WO2017054547A1

WO2017054547A1 - Bidirectional forwarding detection method and apparatus

Info

Publication number: WO2017054547A1
Application number: PCT/CN2016/089458
Authority: WO
Inventors: 张瑜
Original assignee: 中兴通讯股份有限公司
Priority date: 2015-09-28
Filing date: 2016-07-08
Publication date: 2017-04-06
Also published as: CN106559280A

Abstract

Disclosed are a bidirectional forwarding detection method and apparatus. The method comprises: a local end device judging whether a BFD message sent by an opposite end device is received within a bidirectional forwarding detection (BFD) detection period; in the case where the BFD message is received, the local end device detecting the state of a specific flag bit of the BFD message, wherein the specific flag bit is configured to indicate whether a local BFD session of the opposite end device is in a Down state; and in the case where it is detected that the specific flag bit in the BFD message indicates that the local BFD session of the opposite end device is in the Down state, the local end device switching the state of a local BFD session of the local end device to the Down state. By means of the technical solution, the problem in the related art that in the case where a virtual interface fails while a physical port and a three-layer interface are normal, two BFD detection periods are needed to switch the state of a BFD session to a Down state is solved, thereby improving the efficiency of BFD.

Description

Method and device for bidirectional forwarding detection

Technical field

The present application relates to, but is not limited to, the field of communications, and in particular, to a method and apparatus for bidirectional forwarding detection.

Background technique

Bidirectional Forwarding Detection (BFD) is a simple "Hello" protocol. In many respects, it is similar to the neighbor detection part of the well-known routing protocols. A pair of systems periodically send detection messages on the channel of the established session between them if one of the systems in the pair does not receive detection of another system for a sufficient amount of time The message is considered to have failed in a certain part of the bidirectional channel to the other system. Under certain conditions, in order to reduce the load, the transmission and reception rates between systems need to be negotiated.

The detection packet sent by the BFD protocol is a User Datagram Protocol (UDP) packet. The format of the BFD control packet is as shown in Figure 1. The meanings of the fields in the control packet format are as follows: :

Vers: BFD version number, currently 1;

Diag: Diagnostic word indicating the reason for the last session of the local BFD system to go Down;

Sta: BFD local status;

P: If the flag is marked, indicating that the parameter has changed or the transmitting system is connected, the requesting party immediately confirms and responds. Otherwise, the other party is not requested to confirm and respond;

F: The F flag must be set in the response message in response to the P flag being set.

C: forwarding/control separation flag;

A: certification mark;

D: Query request, the setting indicates that the query mode in the transmission system is valid, and is set to instruct the remote system to stop the periodic transmission of the BFD control message;

R: reserved bit;

Detect Mult: Detects the timeout multiple and sets the detection time to the detection time.

Length: length of the packet;

My Discreaminator: BFD session connection local identifier;

Your Discreaminator: The BFD session connects to the remote identifier;

Desired Min Tx Interval: Minimum interval for sending BFD packets.

Required Min RX Interval: Minimum supported BFD reception interval;

Required Min Echo RX Interval: Minimum supported Echo packet reception interval.

2 is a flowchart of a method of bidirectional forwarding detection according to the related art, and a process of determining that a BFD session is Down is shown in FIG. For example, in the asynchronous mode, the system periodically sends BFD control packets to each other. If a system does not receive BFD control packets from the other system within the detection time, it determines that the session is in the Down state. Or in query mode, assume that each system has an independent method to confirm that it is connected to the other system. After the BFD session is established, the system stops sending BFD control packets unless a system needs to explicitly verify connectivity. In the case that the connectivity needs to be explicitly verified, the system sends a series of short BFD control packets. If the returned packets are not received within the detection time, the system determines that the session is in the Down state (system shutdown). Repeat the above process for a system response message.

FIG. 3 is a schematic diagram of a topology structure of an MPLS VPN protection network according to the related art. As shown in FIG. 3, a multi-protocol label switch (MPLS) virtual private network (VPN) protection is provided. In the environment, the service is configured with the active and standby protection paths, and the outer layer of the main service is forwarded through the tunnel.

When the physical output port or the Layer 3 output interface of the primary service is faulty, the devices at both ends of the faulty link can receive the BFD keep-alive message and the session is not received. The state is switched to the Down state, and the service protection function can be switched during the detection period.

