervals (e.g., 5 ms) to handshake confirmation whether the upper BFD and the lower BFD are in an active state.

When the upper level BFD discovers a failure, a request may be initiated for link state detection.

The lower BFD may receive the request and perform status detection. In an embodiment consistent with the present disclosure, in response to receiving a status detection request, a lower BFD may detect whether the lower is down and reply to the upper BFD to indicate that the lower BFD is performing link status detection. In an embodiment consistent with the present disclosure, in the case where a lower BFD detects a present segment interrupt, the lower BFD may reply to the upper BFD to indicate that the lower BFD has detected the present segment interrupt and is switching to a standby path. In an embodiment according to the present disclosure, after the lower BFD completes the handover, the lower BFD may reply to the upper BFD to indicate that the handover of the lower BFD is complete, in a normal state.

The upper BFD may initiate state detection to determine whether the failure is recovered, i.e., whether the service is recovered.

Fig. 3 shows a schematic diagram of a fault detection scenario in which a lower level BFD does not detect a fault, according to an embodiment of the present disclosure.

As shown in fig. 3, the upper BFD and the lower BFD may perform a status confirmation request and a status confirmation reply at regular time intervals (e.g., 5 ms) to handshake confirmation whether the upper BFD and the lower BFD are in an active state.

The lower BFD may receive the request and perform status detection. In an embodiment consistent with the present disclosure, in response to receiving a status detection request, a lower BFD may detect whether the lower is down and reply to the upper BFD to indicate that the lower BFD is performing link status detection. In an embodiment consistent with the present disclosure, in the event that a lower BFD does not detect the present segment interrupt, the lower BFD may reply to the upper BFD to indicate that the lower BFD does not detect the present segment interrupt.

In response to the lower level BFD not detecting the interruption, the upper level BFD may initiate a switch of the local layer to switch to the backup path. After initiating the switch to the first-level backup path, the upper-level BFD may initiate state detection of the current level to determine whether the service is restored, i.e., whether the failure is restored.

Fig. 4 shows a schematic diagram of a fault detection scenario in which a lower level BFD detects a fault but a lower level switchover cannot solve the upper level fault problem, according to an embodiment of the present disclosure.

As shown in fig. 4, the upper BFD and the lower BFD may perform a status confirmation request and a status confirmation reply at regular time intervals (e.g., 5 ms) to handshake confirmation whether the upper BFD and the lower BFD are in an active state.

The lower BFD may receive the request and perform status detection. In an embodiment consistent with the present disclosure, in response to receiving a status detection request, a lower BFD may detect whether the lower is down and reply to the upper BFD to indicate that the lower BFD is performing link status detection. In an embodiment according to the present disclosure, in the event that a lower BFD detects an interruption of the present segment, the lower BFD may reply to the upper BFD to indicate that the lower BFD has detected an interruption of the present segment and is switching to a backup path. In an embodiment according to the present disclosure, after the lower BFD completes the switching, the lower BFD may reply to the upper BFD to indicate that the switching of the lower BFD is completed, in a normal state.

The upper BFD may initiate state detection to determine whether the failure is recovered, i.e., whether the service is recovered. At this point, the upper level BFD may initiate a switch of the local layer to switch to the backup path. After the switchover, the upper BFD may initiate the status detection again to determine whether the failure is recovered, i.e., whether the traffic is recovered.

Fig. 5 shows a flow diagram of a method of fault detection according to an embodiment of the present disclosure. As shown in fig. 5, at S501, the BFD module disposed in the first stage of the network detects whether traffic is interrupted at predetermined time intervals; at S502, in case a traffic interruption is detected, sending a status detection request to a BFD module arranged in a second stage of the network; at S503, receiving a status detection reply from the BFD module in the second stage, the status detection reply including whether the BFD module in the second stage detected the interrupt; at S504, in the case that the BFD module in the second stage detects an interruption, the BFD module in the first stage initiates state detection of the first stage to determine whether the traffic is resumed.

