WO2022161061A1 - 一种故障检测方法、网络设备及系统 - Google Patents

一种故障检测方法、网络设备及系统 Download PDF

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Publication number
WO2022161061A1
WO2022161061A1 PCT/CN2021/141435 CN2021141435W WO2022161061A1 WO 2022161061 A1 WO2022161061 A1 WO 2022161061A1 CN 2021141435 W CN2021141435 W CN 2021141435W WO 2022161061 A1 WO2022161061 A1 WO 2022161061A1
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Prior art keywords
forwarding path
network device
indication information
sid list
policy
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PCT/CN2021/141435
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English (en)
French (fr)
Inventor
李志永
肖亚群
郝建武
方晟
樊利
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华为技术有限公司
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Application filed by 华为技术有限公司 filed Critical 华为技术有限公司
Priority to EP21922651.1A priority Critical patent/EP4287576A1/en
Publication of WO2022161061A1 publication Critical patent/WO2022161061A1/zh
Priority to US18/226,967 priority patent/US20230388177A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
    • H04L41/08—Configuration management of networks or network elements
    • H04L41/0894—Policy-based network configuration management
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
    • H04L41/06—Management of faults, events, alarms or notifications
    • H04L41/0631—Management of faults, events, alarms or notifications using root cause analysis; using analysis of correlation between notifications, alarms or events based on decision criteria, e.g. hierarchy, tree or time analysis
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
    • H04L41/06—Management of faults, events, alarms or notifications
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L43/00—Arrangements for monitoring or testing data switching networks
    • H04L43/08—Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters
    • H04L43/0823—Errors, e.g. transmission errors
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/24—Multipath
    • H04L45/247—Multipath using M:N active or standby paths
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/28—Routing or path finding of packets in data switching networks using route fault recovery
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/34—Source routing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00—Routing or path finding of packets in data switching networks
    • H04L45/50—Routing or path finding of packets in data switching networks using label swapping, e.g. multi-protocol label switch [MPLS]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
    • H04L41/08—Configuration management of networks or network elements
    • H04L41/0895—Configuration of virtualised networks or elements, e.g. virtualised network function or OpenFlow elements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L43/00—Arrangements for monitoring or testing data switching networks
    • H04L43/20—Arrangements for monitoring or testing data switching networks the monitoring system or the monitored elements being virtualised, abstracted or software-defined entities, e.g. SDN or NFV

Definitions

  • the present application relates to the field of communication technologies, and in particular, to a fault detection method, network device and system.
  • BFD Bidirectional forwarding detection
  • SR policy segment routing policy
  • the fault detection process of the BFD mechanism includes: the sender sends a BFD packet to the reflector through the SR policy, and requires the reflector to feed back a response packet of the BFD packet to the sender, so as to determine whether the SR policy is faulty.
  • the response packet of the BFD packet is usually transmitted through Internet protocol (IP) routing, and the transmission path of the response packet determined by the IP routing method (also called IP path) is likely not to pass through the network device that the SR policy passes through, that is, the transmission of the BFD packet and the response packet of the BFD packet do not share the same path.
  • IP Internet protocol
  • the present application provides a fault detection method, network device and system, in which indication information of a segment identification list (SID list) is carried in a BFD message, so that the receiving end can
  • the indication information of the SID list determines the forwarding path that is opposite to the forwarding path for transmitting the BFD message, and sends the response message of the BFD message to the transmitting end based on the determined forwarding path, so as to realize the specific forwarding in the SR policy.
  • Path fault detection thereby improving the accuracy and accuracy of fault detection by the BFD mechanism.
  • BFD detection may refer to, for example, static BFD detection, dynamic BFD detection, or seamless bidirectional forwarding detection (seamless bidirectional forwarding detection, SBFD) detection.
  • the present application provides a fault detection method, which is applied to a first network device.
  • the method may include, for example: the first network device
  • the first BFD packet including the indication information of the first SID list sent by the second network device is received through the first forwarding path of the first SR policy.
  • the first network device can The indication information of a SID list determines a second forwarding path that is reversely shared with the first forwarding path, and sends the first response message of the first BFD message to the second network device through the second forwarding path, The first response packet is used to instruct the second network device to perform fault detection on the first forwarding path.
  • the transmitting end that is, the second network device detected by BFD carries the indication information of the SID list in the BFD message, so that the receiving end (that is, the first network device) can determine and match the SID list based on the indication information of the SID list.
  • the forwarding path that transmits the BFD packet is reversed to the forwarding path of the common path, and based on the determined forwarding path, a response packet of the BFD packet is sent to the transmitting end, by ensuring that the real forwarding path of the BFD packet and the response packet is reversed
  • Common paths are used to achieve accurate fault detection of specific forwarding paths in the SR policy, and improve the accuracy and accuracy of fault detection for the SR policy by the BFD mechanism.
  • the SR policy may be an SR-MPLS policy, corresponding to a multi-protocol label switching (MPLS) network scenario; or, the SR policy may also be an SRv6 policy, corresponding to the internet protocol version 6 (internet protocol version 6). , IPv6).
  • MPLS multi-protocol label switching
  • IPv6 internet protocol version 6
  • the SID list corresponds to the MPLS label stack, and the SID list may include the MPLS label corresponding to at least one network device or link;
  • the SID list corresponds to the list of IPv6 addresses, and the SID list in the The IPv6 address corresponding to at least one network device or link may be included.
  • the reverse common path may refer to the reverse order of the network devices and links that the two tunnels pass through in sequence according to the two SR policies.
  • it can refer to the network devices and links that the two forwarding paths pass through in turn determined according to the two SID lists corresponding to the two forwarding paths.
  • the two forwarding paths of the reverse common path can belong to two SR policies respectively. But understandably, in other possible implementations, for example, when the round-trip path between two endpoints is defined as belonging to a complete SR policy, the two forwarding paths can also be considered to belong to the same SR policy.
  • the method may further include: the first network device generates the first BFD packet. An indication of the SID list. Or, the first network device receives the indication information of the first SID list sent by the second network device. In this way, the first network device may store the corresponding relationship between the indication information of the first SID list and the second forwarding path, so as to obtain the indication according to the first SID list in the first BFD packet after receiving the first BFD packet. The information determines that the second forwarding path is ready.
  • the method may further include: the first network device receives a message sent by the control and management device, where the message includes indication information of the first SID list.
  • the message also includes indication information of the second SID list, wherein the indication information of the second SID list indicates the first forwarding path, and the indication information of the first SID list indicates the second forwarding path;
  • the indication information of the second SID list indicates the second forwarding path, and the indication information of the first SID list indicates the first forwarding path.
  • the message may be a border gateway protocol segment routing policy (border gateway protocol segment routing policy, BGP SR policy) message, and the BGP SR policy message may pass a sub type length value (sub type length value, sub- TLV) field carries the indication information of the first SID list.
  • BGP SR policy message also carries the indication information of the second SID list, then the indication information of the first SID list and the indication information of the second SID list can be carried in a sub-TLV in the BGP SR policy message field, or, the indication information of the first SID list and the indication information of the second SID list may also be respectively carried in two different sub-TLV fields in the BGP SR policy message.
  • the message used to carry the indication information of the first SID list can be not only a BGP SR policy message, but also a network configuration protocol (NETCONF) or a path computation element communication protocol (path computation element). protocol, PCEP) message, etc.
  • NETCONF network configuration protocol
  • PCEP path computation element communication protocol
  • the indication information of the first SID list may also be distributed by the second network device and sent to the control and management device, and then sent by the control and management device to the first network device.
  • the second network device sends the indication information of the first SID list to the control and management device, for example, the indication information of the first SID list may be carried in the link state of the border gateway protocol (border gateway protocol link state, BGP-LS ) message, the indication information of the first SID list is carried by the sub-TLV field in the BGP-LS message.
  • the border gateway protocol border gateway protocol link state, BGP-LS
  • the indication information of the first SID list and the indication information of the second SID list may be carried in a sub-TLV in the BGP-LS message field, or, the indication information of the first SID list and the indication information of the second SID list may also be respectively carried in two different sub-TLV fields in the BGP-LS packet.
  • the message used to carry the indication information of the first SID list can be a BGP-LS message, or a NETCONF or NETCONF message. PCEP messages, etc.
  • the indication information of the first SID list may be used to indicate the SID list corresponding to the second forwarding path. Then, after receiving the first BFD packet, the first network device may directly determine the second forwarding path for transmitting the first response packet corresponding to the first BFD packet according to the indication information of the first SID list, It makes it possible to achieve accurate BFD detection.
  • the indication information of the first SID list may also be used to indicate the SID list corresponding to the first forwarding path.
  • the first network device may store the information of the first SID list. The correspondence between the indication information and the second forwarding path, then, after receiving the first BFD packet, the first network device can directly determine the indication information corresponding to the first SID list according to the indication information of the first SID list. the second forwarding path.
  • the first network device may also store the correspondence between the indication information of the first SID list and the indication information of the second SID list, and the indication information of the second SID list is used to indicate the SID corresponding to the second forwarding path list, then, the first network device determines the second forwarding path according to the indication information of the first SID list, for example, it may include: the first network device determines the information of the second SID list according to the indication information of the first SID list. indication information; then, the first network device determines the second forwarding path according to the indication information of the second SID list. In this way, it is possible to achieve accurate BFD detection.
  • the second forwarding path is faulty.
  • the network device may fail to receive the first response message.
  • the second network device does not receive the first response packet through the second forwarding path within a preset time (for example, 1 second). Since the first forwarding path and the second forwarding path share the same path in the opposite direction, it is still possible to It is determined that the first forwarding path is faulty.
  • the second network device can receive the first response packet. In this case, the second network device determines, according to the received first response packet, that both the first forwarding path and the second forwarding path for transmitting the first BFD packet and the first response packet are normal, that is, the first A forwarding path is not faulty.
  • the method may further include: the first network device sends a second BFD packet to the second network device through the second forwarding path of the second SR policy, where the second BFD packet includes a third BFD packet.
  • Indication information of the SID list is used to instruct the first network device to determine the first forwarding path for sending the second response packet of the second BFD packet; receiving the second response packet; the first network device performs fault detection on the second forwarding path according to the second response packet.
  • the method may further include: the first network device receives a third BFD packet sent by the second network device through the third forwarding path of the first SR policy, where the third BFD packet includes the third BFD packet.
  • the third forwarding path is different from the first forwarding path; the first network device determines the fourth forwarding path according to the indication information of the fourth SID list, and the fourth forwarding path and the third forwarding path share the same reverse direction.
  • the first network device sends a third response packet of the third BFD packet to the second network device through the fourth forwarding path, where the third response packet is used to instruct the second network device to respond to the third BFD packet. Forwarding path for fault detection.
  • the indication information of the first SID list may be a path segment (Path Segment) or a bonding segment identifier (bonding SID, BSID); or, the indication information of the first SID list may also be the first The SID list itself.
  • the indication information of the second SID list may also be Path Segment or BSID or the second SID list itself.
  • the present application further provides a fault detection method, which is applied to a second network device.
  • the method may include, for example: the second network device Send a BFD packet including the indication information of the first SID list to the first network device through the first forwarding path of the first SR policy, where the indication information of the first SID list is used to instruct the first network device to determine the destination for sending the BFD packet.
  • the second forwarding path of the response packet, and the second forwarding path and the first forwarding path share the same path in the opposite direction; if the second network device receives the response packet of the BFD packet from the second forwarding path, The response message performs fault detection on the first forwarding path.
  • the transmitting end that is, the second network device detected by BFD carries the indication information of the SID list in the BFD message, so that the receiving end (that is, the first network device) can determine and match the SID list based on the indication information of the SID list.
  • the forwarding path that transmits the BFD packet is reversed to the forwarding path of the common path, and based on the determined forwarding path, a response packet of the BFD packet is sent to the transmitting end, by ensuring that the real forwarding path of the BFD packet and the response packet is reversed
  • Common paths are used to achieve accurate fault detection of specific forwarding paths in the SR policy, and improve the accuracy and accuracy of fault detection for the SR policy by the BFD mechanism.
  • the method may further include: the second network device receives the first network device Indication information of the first SID list sent.
  • the method may further include: the second network device generates the first SID Indicative information for the list.
  • the second network device may also send the indication information of the first SID list to the first network device, which provides a guarantee for the implementation of the fault detection method provided in the embodiment of the present application.
  • the method may further include: the second network device receives the control and management device Indication information of the first SID list sent.
  • the control management device can generate the instruction information of the first SID list and send it to the second network device; in another case, the instruction information of the first SID list can also be generated and sent by the second network device.
  • the control and management device After being sent to the control and management device, the control and management device sends it to the second network device, wherein, as an example, the second network device sends the indication information of the first SID list to the control and management device, which may include: The second network device sends a BGP-LS packet to the control and management device, where the BGP-LS packet carries the indication information of the first SID list through the sub-TLV field; the second network device receives the first SID list sent by the control and management device
  • the indication information may include: the second network device receives the BGP SR policy message sent by the control and management device, and the BGP SR policy message carries the indication information of the SID list through the sub-TLV field.
  • the indication information of the first SID list may be Path Segment or BSID; or, the indication information of the first SID list may also be the first SID list itself.
  • the indication information of the second SID list may also be Path Segment or BSID or the second SID list itself.
  • the present application provides a fault detection apparatus, the apparatus is applied to a first network device, and the apparatus may include: a receiving unit, a determining unit, and a sending unit.
  • the receiving unit is configured to receive the first bidirectional link detection BFD packet sent by the second network device through the first forwarding path of the first segment routing policy SR policy, where the first BFD packet includes the first segment The indication information of the segment identification list SID list;
  • the determining unit is used to determine the second forwarding path according to the indication information of the first SID list, and the second forwarding path and the first forwarding path are reversely shared;
  • the sending unit used to send a first response packet of the first BFD packet to the second network device through the second forwarding path, where the first response packet is used to instruct the second network device to respond to the The first forwarding path is used for fault detection.
  • the apparatus may further include a generating unit.
  • the generating unit is used to generate the indication information of the first SID list before receiving the first BFD message sent by the second network device through the first forwarding path of the first SR policy.
  • the receiving unit is further configured to receive the indication information of the first SID list sent by the second network device.
  • the receiving unit is further configured to receive a message sent by the control and management device, where the message includes indication information of the first SID list.
  • the message further includes indication information of the second SID list, wherein the indication information of the second SID list indicates the first forwarding path, and the indication information of the first SID list indicates the first forwarding path.
  • the above-mentioned message can be, for example, a BGP SR policy message, and the BGP SR policy message carries the indication information of the first SID list through the sub-TLV field.
  • the indication information of the first SID list is used to indicate the SID list corresponding to the second forwarding path.
  • the indication information of the first SID list is used to indicate the SID list corresponding to the first forwarding path
  • the determining unit is specifically configured to: determine the SID list according to the indication information of the first SID list The indication information of the second SID list; and the second forwarding path is determined according to the indication information of the second SID list.
  • the sending unit is further configured to send a second BFD packet to the second network device through the second forwarding path of the second SR policy, the second BFD packet Including the indication information of the third SID list, the indication information of the third SID list is used to instruct the first network device to determine the first forwarding path for sending the second response message of the second BFD message ;
  • the receiving unit is further configured to receive the second response message from the first forwarding path; then, the device further includes a detection unit, the detection unit is configured to respond to the second response message according to the second response message The second forwarding path is used for fault detection.
  • the receiving unit is further configured to receive a third BFD packet sent by the second network device through a third forwarding path of the first SR policy, and the third BFD packet
  • the instruction information of the fourth SID list is included in the text, and the third forwarding path is different from the first forwarding path;
  • the determining unit is also used to determine the fourth forwarding path according to the instruction information of the fourth SID list, The fourth forwarding path and the third forwarding path share a reverse path;
  • the sending unit is further configured to send the third BFD packet to the second network device through the fourth forwarding path.
  • Three response packets where the third response packet is used to instruct the second network device to perform fault detection on the third forwarding path.
  • the indication information of the first SID list may be Path Segment or BSID; or, the indication information of the first SID list may also be the first SID list itself.
  • the indication information of the second SID list may also be Path Segment or BSID or the second SID list itself.
  • the fault detection device provided in the third aspect is used to perform the relevant operations mentioned in the first aspect.
  • the present application further provides a fault detection apparatus, the apparatus is applied to a second network device, and the apparatus may include: a sending unit, a receiving unit, and a detecting unit.
  • the sending unit is configured to send a BFD packet to the first network device through the first forwarding path of the first SR policy, where the BFD packet includes the indication information of the first SID list, the indication information of the first SID list
  • the information is used to instruct the first network device to determine a second forwarding path for sending the response message of the BFD message, and the second forwarding path and the first forwarding path share the same path in the opposite direction; a receiving unit, configured to Receive a response message of the BFD message from the second forwarding path; and a detection unit, configured to perform fault detection on the first forwarding path according to the response message.
  • the receiving unit is further configured to receive the BFD packet sent by the first network device before sending the BFD packet to the first network device through the first forwarding path of the first SR policy Indication information of the first SID list.
  • the receiving unit is further configured to receive the first SID sent by the control and management device before sending the BFD packet to the first network device through the first forwarding path of the first SR policy Indicative information for the list.
  • the receiving unit is specifically configured to: receive a BGP SR policy message sent by the control and management device, where the BGP SR policy message carries the indication information of the SID list through a sub-TLV field.
  • the sending unit is further configured to send the indication information of the first SID list to the control and management device before receiving the indication information of the first SID list sent by the control and management device.
  • the sending unit is specifically configured to: send a BGP-LS message to the control and management device, where the BGP-LS message carries the indication information of the first SID list through the sub-TLV field.
  • the apparatus further includes a generating unit, and the generating unit is configured to generate the indication information of the first SID list. Then, the sending unit is further configured to send the indication information of the SID list to the first network device.
  • the indication information of the first SID list may be Path Segment or BSID; or, the indication information of the first SID list may also be the first SID list itself.
  • the indication information of the second SID list may also be Path Segment or BSID or the second SID list itself.
  • the fault detection device provided in the fourth aspect is used to perform the relevant operations mentioned in the second aspect above.
  • the present application further provides a network device, where the network device includes: a processor configured to enable the network device to implement the method provided in the first aspect or the second aspect.
  • the network device may further include a memory, the memory is coupled to the processor, and when the processor executes the instructions stored in the memory, the network device can be made to implement the method provided in the first aspect or the second aspect.
  • the network device may also include a communication interface for the network device to communicate with other devices, for example, the communication interface may be a transceiver, circuit, bus, module or other type of communication interface.
  • the instructions in the memory in this application may be stored in advance, or may be downloaded from the Internet and then stored when the network device is used. This application does not specifically limit the source of the instructions in the memory.
  • the present application further provides a network system, the network system includes a first network device and a second network device, wherein: the first network device is configured to execute the method provided in the first aspect above ; the second network device, configured to execute the method provided by the second aspect.
  • the present application provides a chip, including a processor and an interface circuit; the interface circuit is used to receive instructions and transmit them to the processor; the processor is used to execute the instructions provided in the first aspect or the second aspect method corresponding to the instruction.
  • the present application provides a computer-readable storage medium, the computer-readable storage medium stores program codes or instructions that, when run on a computer, cause the computer to execute the above first aspect or the second The method provided by the aspect.
  • the present application provides a computer program product, including a computer program, which implements the method provided in the first aspect or the second aspect when the computer program is executed by a processor.
  • FIG. 1 is a schematic structural diagram of a network system in an embodiment of the application.
  • Fig. 2 is the structural representation of a kind of SR policy in the embodiment of the application
  • FIG. 3 is a flowchart of a fault detection method 100 in an embodiment of the present application.
  • 4a is a schematic diagram of the format of a sub-TLV field in a BGP SR policy message in an embodiment of the application;
  • 4b is a schematic diagram of the format of the sub-TLV field in another BGP SR policy message in the embodiment of the application;
  • Fig. 4c is a schematic diagram of a format of the Value field in the sub-TLV field of Fig. 4a or Fig. 4b in the embodiment of the present application;
  • 5a is a schematic diagram of the format of the SID list TLV field in a BGP-LS message in an embodiment of the application;
  • 5b is a schematic diagram of the format of a sub-TLV field in a SID list TLV field in an embodiment of the application;
  • 5c is a schematic diagram of the format of the sub-TLV field in another SID list TLV field in the embodiment of the application;
  • 6a is a schematic diagram of the format of a BFD message c and a response message C in an embodiment of the present application;
  • 6b is a schematic diagram of the format of a BFD message d and a response message D in an embodiment of the present application;
  • 6c is a schematic diagram of the format of a BFD message e and a response message E in an embodiment of the present application;
  • FIG. 7 is a schematic structural diagram of a fault detection apparatus 700 in an embodiment of the present application.
  • FIG. 8 is a schematic structural diagram of a fault detection apparatus 800 in an embodiment of the present application.
  • FIG. 9 is a schematic structural diagram of a network device 900 in an embodiment of the present application.
  • FIG. 10 is a schematic structural diagram of a network device 1000 in an embodiment of the present application.
  • FIG. 11 is a schematic structural diagram of a network system 1100 in an embodiment of the present application.
  • BFD packets are transmitted from the transmitter to the receiver through the SR policy to be detected.
  • the receiver uses IP routing. Determine the path of the response message from the receiver to the transmitter, and send the response message to the transmitter through the path determined by the IP routing method, and the transmitter will perform fault detection on the SR policy based on the response message.
  • the network system shown in FIG. 1 may include a customer edge (CE) device 01, a CE device 02, a provider edge (PE) device 11, a PE device 12, an operator (provider, P) device 21, P device 22, P device 23 and P device 24, wherein PE device 11 is connected to CE device 01, PE device 11 is connected to PE device 12 through P device 21 and P device 22 in turn, and PE device 11
  • the PE device 12 is also connected to the PE device 12 through the P device 23 and the P device 24 in sequence, and the PE device 12 is connected to the CE device 02 .
