CN111490933B

CN111490933B - Bidirectional forwarding detection switching method and edge device

Info

Publication number: CN111490933B
Application number: CN202010247676.6A
Authority: CN
Inventors: 邢家茂
Original assignee: New H3C Security Technologies Co Ltd
Current assignee: New H3C Security Technologies Co Ltd
Priority date: 2020-03-31
Filing date: 2020-03-31
Publication date: 2022-05-24
Anticipated expiration: 2040-03-31
Also published as: CN111490933A

Abstract

The application provides a bidirectional forwarding detection switching method and edge equipment. The bidirectional forwarding detection switching method is applied to edge equipment, the edge equipment is first end point equipment of a tunnel, the edge equipment presets main path information and standby path information between the edge equipment and second end point equipment of the tunnel, and one or more Pseudo Wires (PW) are established between the edge equipment and the second end point equipment. The method comprises the following steps: when a Central Processing Unit (CPU) of the edge device detects that other devices except the edge device in the main path have faults, setting encapsulation information as first encapsulation information including standby path information, and transmitting first BFD message information corresponding to a first PW; when a forwarding unit of the edge device receives a service message corresponding to the first PW, the service message is encapsulated by using first encapsulation information including standby path information, and the obtained tunnel message is forwarded; and the forwarding unit receives the first BFD message information, encapsulates the first BFD message information by utilizing the first encapsulation information and forwards the obtained BFD message.

Description

Bidirectional forwarding detection switching method and edge device

Technical Field

The present application relates to the field of communications technologies, and in particular, to a bidirectional forwarding detection switching method and an edge device.

Background

At present, redundant paths are often set between endpoint devices at two ends of a tunnel to ensure that a message can be transmitted in the tunnel as much as possible. For example, a main path and a standby path are deployed between end point devices at two ends of a tunnel, and when a device in the main path fails, a message can be transmitted through the standby path, which relates to a path switching technology.

The above technology is also often applied to an actual networking in combination with a Pseudo Wire (abbreviated PW) technology, and Bidirectional Forwarding Detection (BFD) is used to detect and protect the PW. For example: an active/standby path is set between an ingress device and an egress device of an L2VPN technology [ for example, Multi-Protocol Label Switching (abbreviated MPLS) ], and at least one PW is established between the ingress device and the egress device, where each PW is detected and protected by a pair of BFD sessions. When the BFD detects that a main label switching Path (label Switched Path, abbreviated as LSP, namely a main Path) has a fault, the BFD triggers LSP switching, firstly switches a service message to a standby LSP, and then switches a PWBFD session to the standby LSP so as to switch the associated service message and the PWBFD session to the standby LSP.

The inventor finds the following problems in the prior art: in practical application, the BFD-based hierarchical protection function is often required to be realized according to different networking domains. In such an application scenario, a secondary path switch may be caused.

Disclosure of Invention

In order to solve the above problem, the present application provides a bidirectional forwarding detection switching method and an edge device.

In a first aspect, the present application provides a Bidirectional Forwarding Detection (BFD) switching method, which is applied to an edge device, where the edge device is a first endpoint device of a tunnel, the edge device presets main path information and standby path information with a second endpoint device of the tunnel, and one or more Pseudo Wires (PW) are established between the edge device and the second endpoint device; the method comprises the following steps:

when a Central Processing Unit (CPU) of the edge device detects that other devices except the edge device in a main path have faults, setting encapsulation information as first encapsulation information including standby path information, and transmitting first BFD message information corresponding to a first PW;

when a forwarding unit of the edge device receives a service message corresponding to a first PW, packaging the service message by using first packaging information including standby path information, and forwarding the obtained tunnel message;

And the forwarding unit receives the first BFD message information, encapsulates the first BFD message information by using the first encapsulation information, and forwards the obtained BFD message.

Optionally, the CPU stores a correspondence between the PW identifier and the reservation label, and the first BFD packet information includes the first reservation label; then, the encapsulating the first BFD packet information by using the first encapsulation information includes:

replacing a first reserved label in the first BFD message information with a first PW identifier corresponding to the first reserved label to obtain second BFD message information;

and packaging the second BFD message information by using the first packaging information.

Optionally, the forwarding unit stores a corresponding relationship between the PW and the encapsulation information; the setting encapsulation information is first encapsulation information including backup path information, and includes:

and the CPU sends an update message to the forwarding unit, wherein the update message instructs the forwarding unit to update the encapsulation information corresponding to the first PW from second encapsulation information comprising main path information to first encapsulation information, so that the forwarding unit encapsulates the message by using the first encapsulation information.

Optionally, the forwarding unit stores a PW BFD forwarding table, where the PW BFD forwarding table includes a PW identifier, a BFD session identifier, a service identifier, and a path selection switch flag; the update message includes a first flag indicating that the message is encapsulated by the first encapsulation information;

The method further comprises the following steps: and the forwarding unit receives the updating message and sets the path selection switch mark as a first mark.

Optionally, the forwarding unit determines to encapsulate the first BFD packet information and the service packet by using the first encapsulation information according to a path selection switch flag corresponding to the first PW identifier in the PW BFD forwarding table.