In an embodiment according to the present disclosure, in the event that a BFD module in the second stage detects an interrupt, a status detection request may be sent to a BFD module disposed in a third stage of the network; and receiving a status detection reply from the BFD module in the third stage, the status detection reply including whether the BFD module in the third stage detected the interrupt. In the event that the BFD module in the third stage does not detect an interrupt, the BFD module in the second stage initiates a switchover to the second stage backup path. And under the condition that the BFD module in the third stage detects the interruption, the BFD module in the third stage may initiate switching to the standby path of the third stage and perform corresponding detection to determine whether the failure is recovered. This process is similar to the discovery of interrupts in the second stage and the switching of the second stage, and will not be described in detail herein.

Fig. 6 illustrates an exemplary configuration of a computing device 600 capable of implementing embodiments in accordance with the present disclosure.

Computing device 600 is an example of a hardware device to which the above-described aspects of the disclosure can be applied. Computing device 600 may be any machine configured to perform processes and/or computations. Computing device 600 may be, but is not limited to, a workstation, a server, a desktop computer, a laptop computer, a tablet computer, a Personal Data Assistant (PDA), a smart phone, an in-vehicle computer, or a combination thereof.

As shown in fig. 6, computing device 600 may include one or more elements that may be connected to or communicate with bus 602 via one or more interfaces. The bus 602 may include, but is not limited to, an Industry Standard Architecture (ISA) bus, a Micro Channel Architecture (MCA) bus, an Enhanced ISA (EISA) bus, a Video Electronics Standards Association (VESA) local bus, a Peripheral Component Interconnect (PCI) bus, and the like. Computing device 600 may include, for example, one or more processors 604. The one or more processors 604 may be any kind of processor and may include, but are not limited to, one or more general purpose processors or special purpose processors (such as special purpose processing chips). The processor may be configured to implement the methods as shown in fig. 2-5, for example.

The computing device 600 may also include or be connected to a non-transitory storage device 614, which non-transitory storage device 614 may be any non-transitory and may implement a storage of data, and may include, but is not limited to, a disk drive, an optical storage device, solid state memory, a floppy disk, a flexible disk, a hard disk, a magnetic tape, or any other magnetic medium, a compact disk, or any other optical medium, cache memory, and/or any other memory chip or module, and/or any other medium from which a computer can read data, instructions, and/or code. The computing device 600 may also include Random Access Memory (RAM) 610 and Read Only Memory (ROM) 612. The ROM 612 may store programs, utilities or processes to be executed in a nonvolatile manner. The RAM 610 may provide volatile data storage and stores instructions related to the operation of the computing device 600.

In summary, according to a first aspect of the present disclosure, there is provided a method of fault detection with Bidirectional Forwarding Detection (BFD), comprising: a BFD module arranged in a first stage of a network detects whether a service is interrupted at a predetermined time interval; in the event of a detected traffic interruption, sending a status detection request to a BFD module arranged in a second stage of the network; receiving a status detection reply from a BFD module in the second stage, the status detection reply including whether an interrupt is detected by the BFD module in the second stage; and under the condition that the BFD module in the second stage detects interruption, the BFD module in the first stage initiates state detection of the first stage to judge whether the service is recovered or not.

In an embodiment according to the present disclosure, the BFD module in the first stage initiates a switchover to the first stage backup path in the event traffic is not restored.

In an embodiment consistent with the present disclosure, the BFD module in the first stage initiates a switchover to a first stage backup path in the event that the BFD module in the second stage does not detect an interrupt.

In an embodiment according to the present disclosure, after initiating a switchover to a first-level backup path, a BFD module in the first level initiates state detection of the first level to determine whether traffic is resumed.

In an embodiment according to the present disclosure, the method further comprises: sending a status detection request to a BFD module disposed in a third level of the network in the event that the BFD module in the second level detects an interrupt; receiving a status detection reply from a BFD module in the third stage, the status detection reply comprising whether the BFD module in the third stage detects an interrupt.