  • SR policy 1 and SR policy 2 there are SR policy 1 and SR policy 2 between PE device 11 and PE device 12, where PE device 11 is the ingress node of SR policy 1 and SR policy 2, and PE device 12 is the egress of SR policy 1 and SR policy 2 node.
  • both SR policy 1 and SR policy 2 include a forwarding path as an example, and the BFD detection of this forwarding path may also be referred to as BFD detection of the SR policy.
  • SR policy 1 includes P device 21 and P device 22, and SR policy 2 includes P device 23 and P device 24.
  • the operations to be performed may include: S11, PE device 11 sends BFD packet a to PE device 12 through SR policy 1; S12, PE device 12 sends BFD packet a to PE device 12 through IP
  • the routing mode sends the response packet A corresponding to the BFD packet a to the PE device 11 through the P device 24 and the P device 23 in sequence, that is, the IP path 1 passed by the response packet A passes through the PE device 12, P device 24, P device 23 and PE device 11 .
  • the PE device 11 may fail at a preset time.
  • the response message A cannot be received within the specified time period, so the SR policy 1 failure is erroneously determined.
  • the PE device 11 even if the PE device 11 receives the response packet A, for scenarios such as bidirectional detection, since the BFD packet a and the response packet A are not transmitted in the same path, it is possible that the IP path 1 is not faulty. Incorrectly determined that SR policy 1 is normal. In this example, since the network devices traversed by SR policy 1 and IP path 1 are not identical, the current BFD detection result cannot accurately reflect the fault condition of SR policy 1.
  • the operations performed for BFD detection on SR policy 1 and SR policy 1' may include: S21, PE device 11 sends PE device 12 to PE device 12 through SR policy 1 and SR policy 1' respectively. Send the BFD packet a and the BFD packet a'; S22, the PE device 12 sends the response packet A corresponding to the BFD packet a and the BFD packet b to the PE device 11 through the P device 24 and the P device 23 in turn through IP routing.
  • the corresponding response packet A' that is, the IP path 1 through which both the response packet A and the response packet A' pass, is transmitted.
  • the IP path 1 determined based on the IP routing method is the same.
  • an embodiment of the present application provides a fault detection method. If the second network device needs to perform BFD detection on the first forwarding path in the first SR policy to the first network device, the performed operations may include, for example: The second network device sends a first BFD packet to the first network device through the first forwarding path of the first SR policy, where the first BFD packet includes the indication information of the first SID list; when the first network device receives the first BFD packet In the case of the first BFD packet, a second forwarding path that is reversely shared with the first forwarding path can be determined according to the indication information of the first SID list.
  • the device sends a first response packet of the first BFD packet, where the first response packet is used to instruct the second network device to perform fault detection on the first forwarding path.
  • the transmitting end of the BFD detection carries the indication information of the SID list in the BFD message, so that the receiving end can determine the forwarding path that is opposite to the forwarding path for transmitting the BFD message based on the indication information of the SID list, and based on the indication information of the SID list
  • the determined forwarding path sends the response packet of the BFD packet to the transmitting end.
  • the SR policy is a tunnel suitable for SR.
  • the SR policy can include at least one candidate path (candidate path), and each candidate path includes at least one forwarding path.
  • each candidate path includes at least one forwarding path.
  • the valid candidate path includes at least two forwarding paths. If the valid candidate path includes at least two forwarding paths, then, through the weight corresponding to the SID list of each forwarding path, Determine the load sharing ratio of each forwarding path to the traffic, so that the corresponding proportion of traffic is sent through the SID list corresponding to each forwarding path.
  • the SR policy 1 shown in FIG. 1 includes a candidate path 31 and a candidate path 32, wherein the candidate path 31 includes a forwarding path 311 and a forwarding path 312, and the candidate path 32 includes Forwarding path 321 , forwarding path 322 and forwarding path 323 .
  • the preference value corresponding to the candidate path 31 is 7
  • the preference value corresponding to the candidate path 32 is 2
  • the weights corresponding to the forwarding path 311 and the forwarding path 312 are 0.6 and 0.4 respectively
  • the weights corresponding to the forwarding path 321, the forwarding path 322 and the forwarding path 323 are They are 0.3, 0.4 and 0.3 respectively.
  • the SID lists corresponding to the forwarding path 311, the forwarding path 312, the forwarding path 321, the forwarding path 322 and the forwarding path 323 are respectively SID list 1 to SID list 5. Then, for the traffic transmitted through SR policy 1, when SR policy 1 is normal, the traffic will be divided into traffic x and traffic y at a ratio of 6:4, where traffic x passes through the forwarding path in SR policy 1 311 is transmitted, and the traffic y is transmitted through the forwarding path 312 in SR policy 1.
  • the SR policy may be an SR-MPLS policy, corresponding to a multi-protocol label switching (MPLS) network scenario; or, the SR policy may also be an SRv6 policy, corresponding to the internet protocol version 6 (internet protocol version 6). , IPv6).
  • MPLS multi-protocol label switching
  • IPv6 internet protocol version 6
  • the SID list corresponds to the MPLS label stack, and the SID list may include the MPLS label corresponding to at least one network device or link
  • the SID list corresponds to the list of IPv6 addresses, and the SID list in the The IPv6 address corresponding to at least one network device or link may be included.
  • the corresponding SID list will be pushed into the packet header of the traffic.
  • Reverse common path which can include reverse common path of SR policy (for example, when the SR policy includes only one forwarding path) and a certain forwarding path in the SR policy (for example, when the SR policy includes multiple forwarding paths) reverse common path .
  • SR policy reverse shared path it may refer to the reverse order of the network devices and links that pass through in sequence determined according to the two SR policies. For example, in the network system shown in FIG. 1, SR policy 1 sequentially includes PE device 11, a link between PE device 11 and P device 21, and a link between P device 21 and P device 21 and P device 22.
  • P device 22, the link between P device 22 and PE device 12, and PE device 12, and SR policy 3 sequentially includes PE device 12, the link between PE device 12 and P device 22, P device 22, The link between the P device 22 and the P device 21, the P device 21, the link between the P device 21 and the PE device 11, and the PE device 11, thus, determine that SR policy 1 and SR policy 3 are reverse common paths tunnel.
  • SR policy For the forwarding path reverse common path in the SR policy, it can refer to two forwarding paths with opposite SID order included in the SID list corresponding to the forwarding path, and the reverse common path forwarding path can belong to two reverse common paths respectively.
  • SR policy For the forwarding path reverse common path in the SR policy.
  • the forwarding path 41 in the SR policy 1 corresponds to the SID list ⁇ 41021, 41022, 41012>, where , 41021, 41022 and 41012 are the SIDs corresponding to P device 21, P device 22 and PE device 12 in SR policy 1 respectively, and the SID list corresponding to forwarding path 42 is ⁇ 42022, 42021, 42011>, where 42022, 42021 and 42011 are respectively
  • the forwarding path 41 and the forwarding path 42 appear in the opposite order of the network devices determined according to the corresponding SID list, wherein the forwarding path 42 may belong to SR policy 3, which is co-located with SR policy 1 in the reverse direction, thus determines that the forwarding path 41 and the forwarding path 42 are the
  • the order of the SIDs included in the two SID lists corresponding to the forwarding paths of the two reverse common paths is not necessarily in the opposite order.
  • the contents of the SIDs included in the two SID lists may be completely different in nature, while The network devices and links traversed by the forwarding path determined according to the SIDs included in the two SID lists are the same.
  • the SID list of forwarding path 42 in the above example is not ⁇ 41012, 41022, 41021>, but ⁇ 42022, 42021, 42011>, but the order of appearance of network devices indicated by ⁇ 42022, 42021, 42011> is the same as the SID of forwarding path 41
  • the network devices indicated by list appear in reverse order.
  • the SID included in the SID list corresponding to the forwarding path may include the SID corresponding to the network device on the forwarding path.
  • the SID list corresponding to the forwarding path 41 includes: the SID corresponding to the P device 21 and the SID corresponding to the P device 22 or the SID included in the SID list corresponding to the forwarding path may also include the SID corresponding to the link in the forwarding path, for example, the corresponding SID list of the forwarding path 41 includes: PE equipment 11 to The SID corresponding to the link of the P device 21, the SID corresponding to the link from the P device 21 to the P device 22, and the SID corresponding to the link from the P device 22 to the PE device 12; or, the SID list corresponding to the forwarding path includes the The SID may also include both the SID corresponding to the network device on the forwarding path and the SID corresponding to the link on the forwarding path.
  • the SID list corresponding to the forwarding path 41 includes: the link corresponding to the PE device 11 to the P device 21
  • the SID, the SID corresponding to the P device 22, the SID corresponding to the link from the P device 22 to the PE device 12, or the SID list corresponding to the forwarding path 41 includes: the SID and the P device corresponding to the link from the PE device 11 to the P device 21
  • the SID list corresponding to the path can also be other possible situations, such as other possible reasonable types, arrangements or combinations of different types.
  • the types of SIDs included in the SID list corresponding to the two forwarding paths of the reverse common path may be the same or different.
  • the SID list corresponding to the forwarding path 41 includes the SIDs of each network device and each link in the forwarding path 41
  • the SID list corresponding to the forwarding path 42 that is reversely shared with the forwarding path includes The SID of each network device and each link in the forwarding path 42 .
  • the SID list corresponding to the forwarding path 41 may include the SID corresponding to each network device in the forwarding path 41, but not the SID of each link, which is the same as the forwarding path 41.
  • the SID list corresponding to the forwarding path 42 of the reverse common path includes the SIDs of the network devices in the forwarding path 42.
  • the SID list corresponding to the forwarding path 41 includes the SIDs of each link in the forwarding path 41
  • the SID list corresponding to the forwarding path 42 that is reversely shared with the forwarding path includes the SIDs of each network device in the forwarding path 42.
  • the SID list corresponding to the forwarding path 42 includes both the SID corresponding to the network device in the forwarding path 42 and the SID corresponding to the link in the forwarding path 42.
  • the SID list corresponding to the forwarding path 41 is allowed to carry only the SIDs indicating some network devices and/or links on the forwarding path 41, and the SID list corresponding to the forwarding path 42 also only It is used to carry the SID indicating some network devices and/or links on the forwarding path 42, and allows the network devices and/or links indicated in the SID list corresponding to the forwarding path 41 to be different, but according to the two SIDs
  • the list and network topology can still determine the forwarding paths 41 and 42 of the reverse co-channel.
  • the content included in the two SID lists can also be designed in other ways in combination with the application scenario, as long as the reverse common-path forwarding paths in which the two network devices and links appear in the opposite order can be determined according to the two SID lists. .
  • the process of performing BFD detection on the forwarding path 41 in the SR policy 1 may include: S31, the PE device 11 passes the SR policy The forwarding path 41 of 1 sends a BFD packet c to the PE device 12, and the BFD packet c includes the indication information p of the SID list; S32, after the PE device 12 receives the BFD packet c, according to the BFD packet c The indication information of the SID list is determined in the forwarding path 42 that is in the reverse direction with the forwarding path 41; S33, the PE device 12 sends the response message C of the BFD message c to the PE device 11 through the forwarding path 42; S34, if the PE device 11 After receiving the response message C, the forwarding path 41 can be fault detected based on the response message C, for example, it is determined that the forwarding path 41 is normal; S35, if the PE device 11 does not receive the response message within the preset time
  • the forwarding path 41 is faulty. Since the transmission paths of the response packet C and the BFD packet c are reversed and share the same path, the accuracy of the BFD detection result can be guaranteed. In this way, in the BFD detection of the SR policy, it not only ensures that the transmission of the BFD packet and the corresponding response packet can be reversed and shared to achieve accurate fault detection, but also can perform fault detection on any forwarding path in the SR policy. A finer-grained and more accurate BFD detection is achieved.
  • PE devices may be indirectly connected through one or more forwarding devices, wherein the forwarding devices include but are not limited to P devices.
  • the network device in the embodiments of the present application may refer to devices such as routers, switches, repeaters, and firewalls that can bear services.
  • the methods provided by the embodiments of the present application can be applied to a scenario with a bidirectional virtual private network (virtual private network, VPN) connection service, in which a VPN service and a bearer tunnel are deployed between PE devices,
  • VPN virtual private network
  • the tunnel enables BFD detection to implement fast fault detection.
  • the tunnel borne between PE devices may be, for example, SRv6 policy or SR-MPLS policy.
  • the methods provided in the embodiments of the present application may support static BFD detection, dynamic BFD detection, or seamless bidirectional forwarding detection (seamless bidirectional forwarding detection, SBFD) detection, for example.
  • BFD packets can be used to detect the connectivity of paths carrying services.
  • FIG. 3 is a schematic flowchart of a method 100 for fault detection provided by an embodiment of the present application.
  • the method 100 may be applied in a network scenario including a first network device and a second network device.
  • the first network device may be the egress PE device of the SR policy to be detected
  • the second network device may be the ingress PE device of the SR policy.
  • the mode of interaction between the PE device 11 and the PE device 12 when the forwarding path 41 in the SR policy 1 is detected the embodiment of the present application will be described.
  • the device corresponds to the PE device 12 in FIG. 1
  • the second network device corresponds to the PE device 11 .
  • the method 100 may, for example, include the following S101 to S106:
  • the PE device 11 sends a BFD packet c to the PE device 12 through the forwarding path 41 of the SR policy 1, where the BFD packet c includes the indication information of the first SID list.
  • the PE device 12 receives the BFD packet c sent by the PE device 11 through the forwarding path 41 of the SR policy 1.
  • the indication information of the first SID list may be the first SID list itself, for example, the indication information of the first SID list may be the SID list corresponding to the forwarding path 42: ⁇ 42022, 42021, 42011>.
  • the indication information of the first SID list may also be the identification of the first SID list, and the identification of the first SID list may include but is not limited to: the path segment Path Segment corresponding to the first SID list or the binding corresponding to the first SID list.
  • a bonding SID for example, the indication information of the first SID list may be the BSID: 420 that can indicate the ⁇ 42022, 42021, 42011>.
  • the PE device 11 and the PE device 12 may save the indication information of the first SID list, so as to cooperate to implement the method 100.
  • the indication information of the first SID list may be generated by the PE device 11 or the PE device 12.
  • the indication information of the first SID list may be generated by the PE device 11, then the PE device 11 may also send the indication information of the first SID list to the PE device 12, so that the PE device 12 can be based on the first SID list.
  • the indication information of a SID list is that the response message C corresponding to the BFD message c determines the forwarding path that is reversely shared with the forwarding path 41.
  • the indication information of the first SID list may also be generated by the PE device 12, then the PE device 12 may send the indication information of the first SID list to the PE device 11, so that the PE device 11 can In the sent BFD packet c, the indication information of the first SID list is carried to ensure that the BFD detection on the forwarding path 41 is effectively performed.
  • the indication information of the first SID list is the BSID corresponding to the forwarding path 41.
  • Both the PE device 11 and the PE device 12 can obtain the indication information corresponding to the first SID list: BSID 410, so that the PE device 12 can save the mapping relationship between the BSID 410 and the forwarding path 42; alternatively, the PE device 12 can also save the mapping relationship between the BSID 410 and the forwarding path 42.
  • the forwarding path 42 is determined.
  • the BSID 420 may be the indication information of the SID list corresponding to the forwarding path 42, and may be allocated by the PE device 11 or the PE device 12 for the forwarding path 42.
  • the indication information of the first SID list may also be used to indicate the SID list corresponding to the forwarding path 42.
  • the indication information of the first SID list may be generated by the PE device 12, then the PE device 12 may send the indication information of the first SID list to the PE device 11, so that the PE device 11 can send
  • the BFD packet c carries the indication information of the first SID list to ensure that the BFD detection of the forwarding path 41 is carried out effectively.
  • the indication information of the first SID list may also be generated by the PE device 11, then the PE device 11 may also send the indication information of the first SID list to the PE device 12, so that the PE device 12 can Based on the indication information of the first SID list, a forwarding path that is reversely shared with the forwarding path 41 is determined for the response message C corresponding to the BFD message c.
  • the indication information of the first SID list as the Path Segment corresponding to the forwarding path 42 as an example
  • both the PE device 11 and the PE device 12 can obtain the indication information corresponding to the first SID list: Path Segment 420. In this way, the PE device 12 can be based on BFD
  • the indication information of the first SID list in the packet c determines the forwarding path 42.
  • PE11 or PE12 may also generate indication information of the second SID list. If the indication information of the first SID list is used to indicate the SID list corresponding to the forwarding path 41, then the indication information of the second SID list can be used to indicate the SID list corresponding to the forwarding path 42; if the indication information of the first SID list is used to indicate the SID list corresponding to the forwarding path 42 If the SID list corresponding to the forwarding path 42 is indicated, then the indication information of the second SID list can be used to indicate the SID list corresponding to the forwarding path 41.
  • the indication information of the first SID list may be sent by the control and management device to the PE device 11 and the PE device 12.
  • the control and management device may generate the indication information of the first SID list, and send the indication information of the first SID list to the PE device 11 and the PE device 12.
  • the control and management device sends a message 51 to the PE device 11 or the PE device 12, and the message 51 carries the indication information of the first SID list, so that the PE device that receives the indication information of the first SID list from the control and management device, also The indication information of the first SID list can be forwarded to the other end PE device in the SR policy1.
  • the control and management device sends a message 52 to the PE device 11 and the PE device 12, where the message 52 carries the indication information of the first SID list.
  • the PE device 11 or the PE device 12 may also generate indication information of the first SID list, send the indication information of the first SID list to the control and management device, and the control and management device sends the indication information of the first SID list to the PE equipment 11 and PE equipment 12 .
  • the PE device 11 or the PE device 12 sends a message 61 to the control and management device, and the message 61 carries the indication information of the first SID list.
  • the control and management device receives the message 61, it obtains the first SID list from the message 61. and send a message 53 to the PE device 11 and the PE device 12, where the message 53 carries the indication information of the first SID list.
  • the control and management device Before the control and management device receives the message 61, it can also send the relevant information of SR policy 1 and SR policy 3 to PE device 11 and PE device 12, and instruct PE device 11 or PE device 12 to be in the SR policy 1 and SR policy 3
  • the indication information of the corresponding SID list (including the indication information of the above-mentioned first SID list) is allocated to each forwarding path of , and carried in the message 61 and sent to the control management device.
  • message 51, message 52, message 53 or message 61 may also include indication information of the second SID list, wherein the indication information of the second SID list may be used to indicate the forwarding path 41, the first SID list
  • the indication information of the list is used to indicate the forwarding path 42; or, the indication information of the second SID list may also be used to indicate the forwarding path 42, and the indication information of the first SID list indicates the forwarding path 41.
  • the message 51, the message 52, and the message 53 can be, for example, a border gateway protocol segment routing policy (border gateway protocol segment routing policy, BGP SR policy) message, and the BGP SR policy message can pass the extended subtype length value ( The sub type length value, sub-TLV) field carries the indication information of the first SID list.
  • a border gateway protocol segment routing policy border gateway protocol segment routing policy, BGP SR policy
  • BGP SR policy message can pass the extended subtype length value ( The sub type length value, sub-TLV) field carries the indication information of the first SID list.
  • the sub-TLV field used to carry the indication information of the first SID list in the BGP SR policy message may include: a type (Type) field, a length (Length) field, and a reserved (Reserved) field
  • the value of the Type field is used to indicate that the sub-TLV field carries the indication information of the first SID list
  • the value of the Length field is used to indicate the value of the Value field in the sub-TLV field.
  • Length the value of the Value field includes the indication information of the first SID list.
  • the BGP SR policy message also carries the indication information of the second SID list
  • the indication information of the first SID list and the indication information of the second SID list can be carried in the same sub-TLV field
  • the The format of the sub-TLV field is shown in Figure 4b.
  • the Type field, the Length field, the Reserved field, and the Value field it may also include a Flags field. The value of the Flags field is used to indicate the sub-TLV.
  • the quantity of the indication information of the SID list carried in the field and the indication information of the SID list are used to indicate the forwarding path, for example, the value of one bit of the Flags field is used to indicate that the Value field of the sub-TLV field includes the first The indication information of a SID list, the value of another bit of the Flags field is used to indicate that the Value field of the sub-TLV field includes the indication information of the second SID list, and the Value field of the sub-TLV field includes the first The indication information of one SID list and the indication information of the second SID list.
  • the indication information of the first SID list and the indication information of the second SID list can be respectively carried in two sub-TLV fields of the BGP SR policy message, and the format of each sub-TLV field can be referred to 4a , the Value field of the sub-TLV field used to carry the indication information of the first SID list includes the indication information of the first SID list, and the Value field of the sub-TLV field used to carry the indication information of the second SID list includes the first SID list.
  • Two SID list indication information can be respectively carried in two sub-TLV fields of the BGP SR policy message, and the format of each sub-TLV field can be referred to 4a , the Value field of the sub-TLV field used to carry the indication information of the first SID list includes the indication information of the first SID list, and the Value field of the sub-TLV field used to carry the indication information of the second SID list includes the first SID list.
  • the value of the Value field in Figure 4a or Figure 4b is the IPv6 address; if the SR policy is the SR-MPLS policy, then Figure 4a or The value of the Value field in Figure 4b is an MPLS label.
  • the format of the Value field can be seen in Figure 4c, including the Label (Label) field, the Traffic Class (Exp (also called TC)) field, the flag (S) and the Survival Time (TTL) field, wherein the TC field, S and TTL fields are reserved fields and can be set to 0.
  • the message 61 can be, for example, a border gateway protocol link state (border gateway protocol link state, BGP-LS) message, and the BGP-LS message can be carried using the sub-TLV field in the SID list TLV field defined by the BGP-LS protocol. Indication information of the first SID list.