Optionally, the forwarding unit stores a PW BFD forwarding table and a service forwarding table, where the PW BFD forwarding table includes a PW identifier, a BFD session identifier, and a path selection switch identifier, and the service forwarding table includes a PW identifier, a service identifier, and a path selection switch identifier; then the

The encapsulating the service packet by using the first encapsulation information including the backup path information includes: according to a path selection switch mark corresponding to the first PW identifier in the service forwarding table, packaging the service message by using first packaging information;

the encapsulating the first BFD message information by using the first encapsulation information including the standby path information includes: and encapsulating the first BFD message information by using first encapsulation information according to a path selection switch mark corresponding to the first PW identifier in the PW BFD forwarding table.

In a second aspect, the present application provides an edge device comprising: the edge device is a first end point device of a tunnel, the edge device presets main path information and standby path information between the edge device and a second end point device of the tunnel, and one or more pseudo wires PW are established between the edge device and the second end point device; the edge device includes:

the CPU is used for setting the encapsulation information as first encapsulation information including standby path information and transmitting first BFD message information corresponding to the first PW when detecting that other equipment except the edge equipment in the main path fails;

the forwarding unit is configured to, when receiving a service packet corresponding to the first PW, encapsulate the service packet using first encapsulation information including standby path information, and forward the obtained tunnel packet;

and the forwarding unit is further configured to receive the first BFD packet information, encapsulate the first BFD packet information using the first encapsulation information, and forward the obtained BFD packet.

Optionally, the CPU stores a correspondence between the PW identifier and the reservation label, and the first BFD packet information includes the first reservation label; the forwarding unit is specifically configured to:

and encapsulating the second BFD message information by using the first encapsulation information.

Optionally, the forwarding unit stores a corresponding relationship between the PW and the encapsulation information; the CPU is specifically configured to:

and sending an update message to the forwarding unit, wherein the update message instructs the forwarding unit to update the encapsulation information corresponding to the first PW from second encapsulation information including main path information to first encapsulation information, so that the forwarding unit encapsulates the message by using the first encapsulation information.

the forwarding unit is further configured to receive the update message and set the path selection switch flag as a first flag.

Optionally, the forwarding unit is specifically configured to determine to encapsulate the first BFD packet information and the service packet using the first encapsulation information according to a path selection switch flag corresponding to the first PW identifier in the PW BFD forwarding table.

Optionally, the forwarding unit stores a PW BFD forwarding table and a service forwarding table, where the PW BFD forwarding table includes a PW identifier, a BFD session identifier, and a path selection switch identifier, and the service forwarding table includes a PW identifier, a service identifier, and a path selection switch identifier; the forwarding unit is specifically configured to:

according to a path selection switch mark corresponding to the first PW identifier in the service forwarding table, packaging the service message by using first packaging information;

and encapsulating the first BFD message information by using first encapsulation information according to a path selection switch mark corresponding to the first PW identifier in the PW BFD forwarding table.

Compared with the prior art, the embodiment of the application optimizes the switching time of PW BFD through the following improvements, and avoids the switching of a secondary path:

1. the BFD session switching process is executed by the forwarding chip, the switching BFD session is not executed by the CPU any more, the data quantity transmitted from the CPU to the forwarding unit is reduced, and meanwhile, the transmission path of the BFD message is shortened;

2. switching BFD sessions may occur before switching traffic messages.

Drawings

Fig. 1 is a schematic diagram of a network provided in an embodiment of the present application;

fig. 2 is a schematic diagram of an active/standby path networking based on the networking plan shown in fig. 1 according to an embodiment of the present application;

Fig. 3 is a schematic diagram illustrating analysis of a process of reporting a PW BFD DOWN event after a network failure according to an embodiment of the present application;

fig. 4 is a schematic diagram illustrating analysis of a TE FRR switching process according to an embodiment of the present application;

fig. 5 is a schematic switching flow diagram provided in the embodiment of the present application;

FIG. 6 is a schematic diagram of an edge device module according to an embodiment of the present disclosure;

fig. 7-1 is a schematic BFD handover flow chart provided in an embodiment of the present application;

fig. 7-2 is a schematic diagram of a BFD packet encapsulated in a device according to an embodiment of the present application;

fig. 7-3 is a schematic diagram of a BFD packet encapsulated in a device according to another embodiment of the present application;

fig. 7-4 are schematic diagrams illustrating switching of BFD messages provided in the embodiments of the present application;

fig. 8 is a schematic diagram of internal information transmission of an edge device provided in the prior art;

fig. 9 is a schematic diagram of internal information transmission of an edge device according to an embodiment of the present application.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

It is to be understood that although the terms first, second, third, etc. may be used herein to describe various information, such information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present application. The word "if" as used herein may be interpreted as "at … …" or "when … …" or "in response to a determination", depending on the context.

The inventor finds that the prior art has the following problems: in practical application, the BFD-based hierarchical protection function is often required to be realized according to different networking domains. In such an application scenario, a secondary path switch may be caused.