The inventor of the present application found that when the virtual interface of the tunnel fails and the physical port and the Layer 3 interface are normal, the local A device service does not send BFD packets because the output interface is in the Down state. During the detection period, the specified BFD packet is not received, and the state of the session is switched to the Down state. The BFD packet is not sent continuously. However, in the session. The B device will continue to send BFD packets before the state is switched to the Down state. The device can also receive the BPDUs. The process will not immediately change the state of the BFD session to the Down state. During the detection period, the A device will switch the state of the session to the Down state. In the process, the A device needs to be in the BFD session to switch the state of the BFD session to the Down state.

In the related art, when the virtual interface fails and the physical port and the Layer 3 interface are normal, two BFD detection cycles are required to switch the BFD session state to the Down state. Currently, no effective solution has been proposed.

Summary of the invention

The following is an overview of the topics detailed in this document. This Summary is not intended to limit the scope of the claims.

The present application provides a method and apparatus for bidirectional forwarding detection, in order to solve the problem that at least two BFD detection periods are required to determine the state of a BFD session in the case where the virtual interface fails and the physical interface and the Layer 3 interface are normal. The problem of switching to the Down state.

According to an aspect of the present application, a method for bidirectional forwarding detection is provided, which includes: determining, by a local device, whether a BFD packet sent by a peer device is received in a detection period of a bidirectional forwarding detection BFD; In the case of the BFD packet, the local device detects the status of the specific flag bit of the BFD packet, where the specific flag bit is set to indicate whether the local BFD session of the peer device is in the Down state. The local device switches the state of the local BFD session of the local device when the local BFD session in the BFD packet indicates that the local BFD session of the peer device is in the Down state. It is in the Down state.

Optionally, the specific flag bit includes: a local state Sta bit in the BFD message.

Optionally, the method further includes: determining, by the peer device, whether the BFD packet sent by the local device is received in a BFD detection period; and determining that the local device sends the In the case of a BFD packet, the peer device sends the BFD packet to the local device, and the state of the local BFD session of the peer device is switched to the Down state, where the BFD packet is sent. The specific flag bit indicates that the local BFD session of the peer device is in the Down state.

Optionally, in a case that the local device does not receive the BFD packet sent by the peer device in a BFD detection period, the method further includes: the local device device The state of the local BFD session of the local device is switched to the Down state.

According to another aspect of the present application, a method for bidirectional forwarding detection is provided, including: determining, by a peer device, whether a BFD packet sent by the local device is received in a detection period of a bidirectional forwarding detection BFD; In the case of the BFD packet sent by the local device, the peer device sends a BFD packet to the local device, and the state of the local BFD session of the peer device is switched to the Down state, where The BFD packet sent by the peer device includes a specific flag bit, and the specific flag bit is set to indicate whether the local BFD session of the peer device is in the Down state.

Optionally, after the step of the BFD packet being sent to the local device by the peer device, and the state of the local BFD session of the peer device is switched to the Down state, the method further includes: The local device determines whether the BFD packet of the peer device is received in the detection period of the BFD session. If the BFD packet of the peer device is received, the local device detects the peer end. The state of the specific flag bit of the BFD packet of the device; the local device detects the local device when the local device indicates that the local BFD session of the peer device is in the Down state. The state of the local BFD session is switched to the Down state.

Optionally, in a case that the local device does not receive the BFD packet sent by the peer device, the method further includes: the local device, the local BFD session of the local device The state is switched to the Down state.

The application further provides a computer readable storage medium storing computer executable instructions that are implemented when the computer executable instructions are executed.

According to another aspect of the present application, a device for detecting bidirectional forwarding is further applied to the local device, including: a first determining module, configured to determine whether a pair is received during a detection period of a bidirectional forwarding detection BFD a BFD packet sent by the end device; the detecting module is configured to detect a state of the specific flag bit of the BFD packet when the BFD packet is received, where the specific flag bit is set to indicate the Whether the local BFD session of the peer device is in the Down state; the switching module is configured to detect the specific flag bit indication in the BFD packet If the local BFD session of the peer device is in the Down state, the state of the local BFD session of the local device is switched to the Down state.

According to another aspect of the present application, a device for bidirectional forwarding detection is provided, which is applied to a peer device, and includes: a second judging module, configured to determine whether the local end is received during a detection period of a bidirectional forwarding detection BFD a BFD packet sent by the device, where the processing module is configured to send the BFD packet to the local device, and the peer device, if the BFD packet sent by the local device is not received. The state of the local BFD session is switched to the Down state, where the BFD packet sent by the peer device includes a specific flag bit, and the specific flag bit is set to indicate whether the local BFD session of the peer device is in the Down state.