  • the format of the SID list TLV field defined by the BGP-LS protocol in the BGP-LS message is shown in Figure 5a, and the SID list TLV field may include: Type field, Length field, Flags field, Reserved field, message type identifier ( MT ID) field, algorithm (Algorithm) field, Reserved field, weight (Weight) field and at least one sub-TLV field of variable length.
  • the sub-TLV field used to carry the indication information of the first SID list in the BGP-LS packet may include: a Type field, a Length field, and a Value field, where the value of the Type field is Used to indicate that what the sub-TLV field carries is the indication information of the first SID list, the value of the Length field is used to indicate the length of the Value field in the sub-TLV field, and the value of the Value field includes the indication of the first SID list information. If the BGP-LS packet also carries the indication information of the second SID list, then, in one case, the indication information of the first SID list and the indication information of the second SID list can be carried in a sub-TLV field.
  • the format of the TLV field is shown in Figure 5c.
  • the Length field, and the Value field it may also include a Flags field.
  • the value of the Flags field is used to indicate the SID carried in the sub-TLV field.
  • the number of indication information of the list and the indication information of each SID list are used to indicate the forwarding path.
  • the value of the first bit of the Flags field is used to indicate that the Value field of the sub-TLV field includes the first SID list.
  • the value of the second bit of the Flags field is used to indicate that the Value field of the sub-TLV field includes the indication information of the second SID list, and the Value field of the sub-TLV field includes the indication of the first SID list information and indication information of the second SID list.
  • the indication information of the first SID list and the indication information of the second SID list can be respectively carried in two sub-TLV fields of the BGP-LS packet, and the format of each sub-TLV field can refer to 5b , the Value field of the sub-TLV field used to carry the indication information of the first SID list includes the indication information of the first SID list, and the Value field of the sub-TLV field used to carry the indication information of the second SID list includes the first SID list.
  • Two SID list indication information can be respectively carried in two sub-TLV fields of the BGP-LS packet, and the format of each sub-TLV field can refer to 5b , the Value field of the sub-TLV field used to carry the indication information of the first SID list includes the indication information of the first SID list, and the Value field of the sub-TLV field used to carry the indication information of the second SID list includes the first SID list.
  • the SR policy is the SRv6 policy
  • the value of the Value field in Figure 5b or Figure 5c is the IPv6 address
  • the SR policy is the SR-MPLS policy
  • Figure 5b or The value of the Value field in Fig. 5c is an MPLS label, and the format of the Value field can be referred to as shown in Fig. 4c.
  • message 51, message 52, message 53 and message 61 all include the indication information of the first SID list and the indication information of the second SID list
  • the indication information of the first SID list and the indication information of the second SID list in the message 61 can also be carried in a sub-TLV field -TLV field; in another case, if the indication information of the first SID list and the indication information of the second SID list in message 51, message 52 or message 53 are carried in 2 sub-TLV fields, then, The indication information of the first SID list and the indication information of the second SID list in the message 61 may also be carried in two sub-TLV fields.
  • the message 51, the message 52, the message 53 and the message 61 may also be a network configuration protocol (network configuration protocol, NETCONF) or a path computation element communication protocol (path computation element protocol) for carrying the indication information of the first SID list.
  • PCEP path computation element protocol
  • the indication information of the first SID list when the indication information of the first SID list is exchanged between the PE device 11 and the PE device 12, the indication information of the first SID list to be exchanged can be carried in a BGP packet, for example, the BGP packet can be sent through a BGP packet.
  • the TLV field or sub-TLV field in the text carries the indication information of the first SID list.
  • the indication information of the SID list in this embodiment of the present application may be the BSID corresponding to the SID list.
  • the BSID is different from the BSID allocated for the candidate path in the current SR policy.
  • the BSID corresponding to the candidate path is used to indicate the candidate path and cannot identify the path under the candidate path.
  • the specific forwarding path can be called the BSID corresponding to the candidate path is the Path BSID (abbreviation: P-BSID); the BSID corresponding to the forwarding path in this application is used to indicate the specific forwarding path, which can be called the BSID of the SID list level ( Abbreviation: L-BSID).
  • the BSID used to indicate the forwarding path in the context of the embodiments of this application mainly refers to the L-BSID.
  • the above explanation is mainly used to illustrate that the BSID used by the present application to realize the reverse common path detection is at the SID list level, but it does not mean that the contents of the P-BSID and the L-BSID in the same SR policy cannot be the same.
  • the values of P-BSID and L-BSID can be the same.
  • the indication information of the SID list can even be interpreted as the corresponding path of the candidate path.
  • BSID is mainly used to illustrate that the BSID used by the present application to realize the reverse common path detection is at the SID list level, but it does not mean that the contents of the P-BSID and the L-BSID in the same SR policy cannot be the same.
  • the values of P-BSID and L-BSID can be the same.
  • the indication information of the SID list can even be interpreted as the corresponding path of the candidate path.
  • the operations that need to be performed before S101 may include: : S41, the control and management device establishes SR policy 1 and SR policy 2 from PE device 11 to PE device 12, and SR policy 3 and SR policy 4 from PE device 12 to PE device 11;
  • control and management device allocates L-BSIDs to the forwarding paths in each SR policy, for example including:
  • the main SR policy is SR policy 1
  • SR policy 1 includes forwarding path 41, the SID list of forwarding path 41 is ⁇ 41021, 41022, 41012>, and the L-BSID corresponding to forwarding path 41 is 410;
  • the standby SR policy is SR policy 2
  • SR policy 2 includes forwarding path 43, the SID list of forwarding path 43 is ⁇ 43023, 43024, 43012>, and the L-BSID corresponding to forwarding path 43 is 430;
  • the main SR policy is SR policy 3
  • SR policy 3 includes forwarding path 42, the SID list of forwarding path 42 is ⁇ 42022, 42021, 42011>, and the L-BSID corresponding to forwarding path 42 is 420;
  • the standby SR policy is SR policy 4
  • SR policy 4 includes forwarding path 44
  • the SID list of forwarding path 44 is ⁇ 44024, 44023, 44011>
  • the L-BSID corresponding to forwarding path 44 is 440.
  • the control and management device sends the relevant configuration of SR policy 1 and SR policy 2 to the PE device 11, and sends the L-BSID of the forwarding path 42 that is in the reverse direction with the forwarding path 41 in the SR policy 1, and the L-BSID of the forwarding path 42 in the reverse direction with the forwarding path 41 in the SR policy 2.
  • the L-BSID of the forwarding path 44 of the forwarding path 43 reversely shared; the control and management device sends the relevant configuration of SR policy 3 and SR policy 4 to the PE device 12, and sends the reverse shared path with the forwarding path 42 in the SR policy 3.
  • the L-BSID of the forwarding path 41, and the L-BSID of the forwarding path 42 co-located with the forwarding path 44 in the SR policy 4 specifically include:
  • the content sent by the control and management device to the PE device 11 is as follows:
  • the SID list of the forwarding path 41 in the main SR policy 1 is ⁇ 41021, 41022, 41012>, the L-BSID corresponding to the forwarding path 41 is 410, and the L-BSID corresponding to the forwarding path 42 of the reverse common path is 420;
  • the SID list of the forwarding path 43 in the standby SR policy 2 is ⁇ 43023, 43024, 43012>, the L-BSID corresponding to the forwarding path 43 is 430, and the L-BSID corresponding to the forwarding path 44 of the reverse common path is 440;
  • the content sent by the control management device to the PE device 12 is as follows:
  • the SID list of the forwarding path 42 in the main SR policy 3 is ⁇ 42022, 42021, 42011>, the L-BSID corresponding to the forwarding path 42 is 420, and the L-BSID corresponding to the forwarding path 41 of the reverse common path is 410;
  • the SID list of the forwarding path 44 in the standby SR policy 4 is ⁇ 44024, 44023, 44011>, the L-BSID corresponding to the forwarding path 44 is 440, and the L-BSID corresponding to the forwarding path 43 of the reverse common path is 430.
  • the indication information of the first SID list is configured, the indication information of the first SID list is carried in the BFD message c, and the BFD message c is sent to the PE device 12 through the forwarding path 41 in the SR policy 1, and the PE The device 11 initiates fault detection of the forwarding path 41 in the SR policy 1.
  • the method provided in the embodiment of the present application is also applicable to the PE device 11 to perform fault detection on other forwarding paths included in the SR policy 1, and the implementation method is the same as the fault detection method for the forwarding path 41, which is not repeated here.
  • the control and management device in the embodiment of the present application may be any device that can control and manage the devices in the network system, for example, may be a software defined network (software defined network, SDN) controller.
  • SDN software defined network
  • the PE device 12 determines a forwarding path 42 according to the indication information of the first SID list, and the forwarding path 42 and the forwarding path 41 share a reverse path.
  • the indication information of the first SID list is used to instruct the PE device 12 to determine the forwarding path 42 for sending the response message C of the BFD message c, and the forwarding path 42 and the forwarding path 41 share the same path in the opposite direction.
  • the PE device 12 After the PE device 12 receives the BFD packet c sent by the PE device 11 through the forwarding path 41, the PE device 12 obtains the indication information of the first SID list by parsing the BFD packet c, so that the PE device 12 can The indication information of the first SID list determines the forwarding path 42 that is reversely shared with the forwarding path 41. In order to realize that the BFD message c and the response message C can be transmitted through the forwarding path of the reverse shared path, complete accurate fault detection. ready.
  • the PE device 12 can directly determine the forwarding path 42 according to the indication information of the first SID list.
  • S103 may include, for example: the PE device 12 determines the second SID list according to the indication information of the first SID list The indication information; then, the PE device 12 determines the forwarding path 42 according to the indication information of the second SID list. In another case, assuming that the PE device 12 saves the mapping relationship between the indication information of the first SID list and the forwarding path 42, then the PE device 12 in S103 can also directly determine the forwarding according to the indication information of the first SID list Path 42.
  • the PE device 12 sends a response packet C of the BFD packet c to the PE device 11 through the forwarding path 42 , where the response packet C is used to instruct the PE device 11 to perform fault detection on the forwarding path 41 .
  • the PE device 11 may The response message C cannot be received. Then, the PE device 11 does not receive the response packet C through the forwarding path 42 within a preset time (eg, 1 second). Since the forwarding path 41 and the forwarding path 42 share the same path in the opposite direction, it can be determined that the forwarding path 41 is faulty.
  • a preset time eg, 1 second
  • this embodiment of the present application may further include the following S105 to S106 to determine that the forwarding path 41 is fault-free.
  • the PE device 11 receives the response packet C of the BFD packet c from the forwarding path 42 .
  • the PE device 11 performs fault detection on the forwarding path 41 according to the response packet C.
  • S106 may refer to: the PE device 11 determines, according to the received response packet C, that the forwarding path 41 and the forwarding path 42 for transmitting the BFD packet c and the response packet C are normal.
  • the paths 42 are reversely shared, so it is determined that the forwarding path 41 is not faulty.
  • the transmitting end of the BFD detection carries the indication information of the SID list in the BFD message, so that the receiving end can determine the forwarding in the reverse common path with the forwarding path for transmitting the BFD message based on the indication information of the SID list and send the response packet of the BFD packet to the transmitting end based on the determined forwarding path.
  • the specific forwarding path in the SR policy can be accurately identified. Fault detection improves the accuracy and accuracy of fault detection for SR policy by the BFD mechanism.
  • the control and management device can create SR Policy 1 and SR policy 3 of bi-directional co-path, and realize the forward direction of SR Policy 1 and SR policy 3 The association between the forwarding path and the reverse forwarding path, so that the BFD mechanism can realize bidirectional fault detection.
  • the above method 100 only introduces the fault detection of the forwarding path 41 in the SR policy 1 by the PE device 11.
  • the embodiment of the present application may also include the following method 200 to realize the PE device 12 to the forwarding path 42 in the SR policy 3. fault detection, wherein the forwarding path 42 and the forwarding path 41 share the same path in the opposite direction.
  • the method 200 may include, for example:
  • the PE device 12 sends a BFD packet d to the PE device 11 through the forwarding path 42 of the SR policy 3, where the BFD packet d includes the indication information of the third SID list.
  • the PE device 11 receives the BFD packet d sent by the PE device 12 through the forwarding path 42 of the SR policy 3, where the BFD packet d includes the indication information of the third SID list.
  • the PE device 11 determines the forwarding path 41 according to the indication information of the third SID list, and the forwarding path 42 and the forwarding path 41 share a reverse path.
  • the indication information of the third SID list is used to instruct the PE device 11 to determine the forwarding path 41 for sending the response message D of the BFD message d, and the forwarding path 41 and the forwarding path 42 share the same path in the opposite direction.
  • the PE device 11 sends the response packet D of the BFD packet d to the PE device 12 through the forwarding path 41 .
  • the PE device 12 may The response message D cannot be received. Then, since the PE device 12 has not received the response packet D, it can be determined that the forwarding path 42 is faulty.
  • this embodiment of the present application may further include the following S205 to S206:
  • the PE device 12 receives the response packet D from the forwarding path 41 .
  • the PE device 12 performs fault detection on the forwarding path 42 according to the response packet D.
  • the PE device 12 determines, according to the received response packet D, that the forwarding path 42 and the forwarding path 41 for transmitting the BFD packet d and the response packet D are normal, so it is determined that the forwarding path 42 is not faulty.
  • Method 200 may be implemented independently or as a whole with method 100 . If the method 100 and the method 200 are implemented as a whole, the order of implementation of the two is not specifically limited.
  • the SR policy from PE device 11 to PE device 12 is not limited to SR policy 1.
  • SR policy 2 from PE device 11 to PE device 12 can also be constructed as SR
  • the control and management device creates SR policy 1 and SR policy 2, and creates SR policy 3 and SR policy 4 that share the same path with the two.
  • the methods provided in the embodiments perform BFD detection.
  • This embodiment of the present application may further include the following method 300 to implement fault detection on the forwarding paths in other SR policies from the PE device 11 to the PE device 12.
  • the PE device 11 may perform fault detection on the forwarding path 43 in the SR policy 2.
  • the method 300 may include, for example:
  • the PE device 11 sends a BFD packet e to the PE device 12 through the forwarding path 43 of the SR policy 2, where the BFD packet e includes the indication information of the fourth SID list.
  • the PE device 12 receives the BFD message e sent by the PE device 11 through the forwarding path 43 of the SR policy 2, where the BFD message e includes the indication information of the fourth SID list.
  • the PE device 12 determines a forwarding path 44 according to the indication information of the fourth SID list, and the forwarding path 44 and the forwarding path 43 share a reverse path.
  • the indication information of the fourth SID list is used to instruct the PE device 12 to determine the forwarding path 44 for sending the response message E of the BFD message e, and the forwarding path 44 and the forwarding path 43 share the same path in the opposite direction.
  • the PE device 12 sends a response packet E of the BFD packet e to the PE device 11 through the forwarding path 44 .
  • the PE device 11 may The response packet E cannot be received. Then, because the PE device 11 has not received the response packet E, it can determine that the forwarding path 43 is faulty.
  • this embodiment of the present application may further include the following S305 to S306:
  • the PE device 11 receives the response packet E of the BFD packet e from the forwarding path 44 .
  • the PE device 11 performs fault detection on the forwarding path 43 according to the response packet E.
  • the PE device 11 determines that the forwarding path 43 and the forwarding path 44 for transmitting the BFD packet e and the response packet E are both normal, so it is determined that the forwarding path 43 is not faulty.
  • the method 300 may be implemented independently, may be implemented as a whole with the method 100, may be implemented as a whole with the method 200, and may also be implemented as a whole with the method 100 and the method 200. If the method 300 and the method are implemented as a whole, the order of implementation is not specifically limited.
  • the control and management device sends the indication information of the first SID list to the PE device 11 and the PE device 12, and the indication information of the first SID list is the L-BSID as an example. Formats of the BFD message and the response message corresponding to the BFD message are exemplarily described.
  • the BFD packet c may include an MPLS label stack and a payload (payload), wherein the MPLS label stack may include: the SID list corresponding to the forwarding path 41: 41021, 41022 and 41012, and the indication information L-BSID 420 of the first SID list.
  • the response packet C may include an MPLS label stack and payload, wherein the MPLS label stack may include: SID lists corresponding to the forwarding path 42: 42022, 42021, and 42011.
  • the format of the BFD packet d can be seen in Figure 6b.
  • the BFD packet d may include an MPLS label stack and a payload, wherein the MPLS label stack may include: the SID list corresponding to the forwarding path 42: 42022, 42021, and 42011, and the third The indication information L-BSID 410 of the SID list.
  • the response packet C may include the MPLS label stack and the payload, wherein the MPLS label stack may include the SID lists corresponding to the forwarding path 41: 41021, 41022, and 41012.
  • the format of the BFD packet e can refer to Fig. 6c.
  • the BFD packet c may include an MPLS label stack and payload, wherein the MPLS label stack may include: the SID list corresponding to the forwarding path 43: 43023, 43024, and 43012, and the fourth The indication information L-BSID 440 of the SID list.
  • the response packet C may include the MPLS label stack and payload, wherein the MPLS label stack may include: SID lists corresponding to the forwarding path 44: 44024, 44023, and 44011.
  • the payload may include internet protocol (IP), user datagram protocol (user datagram protocol). datagram protocol, UDP) and detection information, wherein the detection information is BFD information.
  • IP internet protocol
  • user datagram protocol user datagram protocol
  • UDP datagram protocol
  • the SID list included in the MPLS label stack in the BFD message and the response message may be the MPLS label corresponding to each hop from the next-hop device to the egress PE device, as shown in Figures 6a to 6c above; or , the SID list included in the MPLS label stack in the BFD message and the response message can also be the SID list obtained by stripping the MPLS label corresponding to the next hop device after determining the next hop at the ingress PE device, for example, in Figure 6a
  • the MPLS label stack of the BFD packet c may include: the SID list corresponding to the forwarding path 41: 41022 and 41012.
  • the SR-MPLS policy scenario is used as an example to illustrate the packet format in the above Figures 6a to 6c.
  • the SID list indication information is carried in the packet.
  • the segment routing header segment routing header, SRH
  • the indication information of the SID list carried in the SRH and the SID list corresponding to the forwarding path can be an IPv6 address.
  • the embodiments of the present application mainly describe the scenario in which SR policy is used as a tunnel implementation technology, the reverse common path detection method can obviously be applied to other possible tunnel implementation technologies that can specify a forwarding path in a certain way.
  • an embodiment of the present application further provides a fault detection method, in which a first network device receives a first detection packet sent by a second network device through a first forwarding path of a first tunnel, and the first detection packet is The message includes indication information of the first forwarding path; the first network device determines a second forwarding path according to the indication information of the first forwarding path, and the second forwarding path and the first forwarding path are reversely shared. path; the first network device sends a first response packet of the first detection packet to the second network device through the second forwarding path, where the first response packet is used to indicate the first response packet of the first detection packet.
  • the second network device detects the first forwarding path.
  • the detection packet may be a detection packet for implementing path fault detection, such as a BFD packet or other fault detection packets, or may be other types of detection packets, such as operation, administration and maintenance (operation, administration and maintenance). maintenance, OAM) messages, etc.
  • the embodiments of the present application provide a fault detection device, which will be described below with reference to the accompanying drawings.
  • FIG. 7 is a schematic structural diagram of a fault detection apparatus 700 according to an embodiment of the present application.
  • the apparatus 700 is applied to a first network device, for example, can perform the function of the PE device 12 in the embodiment shown in FIG. 1 .
  • the apparatus 700 may include: a receiving unit 701 , a determining unit 702 and a sending unit 703 .
  • the receiving unit 701 is configured to receive the first BFD packet sent by the second network device through the first forwarding path of the first SR policy, where the first BFD packet includes an indication of the first segment identifier list SID list information.
  • the specific implementation of the receiving unit 701 receiving the first BFD packet sent by the second network device through the first forwarding path of the first SR policy may refer to the implementation described in FIG. 3 .
  • a determining unit 702 configured to determine a second forwarding path according to the indication information of the first SID list, and the second forwarding path and the first forwarding path share a reverse path.
  • the specific implementation of determining the second forwarding path by the determining unit 702 according to the indication information of the first SID list may refer to S103 in the embodiment described in FIG. 3 .
  • a sending unit 703 configured to send a first response packet of the first BFD packet to the second network device through the second forwarding path, where the first response packet is used to indicate the second network
  • the device performs fault detection on the first forwarding path.
  • the specific implementation of sending the first response packet of the first BFD packet by the sending unit 703 to the second network device through the second forwarding path may be as follows: See S104 in the embodiment described in FIG. 3 .
  • the apparatus 700 may further include a generating unit.
  • the generating unit is used to generate the indication information of the first SID list before receiving the first BFD message sent by the second network device through the first forwarding path of the first SR policy.
  • the receiving unit 701 is further configured to receive the indication information of the first SID list sent by the second network device.
  • the receiving unit 701 is further configured to receive a message sent by the control and management device, where the message includes indication information of the first SID list.
  • the message further includes indication information of the second SID list, wherein the indication information of the second SID list indicates the first forwarding path, and the indication information of the first SID list indicates the first forwarding path.
  • the above-mentioned message can be, for example, a BGP SR policy message, and the BGP SR policy message carries the indication information of the first SID list through the sub-TLV field.
  • the indication information of the first SID list is used to indicate the SID list corresponding to the second forwarding path.
  • the indication information of the first SID list is used to indicate the SID list corresponding to the first forwarding path
  • the determining unit 702 is specifically configured to: determine the SID list according to the indication information of the first SID list.
  • the indication information of the second SID list; and the second forwarding path is determined according to the indication information of the second SID list.