In the networking shown in fig. 1, a PW is established between network elements (Net Element, abbreviation: NE)62 and NE41, and a segment PW is established at NE 31. After configuration and planning, as shown in fig. 2, a Traffic Engineering (Traffic Engineering, abbreviated as TE) protection mechanism for Fast restart routing (Fast route, abbreviated as FRR) is established between NE62 and NE31, and a PW FRR protection mechanism is established between NE62 and NE 41. TE FRR uses 10ms 3 of LSP BFD detection mechanism, PW FRR uses 50ms 3 of PW BFD detection mechanism. PW FRR and TE FRR realize the function of hierarchical protection according to the difference of the network organization domains. Wherein, in fig. 1 and 2: the PE Device is a Provider Edge, an Edge router of a backbone network of a service Provider, and also end point equipment at two ends of the tunnel; p Device is Provider Device, core Device; the SPE Device is a Switching Provider Edge, label Switching forwarding Edge Device.

In a power failure scenario of NE52, a TE FRR of NE62-NE31 responds to a DOWN event of the LSP BFD session of 10ms × 3, and switches a loaded L2VPN service packet and a PW BFD session associated with the L2VPN to a backup LSP. Conventionally, the switching of L2VPN service messages is firstly realized, and then PW BFD sessions associated with the L2VPN are switched. If the time consumed for switching the L2VPN service packet and the PW BFD session is long, a fault of the PW BFD session may be caused, thereby triggering the active/standby switching of the PW FRR, causing a secondary switching of the path, causing a long interruption time of the service in the process, and affecting the performance of protection switching.

As described above with respect to fig. 1 and 2, if switching between L2VPN service and PW BFD takes a lot of time, a failure of PW BFD may be caused, so as to trigger active/standby switching of PW FRR, resulting in secondary switching of paths. The following explains the principle in detail.

And (3) combining the networks in fig. 1 and 2, wherein the detection period of the BFD message is T, and if the BFD message is not received within T × 3, reporting a DOWN event of the BFD. As shown in fig. 3, if the time of the failure is the moment when the BFD message is to be received, since a period has already passed before, two periods pass after, and if the BFD message cannot be received, a DOWN event of the PW BFD session is reported. If the failure moment is the moment when the BFD message is just received, then three periods are passed again, if the BFD message can not be received, then the DOWN event of the PW BFD session is reported. To sum up, after a fault, within [2T, 3T ] time, a DOWN event of a PW BFD session may be reported, thereby triggering the primary/standby switching of a PW FRR, resulting in a secondary switching of a path.

Thus, the inventors found that: reporting of a DOWN event of a PW BFD session, that is, reporting of a fault event of the PW BFD session, needs to be avoided as much as possible.

Taking the case that after the failure occurs, the PW BFD session failure is reported by 2T, and the switching process of the TE FRR is analyzed. The LSP BFD fault detection takes t1 time, then all L2VPN services protected by TE FRR complete switching in t2 time, PW BFD session completes switching in t3 time. If (T1+ T2+ T3) >2T, as shown in fig. 4, a DOWN event of the PW BFD session is reported. To ensure that the DOWN event of the PW BFD session is not reported, it needs to ensure (T1+ T2+ T3) < 2T. time T1 is defined by the BFD fault detection protocol and is [2T _ lspbfd, 3T _ lspbfd ]; the time t2 and t3 are optimizable parts, and under the condition that t2 is kept unchanged, the optimized t3 can also achieve the aim of not reporting PW BFD DOWN events.

One of the improvements of the embodiments of the present application is to optimize t3, i.e., to optimize the switching time of the PWBFD. Specifically, in the embodiment of the present application, organization and update of the BFD packet are not executed by the CPU any more, but are executed by the forwarding unit, and the CPU only needs to set the encapsulation information as the first encapsulation information including the standby path information and transmit the BFD packet information, so that the forwarding unit encapsulates the service packet and the BFD packet information by using the first encapsulation information, and completes the path switching between the service and the BFD session.

Compared with the prior art, the route from the inside of the equipment to the outside of the equipment of the BFD message is changed from 'CPU → BFD message transmitting and receiving component → forwarding unit → equipment output interface' into 'forwarding unit → equipment output interface', so the transmission route of the BFD message is shortened. Correspondingly, the form of the BFD message from the inside of the device to the outside of the device is changed from "CPU (BFD message) → BFD message transceiving component (BFD message) → forwarding unit (BFD message) → device output interface (BFD message)" to "CPU (BFD message information) → BFD message transceiving component (BFD message information) → forwarding unit (BFD message) → device output interface (BFD message)", and since the BFD message information transmitted inside the device is smaller than the BFD message, the amount of data transmitted between the CPU inside the device and the forwarding unit is also greatly reduced. Therefore, the method and the device shorten the updating and organizing time of the BFD messages and optimize the switching time t3 of the BFD session.

The embodiment of the application does not limit the sequence of switching the BFD session and the service message, and the switching of the service message can be executed first and then the switching of the BFD session can be executed. In order to further avoid the false reporting of the DOWN fault of the PW BFD session during the TE FRR switching period, the embodiment of the present application may also perform the switching of the PW BFD session first, and then perform the switching of the L2VPN service packet, as shown in fig. 5. Because the flow of switching the PWBFD session is executed first and T1+ T3 is less than 2T to a great extent, reporting of the DOWN event of the PWBFD session can be further avoided, and thus secondary switching of the path cannot be caused.