In an embodiment according to the present disclosure, the method further comprises: in the event that the BFD module in the third stage does not detect an interrupt, the BFD module in the second stage initiates a switchover to a second stage backup path.

In an embodiment according to the present disclosure, the BFD module in the first stage is configured to initiate a switchover to the first stage backup path in the event of non-restoration of traffic.

In an embodiment according to the present disclosure, in the event that no interrupt is detected by a BFD module in the second stage, the BFD module in the first stage is configured to initiate a switchover to a first stage backup path.

In an embodiment according to the present disclosure, after initiating a switchover to a first level backup path, a BFD module in the first level is configured to initiate a state detection of the first level to determine whether traffic is restored.

According to a fourth aspect of the present disclosure, there is provided an apparatus for fault detection with Bidirectional Forwarding Detection (BFD), the apparatus comprising BFD modules arranged in a first stage of a network and BFD modules arranged in a second stage of the network, wherein the BFD modules in the second stage are configured to: receiving, by the BFD module in the second stage, a status detection request from the BFD module in the first stage in the event that the BFD module in the first stage detects a service interruption at a predetermined time interval; in response to receiving the status detection request, the BFD module in the second stage detects whether the second stage is interrupted and sends a receive status detection reply to the BFD module in the first stage, the status detection reply including whether the BFD module in the second stage detects an interruption.

In an embodiment according to the present disclosure, the method further comprises BFD modules arranged in a third stage, wherein the BFD modules in the second stage are further configured to: sending a state detection request to a BFD module in a third level when the BFD module in the second level detects an interrupt; receiving a status detection reply from a BFD module in the third stage, the status detection reply including whether the BFD module in the third stage detects an interrupt.

In an embodiment according to the present disclosure, the BFD modules in the second stage are further configured to initiate a switchover to a second stage backup path in the event that no interruption is detected by the BFD modules in the third stage.

According to a fifth aspect of the present disclosure, there is provided a non-transitory computer readable storage medium having a program stored thereon, characterized in that, when the program is executed by a computer, the computer is caused to perform the method according to the first aspect of the present disclosure.

According to a ninth aspect of the present disclosure, there is provided a computer program product comprising a computer program which, when executed by a processor, performs the method according to the first aspect of the present disclosure.

According to the method and the device disclosed by the invention, the cooperation of multi-stage BFD and the message synchronization between BFD can be realized, so that the fault switching conflict is reduced, the time interval of outer layer detection can be reduced, and the user experience is improved.

The subject matter of the present disclosure is provided as examples of apparatus, systems, methods, and programs for performing the features described in the present disclosure. However, other features or variations are contemplated in addition to the features described above. It is contemplated that the implementation of the components and functions of the present disclosure may be accomplished with any emerging technology that may replace the technology of any of the implementations described above.

Additionally, the above description provides examples, and does not limit the scope, applicability, or configuration set forth in the claims. Changes may be made in the function and arrangement of elements discussed without departing from the spirit and scope of the disclosure. Various embodiments may omit, substitute, or add various procedures or components as appropriate. For example, features described with respect to certain embodiments may be combined in other embodiments.

In addition, in the description of the present disclosure, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or order.

Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous.

Claims

1. A method of fault detection with Bidirectional Forwarding Detection (BFD), comprising:

a BFD module arranged in a first stage of a network detects whether a service is interrupted at a predetermined time interval;

in the event of a detected traffic disruption, sending a status detection request to a BFD module arranged in a second stage of the network;

receiving a status detection reply from a BFD module in the second stage, the status detection reply including whether the BFD module in the second stage detects an interrupt;

and under the condition that the BFD module in the second stage detects the interruption, the BFD module in the first stage initiates the state detection of the first stage so as to judge whether the service is recovered.

2. The method of claim 1, wherein a BFD module in the first level initiates a switchover to a first level backup path in the event traffic is not restored.

3. The method of claim 1, wherein the BFD module in the first level initiates a switchover to a first level backup path in the event that the BFD module in the second level does not detect an interrupt.