  • the sending unit 703 is further configured to send a second BFD packet to the second network device through the second forwarding path of the second SR policy, and the second BFD packet
  • the text includes the indication information of the third SID list, and the indication information of the third SID list is used to instruct the first network device to determine to send the first forwarding of the second response packet of the second BFD packet path;
  • the receiving unit 701 is further configured to receive the second response message from the first forwarding path; then, the apparatus 700 further includes a detection unit, which is configured to send the second response message according to the second response message. The article performs fault detection on the second forwarding path.
  • the receiving unit 701 is further configured to receive a third BFD packet sent by the second network device through the third forwarding path of the first SR policy, the third BFD packet
  • the message includes the indication information of the fourth SID list, and the third forwarding path is different from the first forwarding path;
  • the determining unit 702 is further configured to determine the fourth forwarding according to the indication information of the fourth SID list path, the fourth forwarding path and the third forwarding path share a reverse path;
  • the sending unit 703 is further configured to send the third BFD report to the second network device through the fourth forwarding path
  • the third response packet is used to instruct the second network device to perform fault detection on the third forwarding path.
  • the indication information of the first SID list may be Path Segment or BSID; or, the indication information of the first SID list may also be the first SID list itself.
  • the indication information of the second SID list may also be Path Segment or BSID or the second SID list itself.
  • an embodiment of the present application further provides a fault detection apparatus 800.
  • the apparatus 800 is applied to a second network device, for example, the function of the PE device 11 in the embodiment shown in FIG. 1 can be performed.
  • the apparatus 800 may include: a sending unit 801 , a receiving unit 802 and a detecting unit 803 .
  • the sending unit 801 is configured to send a BFD packet to the first network device through the first forwarding path of the first SR policy, where the BFD packet includes the indication information of the first SID list, and the information of the first SID list is The indication information is used to instruct the first network device to determine a second forwarding path for sending the response packet of the BFD packet, and the second forwarding path and the first forwarding path share a reverse path.
  • the sending unit 801 sends the BFD packet to the first network device through the first forwarding path of the first SR policy.
  • S101 in the embodiment described in FIG. 3 . .
  • a receiving unit 802 configured to receive a response packet of the BFD packet from the second forwarding path.
  • the detection unit 803 is configured to perform fault detection on the first forwarding path according to the response message.
  • the specific implementation of the detection unit 803 performing fault detection on the first forwarding path according to the response message may refer to S106 in the embodiment shown in FIG. 3 .
  • the receiving unit 802 is further configured to receive all the information sent by the first network device before sending the BFD packet to the first network device through the first forwarding path of the first SR policy. Describe the indication information of the first SID list.
  • the receiving unit 802 is further configured to receive the first sent by the control and management device before sending the BFD packet to the first network device through the first forwarding path of the first SR policy Indicative information of the SID list.
  • the receiving unit 802 is specifically configured to: receive a BGP SR policy message sent by the control and management device, where the BGP SR policy message carries the indication information of the SID list through the sub-TLV field.
  • the sending unit 801 is further configured to send the indication information of the first SID list to the control and management device before receiving the indication information of the first SID list sent by the control and management device.
  • the sending unit 801 is specifically configured to: send a BGP-LS packet to the control and management device, where the BGP-LS packet carries the indication information of the first SID list through the sub-TLV field.
  • the apparatus 800 further includes a generating unit, and the generating unit is configured to generate the indication information of the first SID list. Then, the sending unit 801 is further configured to send the indication information of the SID list to the first network device.
  • the indication information of the first SID list may be Path Segment or BSID; or, the indication information of the first SID list may also be the first SID list itself.
  • the indication information of the second SID list may also be Path Segment or BSID or the second SID list itself.
  • FIG. 9 is a schematic structural diagram of a network device 900 according to an embodiment of the present application.
  • the network device 900 may be any PE device in the embodiment shown in FIG. 1 , or may be the implementation shown in FIG. 7 or FIG. 8 .
  • the network device 900 includes: a processor 910 , a communication interface 920 and a memory 930 .
  • the number of processors 910 in the network device 900 may be one or more, and one processor is taken as an example in FIG. 9 .
  • the processor 910, the communication interface 920, and the memory 930 may be connected through a bus system or other manners, and FIG. 9 takes the connection through the bus system 940 as an example.
  • Processor 910 may be a CPU, NP, or a combination of CPU and NP.
  • the processor 910 may further include hardware chips.
  • the above-mentioned hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD) or a combination thereof.
  • the above-mentioned PLD may be a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), a general-purpose array logic (generic array logic, GAL) or any combination thereof.
  • the processor 910 may perform the related functions of determining the second forwarding path and the like according to the indication information of the first SID list in the above method embodiments.
  • the processor 910 may perform related functions such as performing fault detection on the first forwarding path according to the response message in the foregoing method embodiments.
  • the communication interface 920 is used for receiving and sending messages.
  • the communication interface 920 may include a receiving interface and a sending interface.
  • the receiving interface may be used to receive packets, and the sending interface may be used to send packets.
  • the number of communication interfaces 920 may be one or more.
  • the communication interface 920 may be used to implement the functions of the sending unit 703 shown in FIG. 7 or the receiving unit 802 shown in FIG. 8 .
  • the memory 930 may include volatile memory (English: volatile memory), such as random-access memory (random-access memory, RAM); the memory 930 may also include non-volatile memory (English: non-volatile memory), such as fast Flash memory (English: flash memory), hard disk drive (HDD) or solid-state drive (solid-state drive, SSD); the memory 930 may also include a combination of the above-mentioned types of memory.
  • volatile memory such as random-access memory (random-access memory, RAM
  • non-volatile memory such as fast Flash memory (English: flash memory), hard disk drive (HDD) or solid-state drive (solid-state drive, SSD)
  • the memory 930 may also include a combination of the above-mentioned types of memory.
  • the memory 930 may, for example, store the aforementioned indication information of the first SID list.
  • the memory 930 stores an operating system and programs, executable modules or data structures, or their subsets, or their extended sets, wherein the programs may include various operation instructions for implementing various operations.
  • the operating system may include various system programs for implementing various basic services and handling hardware-based tasks.
  • the processor 910 may read the program in the memory 930 to implement the fault detection method provided by the embodiment of the present application.
  • the memory 930 may store program codes such as program codes for implementing the functions of the determination unit 702 shown in FIG. 7 or the detection unit 803 shown in FIG. 8 .
  • the memory 930 may be a storage device in the network device 900 , or may be a storage device independent of the network device 900 .
  • the bus system 940 may be a peripheral component interconnect (PCI) bus or an extended industry standard architecture (EISA) bus or the like.
  • PCI peripheral component interconnect
  • EISA extended industry standard architecture
  • the bus system 940 can be divided into an address bus, a data bus, a control bus, and the like. For ease of presentation, only one thick line is used in FIG. 9, but it does not mean that there is only one bus or one type of bus.
  • FIG. 10 is a schematic structural diagram of another network device 1000 provided by an embodiment of the present application.
  • the network device 1000 may be configured as any PE device in the foregoing embodiment shown in FIG. 1 , or may be the one shown in FIG. 7 or FIG. 8 .
  • the network device 1000 includes: a main control board 1010 and an interface board 1030 .
  • the main control board 1010 is also called a main processing unit (MPU) or a route processing card (route processor card).
  • the main control board 1010 controls and manages various components in the network device 1000, including route calculation, Equipment maintenance, protocol processing functions.
  • the main control board 1010 includes: a central processing unit 1011 and a memory 1012 .
  • the interface board 1030 is also called a line processing unit (LPU), a line card (line card) or a service board.
  • the interface board 1030 is used to provide various service interfaces and realize data packet forwarding.
  • the service interface includes, but is not limited to, an Ethernet interface, a POS (Packet over SONET/SDH) interface, etc.
  • the Ethernet interface is, for example, a flexible Ethernet service interface (Flexible Ethernet Clients, FlexE Clients).
  • the interface board 1030 includes: a central processing unit 1031 , a network processor 1032 , a forwarding table entry memory 1034 and a physical interface card (ph8sical interface card, PIC) 1033 .
  • the central processing unit 1031 on the interface board 1030 is used to control and manage the interface board 1030 and communicate with the central processing unit 1011 on the main control board 1010 .
  • the network processor 1032 is used to implement packet forwarding processing.
  • the network processor 832 may be in the form of a forwarding chip.
  • the processing of the uplink packet includes: processing of the incoming interface of the packet, and searching of the forwarding table; processing of the downlink packet: searching of the forwarding table, and so on.
  • the physical interface card 1033 is used to realize the interconnection function of the physical layer, the original traffic enters the interface board 1030 through this, and the processed packets are sent from the physical interface card 1033 .
  • the physical interface card 1033 includes at least one physical interface, which is also called a physical port.
  • the physical interface card 1033 may also be referred to as a daughter card, which can be installed on the interface board 1030, and is responsible for converting the optoelectronic signal into a message, and after checking the validity of the message, the message is forwarded to the network processor 1032 for processing.
  • the central processing unit 831 of the interface board 1030 can also perform the functions of the network processor 1032 , such as implementing software forwarding based on a general-purpose CPU, so that the network processor 1032 is not required in the physical interface card 1033 .
  • the network device 1000 includes multiple interface boards, for example, the network device 1000 further includes an interface board 1040 , and the interface board 1040 includes a central processing unit 1041 , a network processor 1042 , a forwarding table entry storage 1044 and a physical interface card 1043 .
  • the network device 1000 further includes a switch fabric board 1020 .
  • the switch fabric unit 1020 may also be referred to as a switch fabric unit (switch fabric unit, SFU).
  • SFU switch fabric unit
  • the switching network board 1020 is used to complete data exchange between the interface boards.
  • the interface board 1030 and the interface board 1040 may communicate through the switch fabric board 820 .
  • the main control board 1010 and the interface board 1030 are coupled.
  • the main control board 1010 , the interface board 1030 , the interface board 1040 , and the switch fabric board 1020 are connected to the system backplane through a system bus to implement intercommunication.
  • an inter-process communication (inter-process communication, IPC) channel is established between the main control board 1010 and the interface board 1030, and the main control board 1010 and the interface board 1030 communicate through the IPC channel.
  • IPC inter-process communication
  • the network device 1000 includes a control plane and a forwarding plane
  • the control plane includes the main control board 1010 and the central processing unit 1031
  • the forwarding plane includes various components that perform forwarding, such as the forwarding entry storage 1034, the physical interface card 1033 and the network processing device 1032.
  • the control plane performs functions such as routers, generating forwarding tables, processing signaling and protocol packets, configuring and maintaining device status, etc.
  • the control plane delivers the generated forwarding tables to the forwarding plane.
  • the network processor 1032 is based on the control plane.
  • the delivered forwarding table forwards the packets received by the physical interface card 1033 by looking up the table.
  • the forwarding table issued by the control plane may be stored in the forwarding table entry storage 1034 .
  • the control plane and forwarding plane may be completely separate and not on the same device.
  • the central processor 1011 may determine the second forwarding path according to the indication information of the first SID list.
  • the network processor 1032 may trigger the physical interface card 1033 to send the first response packet of the first BFD packet to the second network device through the second forwarding path.
  • the network processor 1032 may trigger the physical interface card 1033 to send the BFD packet to the first network device through the first forwarding path of the first SR policy, and send the BFD packet from the second forwarding path Receive a response packet of the BFD packet.
  • the central processing unit 1011 may perform fault detection on the first forwarding path according to the response message.
  • the receiving unit 701, the sending unit 703, etc. in the fault detection apparatus 700 may be equivalent to the physical interface card 1033 or the physical interface card 1043 in the network device 1000; the determining unit 702, etc. in the fault detection apparatus 700 may be equivalent to the network equipment Central processing unit 1011 or central processing unit 1031 in 1000.
  • the sending unit 801, the receiving unit 802, etc. in the fault detection apparatus 800 may be equivalent to the physical interface card 1033 or the physical interface card 1043 in the network device 1000; Central processing unit 1011 or central processing unit 1031.
  • the operations on the interface board 1040 in this embodiment of the present application are the same as the operations on the interface board 1030, and for brevity, details are not repeated here.
  • the network device 1000 in this embodiment may correspond to any node in the foregoing method embodiments, and the main control board 1010 , the interface board 1030 , and/or the interface board 1040 in the network device 1000 may implement the foregoing methods.
  • the functions possessed by any node in the example and/or the various steps performed are not repeated here.
  • main control boards there may be one or more main control boards, and when there are more than one main control board, it may include an active main control board and a backup main control board.
  • a network device may have at least one switching network board, and the switching network board realizes data exchange between multiple interface boards, providing large-capacity data exchange and processing capabilities. Therefore, the data access and processing capabilities of network devices in a distributed architecture are greater than those in a centralized architecture.
  • the form of the network device can also be that there is only one board, that is, there is no switching network board, and the functions of the interface board and the main control board are integrated on this board.
  • the central processing unit on the board can be combined into a central processing unit on this board to perform the functions of the two superimposed, the data exchange and processing capacity of this form of equipment is low (for example, low-end switches or routers and other networks. equipment).
  • the specific architecture used depends on the specific networking deployment scenario.
  • the above nodes may be implemented as virtualized devices.
  • the virtualization device may be a virtual machine (English: Virtual Machine, VM) running a program for sending a message, and the virtual machine is deployed on a hardware device (for example, a physical server).
  • a virtual machine refers to a complete computer system with complete hardware system functions simulated by software and running in a completely isolated environment.
  • Virtual machines can be configured as nodes.
  • each node may be implemented based on a general physical server combined with a Network Functions Virtualization (NFV) technology.
  • NFV Network Functions Virtualization
  • Each node is a virtual host, virtual router or virtual switch.
  • the network system 1100 may include a first network device 1101 and a second network device 1102 .
  • the first network device 1101 may be the PE device 12 shown in FIG. 1 , the fault detection apparatus 700 shown in FIG. 7 , the network device 900 configured as the first network device shown in FIG. 9 , or the device shown in FIG. 10 .
  • the network device 1000 configured as the first network device; the second network device 1102 may be the PE device 11 shown in FIG. 1 , the fault detection apparatus 800 shown in FIG. 8 , and the second network device shown in FIG. 9 and configured as the second network device
  • the network device 900 shown in FIG. 10 or the network device 1000 shown in FIG. 10 is configured as the second network device.
  • An embodiment of the present application also provides a chip, including a processor and an interface circuit, the interface circuit is used to receive instructions and transmit them to the processor; the processor, for example, may be a specific embodiment of the fault detection apparatus 700 shown in FIG. 7 .
  • the implementation form can be used to execute the above method; for another example, it can be a specific implementation form of the fault detection apparatus 800 shown in FIG. 8 , and can be used to execute the above method.
  • the processor is coupled to a memory, and the memory is used to store programs or instructions, and when the programs or instructions are executed by the processor, the chip system enables the method in any of the foregoing method embodiments.
  • the number of processors in the chip system may be one or more.
  • the processor can be implemented by hardware or by software.
  • the processor may be a logic circuit, an integrated circuit, or the like.
  • the processor may be a general-purpose processor implemented by reading software codes stored in memory.
  • the memory may be integrated with the processor, or may be provided separately from the processor, which is not limited in this application.
  • the memory can be a non-transitory processor, such as a read-only memory ROM, which can be integrated with the processor on the same chip, or can be provided on different chips.
  • the setting method of the processor is not particularly limited.
  • the system-on-chip may be a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or a system on chip (SoC), It can also be a central processing unit (CPU), a network processor (NP), a digital signal processing circuit (DSP), or a microcontroller (microcontroller).
  • controller unit, MCU it can also be a programmable logic device (PLD) or other integrated chips.
  • Embodiments of the present application also provide a computer-readable storage medium, including instructions or computer programs, which, when run on a computer, cause the computer to execute the fault detection method provided by the above embodiments.
  • the embodiments of the present application also provide a computer program product including an instruction or a computer program, which, when running on a computer, enables the computer to execute the fault detection method provided by the above embodiments.
  • the disclosed system, apparatus and method may be implemented in other manners.
  • the apparatus embodiments described above are only illustrative.
  • the division of units is only a logical business division. In actual implementation, there may be other division methods.
  • multiple units or components may be combined or integrated. to another system, or some features can be ignored, or not implemented.
  • the shown or discussed mutual coupling or direct coupling or communication connection may be through some interfaces, indirect coupling or communication connection of devices or units, and may be in electrical, mechanical or other forms.
  • Units described as separate components may or may not be physically separated, and components shown as units may or may not be physical units, that is, may be located in one place, or may be distributed to multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution in this embodiment.
  • each service unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically alone, or two or more units may be integrated into one unit.
  • the above-mentioned integrated unit may be implemented in the form of hardware, or may be implemented in the form of a software business unit.
  • the integrated unit if implemented as a software business unit and sold or used as a stand-alone product, may be stored in a computer-readable storage medium.
  • the technical solutions of the present application can be embodied in the form of software products in essence, or the parts that contribute to the prior art, or all or part of the technical solutions, and the computer software products are stored in a storage medium , including several instructions to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods in the various embodiments of the present application.
  • the aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory, ROM), random access memory (Random Access Memory, RAM), magnetic disk or optical disk and other media that can store program codes .
  • the services described in the present invention may be implemented by hardware, software, firmware or any combination thereof.
  • the services may be stored on or transmitted over as one or more instructions or code on a computer-readable medium.
  • Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another.
  • a storage medium can be any available medium that can be accessed by a general purpose or special purpose computer.