The scheme provided by the embodiment of the application can reduce the work done by the CPU in the PW BFD switching process, thereby reducing or avoiding the report of PW BFD faults and effectively avoiding the secondary switching problem of TE FRR and PW FRR hierarchical protection scenes.

The following specifically describes the scheme provided in the embodiments of the present application.

Referring to fig. 6, the present application provides an edge device, which includes a central processing unit CPU, a bidirectional forwarding detection BFD module, and a forwarding unit. The edge device is a first end point device of the tunnel, main path information and standby path information between the edge device and a second end point device of the tunnel are preset by the edge device, and one or more pseudo wires PW are established between the edge device and the second end point device. Each unit is specifically explained as follows.

And the CPU is used for setting the encapsulation information as first encapsulation information including the standby path information and transmitting first BFD message information corresponding to the first PW when detecting that other equipment except the edge equipment in the main path fails.

A forwarding unit, configured to, when receiving a service packet corresponding to the first PW, encapsulate the service packet using first encapsulation information including backup path information, and forward the obtained tunnel packet; and the first BFD message information is received, the first BFD message information is packaged by utilizing the first packaging information, and the obtained BFD message is forwarded.

To better understand the various elements in fig. 6, embodiments of the present application will be described in conjunction with the BFD processing logic shown in fig. 7-1. As shown in fig. 7-1, the BFD switching method applied to the edge device is as follows 702-706.

The edge devices shown in fig. 6 may be NE62 and NE41 shown in fig. 1, wherein NE41 is the second endpoint device if NE62 is the first endpoint device; if NE62 is the second endpoint device, then NE41 is the first endpoint device. Multiple PWs may be set between two endpoint devices, each PW being detected and protected by a pair of BFD sessions.

In an embodiment of the present application, in a network-wide unique LABEL scenario, that is, a PW uses a unique PW LABEL identifier, a BDF session corresponding to a PW is considered as a BFD session for detecting and protecting the PW, where the BFD session is initiated by a local device. For a certain PW, the BFD session identifier of the BFD session corresponding to the PW corresponds to the PW LABEL identifier of the PW.

For example, NE62 and NE41 in fig. 1 establish 3 PWs: PW1, PW2 and PW3, PW1 being detected and protected by a first pair of BFD sessions (BFD session 11 initiated by NE62 to NE41 and BFD session 12 initiated by NE41 to NE 62), PW2 being detected and protected by a second pair of BFD sessions (BFD session 21 initiated by NE62 to NE41 and BFD session 22 initiated by NE41 to NE 62), PW3 being detected and protected by a third pair of BFD sessions (BFD session 31 initiated by NE62 to NE41 and BFD session 32 initiated by NE41 to NE 62).

Then, taking NE62 as an execution body for example, BFD session 11 identifying a BFD session corresponds to PW LABEL 1 identifying PW1, BFD session 21 identifying a BFD session corresponds to PW LABEL2 identifying PW2, and BFD session 31 identifying a BFD session corresponds to PW LABEL 3 identifying PW 3.

In another embodiment of the present application, in a unique LABEL scenario of the whole network, that is, a PW uses a unique PW LABEL identifier, a BDF session corresponding to a PW is considered as a pair of BFD sessions for detecting and protecting the PW, where the pair of BFD sessions includes a BFD session using a local device as an originating terminal and an opposite terminal device as a receiving terminal, and a BFD session using the local device as a receiving terminal and the same opposite terminal device as an originating terminal, and a BFD session identifier of the pair of BFD sessions corresponds to the PW LABEL identifier of the PW.

Then, taking NE62 as an execution subject as an example, BFD session 11 and BFD session 12 corresponding to PW1 correspond to PW LABEL 1, BFD session 21 and BFD session 22 corresponding to PW2 correspond to PW LABEL 2, and BFD session 31 and BFD session 32 corresponding to PW3 correspond to PW LABEL 3.

In yet another embodiment of the present application, in a network-wide unique label scenario, that is, a PW uses a unique PW OUTLABEL identifier, a BDF session corresponding to a PW is considered as a BFD session for detecting and protecting the PW, where the BFD session is initiated by a local device, and for a PW, a BFD session identifier corresponding to the PW corresponds to a PW OUTLABEL n of the PW.

In yet another embodiment of the present application, in a mesh-wide non-unique label scenario, i.e., different PWs use the same PW OUTLABEL identifier, then the reserved label identifier PW may be used at this time. The corresponding relation between the PW and the reserved label is established in the CPU, and the reserved label is in one-to-one corresponding relation with the PW in the equipment, so that the equipment can uniquely identify a certain PW through the reserved label.

In conjunction with fig. 7-1, NE62 is taken as an example for the description.

702. When a Central Processing Unit (CPU) of the edge device detects that other devices except the edge device in the main path have faults, the packaging information is set to be first packaging information including standby path information, and first BFD message information corresponding to the first PW is transmitted.

In one embodiment, the BDF message information includes PW LABEL and BFD payload. The PW LABEL may be the above PW LABEL n, which corresponds to PW n, and may be used to protect and detect a BFD session n of PW n by using the local identifier as an initiator. In another embodiment, the PW LABEL is identified as the aforementioned PW LABEL n, which corresponds to PW n, and may be used to identify a pair of BFD sessions that protect and detect PW n.