In the technical solution of the present application, the local device determines whether the BFD packet sent by the peer device is received in the detection period of the bidirectional forwarding detection BFD. When the BFD packet is received, the local device detects the BFD packet. The status of the specific flag bit of the packet, where the specific flag bit is set to indicate whether the local BFD session of the peer device is in the Down state; the specific flag bit in the BFD packet is detected to indicate that the local BFD session of the peer device is Down. In the case of the state, the local device switches the state of the local BFD session of the local device to the Down state. In the related art, when the virtual interface fails and the physical port and the Layer 3 interface are normal, two BFDs are required. The detection period can detect the problem that the BFD session is in the Down state, which improves the efficiency of BFD.

Other aspects will be apparent upon reading and understanding the drawings and detailed description.

BRIEF abstract

The drawings described herein are intended to provide a further understanding of the present application, and are intended to be a part of this application. In the drawing:

1 is a schematic structural diagram of a BFD packet according to the related art;

2 is a flowchart of a method of bidirectional forwarding detection according to the related art;

3 is a schematic diagram of a topology structure of an MPLS VPN protection network according to the related art;

4 is a flowchart 1 of a method for bidirectional forwarding detection according to an embodiment of the present invention;

FIG. 5 is a second flowchart of a method for bidirectional forwarding detection according to an embodiment of the present invention; FIG.

6 is a block diagram 1 of an apparatus for bidirectional forwarding detection according to an embodiment of the present invention;

7 is a block diagram 2 of an apparatus for bidirectional forwarding detection according to an embodiment of the present invention;

8 is a flow chart of a method of bidirectional forwarding detection in accordance with a preferred embodiment of the present invention.

Preferred embodiment of the invention

The present application will be described in detail below with reference to the drawings in conjunction with the embodiments. It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict.

It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or order.

In this embodiment, a method for bidirectional forwarding detection is provided. FIG. 4 is a flowchart 1 of a method for bidirectional forwarding detection according to an embodiment of the present invention. As shown in FIG. 4, the process includes the following steps:

Step S402, the local device determines whether the BFD packet of the peer device is received in the detection period of the bidirectional forwarding detection BFD.

Step S404: If the BFD packet is received, the local device detects the status of the specific flag bit of the BFD packet, where the specific flag bit is set to indicate whether the local BFD session of the peer device is in the Down state.

In step S406, if the specific flag bit in the BFD packet is detected to indicate that the local BFD session of the peer device is in the Down state, the local device switches the state of the local BFD session of the local device to the Down state.

After the BFD packet is received, if the BFD packet is in the Down state, the local BFD session of the local device is switched to the Down state. The time required for detecting the Down state of the peer device is shortened, and the time required for detecting the Down state of the peer device is shortened, and the physical interface and the Layer 3 interface are faulty in the related art. The BFD session detection period is required to detect the BFD session status to the Down state, which improves the timeliness of BFD.

The method for bidirectional forwarding detection provided by the embodiment of the present invention can be applied to an asynchronous mode or a query. mode. In addition, although the MPLS VPN scenario is taken as an example in the embodiment of the present invention, the method of the bidirectional forwarding detection provided by the embodiment of the present invention may be applied in other application scenarios, which is not limited herein.

Optionally, the specific flag bit may be a new field, or may use an original field. For example, the specific flag bit may be the local state Sta bit in the BFD message.

Optionally, the peer device determines whether the BFD packet sent by the local device is received in the detection period of the BFD session. If the BFD packet sent by the local device is not received, the peer device sends the BFD packet. The packet is sent to the local device, and the local BFD session of the peer device is switched to the Down state. The specific BFD packet indicates that the local BFD session of the peer device is Down. In this way, a BFD packet carrying a specific flag bit is generated.

Optionally, the local device switches the state of the local BFD session of the local device to the Down state when the local device does not receive the BFD packet. In this manner, another manner of switching the state of the local BFD session of the local device to the Down state is provided.

The embodiment of the present invention further provides a method for bidirectional forwarding detection. FIG. 5 is a second flowchart of a method for bidirectional forwarding detection according to an embodiment of the present invention. As shown in FIG. 5, the method includes the following steps:

In step S502, the peer device determines whether the BFD packet sent by the local device is received in the detection period of the bidirectional forwarding detection BFD.