Abstract

一种故障检测方法、网络设备及系统，该方法包括：第一网络设备通过SR policy的第一转发路径接收第二网络设备发送的包括SID list的指示信息的BFD报文后，根据SID list的指示信息确定与第一转发路径反向共路的第二转发路径，并通过第二转发路径向第二网络设备发送BFD报文的响应报文，第二网络设备即可根据响应报文对第一转发路径进行故障检测。这样，发射端通过在BFD报文中携带SID list的指示信息，使得接收端能够确定与传输BFD报文的转发路径反向共路的转发路径，并基于所确定的转发路径向发射端发送该BFD报文的响应报文，实现对SR policy中具体转发路径准确的故障检测。

Description

一种故障检测方法、网络设备及系统
本申请要求于2021年01月29日提交中国国家知识产权局、申请号为202110128378.X、申请名称为“一种故障检测方法、网络设备及系统”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及通信技术领域，特别是涉及一种故障检测方法、网络设备及系统。
背景技术
双向链路检测(bidirectional forwarding detection，BFD)，作为一种能够快速进行端到端检测的机制，被广泛的用于进行分段路由策略(segment routing policy，SR policy)的故障检测。
目前，BFD机制进行故障检测的过程包括：发送端通过SR policy向反射端发出BFD报文，并要求反射端向发送端反馈BFD报文的响应报文，从而确定该SR policy是否存在故障。由于SR policy是单向的隧道，BFD报文的响应报文通常通过互联网协议(internet protocol，IP)路由的方式传输，而IP路由方式所确定的响应报文的传输路径(也可以称为IP路径)很可能并不经过SR policy所经过的网络设备，即，BFD报文和该BFD报文的响应报文的传输并不共路，这样，当IP路径上的设备发生故障时，会导致响应报文无法到达发送段，从而使得发送端基于此误判SR policy发生故障，由此降低了针对SR policy的检测结果的准确性。
基于此，亟待提供一种故障检测方法，既利用到BFD机制可以快速完成检测的特点，又能够克服BFD报文与响应报文传输不共路导致BFD检测结果不够准确的问题，实现BFD机制对SR policy更加准确的故障检测。
发明内容
基于此，本申请提供了一种故障检测方法、网络设备及系统，在BFD报文中携带分段标识列表(segment identification list，SID list)的指示信息，使得接收端能够基于该BFD报文中的SID list的指示信息确定与传输BFD报文的转发路径反向共路的转发路径，并基于所确定的转发路径向发射端发送该BFD报文的响应报文，实现对SR policy中具体转发路径的故障检测，从而提高BFD机制对故障检测的精度和准确性。
本申请中，BFD检测例如可以指静态BFD检测、动态BFD检测或无缝双向转发检测(seamless bidirectional forwarding detection，SBFD)检测。
第一方面，本申请提供了一种故障检测方法，该方法应用于第一网络设备。当第二网络设备和第一网络设备之间存在第一SR policy且该第二网络设备需要对第一SR policy中的第一转发路径进行故障检测时，该方法例如可以包括：第一网络设备通过第一SR policy的第一转发路径接收第二网络设备发送的包括第一SID list的指示信息的第一BFD报文，此时，该第一网络设备可以根据第一BFD报文中的第一SID list的指示信息确定与第一转发路径反向共路的第二转发路径，并通过所述第二转发路径向第二网络设备发送所述第一BFD报文的第一响应报文，该第一响应报文用于指示第二网络设备对第一转发路径进行故障检测。这样，通过该方法，BFD检测的发射端(即第二网络设备)在BFD报文中携带 SID list的指示信息，使得接收端(即第一网络设备)能够基于该SID list的指示信息确定与传输BFD报文的转发路径反向共路的转发路径，并基于所确定的转发路径向发射端发送该BFD报文的响应报文，通过确保BFD报文和响应报文的真实转发路径反向共路，实现对SR policy中具体转发路径准确的故障检测，提高了BFD机制对SR policy进行故障检测的精度和准确性。
其中，SR policy可以是SR-MPLS policy，对应于多协议标签转发(multi-protocol label switching，MPLS)网络场景；或者，SR policy也可以是SRv6policy，对应于第六版互联网协议(internet protocol version 6，IPv6)。在SR-MPLS policy场景中，SID list对应MPLS标签栈，该SID list中可以包括至少一个网络设备或链路对应的MPLS标签；在SRv6policy场景中，SID list对应IPv6地址的列表，该SID list中可以包括至少一个网络设备或链路对应的IPv6地址。
对于任意两个SR policy反向共路，可以是指根据两个SR policy确定的两条隧道依次经过的网络设备以及链路的顺序相反。对于任意两个SR policy中的某两条转发路径反向共路，可以是指根据两条转发路径对应的两个SID list确定的该两条转发路径依次经过的网络设备以及链路的顺序相反。如按照现有设计，反向共路的两条转发路径可以分别属于两个SR policy。但可以理解地，在其他可能的实现中，例如将两个端点之间的往返路径定义为属于一个完整的SR policy时，也可以认为该两条转发路径属于同一个SR policy。
在一种可能的实现方式中，在第一网络设备通过第一SR policy的第一转发路径接收第二网络设备发送的第一BFD报文之前，该方法还可以包括：第一网络设备生成第一SID list的指示信息。或者，第一网络设备接收第二网络设备发送的第一SID list的指示信息。这样，第一网络设备上可以保存有该第一SID list的指示信息和第二转发路径的对应关系，为接收到第一BFD报文后根据第一BFD报文中的第一SID list的指示信息确定第二转发路径作好了准备。
在另一种可能的实现方式中，该方法还可以包括：第一网络设备接收控制管理设备发送的消息，该消息中包括第一SID list的指示信息。此外，该消息中还包括第二SID list的指示信息，其中，第二SID list的指示信息指示所述第一转发路径，第一SID list的指示信息指示所述第二转发路径；或者，第二SID list的指示信息指示所述第二转发路径，第一SID list的指示信息指示所述第一转发路径。
作为一个示例，该消息可以为边界网关协议分段路由策略(border gateway protocol segment routing policy，BGP SR policy)报文，该BGP SR policy报文可以通过子类型长度值(sub type length value，sub-TLV)字段携带该第一SID list的指示信息。如果该BGP SR policy报文中还携带第二SID list的指示信息，那么，第一SID list的指示信息和第二SID list的指示信息可以携带在该BGP SR policy报文中的一个sub-TLV字段中，或者，第一SID list的指示信息和第二SID list的指示信息也可以分别携带在该BGP SR policy报文中两个不同的sub-TLV字段中。需要说明的是，用于承载第一SID list的指示信息的消息，除了可以是BGP SR policy报文，也可以是网络配置协议(network configuration protocol，NETCONF)或路径计算单元通信协议(path computation element protocol，PCEP)报文等。
该实现方式中，第一SID list的指示信息也可以是第二网络设备分配并发送给控制管理设备后，再由控制管理设备发送给第一网络设备的。作为一个示例，第二网络设备向控制管理设备发送第一SID list的指示信息，例如可以将第一SID list的指示信息承载于边界网关协议的链路状态(border gateway protocol link state，BGP-LS)报文中，通过该BGP-LS报文中的sub-TLV字段携带该第一SID list的指示信息。如果该BGP-LS报文中还携带第二SID list的指示信息，那么，第一SID list的指示信息和第二SID list的指示信息可以携带在该BGP-LS报文中的一个sub-TLV字段中，或者，第一SID list的指示信息和第二SID list的指示信息也可以分别携带在该BGP-LS报文中两个不同的sub-TLV字段中。需要说明的是，第二网络设备向控制管理设备发送第一SID list的指示信息时用于承载该第一SID list的指示信息的消息，除了可以是BGP-LS报文，也可以是NETCONF或PCEP报文等。
在一种可能的实现方式中，第一SID list的指示信息可以用于指示所述第二转发路径对应的SID list。那么，第一网络设备在接收到第一BFD报文后，可以直接根据该第一SID list的指示信息，确定用于传输第一BFD报文对应的第一响应报文的第二转发路径，使得实现准确的BFD检测成为可能。
在另一种可能的实现方式中，第一SID list的指示信息也可以用于指示所述第一转发路径对应的SID list，一种情况下，第一网络设备上可以保存第一SID list的指示信息和第二转发路径的对应关系，那么，第一网络设备在接收到第一BFD报文后，可以直接根据该第一SID list的指示信息，确定与该第一SID list的指示信息对应的第二转发路径。另一种情况下，第一网络设备上也可以保存第一SID list的指示信息和第二SID list的指示信息的对应关系，第二SID list的指示信息用于指示第二转发路径对应的SID list，那么，第一网络设备根据所述第一SID list的指示信息确定第二转发路径，例如可以包括：第一网络设备根据所述第一SID list的指示信息确定所述第二SID list的指示信息；接着，第一网络设备根据所述第二SID list的指示信息确定所述第二转发路径。如此，使得实现准确的BFD检测成为可能。
需要说明的是，在一些可能的情形中，如果第二转发路径所经过的网络设备或链路存在故障，或者，如果第一转发路径所经过的网络设备或链路存在故障，那么，第二网络设备可能无法接收到该第一响应报文。那么，第二网络设备在预设的时间(如1秒)内通过第二转发路径未接收到第一响应报文，由于第一转发路径和第二转发路径反向共路，所以，仍然可以确定第一转发路径故障。在另一些可能的情形中，如果第一转发路径和第二转发路径所经过的网络设备和链路均正常，那么，第二网络设备能够接收到该第一响应报文。该情形中，第二网络设备根据所接收到的第一响应报文，确定传输第一BFD报文和第一响应报文的第一转发路径以及第二转发路径均正常，也即可以确定第一转发路径不存在故障。
在一些可能的实现方式中，该方法还可以包括：第一网络设备通过第二SR policy的第二转发路径向第二网络设备发送第二BFD报文，该第二BFD报文中包括第三SID list的指示信息，所述第三SID list的指示信息用于指示第一网络设备确定发送第二BFD报文的第二响应报文的第一转发路径；第一网络设备从第一转发路径接收所述第二响应报文；第一网络设备根据所述第二响应报文对所述第二转发路径进行故障检测。如此，通过该方法， 能够实现SR policy中具体转发路径准确的双向BFD检测。
在另一些可能的实现方式中，该方法还可以包括：第一网络设备通过第一SR policy的第三转发路径接收第二网络设备发送的第三BFD报文，第三BFD报文中包括第四SID list的指示信息，第三转发路径和所述第一转发路径不同；第一网络设备根据第四SID list的指示信息确定第四转发路径，第四转发路径和第三转发路径反向共路；第一网络设备通过所述第四转发路径向第二网络设备发送第三BFD报文的第三响应报文，第三响应报文用于指示所述第二网络设备对所述第三转发路径进行故障检测。这样，通过该方法，能够实现对包括多条转发路径的SR policy中的某一具体转发路径的BFD检测，提高了BFD检测的检测精度。本申请实施例中，第一SID list的指示信息可以为路径分段(Path Segment)或绑定分段标识(bonding SID，BSID)；或者，该第一SID list的指示信息也可以是第一SID list本身。同理，第二SID list的指示信息也可以是Path Segment或BSID或者第二SID list本身。
第二方面，本申请还提供了一种故障检测方法，该方法应用于第二网络设备。当第二网络设备和第一网络设备之间存在第一SR policy且该第二网络设备需要对第一SR policy中的第一转发路径进行故障检测时，该方法例如可以包括：第二网络设备通过第一SR policy的第一转发路径向第一网络设备发送包括第一SID list的指示信息的BFD报文，该第一SID list的指示信息用于指示第一网络设备确定发送BFD报文的响应报文的第二转发路径，第二转发路径与第一转发路径反向共路；如果第二网络设备从第二转发路径接收BFD报文的响应报文，则，第二网络设备根据该响应报文对所述第一转发路径进行故障检测。这样，通过该方法，BFD检测的发射端(即第二网络设备)在BFD报文中携带SID list的指示信息，使得接收端(即第一网络设备)能够基于该SID list的指示信息确定与传输BFD报文的转发路径反向共路的转发路径，并基于所确定的转发路径向发射端发送该BFD报文的响应报文，通过确保BFD报文和响应报文的真实转发路径反向共路，实现对SR policy中具体转发路径准确的故障检测，提高了BFD机制对SR policy进行故障检测的精度和准确性。
在一种可能的实现方式中，在第二网络设备通过第一SR policy的第一转发路径向第一网络设备发送BFD报文之前，该方法还可以包括：第二网络设备接收第一网络设备发送的第一SID list的指示信息。
在另一种可能的实现方式中，在第二网络设备通过第一SR policy的第一转发路径向第一网络设备发送BFD报文之前，该方法还可以包括：第二网络设备生成第一SID list的指示信息。该实现方式中，第二网络设备还可以向第一网络设备发送该第一SID list的指示信息，为本申请实施例提供的故障检测方法的实施提供了保障。
在又一种可能的实现方式中，在第二网络设备通过第一SR policy的第一转发路径向第一网络设备发送BFD报文之前，该方法还可以包括：第二网络设备接收控制管理设备发送的第一SID list的指示信息。一种情况下，控制管理设备可以生成该第一SID list的指示信息并发送给第二网络设备；另一种情况下，该第一SID list的指示信息也可以是第二网络设备生成并发送给控制管理设备后，再由控制管理设备发送给第二网络设备的，其中，作为一个示例，所述第二网络设备向控制管理设备发送所述第一SID list的指示信息，可以包括： 第二网络设备向控制管理设备发送BGP-LS报文，该BGP-LS报文通过sub-TLV字段携带所述第一SID list的指示信息；第二网络设备接收控制管理设备发送的第一SID list的指示信息，可以包括：第二网络设备接收控制管理设备发送的BGP SR policy报文，该BGP SR policy报文通过sub-TLV字段携带所述SID list的指示信息。
本申请中，第一SID list的指示信息可以为Path Segment或BSID；或者，该第一SID list的指示信息也可以是第一SID list本身。同理，第二SID list的指示信息也可以是Path Segment或BSID或者第二SID list本身。
第三方面，本申请提供了一种故障检测装置，该装置应用于第一网络设备，该装置可以包括：接收单元、确定单元和发送单元。其中，接收单元，用于通过第一分段路由策略SR policy的第一转发路径接收第二网络设备发送的第一双向链路检测BFD报文，所述第一BFD报文中包括第一分段标识列表SID list的指示信息；确定单元，用于根据所述第一SID list的指示信息确定第二转发路径，所述第二转发路径和所述第一转发路径反向共路；发送单元，用于通过所述第二转发路径向所述第二网络设备发送所述第一BFD报文的第一响应报文，所述第一响应报文用于指示所述第二网络设备对所述第一转发路径进行故障检测。
在一种可能的实现方式中，该装置还可以包括生成单元。其中，该生成单元，用于在通过第一SR policy的第一转发路径接收第二网络设备发送的第一BFD报文之前，生成所述第一SID list的指示信息。
在一种可能的实现方式中，接收单元，还用于接收所述第二网络设备发送的所述第一SID list的指示信息。
在一种可能的实现方式中，接收单元，还用于接收控制管理设备发送的消息，所述消息中包括所述第一SID list的指示信息。作为一个示例，所述消息中还包括第二SID list的指示信息，其中，所述第二SID list的指示信息指示所述第一转发路径，所述第一SID list的指示信息指示所述第二转发路径；或者，所述第二SID list的指示信息指示所述第二转发路径，所述第一SID list的指示信息指示所述第一转发路径。其中，上述消息例如可以为BGP SR policy报文，所述BGP SR policy报文通过sub-TLV字段携带所述第一SID list的指示信息。
作为一个示例，所述第一SID list的指示信息用于指示所述第二转发路径对应的SID list。
作为另一个示例，所述第一SID list的指示信息用于指示所述第一转发路径对应的SID list，所述确定单元，具体用于：根据所述第一SID list的指示信息确定所述第二SID list的指示信息；并根据所述第二SID list的指示信息确定所述第二转发路径。
在一种可能的实现方式中，所述发送单元，还用于通过第二SR policy的所述第二转发路径向所述第二网络设备发送第二BFD报文，所述第二BFD报文中包括第三SID list的指示信息，所述第三SID list的指示信息用于指示所述第一网络设备确定发送所述第二BFD报文的第二响应报文的所述第一转发路径；所述接收单元，还用于从所述第一转发路径接收所述第二响应报文；那么，该装置还包括检测单元，该检测单元，用于根据所述第二响应报文对所述第二转发路径进行故障检测。
在一种可能的实现方式中，所述接收单元，还用于通过所述第一SR policy的第三转发路径接收所述第二网络设备发送的第三BFD报文，所述第三BFD报文中包括第四SID list的指示信息，所述第三转发路径和所述第一转发路径不同；所述确定单元，还用于根据所述第四SID list的指示信息确定第四转发路径，所述第四转发路径和所述第三转发路径反向共路；所述发送单元，还用于通过所述第四转发路径向所述第二网络设备发送所述第三BFD报文的第三响应报文，所述第三响应报文用于指示所述第二网络设备对所述第三转发路径进行故障检测。
其中，第一SID list的指示信息可以为Path Segment或BSID；或者，该第一SID list的指示信息也可以是第一SID list本身。同理，第二SID list的指示信息也可以是Path Segment或BSID或者第二SID list本身。
该第三方面提供的故障检测装置用于执行上述第一方面提及的相关操作，其具体实现方式以及达到的效果，均可以参见上述第一方面的相关描述，在此不再赘述。
第四方面，本申请还提供了一种故障检测装置，该装置应用于第二网络设备，该装置可以包括：发送单元、接收单元和检测单元。其中，发送单元，用于通过第一SR policy的第一转发路径向第一网络设备发送BFD报文，所述BFD报文中包括第一SID list的指示信息，所述第一SID list的指示信息用于指示所述第一网络设备确定发送所述BFD报文的响应报文的第二转发路径，所述第二转发路径与所述第一转发路径反向共路；接收单元，用于从所述第二转发路径接收所述BFD报文的响应报文；检测单元，用于根据所述响应报文对所述第一转发路径进行故障检测。
在一种可能的实现方式中，所述接收单元，还用于在通过第一SR policy的第一转发路径向第一网络设备发送BFD报文之前，接收所述第一网络设备发送的所述第一SID list的指示信息。
在一种可能的实现方式中，所述接收单元，还用于在通过第一SR policy的第一转发路径向第一网络设备发送BFD报文之前，接收控制管理设备发送的所述第一SID list的指示信息。作为一个示例，该接收单元，具体用于：接收所述控制管理设备发送的BGP SR policy报文，所述BGP SR policy报文通过sub-TLV字段携带所述SID list的指示信息。该实现方式中，发送单元，还用于在接收控制管理设备发送的所述第一SID list的指示信息之前，向控制管理设备发送所述第一SID list的指示信息。其中，该发送单元，具体用于：向所述控制管理设备发送BGP-LS报文，所述BGP-LS报文通过sub-TLV字段携带所述第一SID list的指示信息。
在一种可能的实现方式中，所述装置还包括生成单元，该生成单元用于生成所述第一SID list的指示信息。那么，所述发送单元，还用于向所述第一网络设备发送所述SID list的指示信息。
其中，第一SID list的指示信息可以为Path Segment或BSID；或者，该第一SID list的指示信息也可以是第一SID list本身。同理，第二SID list的指示信息也可以是Path Segment或BSID或者第二SID list本身。
该第四方面提供的故障检测装置用于执行上述第二方面提及的相关操作，其具体实现 方式以及达到的效果，均可以参见上述第二方面的相关描述，在此不再赘述。
第五方面，本申请还提供了一种网络设备，所述网络设备包括：处理器，用于使得该网络设备实现上述第一方面或第二方面提供的所述方法。该网络设备还可以包括存储器，存储器与处理器耦合，处理器执行存储器中存储的指令时，可以使得该网络设备实现上述第一方面或第二方面提供的方法。该网络设备还可以包括通信接口，通信接口用于该网络设备与其它设备进行通信，示例性的，通信接口可以是收发器、电路、总线、模块或其它类型的通信接口。本申请中存储器中的指令可以预先存储，也可以使用该网络设备时从互联网下载后存储，本申请对于存储器中指令的来源不进行具体限定。
第六方面，本申请还提供了一种网络系统，所述网络系统包括第一网络设备和第二网络设备，其中：所述第一网络设备，用于执行上述第一方面提供的所述方法；所述第二网络设备，用于执行上述第二方面提供的所述方法。
第七方面，本申请提供了一种芯片，包括处理器和接口电路；接口电路，用于接收指令并传输至处理器；处理器，用于执行如第一方面或第二方面提供的所述方法对应的指令。
第八方面，本申请提供了一种计算机可读存储介质，所述计算机可读存储介质存储有程序代码或指令，当其在计算机上运行时，使得所述计算机执行以上第一方面或第二方面提供的所述方法。
第九方面，本申请提供了一种计算机程序产品，包括计算机程序，所述计算机程序被处理器执行时实现以上第一方面或第二方面提供的所述方法。
附图说明
图1为本申请实施例中一种网络系统的结构示意图；
图2为本申请实施例中一种SR policy的结构示意图；
图3为本申请实施例中一种故障检测方法100的流程图；
图4a为本申请实施例中一种BGP SR policy报文中sub-TLV字段的格式示意图；
图4b为本申请实施例中另一种BGP SR policy报文中sub-TLV字段的格式示意图；
图4c为本申请实施例中图4a或图4b的sub-TLV字段中Value字段的一格式示意图；
图5a为本申请实施例中一种BGP-LS报文中SID list TLV字段的格式示意图；
图5b为本申请实施例中一种SID list TLV字段中sub-TLV字段的格式示意图；
图5c为本申请实施例中另一种SID list TLV字段中sub-TLV字段的格式示意图；
图6a为本申请实施例中一种BFD报文c和响应报文C的格式示意图；
图6b为本申请实施例中一种BFD报文d和响应报文D的格式示意图；
图6c为本申请实施例中一种BFD报文e和响应报文E的格式示意图；
图7为本申请实施例中一种故障检测装置700的结构示意图；
图8为本申请实施例中一种故障检测装置800的结构示意图；
图9为本申请实施例中一种网络设备900的结构示意图；
图10为本申请实施例中一种网络设备1000的结构示意图；
图11为本申请实施例中一种网络系统1100的结构示意图。
具体实施方式
目前，对SR policy进行BFD检测的过程中，BFD报文经过待检测的SR policy从发射端传输到接收端，但是，接收端发送该BFD报文的响应报文时，则通过IP路由的方式确定该响应报文从接收端到发射端的路径，并经过按照IP路由方式所确定的路径向发射端发送该响应报文，由发射端基于该响应报文对SR policy进行故障检测。
举例来说，在图1所示的网络系统中，可以包括用户侧边缘(customer edge，CE)设备01、CE设备02、运营商边缘(provider edge，PE)设备11、PE设备12、运营商(provider，P)设备21、P设备22、P设备23和P设备24，其中，PE设备11连接CE设备01，PE设备11依次通过P设备21、P设备22连接PE设备12，PE设备11也依次通过P设备23、P设备24连接PE设备12，PE设备12连接CE设备02。假设PE设备11和PE设备12之间具有SR policy 1和SR policy 2，其中，PE设备11为SR policy 1和SR policy 2的入口节点，PE设备12为该SR policy 1和SR policy 2的出口节点。为便于描述，以下两个示例以SR policy 1和SR policy 2均包括一条转发路径为例，对该一条转发路径的BFD检测因而也可以称为对SR policy的BFD检测。SR policy 1包括P设备21和P设备22，SR policy 2包括P设备23和P设备24。