4. A method according to claim 2 or 3, wherein after initiating a switchover to a first level backup path, a BFD module in the first level initiates a first level of state detection to determine whether traffic is resumed.

5. A method of fault detection with Bidirectional Forwarding Detection (BFD), comprising:

in the event that a BFD module disposed in a first level of the network detects a traffic disruption at a predetermined time interval, a BFD module disposed in a second level of the network receives a status detection request from the BFD module in the first level;

in response to receiving the status detection request, the BFD module in the second stage detects whether the second stage is interrupted and sends a receive status detection reply to the BFD module in the first stage, the status detection reply including whether the BFD module in the second stage detects an interruption.

6. The method of claim 5, further comprising:

sending a status detection request to a BFD module disposed in a third level of the network in the event that the BFD module in the second level detects an interrupt;

receiving a status detection reply from a BFD module in the third stage, the status detection reply comprising whether the BFD module in the third stage detects an interrupt.

7. The method of claim 6, further comprising:

in the event that the BFD module in the third stage does not detect an interrupt, the BFD module in the second stage initiates a switchover to a second stage backup path.

8. An apparatus for fault detection with Bidirectional Forwarding Detection (BFD), the apparatus comprising BFD modules arranged in a first stage of a network and BFD modules arranged in a second stage of the network, wherein the BFD modules in the first stage are configured to:

detecting whether the service is interrupted at a preset time interval;

under the condition that service interruption is detected, sending a state detection request to a BFD module in the second level;

and initiating the state detection of the first level to judge whether the service is recovered or not under the condition that the BFD module in the second level detects the interruption.

9. The apparatus of claim 8, wherein the BFD module in the first stage is configured to initiate a switchover to a first stage backup path in the event traffic is not restored.

10. The apparatus of claim 8, wherein, in the event that no interrupt is detected by a BFD module in the second stage, the BFD module in the first stage is configured to initiate a switchover to a first stage backup path.

11. An apparatus according to claim 9 or 10, wherein, after initiating a switchover to a first level backup path, a BFD module in the first level is configured to initiate a state detection of the first level to determine whether traffic is resumed.

12. An apparatus for failure detection with Bidirectional Forwarding Detection (BFD), the apparatus comprising BFD modules disposed in a first stage of a network and BFD modules disposed in a second stage of the network, wherein the BFD modules in the second stage are configured to:

receiving, by the BFD module in the second stage, a status detection request from the BFD module in the first stage in the event that the BFD module in the first stage detects a service interruption at a predetermined time interval;

13. The apparatus of claim 12, further comprising BFD modules arranged in a third stage, wherein BFD modules in the second stage are further configured to:

sending a state detection request to a BFD module in a third level when the BFD module in the second level detects an interrupt;

receiving a status detection reply from a BFD module in the third stage, the status detection reply including whether the BFD module in the third stage detects an interrupt.

14. The apparatus of claim 13, in the event that no interrupt is detected by a BFD module in the third stage, the BFD module in the second stage is further configured to initiate a switchover to a second stage backup path.

15. A non-transitory computer-readable storage medium on which a program is stored, the program, when executed by a computer, causing the computer to perform the method according to any one of claims 1-4.

16. A non-transitory computer-readable storage medium on which a program is stored, the program, when executed by a computer, causing the computer to perform the method according to any one of claims 5-7.

17. An apparatus for fault detection, comprising a memory and a processor, the memory communicatively coupled with the processor, the memory having stored therein a program that, when executed by the processor, causes the processor to perform the method of any of claims 1-4.

18. An apparatus for fault detection, comprising a memory and a processor, the memory communicatively coupled with the processor, the memory having stored therein a program that, when executed by the processor, causes the processor to perform the method of any of claims 5-7.

19. A computer program product comprising a computer program which, when executed by a processor, carries out the method according to any one of claims 1-4.

20. A computer program product comprising a computer program which, when executed by a processor, carries out the method according to any one of claims 5-7.