Step S504: If the BFD packet sent by the local device is not received, the peer device sends the BFD packet to the local device, and the state of the local BFD session of the peer device is switched to the Down state, where the peer device sends The BFD packet includes a specific flag bit, and the specific flag bit is set to indicate whether the local BFD session of the peer device is in the Down state.

Optionally, after the step of the BFD packet sent by the peer device to the local device and the state of the local BFD session of the peer device is switched to the Down state, the method for detecting the bidirectional forwarding further includes: determining by the local device Whether the BFD packet of the peer device is received during the detection period of the BFD session. When the BFD packet of the peer device is received, the local device detects the state of the specific flag bit of the BFD packet of the peer device. The local device will perform local BFD session of the local device when the local device indicates that the local BFD session of the peer device is in the Down state. The state is switched to the Down state.

Optionally, the local device switches the state of the local BFD session of the local device to the Down state when the local device does not receive the BFD packet from the peer device.

Through the description of the above embodiments, those skilled in the art can clearly understand that the method according to the above embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, by hardware, but in many cases, the former is A better implementation. Based on such understanding, the technical solution of the present application, which is essential or contributes to the related art, may be embodied in the form of a software product stored in a storage medium (such as ROM/RAM, disk, CD-ROM). The instructions include a number of instructions for causing a terminal device (which may be a cell phone, computer, server, or network device, etc.) to perform the methods described in various embodiments of the present invention.

Embodiments of the present invention further provide a computer readable storage medium storing computer executable instructions that are implemented when the computer executable instructions are executed.

In this embodiment, a device for bidirectional forwarding detection is further provided, which is applied to the local device. The device is configured to implement the foregoing embodiments and preferred embodiments, and details are not described herein. As used below, the term "module" may implement a combination of software and/or hardware of a predetermined function. Although the apparatus described in the following embodiments is preferably implemented in software, hardware, or a combination of software and hardware, is also possible and contemplated.

FIG. 6 is a block diagram of an apparatus for bidirectional forwarding detection according to an embodiment of the present invention. As shown in FIG. 6, the apparatus includes: a first judging module 62, a detecting module 64, and a switching module 66, where

The first judging module 62 is configured to determine whether the BFD packet sent by the peer device is received during the detection period of the bidirectional forwarding detection BFD. The detecting module 64 is coupled to the first judging module 62 and configured to receive the BFD. In the case of the packet, the state of the specific flag bit of the BFD packet is detected, wherein the specific flag bit is set to indicate whether the local BFD session of the peer device is in the Down state; the switching module 66 is coupled to the detecting module 64, and is configured to be in the If the local BFD session of the local device is in the Down state, the local BFD session of the local device is switched to the Down state.

Optionally, the switching module 66 is further configured to: when the local device does not receive the BFD packet. The state of the local BFD session of the local device is switched to the Down state.

The embodiment also provides a device for detecting the bidirectional forwarding, which is applied to the peer device, and the device is configured to implement the foregoing embodiments and preferred embodiments, and details are not described herein. As used below, the term "module" may implement a combination of software and/or hardware of a predetermined function. Although the apparatus described in the following embodiments is preferably implemented in software, hardware, or a combination of software and hardware, is also possible and contemplated.

FIG. 7 is a block diagram 2 of an apparatus for bidirectional forwarding detection according to an embodiment of the present invention. As shown in FIG. 7, the apparatus includes: a second judging module 72 and a processing module 74, where

The second judging module 72 is configured to determine whether the BFD packet sent by the local device is received in the detection period of the bidirectional forwarding detection BFD; the processing module 74 is coupled to the second judging module 72, and is configured not to receive the BFD packet. In the case of a BFD packet sent by the peer device, the BFD packet is sent to the local device, and the state of the local BFD session of the peer device is switched to the Down state. The BFD packet sent by the peer device includes the specific flag. The bit is set to indicate whether the local BFD session of the peer device is in the Down state.

It should be noted that each of the above modules may be implemented by software or hardware. For the latter, the foregoing may be implemented by, but not limited to, the foregoing modules are all located in the same processor; or, the modules are located in multiple In the processor.

The embodiment further provides a system for bidirectional forwarding detection, which includes the above-mentioned device applied to the bidirectional forwarding detection of the local device and the device applied to the bidirectional forwarding detection of the peer device.