作为一个示例，当PE设备11需要对SR policy 1进行BFD检测时，执行的操作可以包括：S11，PE设备11通过SR policy 1向PE设备12发送BFD报文a；S12，PE设备12通过IP路由方式依次经过P设备24和P设备23向PE设备11发送BFD报文a对应的响应报文A，即，该响应报文A所经过的IP路径1依次经过PE设备12、P设备24、P设备23和PE设备11。一方面，如果IP路径1所经过的网络设备或链路故障，例如P设备23故障、P设备24故障或IP路径1中包括的至少一段链路故障，可能导致PE设备11在预设的时间内无法接收到响应报文A，从而错误的确定SR policy 1故障。另一方面，即使PE设备11接收到了响应报文A，对于诸如双向检测的场景，由于BFD报文a和响应报文A传输不共路，也可能在IP路径1不存在故障的情况下，错误的确定SR policy 1正常。在该示例中，由于SR policy 1和IP路径1所经过的网络设备不完全相同，所以，目前的BFD检测结果不能够准确的反映SR policy 1的故障情况。
作为另一个示例，对SR policy 1和SR policy 1’(图中未示出)进行BFD检测执行的操作可以包括：S21，PE设备11分别通过SR policy 1和SR policy 1’分别向PE设备12发送BFD报文a和BFD报文a’；S22，PE设备12通过IP路由方式依次经过P设备24和P设备23向PE设备11发送BFD报文a对应的响应报文A以及BFD报文b对应的响应报文A’，即，响应报文A和响应报文A’均经过的IP路径1进行传输。在该示例中，对于SR policy 1和SR policy 2，基于IP路由方式确定的IP路径1相同。如此，即使SR policy1所经过的设备或链路未出现故障，而SR policy 1’所经过的设备或链路出现故障，由于SR policy 1和SR policy 1’的BFD响应报文的传输路径均为IP路径1，因而，只要IP路径1所包括的设备或链路出现故障，则PE11均会根据未接收到响应报文而确定SR policy 1和SR policy 1’存在故障。由此导致无法实现路径级的细粒度检测。
基于此，本申请实施例提供了一种故障检测方法，如果第二网络设备需要对到第一网 络设备的第一SR policy中的第一转发路径进行BFD检测，则执行的操作例如可以包括：第二网络设备通过第一SR policy的第一转发路径向第一网络设备发送第一BFD报文，该第一BFD报文中包括第一SID list的指示信息；当第一网络设备接收到该第一BFD报文时，能够根据第一SID list的指示信息确定与第一转发路径反向共路的第二转发路径，从而，第一网络设备即可通过该第二转发路径向第二网络设备发送所述第一BFD报文的第一响应报文，该第一响应报文用于指示第二网络设备对第一转发路径进行故障检测。这样，BFD检测的发射端在BFD报文中携带SID list的指示信息，使得接收端能够基于该SID list的指示信息确定与传输BFD报文的转发路径反向共路的转发路径，并基于所确定的转发路径向发射端发送该BFD报文的响应报文，通过确保BFD报文和响应报文的真实转发路径反向共路，实现对SR policy中具体转发路径准确的故障检测，提高了BFD机制对SR policy进行故障检测的精度和准确性。
为便于理解本申请实施例，以下先对本申请实施例涉及的一些概念的含义进行解释。
SR policy是一种适用于SR的隧道，SR policy可以包括至少一条候选路径(candidate path)，每条候选路径包括至少一条转发路径。流量经过SR policy转发时，可以先查看该SR policy的各候选路径的偏好值(preference)，选择偏好值最高的候选路径作为有效候选路径(也可以称为活动候选路径)；接着，如果该有效候选路径中包括一条转发路径，则，通过该条转发路径对应的SID list发送该流量，如果该有效候选路径中包括至少两条转发路径，则，通过每条转发路径的SID list对应的权重，确定每条转发路径对该流量的负载分担比例，从而通过各条转发路径对应的SID list发送对应比例的流量。
以图1所示的SR policy 1为例，假设该SR policy 1如图2所示，包括候选路径31和候选路径32，其中，候选路径31包括转发路径311和转发路径312，候选路径32包括转发路径321、转发路径322和转发路径323。候选路径31对应的偏好值为7，候选路径32对应的偏好值为2，转发路径311和转发路径312对应的权重分别为0.6和0.4，转发路径321、转发路径322和转发路径323对应的权重分别为0.3、0.4和0.3，转发路径311、转发路径312、转发路径321、转发路径322和转发路径323对应的SID list分别为SID list 1～SID list 5。那么，对于经过SR policy 1传输的流量，在SR policy 1正常的情况下，该流量会被以6:4的比例划分为流量x和流量y，其中，流量x经过SR policy 1中的转发路径311传输，流量y经过SR policy 1中的转发路径312传输。
其中，SR policy可以是SR-MPLS policy，对应于多协议标签转发(multi-protocol label switching，MPLS)网络场景；或者，SR policy也可以是SRv6policy，对应于第六版互联网协议(internet protocol version 6，IPv6)。在SR-MPLS policy场景中，SID list对应MPLS标签栈，该SID list中可以包括至少一个网络设备或链路对应的MPLS标签；在SRv6policy场景中，SID list对应IPv6地址的列表，该SID list中可以包括至少一个网络设备或链路对应的IPv6地址。对于需要经过该SR Policy 1传输的流量，对应的SID list将被压入到流量的报文头中。
反向共路，可以包括SR policy反向共路(如SR policy仅包括一条转发路径的情形)以及SR policy中的某条转发路径(如SR policy包括多条转发路径的情形)反向共路。对 于SR policy反向共路，可以是指根据两个SR policy确定的依次经过的网络设备以及链路的顺序相反。例如，在图1所示的网络系统中，SR policy 1依次包括PE设备11、PE设备11和P设备21之间的链路、P设备21、P设备21和P设备22之间的链路、P设备22、P设备22和PE设备12之间的链路、以及PE设备12，而SR policy 3依次包括PE设备12、PE设备12和P设备22之间的链路、P设备22、P设备22和P设备21之间的链路、P设备21、P设备21和PE设备11之间的链路、以及PE设备11，从而，确定SR policy 1和SR policy 3为反向共路的隧道。对于SR policy中的转发路径反向共路，可以是指转发路径对应的SID list中包括的SID顺序相反的两条转发路径，反向共路的转发路径可以分别属于两条反向共路的SR policy。例如，以SID list中包括的SID为网络设备对应的MPLS标签为例，在图1所示的网络系统中，SR policy 1中的转发路径41对应SID list为<41021、41022、41012>，其中，41021、41022和41012分别为SR policy 1内P设备21、P设备22和PE设备12对应的SID，转发路径42对应SID list为<42022、42021、42011>，其中，42022、42021和42011分别为SR policy 3内P设备22、P设备21和PE设备11对应的SID，可见，转发路径41和转发路径42根据对应的SID list确定的网络设备出现的顺序相反，其中，转发路径42可以属于与SR policy 1反向共路的SR policy 3，从而，确定转发路径41和转发路径42为反向共路的转发路径。需要说明的是，两条反向共路的转发路径所对应的两个SID list包括的SID的顺序未必是顺序相反的关系，两个SID list中包括的SID的内容实质上可以完全不同，而是根据两个SID list各自包括的SID而确定的转发路径所经过的网络设备和链路相同。例如，上述示例中转发路径42的SID list并非<41012、41022、41021>，而是<42022、42021、42011>，但<42022、42021、42011>指示的网络设备出现顺序与转发路径41的SID list所指示的网络设备出现顺序是相反的。
需要说明的是，转发路径对应的SID list中包括的SID可以包括该转发路径上的网络设备对应的SID，例如，转发路径41对应SID list中包括：P设备21对应的SID、P设备22对应的SID和PE设备12对应的SID；或者，转发路径对应的SID list中包括的SID也可以包括该转发路径中链路对应的SID，例如，转发路径41对应SID list中包括：PE设备11到P设备21的链路对应的SID、P设备21到P设备22的链路对应的SID、P设备22到PE设备12的链路对应的SID；又或者，转发路径对应的SID list中包括的SID还可以既包括该转发路径上网络设备对应的SID也包括该转发路径上链路对应的SID，又例如，转发路径41对应SID list中包括：PE设备11到P设备21的链路对应的SID、P设备22对应的SID、P设备22到PE设备12的链路对应的SID，或者，转发路径41对应SID list中包括：PE设备11到P设备21的链路对应的SID、P设备21对应的SID、P设备21到P设备22的链路对应的SID、P设备22对应的SID、P设备22到PE设备12的链路对应的SID和PE设备12对应的SID，或者，转发路径对应的SID list也可以是其他可能的情形，如其他可能的合理类型、排列方式或不同类型的组合方式。
反向共路的两条转发路径对应的SID list中所包括的SID的类型可以相同，也可以不同。例如，作为简单的一种实现，转发路径41对应SID list中包括该转发路径41中各网络设备和各链路的SID，与该转发路径反向共路的转发路径42对应的SID list中包括该转发路径 42中该各网络设备和该各链路的SID。再例如，对于各链路开销(cost)值相同的情况，转发路径41对应SID list中可以包括该转发路径41中各网络设备对应的SID，而不包括各链路的SID，与该转发路径反向共路的转发路径42对应的SID list中包括该转发路径42中该各网络设备的SID。再例如，转发路径41对应SID list中包括该转发路径41中各链路的SID，与该转发路径反向共路的转发路径42对应的SID list中包括该转发路径42中各网络设备的SID，或者，转发路径42对应的SID list中既包括该转发路径42中网络设备对应的SID也包括该转发路径42中链路对应的SID。甚至，在一些可能的情形中，也允许转发路径41对应的SID list中只用于携带指示转发路径41上的部分网络设备和/或链路的SID，转发路径42对应的SID list中也只用于携带指示转发路径42上的部分网络设备和/或链路的SID，且允许与转发路径41对应的SID list中指示的网络设备和/或链路有所不同，但根据该两个SID list和网络拓扑仍旧可以确定出反向共路的转发路径41和42。以上仅作为示例，两个SID list包括的内容还可以结合应用场景设计为其他方式，只要根据两个SID list能够确定出两条网络设备和链路出现顺序相反的反向共路转发路径即可。
以上描述涉及路径经过的网络设备和链路相同的两条反向共路转发路径的情形，在其他可能的设定中，也允许结合实际应用场景、组网结构、设备布署等情况，在合理范围内适当放宽反向共路的两条路径所需满足的条件，如将满足一定比例的经过相同网络设备和/或链路作为设定条件，或者将经过某些特定的相同网络设备和/或链路作为设定条件等。这些设定应当是在相应的网络场景下合乎情理的，相较于本申请背景技术提及的完全基于IP转发响应报文的方式，能够对BFD的检测准确度有所提升的。
举例来说，在图1所示的网络系统中，按照本申请实施例提供的故障检测方法，对SR policy 1中的转发路径41进行BFD检测的过程可以包括：S31，PE设备11通过SR policy 1的转发路径41向PE设备12发送BFD报文c，该BFD报文c中包括SID list的指示信息p；S32，PE设备12接收到该BFD报文c后，根据该BFD报文c中的SID list的指示信息确定在与转发路径41反向共路的转发路径42；S33，PE设备12通过转发路径42向PE设备11发送BFD报文c的响应报文C；S34，如果PE设备11接收到该响应报文C，可以基于该响应报文C对转发路径41进行故障检测，例如确定转发路径41正常；S35，如果PE设备11在预设的时间内未接收到该响应报文C，可以确定转发路径41故障，由于响应报文C和BFD报文c的传输路径反向共路，所以，能够保证该BFD检测结果的准确性。如此，在对SR policy的BFD检测中，不仅确保BFD报文和对应的响应报文的传输可以反向共路，达到准确的故障检测，而且能够对SR policy中的任意转发路径进行故障检测，实现了更细粒度和更精确的BFD检测。
在图1所示的网络系统中，PE设备之间可以通过一个或多个转发设备间接连接，其中，转发设备包括但不限于P设备。
需要说明的是，本申请实施例中的网络设备可以指能够承载业务的路由器、交换机、转发器、防火墙等设备。
需要说明的是，本申请各实施例提供的方法，可以应用于有双向虚拟专用网(virtual private network，VPN)连接业务的场景，在该场景下PE设备之间部署VPN业务和承载的 隧道，该隧道启动BFD检测，实现快速故障检测。其中，PE设备之间承载的隧道例如可以是SRv6policy或SR-MPLS policy等类型。
需要说明的是，本申请实施例提供的方法例如可以支持静态BFD检测、动态BFD检测或无缝双向转发检测(seamless bidirectional forwarding detection，SBFD)检测。BFD报文，可以用于对承载业务的路径的连通性进行检测。
为便于理解本申请实施例提供的故障检测方法，下面将结合附图对该方法进行说明。
图3为本申请实施例提供的一种故障检测的方法100的流程示意图。该方法100可以应用于包括第一网络设备和第二网络设备的网络场景中。作为一种示例，第一网络设备可以为待检测的SR policy的出口PE设备，第二网络设备为该SR policy的入口PE设备。为了方便理解，以图1示出的网络系统的结构中，检测SR policy 1中转发路径41时PE设备11和PE设备12之间交互的方式，对本申请实施例进行描述，其中，第一网络设备对应图1中的PE设备12，第二网络设备对应PE设备11。具体实现时，该方法100例如可以包括下述S101～S106：
S101，PE设备11通过SR policy 1的转发路径41向PE设备12发送BFD报文c，所述BFD报文c中包括第一SID list的指示信息。
S102，PE设备12通过SR policy 1的转发路径41接收PE设备11发送的BFD报文c。
第一SID list的指示信息可以是第一SID list本身，例如，第一SID list的指示信息可以是转发路径42对应的SID list：<42022、42021、42011>。或者，第一SID list的指示信息也可以是第一SID list的标识，第一SID list的标识可以包括但不限于：第一SID list对应的路径分段Path Segment或第一SID list对应的绑定分段标识(bonding SID，BSID)，例如，第一SID list的指示信息可以是能够指示该<42022、42021、42011>的BSID：420。
在S101之前，PE设备11和PE设备12上可以保存该第一SID list的指示信息，以便配合实现该方法100。
在一些可能的实现方式中，如果该网络系统中不包括控制管理设备，那么，该第一SID list的指示信息可以是PE设备11或PE设备12生成的。
一种情况下，该第一SID list的指示信息可以是PE设备11生成的，那么，PE设备11还可以将该第一SID list的指示信息发送给PE设备12，以便PE设备12能够基于第一SID list的指示信息为BFD报文c对应的响应报文C确定与转发路径41反向共路的转发路径。另一种情况下，该第一SID list的指示信息也可以是PE设备12生成的，那么，该PE设备12可以将该第一SID list的指示信息发送给PE设备11，以便PE设备11能够在发送的BFD报文c中携带该第一SID list的指示信息，确保对转发路径41的BFD检测有效的进行。
作为一个示例，第一SID list的指示信息为转发路径41对应的BSID。PE设备11和PE设备12均可获得第一SID list对应的指示信息：BSID 410，这样，PE设备12可以保存该BSID 410和转发路径42之间的映射关系；或者，PE设备12也可以保存BSID 410和转发路径42对应的BSID 420之间的映射关系、以及BSID 420和转发路径42之间的映射关系，从而，确保PE设备12能够基于BFD报文c中的第一SID list的指示信息确定转发路径42。其中，BSID 420可以是转发路径42对应的SID list的指示信息，可以是PE设备11 或PE设备12为该转发路径42分配的。
作为另一个示例，第一SID list的指示信息也可以用于指示转发路径42对应的SID list。一种情况下，该第一SID list的指示信息可以是PE设备12生成的，那么，该PE设备12可以将该第一SID list的指示信息发送给PE设备11，以便PE设备11能够在发送的BFD报文c中携带该第一SID list的指示信息，确保对转发路径41的BFD检测有效的进行。另一种情况下，该第一SID list的指示信息也可以是PE设备11生成的，那么，PE设备11还可以将该第一SID list的指示信息发送给PE设备12，以便PE设备12能够基于第一SID list的指示信息为BFD报文c对应的响应报文C确定与转发路径41反向共路的转发路径。以第一SID list的指示信息为转发路径42对应的Path Segment为例，PE设备11和PE设备12均可获得第一SID list对应的指示信息：Path Segment 420，这样，PE设备12能够基于BFD报文c中的第一SID list的指示信息确定转发路径42。
需要说明的是，PE11或PE12还可以生成第二SID list的指示信息。如果第一SID list的指示信息用于指示转发路径41对应的SID list，那么，第二SID list的指示信息可以用于指示转发路径42对应的SID list；如果第一SID list的指示信息用于指示转发路径42对应的SID list，那么，第二SID list的指示信息可以用于指示转发路径41对应的SID list。
在另一些可能的实现方式中，如果该网络系统中包括控制管理设备，那么，该第一SID list的指示信息可以由该控制管理设备发送给PE设备11和PE设备12。
作为一个示例，控制管理设备可以生成第一SID list的指示信息，并将第一SID list的指示信息发送给PE设备11和PE设备12。例如，控制管理设备向PE设备11或PE设备12发送消息51，该消息51中携带第一SID list的指示信息，这样，从控制管理设备接收到第一SID list的指示信息的PE设备，还可以将该第一SID list的指示信息转发给该SR policy1中的另一端PE设备。又例如，控制管理设备向PE设备11和PE设备12发送消息52，该消息52中携带第一SID list的指示信息。
作为另一个示例，PE设备11或PE设备12也可以生成第一SID list的指示信息，将第一SID list的指示信息发送控制管理设备，控制管理设备将该第一SID list的指示信息发送给PE设备11和PE设备12。例如，PE设备11或PE设备12向控制管理设备发送消息61，该消息61中携带第一SID list的指示信息，控制管理设备接收到该消息61后，从该消息61中获得第一SID list的指示信息，并向PE设备11和PE设备12发送消息53，该消息53中携带第一SID list的指示信息。在控制管理设备接收消息61之前，还可以向PE设备11和PE设备12发送SR policy 1和SR policy 3的相关信息，并指示PE设备11或PE设备12为该SR policy 1和SR policy 3中的各转发路径分配对应的SID list的指示信息(包括上述第一SID list的指示信息)，并携带在消息61中发送给控制管理设备。
上述两个示例中，消息51、消息52、消息53或消息61中，还可以包括第二SID list的指示信息，其中，第二SID list的指示信息可以用于指示转发路径41，第一SID list的指示信息用于指示转发路径42；或者，第二SID list的指示信息也可以用于指示转发路径42，第一SID list的指示信息指示转发路径41。
其中，消息51、消息52、消息53例如可以是边界网关协议分段路由策略(border gateway protocol segment routing policy，BGP SR policy)报文，该BGP SR policy报文可以通过扩展的子类型长度值(sub type length value，sub-TLV)字段携带第一SID list的指示信息。如图4a所示，该BGP SR policy报文中用于承载第一SID list的指示信息的sub-TLV字段，可以包括：类型(Type)字段、长度(Length)字段、预留(Reserved)字段和值(Value)字段，其中，Type字段的取值用于指示该sub-TLV字段承载的是第一SID list的指示信息，Length字段的取值用于指示该sub-TLV字段中Value字段的长度，Value字段的取值包括第一SID list的指示信息。如果该BGP SR policy报文还携带第二SID list的指示信息，那么，一种情况下，第一SID list的指示信息和第二SID list的指示信息可以携带在同一个sub-TLV字段，该sub-TLV字段的格式如图4b所示，除了包括：Type字段、Length字段、Reserved字段和Value字段外，还可以包括标志(Flags)字段，该Flags字段的取值用于指示该sub-TLV字段中承载的SID list的指示信息的数量以及SID list的指示信息用于指示的转发路径，如，该Flags字段的一比特位的取值用于指示该sub-TLV字段的Value字段中包括第一SID list的指示信息，该Flags字段的另一比特位的取值用于指示该sub-TLV字段的Value字段中包括第二SID list的指示信息，该sub-TLV字段的Value字段中包括第一SID list的指示信息和第二SID list的指示信息。另一种情况下，第一SID list的指示信息和第二SID list的指示信息可以分别携带在BGP SR policy报文的两个sub-TLV字段，每个sub-TLV字段的格式均可以参见4a，用于承载第一SID list的指示信息的sub-TLV字段的Value字段中包括第一SID list的指示信息，用于承载第二SID list的指示信息的sub-TLV字段的Value字段中包括第二SID list的指示信息。以SID list的指示信息为BSID为例，如果该SR policy为SRv6policy，则，图4a或图4b中Value字段的取值为IPv6地址；如果该SR policy为SR-MPLS policy，则，图4a或图4b中Value字段的取值为MPLS标签，Value字段的格式可以参见图4c所示，包括标签(Label)字段、流量等级(Exp(也称为TC))字段、标志位(S)和存活时间(TTL)字段，其中，TC字段、S和TTL字段为保留字段，可以设置为0。