In a specific embodiment, the CPU encapsulates the first BFD packet information using the internal encapsulation information to obtain an internal encapsulation BFD packet, and then transmits the internal encapsulation BFD packet.

In one example, FIG. 7-2 illustrates an internally encapsulated message format. The internal encapsulation header may be empty, or may be an ETH header of DMAC + SMAC + VLAN TAG, or may be other packet header information in a predefined format. Wherein, DMAC is the destination MAC address, SMAC is the source MAC address, VLAN TAG is the VLAN label. The message format shown in fig. 7-2 is suitable for a full-network unique LABEL scenario, i.e. a PW uses a unique PW LABEL,

The internal encapsulation format of the embodiment of the application is used for identifying the message as a PW BFD message, and the internal encapsulation format is not limited as long as each unit in the device has a good negotiation.

In another example, fig. 7-3 shows another internally encapsulated message format, and the message format shown in fig. 7-3 is suitable for a full-network non-unique LABEL scenario, that is, different PWs may use the same PW LABEL identifier. In the message format, PW LABEL identification of BFD message information is represented by a reserved LABEL. The reserved label in the figure is in one-to-one correspondence with the PW inside the equipment, so that the equipment can uniquely identify a certain PW through the reserved label.

In the prior art, the organization and update process of the BFD messages is processed by the CPU, and the CPU often processes other services, so in the embodiment of the present application, in order to speed up the organization and update process of the BFD messages and save the sending time of the BFD messages, the organization and update process of the BFD messages are transferred to the forwarding unit for processing. Step 704 mainly describes the procedure of switching BFD sessions, which is described in detail below.

704. And the forwarding unit of the edge equipment receives the first BFD message information, encapsulates the first BFD message information by using the first encapsulation information, and forwards the obtained BFD message. The first encapsulation information comprises standby path information.

In the embodiment of the present application, the path information includes an egress interface and a path identifier for indicating whether the path is a primary path or a backup path. For example, LSP LABEL1 may represent a main path, output 1 represents an outgoing interface of the device in the main path, LSP LABEL2 may represent an alternate path, and output 2 represents an outgoing interface of the device in the alternate path.

In one example, the first encapsulation information includes: DMAC, SMAC, VLAN TAG, LSP LABEL and OUTPORT. Wherein, DMAC is the destination MAC address, SMAC is the source MAC address, VLAN TAG is VLAN label.

In an embodiment, in a full-network unique label scenario, please refer to fig. 7-2 for a process of encapsulating a BFD packet inside a device. And the forwarding unit receives the internal encapsulation BFD message, then encapsulates the internal encapsulation BFD message by utilizing the first encapsulation information, and obtains and forwards the BFD message encapsulated by the public network.

In another embodiment, in a full-network non-unique label scenario, please refer to fig. 7-3 for the encapsulation process of the BFD packet inside the device. Specifically, the CPU stores a correspondence between the PW identifier and the reservation label, and the first BFD packet information includes the first reservation label.

In one example, the process of encapsulating, by the forwarding unit, the first BFD packet information with the first encapsulation information is as follows:

Fig. 7-4 show the switching process of the BFD packet, as shown in the figure, the DMAC, VLAN TAG, and LSP ble of the switched BFD packet are the standby path information, and the output interface is also modified to the OUT PORT2 of the standby path information.

706. And when receiving the service message corresponding to the first PW, the forwarding unit encapsulates the service message by using the included first encapsulation information and forwards the obtained tunnel message. Step 706 mainly describes the process of switching the service packet, i.e. completing the service switching. The service packet encapsulation process may refer to the BFD packet encapsulation process, which is not described in detail in this embodiment.

The BFD message and the tunnel message are obtained by packaging the standby path information, so that the BFD message and the tunnel message can be transmitted in the standby path in the subsequent process.

In the embodiment of the application, the BFD session switching process is carried out before the service message is switched, so that reporting of a DOWN event of the PWBFD session can be avoided to a great extent. In other embodiments, it is understood that 706 may also be performed before 704, or may be performed synchronously with 704. And is not particularly limited herein.

In addition, in the prior art, after one BFD message is encapsulated and forwarded, the next BFD message is encapsulated and forwarded, so that the switching of the BFD sessions in the prior art is limited by the number of BFD sessions (i.e., the number of BFD messages), and the more BFD sessions, the more time is consumed for switching the BFD sessions. Taking the existing edge device shown in fig. 8 as an example, the organization and update of the BFD messages are completed in the control management component 1(CPU), and the switching process of the conventional PW BFD session is as follows: exchanging public network encapsulation and updating public network output interfaces of BFD messages protected by TE FRR one by one; and the updated BFD message is sent to the BFD message receiving and sending component 2, and the BFD message receiving and sending component 2 sends and receives the BFD message to a forwarding chip. The operation is serial, and the operation time consumption has a direct relation with the number of BFD messages (namely PW BFD sessions).

Therefore, in the prior art, a path from the inside of the device to the outside of the device for the BFD packet is "CPU → BFD packet transceiving component → forwarding unit → device egress interface", and a form from the inside of the device to the outside of the device for the BFD packet is "CPU (BFD packet) → BFD packet transceiving component (BFD packet) → forwarding unit (BFD packet) → device egress interface (BFD packet)".