Embodiments of the present invention also provide a software for performing the technical solutions described in the above embodiments and preferred embodiments.

Embodiments of the present invention also provide a storage medium. In this embodiment, the above storage medium may be configured to store program code for performing the following steps:

Step S402, the local device determines whether a BFD packet sent by the peer device is received in a detection period of the bidirectional forwarding detection BFD.

In step S404, the local device detects the status of the specific flag bit of the BFD packet, where the specific flag bit is set to indicate that the local BFD session of the peer device is Whether it is in the Down state;

In step S406, the local device switches the state of the local BFD session of the local device to the Down state when the local BFD session of the local device is in the Down state.

Step S504: If the BFD packet sent by the local device is not received, the peer device sends the BFD packet to the local device, and the state of the local BFD session of the peer device is switched to the Down state. The BFD packet sent by the end device includes a specific flag bit, and the specific flag bit is set to indicate whether the local BFD session of the peer device is in the Down state.

Optionally, in the embodiment, the foregoing storage medium may include, but is not limited to, a USB flash drive, a Read-Only Memory (ROM), and a Random Access Memory (RAM). A variety of media that can store program code, such as a hard disk, a disk, or an optical disk.

For example, the specific examples in this embodiment may refer to the examples described in the foregoing embodiments and the optional embodiments, and details are not described herein again.

In order to make the description of the embodiments of the present invention more clear, the following description and description are given in conjunction with the preferred embodiments.

The preferred embodiment of the present invention provides an MPLS VPN protection network as an example, and provides a method for improving the efficiency of the BFD in the MPLS VPN protection network. When the network side link fails, the BFD can be more effectively and quickly perceived. Requirements for fast service switching in an MPLS VPN network environment.

In the related art, when the tunnel virtual interface is faulty, the device can still receive the BFD packet. The state of the BFD session is switched to the Down state. The BFD session is received in the detection period.

In a preferred embodiment of the present invention, in the preferred embodiment of the present invention, the device B in the above scenario is not in the time of one detection cycle, in consideration of the presence of the Sta flag in the local BFD packet. When the BFD packet is received, the Stabit bit in the BFD packet is set to "01", that is, the local BFD session is in the Down state. After receiving the packet, the device A first checks the Sta bit. If it is "01", Even if a BFD packet is received, the local session is still Down.

FIG. 8 is a flowchart of a method for bidirectional forwarding detection according to a preferred embodiment of the present invention. As shown in FIG. 8, the process includes the following steps:

Step S801, determining whether a BFD keep-alive packet (ie, a BFD packet) is received in one cycle;

Step S802, when receiving the BFD keep-alive message, detecting whether the Sta bit is set to "01";

Step S803, if the Sta bit is not set to "01", the BFD session remains in the Up state, and waits for the next period of BFD;

Step S804, if the Sta position is "01", step S806 is performed;

In step S805, if the BFD keep-alive packet is not detected, the Sta location is set to "01" when the BFD packet is encapsulated.

In step S806, the state of the local BFD session is switched to the Down state.

In the above manner, the rule for determining that the BFD session is in the Down state is improved. The conditions for determining that the BFD session is in the Down state are two, namely:

1) The Sta position in the received BFD packet is "01";

2) No BFD packets were received during the detection period.

If the above two conditions are met, the local BFD session is deleted, so that the link fault is detected during the detection period, so that the service protection can be switched more quickly. This section solves the problem that when the virtual interface of the tunnel is Down but the physical port is still Up, the detection time of two detection cycles is required to ensure the switching performance of the service.

Obviously, those skilled in the art should understand that the above modules or steps of the present application can be implemented by a general computing device, which can be concentrated on a single computing device or distributed in a network composed of multiple computing devices. Alternatively, they may be implemented by program code executable by the computing device such that they may be stored in the storage device by the computing device and, in some cases, may be different from the order herein. The steps shown or described are performed, or they are separately fabricated into individual integrated circuit modules, or a plurality of modules or steps thereof are fabricated as a single integrated circuit module. Thus, the application is not limited to any particular hardware and software. Combine.