消息61例如可以是边界网关协议链路状态(border gateway protocol link state，BGP-LS)报文，该BGP-LS报文可以使用BGP-LS协议定义的SID list TLV字段中的sub-TLV字段携带该第一SID list的指示信息。其中，BGP-LS报文中BGP-LS协议定义的SID list TLV字段的格式如图5a所示，该SID list TLV字段可以包括：Type字段、Length字段、Flags字段、Reserved字段、消息类型标识(MT ID)字段、算法(Algorithm)字段、Reserved字段、权重(Weight)字段和可变长度的至少一个sub-TLV字段。如图5b所示，该BGP-LS报文中用于承载第一SID list的指示信息的sub-TLV字段，可以包括：Type字段、Length字段、和值Value字段，其中，Type字段的取值用于指示该sub-TLV字段承载的是第一SID list的指示信息，Length字段的取值用于指示该sub-TLV字段中Value字段的长度，Value字段的取值包括第一SID list的指示信息。如果该BGP-LS报文还携带第二SID list的指示信息，那么，一种情况下，第一SID list的指示信息和第二SID list的指示信息可以携带在一个sub-TLV字段，该sub-TLV字段的格式如图5c所示，除了包括：Type字段、Length字段、和Value字段外，还可以包括标志Flags字段，该Flags字段的取值用于指示该sub-TLV 字段中承载的SID list的指示信息的数量以及各SID list的指示信息用于指示的转发路径，如，该Flags字段的第一位的取值用于指示该sub-TLV字段的Value字段中包括第一SID list的指示信息，该Flags字段的第二位的取值用于指示该sub-TLV字段的Value字段中包括第二SID list的指示信息，该sub-TLV字段的Value字段中包括第一SID list的指示信息和第二SID list的指示信息。另一种情况下，第一SID list的指示信息和第二SID list的指示信息可以分别携带在BGP-LS报文的两个sub-TLV字段，每个sub-TLV字段的格式均可以参见5b，用于承载第一SID list的指示信息的sub-TLV字段的Value字段中包括第一SID list的指示信息，用于承载第二SID list的指示信息的sub-TLV字段的Value字段中包括第二SID list的指示信息。以SID list的指示信息为BSID为例，如果该SR policy为SRv6policy，则，图5b或图5c中Value字段的取值为IPv6地址；如果该SR policy为SR-MPLS policy，则，图5b或图5c中Value字段的取值为MPLS标签，Value字段的格式可以参见图4c所示。
假设消息51、消息52、消息53和消息61中均包括第一SID list的指示信息和第二SID list的指示信息，一种情况下，如果消息51、消息52或消息53中的第一SID list的指示信息和第二SID list的指示信息被携带在一个sub-TLV字段中，则，消息61中的第一SID list的指示信息和第二SID list的指示信息也可以被携带在一个sub-TLV字段中；另一种情况下，如果消息51、消息52或消息53中的第一SID list的指示信息和第二SID list的指示信息被携带在2个sub-TLV字段中，则，消息61中的第一SID list的指示信息和第二SID list的指示信息也可以被携带在2个sub-TLV字段中。
此外，该消息51、消息52、消息53和消息61也可以是用于承载第一SID list的指示信息的网络配置协议(network configuration protocol，NETCONF)或路径计算单元通信协议(path computation element protocol，PCEP)报文，具体实现在本申请实施例中不作赘述。
需要说明的是，PE设备11和PE设备12之间交互第一SID list的指示信息时，可以将待交互的该第一SID list的指示信息承载于BGP报文中，例如，可以通过BGP报文中的TLV字段或sub-TLV字段携带该第一SID list的指示信息。
本申请实施例中SID list的指示信息可以是该SID list对应的BSID，该BSID与目前SR policy中为候选路径分配的BSID不同，候选路径对应的BSID用于指示候选路径而无法标识候选路径下具体的转发路径，可以称为候选路径对应的BSID为Path BSID(简称：P-BSID)；本申请中的转发路径对应的BSID用于指示具体的转发路径，可以称为SID list级的BSID(简称：L-BSID)。本申请实施例中上下文中出现的用于指示转发路径的BSID主要指L-BSID。上述解释主要用于说明本申请为实现反向共路检测所需使用的BSID为SID list级的，但并不是说在同一SR policy中P-BSID和L-BSID的内容不能相同。例如，至少对于SR policy的候选路径中仅包括一个SR list的情形，P-BSID和L-BSID的值是可以相同的，在此情形下，SID list的指示信息甚至也可以解读成候选路径对应的BSID。
举例来说，在控制管理设备向PE设备11和PE设备12发送第一SID list的指示信息，且第一SID list的指示信息为L-BSID的情况下，在S101之前需要执行的操作可以包括：S41，控制管理设备建立PE设备11到PE设备12的SR policy 1和SR policy 2，以及PE 设备12到PE设备11的SR policy 3和SR policy 4；
S42，控制管理设备为各SR policy中的转发路径分配L-BSID，例如包括：
对于PE设备11到PE设备12方向，配置如下：
主SR policy为SR policy 1，SR policy 1包括转发路径41，转发路径41的SID list为<41021,41022,41012>，转发路径41对应的L-BSID为410；
备SR policy为SR policy 2，SR policy 2包括转发路径43，转发路径43的SID list为<43023,43024,43012>，转发路径43对应的L-BSID为430；
对于PE设备12到PE设备11方向，配置如下：
主SR policy为SR policy 3，SR policy 3包括转发路径42，转发路径42的SID list为<42022,42021,42011>，转发路径42对应的L-BSID为420；
备SR policy为SR policy 4，SR policy 4包括转发路径44，转发路径44的SID list为<44024,44023,44011>，转发路径44对应的L-BSID为440。
S43，控制管理设备向PE设备11发送SR policy 1和SR policy 2的相关配置，并且发送与SR policy 1中转发路径41反向共路的转发路径42的L-BSID，以及与SR policy 2中转发路径43反向共路的转发路径44的L-BSID；控制管理设备向PE设备12发送SR policy 3和SR policy 4的相关配置，并且发送与SR policy 3中转发路径42反向共路的转发路径41的L-BSID，以及与SR policy 4中转发路径44反向共路的转发路径42的L-BSID，具体包括：
控制管理设备向PE设备11发送的内容如下：
主SR policy 1中转发路径41的SID list为<41021,41022,41012>，转发路径41对应的L-BSID为410，反向共路的转发路径42对应的L-BSID为420；
备SR policy 2中转发路径43的SID list为<43023,43024,43012>，转发路径43对应的L-BSID为430，反向共路的转发路径44对应的L-BSID为440；
控制管理设备向PE设备12发送的内容如下：
主SR policy 3中转发路径42的SID list为<42022,42021,42011>，转发路径42对应的L-BSID为420，反向共路的转发路径41对应的L-BSID为410；
备SR policy 4中转发路径44的SID list为<44024,44023,44011>，转发路径44对应的L-BSID为440，反向共路的转发路径43对应的L-BSID为430。
如此，配置第一SID list的指示信息，在BFD报文c中携带该第一SID list的指示信息，并将该BFD报文c经过SR policy 1中的转发路径41发送给PE设备12，PE设备11发起对该SR policy 1中转发路径41的故障检测。同理，本申请实施例提供的方法也适用于PE设备11对SR policy 1中包括的其他转发路径进行故障检测，实现方式与对转发路径41的故障检测方式相同，在此不再赘述。
本申请实施例中的控制管理设备，可以是能够对网络系统中的设备进行控制管理的任意设备，例如可以是软件定义网络(software defined network，SDN)控制器。
S103，PE设备12根据所述第一SID list的指示信息确定转发路径42，所述转发路径42和转发路径41反向共路。
其中，该第一SID list的指示信息用于指示PE设备12确定发送BFD报文c的响应报文C的转发路径42，转发路径42与转发路径41反向共路。
具体实现时，PE设备12通过转发路径41接收PE设备11发送的BFD报文c后，PE设备12通过解析该BFD报文c获得第一SID list的指示信息，从而，PE设备12可以基于该第一SID list的指示信息确定与转发路径41反向共路的转发路径42，为实现BFD报文c和响应报文C能够经过反向共路的转发路径传输，完成准确的故障检测做好了准备。
作为一个示例，如果第一SID list的指示信息用于指示转发路径42对应的SID list，那么，S103中PE设备12可以根据该第一SID list的指示信息直接确定转发路径42。
作为另一个示例，如果第一SID list的指示信息用于指示转发路径41对应的SID list，那么，一种情况下，假设PE设备12上保存第一SID list的指示信息和第二SID list的指示信息之间的映射关系，第二SID list的指示信息用于指示转发路径42对应的SID list，则，S103例如可以包括：PE设备12根据该第一SID list的指示信息确定第二SID list的指示信息；接着，PE设备12根据第二SID list的指示信息确定转发路径42。另一种情况下，假设PE设备12上保存第一SID list的指示信息和转发路径42之间的映射关系，则，S103中PE设备12也可以直接根据该第一SID list的指示信息确定转发路径42。
S104，PE设备12通过转发路径42向所PE设备11发送BFD报文c的响应报文C，响应报文C用于指示PE设备11对转发路径41进行故障检测。
在一些可能的情形中，如果S104执行时转发路径42所经过的网络设备或链路存在故障，或者，如果S104之前转发路径41所经过的网络设备或链路存在故障，那么，PE设备11可能无法接收到该响应报文C。那么，PE设备11在预设的时间(如1秒)内通过转发路径42未接收到响应报文C，由于转发路径41和转发路径42反向共路，所以，可以确定转发路径41故障。
在另一些可能的情形中，如果S104执行时转发路径42所经过的网络设备和链路均正常，那么，本申请实施例还可以包括下述S105～S106，以确定转发路径41无故障。
S105，PE设备11从转发路径42接收BFD报文c的响应报文C。
S106，PE设备11根据所述响应报文C对转发路径41进行故障检测。
具体实现时，S106可以是指：PE设备11根据所接收到的响应报文C，确定传输BFD报文c和响应报文C的转发路径41以及转发路径42均正常，由于转发路径41和转发路径42反向共路，所以，确定转发路径41不存在故障。
可见，通过该方法100，BFD检测的发射端在BFD报文中携带SID list的指示信息，使得接收端能够基于该SID list的指示信息确定与传输BFD报文的转发路径反向共路的转发路径，并基于所确定的转发路径向发射端发送该BFD报文的响应报文，通过确保BFD报文和响应报文的真实转发路径反向共路，实现对SR policy中具体转发路径准确的故障检测，提高了BFD机制对SR policy进行故障检测的精度和准确性。
在一些可能的实现方式中，考虑到建立了双向共路的SR policy，例如，控制管理设备能够创建双向共路径的SR Policy 1和SR policy 3，并将SR Policy 1和SR policy 3实现正 向转发路径和反向转发路径的关联，从而，采用该BFD机制能够实现双向的故障检测。上述方法100中仅介绍了PE设备11对SR policy 1中转发路径41的故障检测，同理，本申请实施例还可以包括下述方法200，实现PE设备12对SR policy 3中的转发路径42的故障检测，其中转发路径42与转发路径41反向共路。具体实现时，该方法200例如可以包括：
S201，PE设备12通过SR policy 3的转发路径42向PE设备11发送BFD报文d，该BFD报文d包括第三SID list的指示信息。
S202，PE设备11通过SR policy 3的转发路径42接收PE设备12发送的BFD报文d，该BFD报文d中包括第三SID list的指示信息。
S203，PE设备11根据所述第三SID list的指示信息确定转发路径41，所述转发路径42和转发路径41反向共路。
该第三SID list的指示信息用于指示PE设备11确定发送BFD报文d的响应报文D的转发路径41，转发路径41与转发路径42反向共路。
S204，PE设备11通过转发路径41向PE设备12发送BFD报文d的响应报文D。
在一些可能的情形中，如果S204执行时转发路径41所经过的网络设备或链路存在故障，或者，如果S204之前转发路径42所经过的网络设备或链路存在故障，那么，PE设备12可能无法接收到该响应报文D。那么，PE设备12由于未接收到响应报文D，可以确定转发路径42故障。
在另一些可能的情形中，如果S204执行时转发路径41所经过的网络设备和链路均正常，那么，可选的，本申请实施例还可以包括下述S205～S206：
S205，PE设备12从转发路径41接收响应报文D。
S206，PE设备12根据响应报文D对转发路径42进行故障检测。
PE设备12根据所接收到的响应报文D，确定传输BFD报文d和响应报文D的转发路径42以及转发路径41均正常，所以，确定转发路径42不存在故障。
上述S201～S206的具体实现方式以及达到的效果，可以参见方法100中的相关描述，在此不再赘述。
方法200可以单独实施，也可以和方法100作为一个整体实施。如果方法100和方法200作为一个整体实施，则，不对两者实施的先后顺序进行具体限定。
在一些可能的实现方式中，PE设备11到PE设备12的SR policy不止SR policy 1，例如，为了提高该网络系统的可靠性，还可以构建PE设备11到PE设备12的SR policy 2作为SR policy 1的备隧道，例如，控制管理设备创建SR policy 1和SR policy 2，并且创建与两者反向共路的SR policy 3和SR policy 4，部署完成后对主备SR policy均按照本申请实施例提供的方法进行BFD检测。本申请实施例还可以包括下述方法300，实现对PE设备11到PE设备12的其他SR policy中转发路径的故障检测，例如，PE设备11可以对SR policy 2中转发路径43进行故障检测。具体实现时，该方法300例如可以包括：
S301，PE设备11通过SR policy 2的转发路径43向PE设备12发送BFD报文e，所述BFD报文e中包括第四SID list的指示信息。
S302，PE设备12通过SR policy 2的转发路径43接收PE设备11发送的BFD报文e，该BFD报文e中包括第四SID list的指示信息。
S303，PE设备12根据所述第四SID list的指示信息确定转发路径44，所述转发路径44和转发路径43反向共路。
该第四SID list的指示信息用于指示PE设备12确定发送BFD报文e的响应报文E的转发路径44，转发路径44与转发路径43反向共路。
S304，PE设备12通过转发路径44向所PE设备11发送BFD报文e的响应报文E。
在一些可能的情形中，如果S304执行时转发路径44所经过的网络设备或链路存在故障，或者，如果S304之前转发路径43所经过的网络设备或链路存在故障，那么，PE设备11可能无法接收到该响应报文E。那么，PE设备11由于未接收到响应报文E，可以确定转发路径43故障。
在另一些可能的情形中，如果S304执行时转发路径44所经过的网络设备和链路均正常，那么，可选的，本申请实施例还可以包括下述S305～S306：
S305，PE设备11从转发路径44接收BFD报文e的响应报文E。
S306，PE设备11根据所述响应报文E对转发路径43进行故障检测。
PE设备11根据所接收到的响应报文E，确定传输BFD报文e和响应报文E的转发路径43以及转发路径44均正常，所以，确定转发路径43不存在故障。
上述S301～S306的具体实现方式以及达到的效果，可以参见方法100中的相关描述，在此不再赘述。
方法300可以单独实施，也可以和方法100作为一个整体实施，也可以和方法200作为一个整体实施，还可以和方法100、方法200作为一个整体实施。如果方法300与方法作为一个整体实施，则，不对实施的先后顺序进行具体限定。
下面,以SR-MPLS policy场景下，控制管理设备向PE设备11和PE设备12发送第一SID list的指示信息，且第一SID list的指示信息为L-BSID为例，对上述各方法中BFD报文以及BFD报文对应的响应报文的格式进行示例性说明。
其中，BFD报文c的格式可以参见图6a，该BFD报文c可以包括MPLS标签栈和有效载荷(payload)，其中，MPLS标签栈中可以包括：转发路径41对应的SID list：41021、41022和41012，以及第一SID list的指示信息L-BSID 420。响应报文C中可以包括MPLS标签栈和payload，其中，MPLS标签栈中可以包括：转发路径42对应的SID list：42022、42021和42011。
BFD报文d的格式可以参见图6b，该BFD报文d可以包括MPLS标签栈和payload，其中，MPLS标签栈中可以包括：转发路径42对应的SID list：42022、42021和42011，以及第三SID list的指示信息L-BSID 410。响应报文C中可以包括MPLS标签栈和payload，其中，MPLS标签栈中可以包括转发路径41对应的SID list：41021、41022和41012。
BFD报文e的格式可以参见图6c，该BFD报文c可以包括MPLS标签栈和payload，其中，MPLS标签栈中可以包括：转发路径43对应的SID list：43023、43024和43012，以 及第四SID list的指示信息L-BSID 440。响应报文C中可以包括MPLS标签栈和payload，其中，MPLS标签栈中可以包括：转发路径44对应的SID list：44024、44023和44011。
上述BFD报文c、BFD报文d、BFD报文e、响应报文C、响应报文D和响应报文E中，payload可以包括互联网协议(internet protocol，IP)、用户数据报协议(user datagram protocol，UDP)和检测信息，其中，检测信息为BFD信息。
需要说明的是，BFD报文以及响应报文中MPLS标签栈包括的SID list可以是从下一跳设备到出口PE设备中各跳对应的MPLS标签，如上述图6a～图6c所示；或者，BFD报文以及响应报文中MPLS标签栈包括的SID list也可以是在入口PE设备处确定下一跳之后，剥掉下一跳设备对应MPLS标签后得到的SID list，例如，图6a中的BFD报文c的MPLS标签栈中可以包括：转发路径41对应的SID list：41022和41012。
需要说明的是，上述图6a～图6c中以SR-MPLS policy场景为例进行报文格式说明，如果在SRv6policy场景中，携带SID list的指示信息的即为报文中的分段路由头(segment routing header，SRH)，该SRH中携带的SID list的指示信息以及转发路径对应的SID list可以为IPv6地址。此外，虽然本申请实施例主要描述了SR policy作为隧道实现技术的场景，但该反向共路检测方法可以显然地应用到其他可能的可以通过某种方式指定转发路径的隧道实现技术中。因而，本申请实施例还提供一种故障检测方法，在该方法中，第一网络设备通过第一隧道的第一转发路径接收第二网络设备发送的第一检测报文，所述第一检测报文中包括第一转发路径的指示信息；所述第一网络设备根据所述第一转发路径的指示信息确定第二转发路径，所述第二转发路径和所述第一转发路径反向共路；所述第一网络设备通过所述第二转发路径向所述第二网络设备发送所述第一检测报文的第一响应报文，所述第一响应报文用于指示所述第二网络设备对所述第一转发路径进行检测。所述检测报文可以是用于实现路径故障检测的检测报文，如BFD报文或其他故障检测报文，也可以是其他类型的检测报文，如操作、管理和维护(operation,administration and maintenance，OAM)报文等。
基于上述方法实施例，本申请实施例提供了一种故障检测装置，下面将结合附图对该装置进行说明。
图7为本申请实施例提供的一种故障检测装置700的结构示意图，该装置700应用于第一网络设备，例如可以执行图1所示实施例中PE设备12的功能。该装置700可以包括：接收单元701、确定单元702和发送单元703。
其中，接收单元701，用于通过第一SR policy的第一转发路径接收第二网络设备发送的第一BFD报文，所述第一BFD报文中包括第一分段标识列表SID list的指示信息。
当装置700应用于图1所示的PE设备12时，接收单元701通过第一SR policy的第一转发路径接收第二网络设备发送的第一BFD报文的具体实现可以参见图3所述实施例中S101和S102。
确定单元702，用于根据所述第一SID list的指示信息确定第二转发路径，所述第二转发路径和所述第一转发路径反向共路。
当装置700应用于图1所示的PE设备12时，确定单元702据所述第一SID list的指示信息确定第二转发路径的具体实现可以参见图3所述实施例中S103。
发送单元703，用于通过所述第二转发路径向所述第二网络设备发送所述第一BFD报文的第一响应报文，所述第一响应报文用于指示所述第二网络设备对所述第一转发路径进行故障检测。
当装置700应用于图1所示的PE设备12时，发送单元703通过所述第二转发路径向所述第二网络设备发送所述第一BFD报文的第一响应报文的具体实现可以参见图3所述实施例中S104。
在一种可能的实现方式中，该装置700还可以包括生成单元。其中，该生成单元，用于在通过第一SR policy的第一转发路径接收第二网络设备发送的第一BFD报文之前，生成所述第一SID list的指示信息。
在一种可能的实现方式中，接收单元701，还用于接收所述第二网络设备发送的所述第一SID list的指示信息。
在一种可能的实现方式中，接收单元701，还用于接收控制管理设备发送的消息，所述消息中包括所述第一SID list的指示信息。作为一个示例，所述消息中还包括第二SID list的指示信息，其中，所述第二SID list的指示信息指示所述第一转发路径，所述第一SID list的指示信息指示所述第二转发路径；或者，所述第二SID list的指示信息指示所述第二转发路径，所述第一SID list的指示信息指示所述第一转发路径。其中，上述消息例如可以为BGP SR policy报文，所述BGP SR policy报文通过sub-TLV字段携带所述第一SID list的指示信息。
作为一个示例，所述第一SID list的指示信息用于指示所述第二转发路径对应的SID list。
作为另一个示例，所述第一SID list的指示信息用于指示所述第一转发路径对应的SID list，所述确定单元702，具体用于：根据所述第一SID list的指示信息确定所述第二SID list的指示信息；并根据所述第二SID list的指示信息确定所述第二转发路径。
在一种可能的实现方式中，所述发送单元703，还用于通过第二SR policy的所述第二转发路径向所述第二网络设备发送第二BFD报文，所述第二BFD报文中包括第三SID list的指示信息，所述第三SID list的指示信息用于指示所述第一网络设备确定发送所述第二BFD报文的第二响应报文的所述第一转发路径；所述接收单元701，还用于从所述第一转发路径接收所述第二响应报文；那么，该装置700还包括检测单元，该检测单元，用于根据所述第二响应报文对所述第二转发路径进行故障检测。
在一种可能的实现方式中，所述接收单元701，还用于通过所述第一SR policy的第三转发路径接收所述第二网络设备发送的第三BFD报文，所述第三BFD报文中包括第四SID list的指示信息，所述第三转发路径和所述第一转发路径不同；所述确定单元702，还用于根据所述第四SID list的指示信息确定第四转发路径，所述第四转发路径和所述第三转发路径反向共路；所述发送单元703，还用于通过所述第四转发路径向所述第二网络设备发送所述第三BFD报文的第三响应报文，所述第三响应报文用于指示所述第二网络设备对所述 第三转发路径进行故障检测。
其中，第一SID list的指示信息可以为Path Segment或BSID；或者，该第一SID list的指示信息也可以是第一SID list本身。同理，第二SID list的指示信息也可以是Path Segment或BSID或者第二SID list本身。
关于故障检测装置700具体可执行的功能和实现，可以参见图3所示实施例中关于PE设备12的相应描述，此处不再赘述。
此外，本申请实施例还提供了一种故障检测装置800，如图8所示，该装置800应用于第二网络设备，例如可以执行图1所示实施例中PE设备11的功能。该装置800可以包括：发送单元801、接收单元802和检测单元803。
其中，发送单元801，用于通过第一SR policy的第一转发路径向第一网络设备发送BFD报文，所述BFD报文中包括第一SID list的指示信息，所述第一SID list的指示信息用于指示所述第一网络设备确定发送所述BFD报文的响应报文的第二转发路径，所述第二转发路径与所述第一转发路径反向共路。