In the embodiment of the application, the organization and the update of the BFD message are not executed by the CPU any more, but executed by the forwarding unit, and the CPU only needs to set the encapsulation information as the first encapsulation information including the standby path information and transmit the BFD message information, so that the forwarding unit can encapsulate the service message and the BFD message information by using the first encapsulation information, and complete the path switching between the service and the BFD session. As shown in fig. 9, for the transmission path of "CPU → BFD message transceiving component 2 → forwarding chip" inside the device, the BFD message transmission in the embodiment of the present application is improved to BFD message information transmission, so that the amount of data transmitted between the CPU and the forwarding unit inside the device is also greatly reduced. In the embodiment of the present application, the encapsulation logic of the BFD packet is executed by the sweep forwarding unit, and the transmission path of the BFD packet is changed from "CPU → BFD packet transceiving component → forwarding unit → device output interface" to "forwarding unit → device output interface", and the transmission path of the BFD packet is shortened.

In summary, the embodiment of the present application optimizes the switching time of the PW BFD by the following improvements, and avoids the switching of the secondary path:

1. the BFD session switching process is executed by the forwarding chip, the switching BFD session is not executed by the CPU any more, the data amount transmitted from the CPU to the forwarding unit is reduced, and meanwhile, the transmission path of the BFD message is shortened;

2. Switching BFD sessions may occur before switching traffic messages.

In some embodiments, the forwarding unit stores a corresponding relationship between the PW and the encapsulation information; then, setting the encapsulation information as the first encapsulation information including the backup path information, including:

and the CPU sends an updating message to the forwarding unit, and the updating message instructs the forwarding unit to update the encapsulation information corresponding to the first PW from second encapsulation information comprising main path information to first encapsulation information so that the forwarding unit encapsulates the message by utilizing the first encapsulation information.

In a specific embodiment, the update message includes a first flag, and the forwarding unit sets the path selection switch flag to the first flag after receiving the update message.

In some embodiments, the correspondence between the PW and the encapsulation information may be represented by a PW BFD forwarding table, where the PW BFD forwarding table includes a PW identifier, a BFD session identifier, a service identifier, and a path selection switch flag. And when the route selection switch mark is the first mark, indicating that the message is packaged by using the first packaging information. And when the path selection switch is the second mark, indicating that the message is encapsulated by using second encapsulation information, wherein the second encapsulation information comprises main path information. The first flag and the second flag may be custom set, and in one example, the first flag may be 1 and the second flag may be 0.

In an embodiment of the present application, the PW BFD forwarding table refers to table 1.

TABLE 1

PW identification

BFD session identification

Service identification

Route selection switch sign

In an embodiment, all PWs and services may correspond to a path selection switch flag, that is, a path selection switch controls BFD sessions and service packets corresponding to all PW identifiers to switch to a standby path. In the embodiment, the switching setting of all PW BFD sessions and service messages can be realized by setting the path selection switch mark once, namely, after the path selection switch mark is set, the messages are encapsulated by using encapsulation information indicated after the setting, so that the method is simple and convenient, and the technical effect of disassociating the time consumed by switching the PW BFD sessions and the number of the PW BFD sessions is achieved. The embodiment can also realize the switching of the service message and the BFD session at the same time. Specific examples are shown in Table 2.

TABLE 2

As can be seen from table 2, the BFD sessions and service messages corresponding to PW LABEL 1 to PW LABEL3 are all selected to be switched to the standby path. Then, when the subsequent forwarding unit executes the encapsulation of the BFD message and the service message corresponding to PW LABEL 1 to PW LABEL3, the BFD message and the service message are encapsulated by using the backup path information. By using the PW BFD forwarding table shown in table 2, the encapsulation information required by the BFD session and the service packet corresponding to each PW can be directly obtained. By applying the table, when the forwarding unit encapsulates a service message corresponding to a certain PW, the forwarding unit can simultaneously encapsulate the BFD message corresponding to the PW, and at the moment, encapsulation information used when the service message is encapsulated is directly multiplexed. The embodiment can simultaneously complete the switching of the service message and the BFD session.

In another embodiment, in consideration of a scenario that part of the BFD sessions need to be switched to the standby path and part of the BFD sessions do not need to be switched to the standby path, each PW and service may correspond to a path selection switch flag, that is, a path selection switch controls a BFD session and service packet corresponding to a PW identifier to be switched to the standby path. Specific examples are shown in Table 3.

TABLE 3

PW identification	BFD session identification	Service identification	Route selection switch sign
				PW LABEL 1	PW BFD1	Service 1	1
PW LABEL 2	PW BFD2	Service 2	1
				PW LABEL 3	PW BFD3	Service 3	0

As can be seen from table 3, the BFD sessions corresponding to PW LABEL 1 to PW LABEL 2 all select to switch to the alternate path, while PW LABEL 3 does not select to switch to the alternate path. Then, when the subsequent forwarding unit executes the encapsulation of the BFD message and the service message corresponding to the PW LABEL 1 to PW LABEL 2, the BFD message is encapsulated by using the backup path information, and when the BFD message and the service message corresponding to the PW LABEL 3 are encapsulated, the BFD message and the service message are encapsulated by using the main path information.