One of ordinary skill in the art will appreciate that all or a portion of the above steps may be performed by a program to instruct related hardware, such as a processor, which may be stored in a computer readable storage medium, such as a read only memory, disk or optical disk. Wait. Alternatively, all or part of the steps of the above embodiments may also be implemented using one or more integrated circuits. Correspondingly, each module/unit in the above embodiment may be implemented in the form of hardware, for example, by implementing an integrated circuit to implement its corresponding function, or may be implemented in the form of a software function module, for example, executing a program stored in the memory by a processor. / instruction to achieve its corresponding function. Embodiments of the invention are not limited to any specific form of combination of hardware and software.

The above description is only the preferred embodiment of the present invention, and is not intended to limit the present application, and various changes and modifications may be made to the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this application are intended to be included within the scope of the present application.

Industrial applicability

In the technical solution of the present application, the local device determines whether the BFD packet sent by the peer device is received in the detection period of the bidirectional forwarding detection BFD; if the BFD packet is received, the local device detects the BFD packet. If the local BFD session of the local device is in the Down state, the local device will switch the state of the local BFD session of the local device to the Down state. If the physical interface and the Layer 3 interface are faulty, the two BFD sessions can detect the BFD session in the Down state and improve the efficiency of BFD.

Claims

A method for bidirectional forwarding detection, comprising:

The local device determines whether the BFD packet sent by the peer device is received during the detection period of the bidirectional forwarding detection BFD.

When the BFD packet is received, the local device detects the status of the specific flag bit of the BFD packet, where the specific flag bit is set to indicate whether the local BFD session of the peer device is In the Down state;

The local device switches the state of the local BFD session of the local device when the local BFD session in the BFD packet indicates that the local BFD session of the peer device is in the Down state. It is in the Down state.
The method of claim 1, wherein the specific flag bit comprises: a local state Sta bit in the BFD message.
The method of claim 1 further comprising:

The peer device determines whether the BFD packet sent by the local device is received in a BFD detection period;

When it is determined that the BFD packet sent by the local device is not received, the peer device sends the BFD packet to the local device, and the local BFD session of the peer device is The state is switched to the Down state, where the specific flag bit of the BFD packet indicates that the local BFD session of the peer device is in the Down state.
The method according to any one of claims 1 to 3, wherein, in a case where the local device does not receive the BFD packet sent by the peer device within a detection period of a BFD, The method further includes:

The local device switches the state of the local BFD session of the local device to the Down state.
A method for bidirectional forwarding detection, comprising:

The peer device determines whether the BFD packet sent by the local device is received in the detection period of the bidirectional forwarding detection BFD.

In the case that the BFD packet sent by the local device is not received, the peer device sends the BFD packet. Sending a BFD packet to the local device, and switching the state of the local BFD session of the peer device to the Down state, where the BFD packet sent by the peer device includes a specific flag bit, the specific flag The bit is set to indicate whether the local BFD session of the peer device is in the Down state.
The method of claim 5, wherein the specific flag bit comprises: a local state Sta bit in the BFD message.
The method according to claim 5, after the step of the peer device transmitting the BFD packet to the local device and switching the state of the local BFD session of the peer device to the Down state, the method Also includes:

The local device determines whether the BFD packet of the peer device is received in a BFD detection period;

In the case that the BFD packet of the peer device is received, the local device detects the state of the specific flag bit of the BFD packet of the peer device;

The local device switches the state of the local BFD session of the local device to the Down state, when the local device indicates that the local BFD session of the peer device is in the Down state.
The method of claim 7, wherein, in the case that the local device does not receive the BFD packet sent by the peer device, the method further includes:

The local device switches the state of the local BFD session of the local device to the Down state.
A device for bidirectional forwarding detection is applied to a local device, including:

The first judging module is configured to determine whether the BFD packet sent by the peer device is received in the detection period of the bidirectional forwarding detection BFD;

The detecting module is configured to: when the BFD packet is received, detect a status of the specific flag bit of the BFD packet, where the specific flag bit is set to indicate whether the local BFD session of the peer device is In the Down state;

The switching module is configured to switch the state of the local BFD session to the Down state when the local BFD session of the peer device is in the Down state.
A device for bidirectional forwarding detection, applied to a peer device, including:

The second judging module is configured to determine whether the BFD packet sent by the local device is received in the detection period of the bidirectional forwarding detection BFD;

a processing module, configured to send a BFD packet to the local device, and switch the state of the local BFD session to a Down state, where the BFD packet sent by the local device is not received, where The BFD packet sent by the peer device includes a specific flag bit, and the specific flag bit is set to indicate whether the local BFD session is in the Down state.