当装置800应用于图1所示的PE设备11时，发送单元801通过第一SR policy的第一转发路径向第一网络设备发送BFD报文的具体实现可以参见图3所述实施例中S101。
接收单元802，用于从所述第二转发路径接收所述BFD报文的响应报文。
当装置800应用于图1所示的PE设备11时，接收单元802从所述第二转发路径接收所述BFD报文的响应报文的具体实现可以参见图3所述实施例中S104和S105。
检测单元803，用于根据所述响应报文对所述第一转发路径进行故障检测。
当装置800应用于图1所示的PE设备11时，检测单元803根据所述响应报文对所述第一转发路径进行故障检测的具体实现可以参见图3所述实施例中S106。
在一种可能的实现方式中，所述接收单元802，还用于在通过第一SR policy的第一转发路径向第一网络设备发送BFD报文之前，接收所述第一网络设备发送的所述第一SID list的指示信息。
在一种可能的实现方式中，所述接收单元802，还用于在通过第一SR policy的第一转发路径向第一网络设备发送BFD报文之前，接收控制管理设备发送的所述第一SID list的指示信息。作为一个示例，该接收单元802，具体用于：接收所述控制管理设备发送的BGP SR policy报文，所述BGP SR policy报文通过sub-TLV字段携带所述SID list的指示信息。该实现方式中，发送单元801，还用于在接收控制管理设备发送的所述第一SID list的指示信息之前，向控制管理设备发送所述第一SID list的指示信息。其中，该发送单元801，具体用于：向所述控制管理设备发送BGP-LS报文，所述BGP-LS报文通过sub-TLV字段携带所述第一SID list的指示信息。
在一种可能的实现方式中，所述装置800还包括生成单元，该生成单元用于生成所述第一SID list的指示信息。那么，所述发送单元801，还用于向所述第一网络设备发送所述SID list的指示信息。
其中，第一SID list的指示信息可以为Path Segment或BSID；或者，该第一SID list的指示信息也可以是第一SID list本身。同理，第二SID list的指示信息也可以是Path  Segment或BSID或者第二SID list本身。
关于故障检测装置800具体可执行的功能和实现，可以参见图3所示实施例中关于PE设备11的相应描述，此处不再赘述。
图9为本申请实施例提供的一种网络设备900的结构示意图，该网络设备900例如可以是图1所示实施例中的任意一个PE设备，或者也可以是图7或图8所示实施例中的故障检测装置的设备实现。
请参阅图9所示，网络设备900包括：处理器910、通信接口920和存储器930。其中网络设备900中的处理器910的数量可以一个或多个，图9中以一个处理器为例。本申请实施例中，处理器910、通信接口920和存储器930可通过总线系统或其它方式连接，其中，图9中以通过总线系统940连接为例。
处理器910可以是CPU、NP、或者CPU和NP的组合。处理器910还可以进一步包括硬件芯片。上述硬件芯片可以是专用集成电路(application-specific integrated circuit，ASIC)，可编程逻辑器件(programmable logic device，PLD)或其组合。上述PLD可以是复杂可编程逻辑器件(complex programmable logic device，CPLD)，现场可编程逻辑门阵列(field-programmable gate array，FPGA)，通用阵列逻辑(generic array logic,GAL)或其任意组合。
当网络设备900包括第一网络设备时，处理器910可以执行上述方法实施例中根据所述第一SID list的指示信息确定第二转发路径等的相关功能。当网络设备900为第二网络设备时，处理器910可以执行上述方法实施例中根据所述响应报文对所述第一转发路径进行故障检测等的相关功能。
通信接口920用于接收和发送报文，具体地，通信接口920可以包括接收接口和发送接口。其中，接收接口可以用于接收报文，发送接口可以用于发送报文。通信接口920的个数可以为一个或多个。作为一种可能的实现，通信接口920可以用于实现图7示出的发送单元703或图8示出的接收单元802的功能。
存储器930可以包括易失性存储器(英文：volatile memory)，例如随机存取存储器(random-access memory，RAM)；存储器930也可以包括非易失性存储器(英文：non-volatile memory)，例如快闪存储器(英文：flash memory)，硬盘(hard disk drive，HDD)或固态硬盘(solid-state drive，SSD)；存储器930还可以包括上述种类的存储器的组合。存储器930例如可以存储前文提及的第一SID list的指示信息。
可选地，存储器930存储有操作系统和程序、可执行模块或者数据结构，或者它们的子集，或者它们的扩展集，其中，程序可包括各种操作指令，用于实现各种操作。操作系统可包括各种系统程序，用于实现各种基础业务以及处理基于硬件的任务。处理器910可以读取存储器930中的程序，实现本申请实施例提供的故障检测的方法。作为一种可能的实现，存储器930中可以存储诸如用于实现图7示出的确定单元702或图8示出的检测单元803功能的程序代码。
其中，存储器930可以为网络设备900中的存储器件，也可以为独立于网络设备900的存储装置。
总线系统940可以是外设部件互连标准(peripheral component interconnect，PCI)总线或扩展工业标准结构(extended industry standard architecture，EISA)总线等。总线系统940可以分为地址总线、数据总线、控制总线等。为便于表示，图9中仅用一条粗线表示，但并不表示仅有一根总线或一种类型的总线。
图10是本申请实施例提供的另一种网络设备1000的结构示意图，网络设备1000可以配置为前述图1所示实施例中的任意一个PE设备，或者也可以是图7或图8所示实施例中的故障检测装置的设备实现。
网络设备1000包括：主控板1010和接口板1030。
主控板1010也称为主处理单元(main processing unit，MPU)或路由处理卡(route processor card)，主控板1010对网络设备1000中各个组件的控制和管理，包括路由计算、设备管理、设备维护、协议处理功能。主控板1010包括：中央处理器1011和存储器1012。
接口板1030也称为线路接口单元卡(line processing unit，LPU)、线卡(line card)或业务板。接口板1030用于提供各种业务接口并实现数据包的转发。业务接口包括而不限于以太网接口、POS(Packet over SONET/SDH)接口等，以太网接口例如是灵活以太网业务接口(Flexible Ethernet Clients，FlexE Clients)。接口板1030包括：中央处理器1031、网络处理器1032、转发表项存储器1034和物理接口卡(ph8sical interface card，PIC)1033。
接口板1030上的中央处理器1031用于对接口板1030进行控制管理并与主控板1010上的中央处理器1011进行通信。
网络处理器1032用于实现报文的转发处理。网络处理器832的形态可以是转发芯片。具体而言，上行报文的处理包括：报文入接口的处理，转发表查找；下行报文的处理：转发表查找等等。
物理接口卡1033用于实现物理层的对接功能，原始的流量由此进入接口板1030，以及处理后的报文从该物理接口卡1033发出。物理接口卡1033包括至少一个物理接口，物理接口也称物理口。物理接口卡1033也可称为子卡，可安装在接口板1030上，负责将光电信号转换为报文并对报文进行合法性检查后转发给网络处理器1032处理。在一些实施例中，接口板1030的中央处理器831也可执行网络处理器1032的功能，比如基于通用CPU实现软件转发，从而物理接口卡1033中不需要网络处理器1032。
可选地，网络设备1000包括多个接口板，例如网络设备1000还包括接口板1040，接口板1040包括：中央处理器1041、网络处理器1042、转发表项存储器1044和物理接口卡1043。
可选地，网络设备1000还包括交换网板1020。交换网板1020也可以称为交换网板单元(switch fabric unit，SFU)。在网络设备有多个接口板1030的情况下，交换网板1020用于完成各接口板之间的数据交换。例如，接口板1030和接口板1040之间可以通过交换网板820通信。
主控板1010和接口板1030耦合。例如。主控板1010、接口板1030和接口板1040，以及交换网板1020之间通过系统总线与系统背板相连实现互通。在一种可能的实现方式中，主控板1010和接口板1030之间建立进程间通信协议(inter-process communication，IPC) 通道，主控板1010和接口板1030之间通过IPC通道进行通信。
在逻辑上，网络设备1000包括控制面和转发面，控制面包括主控板1010和中央处理器1031，转发面包括执行转发的各个组件，比如转发表项存储器1034、物理接口卡1033和网络处理器1032。控制面执行路由器、生成转发表、处理信令和协议报文、配置与维护设备的状态等功能，控制面将生成的转发表下发给转发面，在转发面，网络处理器1032基于控制面下发的转发表对物理接口卡1033收到的报文查表转发。控制面下发的转发表可以保存在转发表项存储器1034中。在一些实施例中，控制面和转发面可以完全分离，不在同一设备上。
如果网络设备1000被配置为第一网络设备时，中央处理器1011可以根据所述第一SID list的指示信息确定第二转发路径。网络处理器1032可以触发物理接口卡1033通过所述第二转发路径向所述第二网络设备发送所述第一BFD报文的第一响应报文。
如果网络设备1000被配置为第二网络设备，网络处理器1032可以触发物理接口卡1033通过第一SR policy的第一转发路径向第一网络设备发送BFD报文，以及从所述第二转发路径接收所述BFD报文的响应报文。中央处理器1011可以根据所述响应报文对所述第一转发路径进行故障检测。
应理解，故障检测装置700中的接收单元701、发送单元703等可以相当于网络设备1000中的物理接口卡1033或物理接口卡1043；故障检测装置700中的确定单元702等可以相当于网络设备1000中的中央处理器1011或中央处理器1031。故障检测装置800中的发送单元801、接收单元802等可以相当于网络设备1000中的物理接口卡1033或物理接口卡1043；故障检测装置800中的检测单元803等可以相当于网络设备1000中的中央处理器1011或中央处理器1031。
应理解，本申请实施例中接口板1040上的操作与接口板1030的操作一致，为了简洁，不再赘述。应理解，本实施例的网络设备1000可对应于上述各个方法实施例中的任意一个节点，该网络设备1000中的主控板1010、接口板1030和/或接口板1040可以实现上述各个方法实施例中的任意一个节点所具有的功能和/或所实施的各种步骤，为了简洁，在此不再赘述。
应理解，主控板可能有一块或多块，有多块的时候可以包括主用主控板和备用主控板。接口板可能有一块或多块，网络设备的数据处理能力越强，提供的接口板越多。接口板上的物理接口卡也可以有一块或多块。交换网板可能没有，也可能有一块或多块，有多块的时候可以共同实现负荷分担冗余备份。在集中式转发架构下，网络设备可以不需要交换网板，接口板承担整个系统的业务数据的处理功能。在分布式转发架构下，网络设备可以有至少一块交换网板，通过交换网板实现多块接口板之间的数据交换，提供大容量的数据交换和处理能力。所以，分布式架构的网络设备的数据接入和处理能力要大于集中式架构的设备。可选地，网络设备的形态也可以是只有一块板卡，即没有交换网板，接口板和主控板的功能集成在该一块板卡上，此时接口板上的中央处理器和主控板上的中央处理器在该一块板卡上可以合并为一个中央处理器，执行两者叠加后的功能，这种形态设备的数据交换和处理能力较低(例如，低端交换机或路由器等网络设备)。具体采用哪种架构，取决于具 体的组网部署场景。
在一些可能的实施例中，上述各节点可以实现为虚拟化设备。例如，虚拟化设备可以是运行有用于发送报文功能的程序的虚拟机(英文：Virtual Machine，VM)，虚拟机部署在硬件设备上(例如，物理服务器)。虚拟机指通过软件模拟的具有完整硬件系统功能的、运行在一个完全隔离环境中的完整计算机系统。可以将虚拟机配置为各节点。例如，可以基于通用的物理服务器结合网络功能虚拟化(Network Functions Virtualization，NFV)技术来实现各节点。各节点为虚拟主机、虚拟路由器或虚拟交换机。本领域技术人员通过阅读本申请即可结合NFV技术在通用物理服务器上虚拟出具有上述功能的各节点，此处不再赘述。
应理解，上述各种产品形态的网络设备，分别具有上述方法实施例中各节点的任意功能，此处不再赘述。
本申请实施例还提供了一种网络系统1100，如图11所示。该网络系统1100可以包括第一网络设备1101和第二网络设备1102。其中，第一网络设备1101可以是图1所示的PE设备12、图7所示的故障检测装置700、图9所示的被配置为第一网络设备的网络设备900或者图10所示的被配置为第一网络设备的网络设备1000；第二网络设备1102可以是图1所示的PE设备11、图8所示的故障检测装置800、图9所示的被配置为第二网络设备的网络设备900或者图10所示的被配置为第二网络设备的网络设备1000。
本申请实施例还提供了一种芯片，包括处理器和接口电路，接口电路，用于接收指令并传输至处理器；处理器，例如可以是图7示出的故障检测装置700的一种具体实现形式，可以用于执行上述方法；又例如可以是图8示出的故障检测装置800的一种具体实现形式，可以用于执行上述方法。其中，所述处理器与存储器耦合，所述存储器用于存储程序或指令，当所述程序或指令被所述处理器执行时，使得该芯片系统实现上述任一方法实施例中的方法。
可选地，该芯片系统中的处理器可以为一个或多个。该处理器可以通过硬件实现也可以通过软件实现。当通过硬件实现时，该处理器可以是逻辑电路、集成电路等。当通过软件实现时，该处理器可以是一个通用处理器，通过读取存储器中存储的软件代码来实现。
可选地，该芯片系统中的存储器也可以为一个或多个。该存储器可以与处理器集成在一起，也可以和处理器分离设置，本申请并不限定。示例性的，存储器可以是非瞬时性处理器，例如只读存储器ROM，其可以与处理器集成在同一块芯片上，也可以分别设置在不同的芯片上，本申请对存储器的类型，以及存储器与处理器的设置方式不作具体限定。
示例性的，该芯片系统可以是现场可编程门阵列(field programmable gate array，FPGA)，可以是专用集成芯片(application specific integrated circuit，ASIC)，还可以是系统芯片(system on chip，SoC)，还可以是中央处理器(central processor unit，CPU)，还可以是网络处理器(network processor，NP)，还可以是数字信号处理电路(digital signal processor，DSP)，还可以是微控制器(micro controller unit，MCU)，还可以是可编程控制器(programmable logic device，PLD)或其他集成芯片。
本申请实施例还提供了一种计算机可读存储介质，包括指令或计算机程序，当其在计 算机上运行时，使得计算机执行以上实施例提供的故障检测的方法。
本申请实施例还提供了一种包含指令或计算机程序的计算机程序产品，当其在计算机上运行时，使得计算机执行以上实施例提供的故障检测的方法。
本申请的说明书和权利要求书及上述附图中的术语“第一”、“第二”、“第三”、“第四”等(如果存在)是用于区别类似的对象，而不必用于描述特定的顺序或先后次序。应该理解这样使用的数据在适当情况下可以互换，以便这里描述的实施例能够以除了在这里图示或描述的内容以外的顺序实施。此外，术语“包括”和“具有”以及他们的任何变形，意图在于覆盖不排他的包含，例如，包含了一系列步骤或单元的过程、方法、系统、产品或设备不必限于清楚地列出的那些步骤或单元，而是可包括没有清楚地列出的或对于这些过程、方法、产品或设备固有的其它步骤或单元。
所属领域的技术人员可以清楚地了解到，为描述的方便和简洁，上述描述的系统，装置和单元的具体工作过程，可以参考前述方法实施例中的对应过程，在此不再赘述。
在本申请所提供的几个实施例中，应该理解到，所揭露的系统，装置和方法，可以通过其它的方式实现。例如，以上所描述的装置实施例仅仅是示意性的，例如，单元的划分，仅仅为一种逻辑业务划分，实际实现时可以有另外的划分方式，例如多个单元或组件可以结合或者可以集成到另一个系统，或一些特征可以忽略，或不执行。另一点，所显示或讨论的相互之间的耦合或直接耦合或通信连接可以是通过一些接口，装置或单元的间接耦合或通信连接，可以是电性，机械或其它的形式。
作为分离部件说明的单元可以是或者也可以不是物理上分开的，作为单元显示的部件可以是或者也可以不是物理单元，即可以位于一个地方，或者也可以分布到多个网络单元上。可以根据实际的需要选择其中的部分或者全部单元来实现本实施例方案的目的。
另外，在本申请各个实施例中的各业务单元可以集成在一个处理单元中，也可以是各个单元单独物理存在，也可以两个或两个以上单元集成在一个单元中。上述集成的单元既可以采用硬件的形式实现，也可以采用软件业务单元的形式实现。
集成的单元如果以软件业务单元的形式实现并作为独立的产品销售或使用时，可以存储在一个计算机可读取存储介质中。基于这样的理解，本申请的技术方案本质上或者说对现有技术做出贡献的部分或者该技术方案的全部或部分可以以软件产品的形式体现出来，该计算机软件产品存储在一个存储介质中，包括若干指令用以使得一台计算机设备(可以是个人计算机，服务器，或者网络设备等)执行本申请各个实施例方法的全部或部分步骤。而前述的存储介质包括：U盘、移动硬盘、只读存储器(Read-Only Memory，ROM)、随机存取存储器(Random Access Memory，RAM)、磁碟或者光盘等各种可以存储程序代码的介质。
本领域技术人员应该可以意识到，在上述一个或多个示例中，本发明所描述的业务可以用硬件、软件、固件或它们的任意组合来实现。当使用软件实现时，可以将这些业务存储在计算机可读介质中或者作为计算机可读介质上的一个或多个指令或代码进行传输。计算机可读介质包括计算机存储介质和通信介质，其中通信介质包括便于从一个地方向另一个地方传送计算机程序的任何介质。存储介质可以是通用或专用计算机能够存取的任何可 用介质。
以上的具体实施方式，对本发明的目的、技术方案和有益效果进行了进一步详细说明，所应理解的是，以上仅为本发明的具体实施方式而已。
以上实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的范围。

Claims (19)

  1. 一种故障检测方法，其特征在于，包括：
    第一网络设备通过第一分段路由策略SR policy的第一转发路径接收第二网络设备发送的第一双向链路检测BFD报文，所述第一BFD报文中包括第一分段标识列表SID list的指示信息；
    所述第一网络设备根据所述第一SID list的指示信息确定第二转发路径，所述第二转发路径和所述第一转发路径反向共路；
    所述第一网络设备通过所述第二转发路径向所述第二网络设备发送所述第一BFD报文的第一响应报文，所述第一响应报文用于指示所述第二网络设备对所述第一转发路径进行故障检测。
  2. 根据权利要求1所述的方法，其特征在于，在第一网络设备通过第一SR policy的第一转发路径接收第二网络设备发送的第一BFD报文之前，所述方法还包括：
    所述第一网络设备生成所述第一SID list的指示信息；
    或者，所述第一网络设备接收所述第二网络设备发送的所述第一SID list的指示信息。
  3. 根据权利要求1所述的方法，其特征在于，所述方法还包括：
    所述第一网络设备接收控制管理设备发送的消息，所述消息中包括所述第一SID list的指示信息。
  4. 根据权利要求3所述的方法，其特征在于，所述消息中还包括第二SID list的指示信息，其中，所述第二SID list的指示信息指示所述第一转发路径，所述第一SID list的指示信息指示所述第二转发路径；或者，所述第二SID list的指示信息指示所述第二转发路径，所述第一SID list的指示信息指示所述第一转发路径。
  5. 根据权利要求3或4所述的方法，其特征在于，所述消息为边界网关协议分段路由策略BGP SR policy报文，所述BGP SR policy报文通过子类型长度值sub-TLV字段携带所述第一SID list的指示信息。
  6. 根据权利要求1-5任一项所述的方法，其特征在于，所述第一SID list的指示信息用于指示所述第二转发路径对应的SID list。
  7. 根据权利要求1-5任一项所述的方法，其特征在于，所述第一SID list的指示信息用于指示所述第一转发路径对应的SID list，所述第一网络设备根据所述第一SID list的指示信息确定第二转发路径，包括：
    所述第一网络设备根据所述第一SID list的指示信息确定所述第二SID list的指示信息；
    所述第一网络设备根据所述第二SID list的指示信息确定所述第二转发路径。
  8. 根据权利要求1-7任一项所述的方法，其特征在于，所述方法还包括：
    所述第一网络设备通过第二SR policy的所述第二转发路径向所述第二网络设备发送第二BFD报文，所述第二BFD报文中包括第三SID list的指示信息，所述第三SID list的指示信息用于指示所述第一网络设备确定发送所述第二BFD报文的第二响应报文的所述第一转发路径；
    所述第一网络设备从所述第一转发路径接收所述第二响应报文；
    所述第一网络设备根据所述第二响应报文对所述第二转发路径进行故障检测。
  9. 根据权利要求1-8任一项所述的方法，其特征在于，所述方法还包括：
    所述第一网络设备通过所述第一SR policy的第三转发路径接收所述第二网络设备发送的第三BFD报文，所述第三BFD报文中包括第四SID list的指示信息，所述第三转发路径和所述第一转发路径不同；
    所述第一网络设备根据所述第四SID list的指示信息确定第四转发路径，所述第四转发路径和所述第三转发路径反向共路；
    所述第一网络设备通过所述第四转发路径向所述第二网络设备发送所述第三BFD报文的第三响应报文，所述第三响应报文用于指示所述第二网络设备对所述第三转发路径进行故障检测。
  10. 一种故障检测方法，其特征在于，包括：
    第二网络设备通过第一分段路由策略SR policy的第一转发路径向第一网络设备发送双向链路检测BFD报文，所述BFD报文中包括第一分段标识列表SID list的指示信息，所述第一SID list的指示信息用于指示所述第一网络设备确定发送所述BFD报文的响应报文的第二转发路径，所述第二转发路径与所述第一转发路径反向共路；
    所述第二网络设备从所述第二转发路径接收所述BFD报文的响应报文；
    所述第二网络设备根据所述响应报文对所述第一转发路径进行故障检测。
  11. 根据权利要求10所述的方法，其特征在于，在所述第二网络设备通过第一SR policy的第一转发路径向第一网络设备发送BFD报文之前，所述方法还包括：
    所述第二网络设备接收所述第一网络设备发送的所述第一SID list的指示信息；
    或者，所述第二网络设备接收控制管理设备发送的所述第一SID list的指示信息。
  12. 根据权利要求10所述的方法，其特征在于，所述方法还包括：
    所述第二网络设备生成所述第一SID list的指示信息。
  13. 根据权利要求12所述的方法，其特征在于，所述方法还包括：
    所述第二网络设备向控制管理设备发送所述第一SID list的指示信息。
  14. 根据权利要求13所述的方法，其特征在于，所述第二网络设备向控制管理设备发送所述第一SID list的指示信息，包括：
    所述第二网络设备向所述控制管理设备发送边界网关协议的链路状态BGP-LS报文，所述BGP-LS报文通过子类型长度值sub-TLV字段携带所述第一SID list的指示信息。
  15. 根据权利要求1-14任一项所述的方法，其特征在于，所述第一SID list的指示信息为路径分段Path Segment或绑定分段标识BSID。
  16. 一种网络设备，其特征在于，包括：
    存储器，所述存储器包括计算机可读指令；
    与所述存储器通信的处理器，所述处理器用于执行所述计算机可读指令，使得所述网络设备执行权利要求1-15任一项所述的方法。
  17. 一种网络系统，其特征在于，所述网络系统包括：第一网络设备和第二网络设备，其中，所述第一网络设备，用于执行权利要求1-9或15任一项所述的方法；
    所述第二网络设备，用于执行权利要求10-15任一项所述的方法。
  18. 一种计算机可读存储介质，其特征在于，包括程序或指令，当其被处理器执行时实现如权利要求1-15任一项所述的方法。
  19. 一种计算机程序产品，其特征在于，包括计算机程序，所述计算机程序被处理器执行时实现权利要求1-15任一项所述的方法。
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