In certain embodiments, the forwarding unit stores a PW BFD forwarding table and a traffic forwarding table. Wherein, the PW BFD forwarding table includes PW identifier, BFD session identifier, and path selection switch identifier, as shown in Table 4; the service forwarding table includes PW identifiers, service identifiers, and path selection switch identifiers, as shown in table 5.

TABLE 4

PW identification

BFD session identification

Route selection switch sign

TABLE 5

PW identification

Service identification

Route selection switch sign

And when the route selection switch mark is the first mark, indicating that the message is packaged by using the first packaging information. And when the path selection switch is the second mark, indicating that the message is encapsulated by using second encapsulation information, wherein the second encapsulation information comprises main path information. The first flag and the second flag may be custom set, and in one example, the first flag may be 1 and the second flag may be 0. It should be understood that, when determining to set the path selection switch flag corresponding to a certain PW identifier as the first flag, the forwarding unit should set the path selection switch flag corresponding to the PW identifier in tables 4 and 5 as the first flag.

Based on table 4 and table 5, the forwarding unit encapsulates the service packet by using the first encapsulation information according to the path selection switch flag corresponding to the first PW identifier in the service forwarding table; and packaging the first BFD message information by using the first packaging information according to a path selection switch mark corresponding to the first PW identifier in the PW BFD forwarding table.

In an embodiment, all PWs and services may correspond to a path selection switch flag, that is, a path selection switch controls BFD sessions and service packets corresponding to all PW identifiers to switch to a standby path. In the embodiment, all PW BFD sessions or service messages can be switched and set by setting the path selection switch mark once. Taking the BFD session as an example, after the path selection switch mark is set, the message is encapsulated by using encapsulation information indicated after the setting, the method is simple and convenient, and the time consumed by switching the PW BFD session and the number of the PW BFD sessions are disassociated. Specific examples are shown in Table 6-1 and Table 6-2.

TABLE 6-1

TABLE 6-2

As can be seen from tables 6-1 and 6-2, the BFD sessions and service messages corresponding to PW LABEL 1 to PW LABEL 3 are all selected to be switched to the standby path. Then, when the subsequent forwarding unit executes the encapsulation of the BFD message and the service message corresponding to the PW LABEL 1 to PW LABEL 3, the BFD message and the service message are encapsulated by using the backup path information. And applying the table 6-1, the forwarding unit encapsulates the service message corresponding to a certain PW by using the first encapsulation information, and the forwarding unit determines to encapsulate the BFD message corresponding to the PW by using the first encapsulation information based on the table 6-2.

In another embodiment, in consideration of a scenario that part of the BFD sessions need to be switched to the standby path and part of the BFD sessions do not need to be switched to the standby path, each PW and service may correspond to a path selection switch flag, that is, a path selection switch controls a BFD session and service packet corresponding to a PW identifier to be switched to the standby path. Specifically, the examples are shown in tables 7-1 and 7-2.

TABLE 7-1

PW identification	Service identification	Route selection switch sign
			PW LABEL 1	Service 1	1
PW LABEL 2	Service 2	1
			PW LABEL 3	Service 3	0

TABLE 7-2

PW identification	BFD session identification	Route selection switch sign
			PW LABEL 1	PW BFD1	1
PW LABEL 2	PW BFD2	1
			PW LABEL 3	PW BFD3	0

As can be seen from tables 7-1 and 7-2, the BFD sessions corresponding to PW LABEL 1 to PW LABEL 2 all select to switch to the alternate path, while PW LABEL 3 does not select to switch to the alternate path. Then, when the subsequent forwarding unit executes the encapsulation of the BFD message and the service message corresponding to the PW LABEL 1 to PW LABEL 2, the BFD message is encapsulated by using the backup path information, and when the BFD message and the service message corresponding to the PW LABEL 3 are encapsulated, the BFD message and the service message are encapsulated by using the main path information.

An embodiment of the present application provides an edge device, as shown in fig. 6, including: the device comprises a Central Processing Unit (CPU) and a forwarding unit, wherein the edge device is a first end point device of the tunnel, the edge device presets main path information and standby path information between the edge device and a second end point device of the tunnel, and one or more Pseudo Wires (PW) are established between the edge device and the second end point device. The respective units are explained specifically as follows.

The CPU is used for setting the encapsulation information as first encapsulation information including standby path information and transmitting first BFD message information corresponding to the first PW when the faults of other equipment except the edge equipment in the main path are detected;

a forwarding unit, configured to, when receiving a service packet corresponding to the first PW, encapsulate the service packet using first encapsulation information including backup path information, and forward the obtained tunnel packet;

and the forwarding unit is further used for receiving the first BFD message information, packaging the first BFD message information by using the first packaging information, and forwarding the obtained BFD message.

and sending an update message to the forwarding unit, wherein the update message instructs the forwarding unit to update the encapsulation information corresponding to the first PW from second encapsulation information comprising main path information to first encapsulation information, so that the forwarding unit encapsulates the message by using the first encapsulation information.

Optionally, the forwarding unit stores a PW BFD forwarding table, where the PW BFD forwarding table includes a PW identifier, a BFD session identifier, a service identifier, and a path selection switch flag; the update message includes a first flag indicating that the message is encapsulated by using the first encapsulation information;

and the forwarding unit is also used for receiving the updating message and setting the path selection switch mark as a first mark.

Optionally, the forwarding unit is specifically configured to determine to encapsulate the first BFD packet information and the service packet by using the first encapsulation information according to a path selection switch flag corresponding to the first PW identifier in the PW BFD forwarding table.

According to a path selection switch mark corresponding to the first PW identifier in the service forwarding table, packaging a service message by using first packaging information;

and packaging the first BFD message information by using the first packaging information according to a path selection switch mark corresponding to the first PW identifier in the PW BFD forwarding table.

The explanation of the above units can refer to the description in the previous embodiment, and is not repeated herein.

The implementation process of the functions and actions of each unit in the module/device is specifically described in the implementation process of the corresponding step in the method, and is not described herein again.

For the module/device embodiment, since it substantially corresponds to the method embodiment, reference may be made to the partial description of the method embodiment for relevant points. The above-described module/device embodiments are only illustrative, wherein the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the scheme of the application. One of ordinary skill in the art can understand and implement it without inventive effort.

The above description is only a preferred embodiment of the present application and should not be taken as limiting the present application, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A Bidirectional Forwarding Detection (BFD) switching method is characterized in that the BFD switching method is applied to edge equipment, the edge equipment is first end point equipment of a tunnel, the edge equipment presets main path information and standby path information between the edge equipment and second end point equipment of the tunnel, and one or more Pseudo Wires (PW) are established between the edge equipment and the second end point equipment; the method comprises the following steps:

when a forwarding unit of the edge device receives a service message corresponding to a first PW, encapsulating the service message by using first encapsulation information including standby path information, and forwarding the obtained tunnel message;

2. The method according to claim 1, wherein the CPU stores a correspondence between a PW identification and a reservation label, and the first BFD packet information includes a first reservation label; then, the encapsulating the first BFD packet information by using the first encapsulation information includes:

3. The method according to claim 1, wherein the forwarding unit stores a correspondence between the PW and the encapsulation information; the setting encapsulation information is first encapsulation information including backup path information, and includes:

4. The method of claim 3, wherein the forwarding unit stores a PW BFD forwarding table, the PW BFD forwarding table including a PW identification, a BFD session identification, a traffic identification, a path selection switch flag; the update message includes a first flag indicating that the packet is encapsulated by the first encapsulation information;

5. The method according to claim 4, wherein the forwarding unit determines to encapsulate the first BFD packet information and the service packet using the first encapsulation information according to a path selection switch flag corresponding to a first PW identifier in the PW BFD forwarding table.

6. The method of claim 3, wherein the forwarding unit stores a PW BFD forwarding table comprising a PW identification, a BFD session identification, a path selection switch identification, and a traffic forwarding table comprising a PW identification, a traffic identification, a path selection switch identification; then the

The encapsulating the service packet by using the first encapsulation information including the standby path information includes: according to a path selection switch mark corresponding to the first PW identifier in the service forwarding table, packaging the service message by using first packaging information;

the encapsulating the first BFD message information by using the first encapsulation information including the standby path information comprises: and encapsulating the first BFD message information by using first encapsulation information according to a path selection switch mark corresponding to the first PW identifier in the PW BFD forwarding table.

7. An edge device, comprising: the system comprises a Central Processing Unit (CPU) and a forwarding unit, wherein the edge device is a first endpoint device of a tunnel, the edge device presets main path information and standby path information between the edge device and a second endpoint device of the tunnel, and one or more Pseudo Wires (PW) are established between the edge device and the second endpoint device; the edge device includes:

the CPU is used for setting the encapsulation information as first encapsulation information including standby path information when detecting that other equipment except the edge equipment in the main path fails, and transmitting first BFD message information corresponding to the first PW;

the forwarding unit is configured to, when receiving a service packet corresponding to the first PW, encapsulate the service packet using first encapsulation information including standby path information, and forward an obtained tunnel packet;

8. The edge device according to claim 7, wherein the CPU stores a correspondence between a PW identifier and a reservation label, and the first BFD packet information includes a first reservation label; the forwarding unit is specifically configured to:

9. The edge device according to claim 7, wherein the forwarding unit stores a correspondence between the PW and the encapsulation information; the CPU is specifically configured to:

10. The edge device of claim 9, wherein the forwarding unit stores a PW BFD forwarding table that includes a PW identification, a BFD session identification, a service identification, a path selection switch flag; the update message includes a first flag indicating that the packet is encapsulated by the first encapsulation information;

11. The edge device of claim 10, wherein the forwarding unit is specifically configured to determine to encapsulate the first BFD packet information and the service packet with the first encapsulation information according to a path selection switch flag in the PW BFD forwarding table corresponding to a first PW identifier.

12. The edge device of claim 9, wherein the forwarding unit stores a PW BFD forwarding table that includes a PW identification, a BFD session identification, and a path selection switch flag, and a traffic forwarding table that includes a PW identification, a traffic identification, and a path selection switch flag; the forwarding unit is specifically configured to: