CN114531396A

CN114531396A - Fault back-switching method and device in Ethernet virtual private network

Info

Publication number: CN114531396A
Application number: CN202011197017.2A
Authority: CN
Inventors: 詹兰兰
Original assignee: Beijing Huawei Digital Technologies Co Ltd
Current assignee: Beijing Huawei Digital Technologies Co Ltd
Priority date: 2020-10-31
Filing date: 2020-10-31
Publication date: 2022-05-24
Anticipated expiration: 2040-10-31
Also published as: CN114531396B

Abstract

A failure switching-back method and device in Ethernet virtual private network is used for fast convergence of unicast routing in the failure switching-back process. The method comprises the following steps: the CE is accessed to the first PE and the second PE, the first PE and the second PE work in a single active mode, when the first PE is switched to a non DF from a DF corresponding to the CE, the first PE updates the MAC routing information of the CE and indicates the MAC routing information of the CE to correspond to a low priority, so that the far-end PE can select a proper forwarding path for a message sent to the CE according to the priority of each MAC routing information of the CE, the unicast routing of the CE is optimized, the unicast routing can be quickly converged to the current DF, the forwarding time of the message is effectively shortened, and the too long bypassing time of the message in a network is avoided.

Description

Fault back-switching method and device in Ethernet virtual private network

Technical Field

The present application relates to the field of communications technologies, and in particular, to a method and an apparatus for switching back a fault in an ethernet virtual private network.

Background

In the prior art, an Ethernet Virtual Private Network (EVPN) may work in a dual homing scenario as shown in fig. 1. The dual-homed single-living scenario refers to that a customer edge device (CE) 1 accesses an operator edge device (PE) 1 and a PE2, but the PE1 and the PE2 work in a single-living mode or a single-redundant mode, that is, only one of the PE1 and the PE2 is responsible for forwarding a message of the CE1 at the same time. The PE responsible for forwarding the CE1 message may also be referred to as a Designated Forwarder (DF), and the PE not responsible for forwarding the CE1 message may also be referred to as a non-designated forwarder (non DF).

In the dual homing scenario shown in fig. 1, PE1 is the DF of CE1 and PE2 is the non DF of CE1 under normal conditions. If the link between CE1 and PE1 fails, PE1 will switch to the non DF of CE1 and PE2 will switch to the DF of CE1, which is called the failure tangent procedure. In the process of fault tangent, as shown in fig. 2, in order to reduce packet loss, on one hand, PE1 may redirect, based on Media Access Control (MAC), a fast reroute (FRR) link established between PE2 and PE1, and send a received downlink packet of CE1 from PE3 to PE2 through the MAC FRR link, and then send the downlink packet of CE1 to CE1 by PE 2. On the other hand, PE1 may not withdraw the MAC route of CE1, but wait for its aging, so that PE3 may keep the unicast to PE1 before the MAC route of CE1 ages, and then switch the unicast to PE2 according to the fast convergence mechanism.

When the link between CE1 and PE1 is restored, PE1 can switch to the DF of CE1 again, and PE2 can switch to the non DF of CE1 again, which is called a fail-back procedure. In a failover process, as shown in fig. 3, to avoid broadcast flooding, PE2 may not withdraw the MAC route of the CE1, but wait for it to age. Thus, before PE1 receives the uplink packet from CE1, the downlink packet from CE1 of PE3 may continue to be unicast-transmitted to PE2, and after bypassing to PE1 via the MAC FRR link, it is finally transmitted to CE 1. However, before the MAC route of the CE1 corresponding to the PE2 is aged, if the CE1 already cuts the upstream traffic back to the PE1, because the Ethernet Segment Identifiers (ESIs) of the PE1 and the PE2 are the same, the unicast traffic of the PE3 cannot be guaranteed to be cut to the PE1, and the bypass time is too long.

Disclosure of Invention

The method and the device for switching back the fault in the Ethernet virtual private network are used for optimizing the unicast route in the flow switching back process and improving the path switching efficiency of the flow under the double-homed single-living scene.

In a first aspect, the present application provides a method for switching back a failure in an ethernet virtual private network, where the method may be performed by a first PE or a component (e.g., a chip or a circuit) configured in the first PE. The method comprises the following steps: the first PE determines that DF corresponding to the CE is switched into non DF, the CE is accessed into the first PE and the second PE, and the first PE and the second PE work in a single active mode; and the first PE sends a first route notification message to the far-end PE, wherein the first route notification message is used for notifying first MAC (media access control) route information of the CE, and the priority of the first MAC route information is lower than the preset priority.

By adopting the technical scheme, when a certain PE accessed by the CE is switched to a non-DF from a DF corresponding to the CE, the PE updates the MAC routing information of the CE and indicates the corresponding low priority, so that a far-end PE can select a proper forwarding path for a message sent to the CE according to the priority of each MAC routing information of the CE, thereby optimizing the unicast routing of the CE, enabling the unicast routing to be converged to the current DF quickly, effectively shortening the forwarding time of the message and avoiding the overlong bypass time of the message in a network.

In one possible design, if the far-end PE is an IBGP neighbor of the first PE, the priority of the first MAC routing information may be indicated by a LOCAL _ PREF attribute of the first MAC routing information; as such, the priority of the first MAC routing information being lower than the preset priority may refer to: the attribute value of the LOCAL _ PREF attribute in the first MAC routing information is smaller than the attribute value of the LOCAL _ PREF attribute corresponding to the preset priority.

In one possible design, if the remote PE is an EBGP neighbor of the first PE, the priority of the first MAC routing information may be indicated by the MED attribute of the first MAC routing information; as such, the priority of the first MAC routing information being lower than the preset priority may be: the attribute value of the MED attribute of the first MAC routing information is greater than the attribute value of the MED attribute corresponding to the preset priority.

In a second aspect, the present application provides another method for switching back a failure in an ethernet virtual private network, where the method may be performed by a remote PE, and may also be performed by a component (e.g., a chip or a circuit) configured in the remote PE. The method comprises the following steps: the far-end PE receives a route notification message from the second PE, the route notification message is used for notifying second MAC (media access control) route information of the CE, the CE is accessed into the first PE and the second PE, and the first PE and the second PE work in a single-activity mode; and if the second MAC routing information is the MAC routing information of the CE received by the far-end PE for the last time, the far-end PE determines to forward the message of the CE through the second PE according to the second MAC routing information.

By adopting the technical scheme, when the second PE is switched to the DF from the non DF corresponding to the CE and correspondingly notifies the second MAC routing information of the CE in the fault switching process, the unicast routing from the remote CE to the CE can be quickly converged to the DF corresponding to the CE at the moment by setting the routing principle of the remote PE to take the MAC routing information updated last time as the priority, so that the forwarding time of the message is effectively shortened, and the bypass time of the message in a network is avoided to be overlong.

In a third aspect, the present application provides a fault switchback device, where the device has a function of implementing the first PE in the foregoing aspects, or has a function of implementing the far-end PE in the foregoing aspects, and the device may be an operator edge device, or may be a chip included in the operator edge device.

The functions of the above-mentioned devices can be realized by hardware, or by hardware executing corresponding software, or by a combination of hardware and software, and the hardware or software includes one or more modules or units or means (means) corresponding to the above-mentioned functions.

In one possible design, the apparatus includes a processing module and a transceiver module in a structure, where the processing module is configured to support the apparatus to perform a function corresponding to the first PE in the above aspects or perform a function corresponding to the remote PE in the above aspects. The transceiver module is configured to support communication between the apparatus and other communication devices, for example, when the apparatus is a first PE, the transceiver module may send a route update packet to a far-end PE. The apparatus may also include a memory module, coupled to the processing module, that stores program instructions and data necessary for the apparatus. As an example, the processing module may be a processor, the communication module may be a transceiver, the storage module may be a memory, and the memory may be integrated with the processor or provided separately from the processor.

In another possible design, the apparatus may be configured to include a processor and may also include a memory. The processor is coupled to the memory and is operable to execute computer program instructions stored in the memory to cause the apparatus to perform the methods of the various aspects described above. Optionally, the apparatus further comprises a communication interface, the processor being coupled to the communication interface. When the apparatus is a first PE or a remote PE, the communication interface may be a transceiver or an input/output interface; when the apparatus is a chip included in the first PE or a chip included in the remote PE, the communication interface may be an input/output interface of the chip. Alternatively, the transceiver may be a transmit-receive circuit and the input/output interface may be an input/output circuit.

In a fourth aspect, an embodiment of the present application provides a chip system, including: a processor coupled with a memory for storing a program or instructions that, when executed by the processor, cause the system-on-chip to implement the method of the above aspects.

Optionally, the system-on-chip further comprises an interface circuit for interacting code instructions to the processor.

Optionally, the number of processors in the chip system may be one or more, and the processors may be implemented by hardware or software. When implemented in hardware, the processor may be a logic circuit, an integrated circuit, or the like. When implemented in software, the processor may be a general-purpose processor implemented by reading software code stored in a memory.

Optionally, the memory in the system on chip may also be one or more. The memory may be integral to the processor or may be separate from the processor. Illustratively, the memory may be a non-transitory processor, such as a read only memory ROM, which may be integrated on the same chip as the processor or may be separately provided on different chips.

In a fifth aspect, embodiments of the present application provide a computer-readable storage medium having stored thereon a computer program or instructions which, when executed, cause a method in any one of the possible designs of the above-described aspect or aspects to be implemented.

In a sixth aspect, embodiments of the present application provide a computer program product which, when executed by a communication device, causes a method in any one of the possible designs of the above-described aspects or aspects to be implemented.

In a seventh aspect, an embodiment of the present application provides a communication system, where the communication system includes a CE, a first PE, and a second PE. Optionally, the communication system may further include a far-end PE. Optionally, the communication system may further include a far-end CE.

Drawings

Fig. 1 and 2 are schematic diagrams of a fault tangent procedure in an EVPN network in the prior art;

fig. 3 is a schematic diagram of a fault back-off process in a prior art EVPN network;

fig. 4 is a schematic flowchart of a fault back-switch method in an EVPN network according to an embodiment of the present disclosure;

fig. 5 is a schematic diagram illustrating that a first PE that switches to a non DF in this embodiment of the present application instructs a remote PE to select a packet forwarding path by reducing the priority of MAC routing information;

fig. 6a and fig. 6b are an example of a message structure and an attribute structure according to the embodiment of the present application;

fig. 7 is a schematic flowchart of another method for switching back a failure in an EVPN network according to an embodiment of the present disclosure;

fig. 8 is a schematic diagram illustrating that a remote PE selects a packet forwarding path according to the last received MAC routing information in the embodiment of the present application;

fig. 9 is a schematic structural diagram of a communication device according to an embodiment of the present application;

fig. 10 is another schematic structural diagram of a communication device according to an embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the embodiments of the present application will be described in further detail with reference to the accompanying drawings.

It should be noted that the terms "system" and "network" in the embodiments of the present application may be used interchangeably. The "plurality" means two or more, and in view of this, the "plurality" may also be understood as "at least two" in the embodiments of the present application. "at least one" is to be understood as meaning one or more, for example one, two or more. For example, the inclusion of at least one means that one, two or more are included, and does not limit which is included. For example, at least one of A, B and C is included, then inclusion can be A, B, C, A and B, A and C, B and C, or A and B and C. Similarly, the understanding of the description of "at least one" and the like is similar. "and/or" describes the association relationship of the associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" generally indicates that the preceding and following related objects are in an "or" relationship, unless otherwise specified.

Unless stated to the contrary, the embodiments of the present application refer to the ordinal numbers "first", "second", etc., for distinguishing between a plurality of objects, and do not define the order, sequence, priority, or importance of the plurality of objects, and the descriptions of "first", "second", etc., do not define that the objects are necessarily different.

Please refer to fig. 4, which is a flowchart illustrating a method for switching back a failure in an EVPN network according to an embodiment of the present disclosure. The method comprises the following steps:

step S401, the first PE determines that the designated forwarder DF corresponding to the CE is switched to a non-designated forwarder non DF.

In the embodiment of the present application, a CE accesses a first PE and a second PE.

In one possible embodiment, a CE may have dual homing access to a first PE and a second PE. The dual homing of the CE into the first PE and the second PE may also be referred to as the dual homing of the CE to the first PE and the second PE, or the dual homing of the CE to the first PE and the second PE, which means that the CE and the first PE and the second PE have a connection, and a message from or to the CE may be forwarded by the first PE or the second PE.

The first PE and the second PE operate in a single active mode, which may also be referred to as a single redundant mode or by other names, without limitation. The single live mode specifically means that at the same time, only one of the first PE and the second PE is responsible for forwarding the message of the CE as the DF corresponding to the CE, and the other PE is not responsible for forwarding the message of the CE as the non DF corresponding to the CE. Thus, if a first PE switches from a DF corresponding to that CE to a non DF, it means that a second PE switches from the non DF corresponding to that CE to a DF.

Optionally, the second PE may be a PE that is selected as a DF by default or by priority from two PEs that the CE is dually accessed, or a PE that has been selected as a DF previously according to some preset selection rule. In this way, when the communication link between the CE and the second PE is normal, the second PE is responsible for forwarding the packet of the CE as the DF corresponding to the CE. If the communication link between the CE and the second PE fails, the second PE and the first PE may perform the failure tangent processing correspondingly, so that the second PE is switched from the DF corresponding to the CE to the non DF, and the first PE is switched from the non DF corresponding to the CE to the DF. After the communication link between the CE and the second PE is restored, the second PE and the first PE may perform failure switchback processing, so that the second PE is switched back to the DF by the non DF corresponding to the CE, and the first PE is switched back to the non DF by the DF corresponding to the CE.

In another possible embodiment, the CE may also access more other PEs in a multi-homed manner, which is not limited in this application. If the CE accesses more other PEs in a multi-homing manner, the second PE may refer to a PE that is selected as the DF by default or preferentially among the PEs that the CE accesses in a multi-homing manner, or a PE that has been selected as the DF previously according to some preset rule. The first PE may refer to a PE elected as the DF for a CE after a failure of a communication link between the CE and a second PE. It can be understood that, in this case, after the communication link between the CE and the second PE is recovered, the second PE may switch to the DF corresponding to the CE again through the failure switchback process, and accordingly, the first PE may switch to the non DF corresponding to the CE again. And other PEs may always exist as non DFs corresponding to the CE in the process.

The technical solution of the embodiment of the present application is specifically described below by taking CE dual homing as an example.

Step S402, the first PE sends a first route notification message to the far-end PE, the first route notification message is used for notifying first MAC route information of the CE, and the priority of the first MAC route information is lower than the preset priority.

Accordingly, the far-end PE may receive the first route advertisement packet from the first PE.

In this embodiment, the remote PE is a PE to which the remote CE communicating with the CE accesses. The remote CE may access one PE, or access multiple PEs in a multi-homing manner, which is not limited in this application. If a far-end CE accesses multiple PEs in a multi-homing manner, the far-end PE may refer to a DF among the multiple PEs accessed by the far-end CE. By sending the first route notification message to the PE serving as the DF in the multiple PEs accessed by the far-end CE, the PE serving as the DF can select a proper forwarding path for a message from the far-end CE and sent to the CE according to the first MAC routing information of the CE in the first route notification message. Optionally, the first PE may send the first route advertisement packet to each of the multiple PEs accessed by the far-end CE, or the first PE may also send the first route advertisement packet to a non DF in the multiple PEs accessed by the far-end CE, so that the PEs serving as the non DF may record the first MAC routing information, and update a routing table entry corresponding to the CE in its routing forwarding table according to the first MAC routing information, so that after the non DF is switched to the DF, corresponding processing may be performed according to the first MAC routing information.

For example, as shown in fig. 5, after the first PE is switched from the DF corresponding to the CE to a non DF, the first PE may send a first route advertisement message to the far-end PE, update the MAC routing information of the CE via the first PE to the first MAC routing information through the first route advertisement message, and indicate a priority of the first MAC routing information, where the priority of the first MAC routing information is lower than a preset priority.

Optionally, after the second PE is switched from the non DF corresponding to the CE to the DF, if the second PE receives the uplink packet from the CE, the second PE may send a second route advertisement packet to the remote PE, notify, through the second route advertisement packet, second MAC routing information of the CE via the second PE, and indicate a priority of the second MAC routing information, where the priority of the second MAC routing information is greater than or equal to a preset priority.

It should be noted that the first route advertisement packet and the second route advertisement packet may have other names, and the present application is not limited thereto, for example, the two packets may be referred to as a route update packet and a route advertisement packet, respectively, so that when the non DF of the CE is switched to the DF, the first PE has advertised the MAC routing information of the CE that passes through the first PE once. Optionally, the two messages may be the same type of message, for example, MAC route advertisement messages. The preset priority may also be referred to as a default priority, a normal priority, or the like, without limitation.

In other words, in the failure back-switch process, after the DF corresponding to the CE is switched to the non DF, the first PE may advertise the MAC routing information of the CE via the first PE once in the EVPN network (for clarity of description, it is referred to as first MAC routing information herein) and indicate that the first MAC routing information is of low priority. Optionally, after the non DF corresponding to the CE is switched to the DF, if the uplink packet from the CE is received, the second PE may also notify MAC routing information of the CE via the second PE once in the EVPN network (for clarity of description, it is referred to as second MAC routing information here), and indicate that the second MAC routing information is a preset priority (may also be referred to as default priority, normal priority, etc.) or a high priority.

Furthermore, the far-end PE may select a suitable path for forwarding a packet from the far-end CE and sent to the CE according to the priority of each received MAC routing information of the CE, where the packet specifically refers to a unicast packet from the far-end CE to the CE, and optionally may be a unicast data packet. Specifically, after receiving the first MAC routing information from the first PE, the far-end PE may forward, according to the first MAC routing information, a packet from the far-end CE and addressed to the CE to the first PE before receiving the second MAC routing information from the second PE (i.e., before the second PE receives the uplink packet from the CE and triggers the MAC routing advertisement), because only one route pointing to the CE of the first MAC routing information is reachable at this time. At this time, since the first PE has been switched to the non DF corresponding to the CE, the first PE may forward the packet to the second PE through the MAC FRR link, and the second PE then forwards the packet to the CE. That is to say, in this situation, the forwarding path of the unicast packet from the remote CE to the CE is { remote CE- > remote PE- > first PE- > second PE- > the CE }, and the forwarding path needs to bypass the MAC FRR link between the first PE and the second PE.

After receiving the first MAC routing information from the first PE, the far-end PE receives the second MAC routing information from the second PE (i.e., after the second PE receives the uplink packet from the CE and triggers the MAC routing advertisement), because both of the routes directed to the CE of the first MAC routing information and the second MAC routing information are reachable at this time, but the priority of the first MAC routing information is lower than that of the second MAC routing information, the far-end PE may forward the packet from the far-end CE and addressed to the CE to the second PE according to the second MAC routing information on the basis of the MAC routing information with higher priority, and forward the packet to the CE by the second PE. That is to say, in this situation, the forwarding path preferentially adopted by the packet from the remote CE to the CE is { remote CE- > remote PE- > second PE- > the CE }, and the forwarding path does not need to bypass the MAC FRR link between the first PE and the second PE, so that the bypassing time of the packet can be effectively shortened. The forwarding path originally via the first PE may be considered an alternative forwarding path in this case.

By adopting the technical scheme, when a certain PE accessed by a CE is switched from a DF corresponding to the CE to a non DF, the PE updates the MAC routing information of the CE and indicates the corresponding low priority, so that the far-end PE can select a proper forwarding path for the message sent to the CE according to the priority of each MAC routing information of the CE, thereby optimizing the unicast routing of the CE, ensuring that the unicast routing can be converged to the current DF more quickly and effectively shortening the forwarding time of the message.

In this embodiment of the application, the priority of the MAC routing information advertised by the first route advertisement packet or the second route advertisement packet may be indicated in a variety of ways. Illustratively, taking the first MAC routing information as an example, in one possible implementation, if the remote PE is an Internal Border Gateway Protocol (IBGP) neighbor of the first PE, the priority of the first MAC routing information may be indicated by a LOCAL _ priority (LOCAL _ PREF) attribute of the first MAC routing information.

The protocol specifies that the LOCAL _ PREF attribute in Border Gateway Protocol (BGP) routing is a well-established attribute. This attribute, which is a known mandatory attribute, must be included when a router updates a route to its IBGP neighbor. The router may calculate the priority of each external route based on a locally configured policy, and indicate the corresponding priority of each external route through a LOCAL _ PREF attribute when advertising the external route to its IBGP neighbor. The greater the attribute value of the LOCAL _ PREF attribute, the higher the priority of the corresponding MAC route, and the smaller the attribute value, the lower the priority of the corresponding MAC route. Illustratively, the attribute value of the LOCAL _ PREF attribute may be represented by a 4-byte unsigned integer.

Therefore, that the priority of the first MAC routing information is lower than the preset priority may mean that the attribute value of the LOCAL _ PREF attribute of the first MAC routing information is smaller than the attribute value of the LOCAL _ PREF attribute corresponding to the preset priority.

Similarly, if the remote PE is an IBGP neighbor of the second PE, the priority of the second MAC routing information may also be indicated by the LOCAL _ PREF attribute of the second MAC routing information. Therefore, that the attribute value of the second MAC routing information is greater than or equal to the preset priority may mean that the attribute value of the LOCAL _ PREF attribute of the second MAC routing information is greater than or equal to the attribute value of the LOCAL _ PREF attribute corresponding to the preset priority. It is understood that since the first PE and the second PE are two PEs connected to the same CE, both belong to the same Autonomous System (AS), when a far-end PE is an IBGP neighbor of the first PE, the far-end PE is also an IBGP neighbor of the second PE.

Optionally, the attribute value of the LOCAL _ PREF attribute corresponding to the preset priority may be a default attribute value of the LOCAL _ PREF attribute. Illustratively, the default attribute value of the LOCAL _ PREF attribute may be 100.

The protocol also specifies that the LOCAL router should also use the priority of the route indicated by the LOCAL _ PREF attribute for routing calculations, and that high priority routes should be preferentially selected. Therefore, with the above technical solution, when the first PE is switched from the DF of the CE to the non DF, the first PE may update the first MAC routing information for IBGP neighbors, and reduce the priority of the first MAC routing information by modifying the attribute value of the LOCAL _ PREF attribute of the first MAC routing information, thereby guiding the remote PE to select a proper packet forwarding path according to the priority of the routing.

Exemplarily, assuming that the default attribute value of the LOCAL _ PREF attribute is 100, when the first PE is switched from the DF of the CE to the non DF, the first PE may advertise the first MAC routing information of the CE, and set the attribute value of the LOCAL _ PREF attribute of the first MAC routing information to be smaller than the default attribute value of the LOCAL _ PREF attribute, for example, to be 50, which indicates that the priority of the first MAC routing information is a low priority, and the packet forwarding path indicated by the first MAC routing information and reaching the CE via the first PE is an alternative path. When the second PE is switched to DF by the non DF of the CE and receives an uplink packet from the CE, the second PE may also notify the second MAC routing information of the CE, and set an attribute value of a LOCAL _ PREF attribute of the second MAC routing information to be equal to a default attribute value of the LOCAL _ PREF attribute, for example, to be 100, which indicates that the priority of the first MAC routing information is a normal priority or a default priority or a high priority, and a packet forwarding path indicated by the second MAC routing information and reaching the CE via the second PE is a main path (or may also be referred to as a default path, a preferred path, or the like). Thus, after the far-end PE receives the first MAC routing information from the first PE and the second MAC routing information from the second PE, the far-end PE may perform path selection on the packet sent to the CE according to the first MAC routing information and the second MAC routing information, and preferentially adopt the packet forwarding path indicated by the second MAC routing information with a higher priority, and send the packet to the second PE, that is, the current DF.

In another possible embodiment, if the far-end PE is an External Border Gateway Protocol (EBGP) neighbor of the first PE, the priority of the first MAC routing information may be indicated by a multi-exit identifier (MED) attribute of the first MAC routing information. The multi-egress identification attribute may also be referred to as a multi-egress discrimination attribute.

The protocol specifies that the MED attribute in BGP routing is an optional non-transitive attribute used between different ASs to distinguish different egress or ingress points when multiple links exist to the same AS. For a router, if a route with the MED attribute is received from an EBGP neighbor, the attribute may be passed to all IBGP neighbors within the local AS. But the MED attribute passed from one EBGP neighbor must not be passed on to another EBGP neighbor of itself. Routers may modify the MED value of a route learned from an EBGP neighbor by local configuration, but it should be noted that if the MED value of a route learned from an EBGP neighbor is modified by configuration at a router, such modification must be done before determining the priority of the route and routing.

The attribute value of the MED attribute may be referred to as metric (or cost), and for example, the attribute value of the MED attribute may be represented by an unsigned integer of 4 bytes. For a router, when other conditions are the same, a route with a smaller metric should be prioritized, that is, the smaller the attribute value of the MED attribute, the higher the priority of the corresponding route is indicated, and the larger the attribute value, the lower the priority of the corresponding route is indicated.

Therefore, that the priority of the first MAC routing information is lower than the preset priority may mean that the attribute value of the MED attribute of the first MAC routing information is greater than the attribute value of the MED attribute corresponding to the preset priority.

Similarly, if the remote PE is an EBGP neighbor of the second PE, the priority of the second MAC routing information may also be indicated by the MED attribute of the second MAC routing information. Therefore, the priority of the second MAC routing information being greater than or equal to the preset priority means that the attribute value of the MED attribute of the second MAC routing information is less than or equal to the attribute value of the MED attribute corresponding to the preset priority. It can be understood that, since the first PE and the second PE are two PEs connected to the same CE, and both of the two PEs belong to the same AS, when the remote PE is an EBGP neighbor of the first PE, the remote PE is also an IBGP neighbor of the second PE.

Optionally, the attribute value of the MED attribute corresponding to the preset priority may be a default attribute value of the MED attribute. Illustratively, the default attribute value of the MED attribute may be 0.

Therefore, with the above technical solution, when the first PE is switched from the DF of the CE to the non DF, the first PE may update the first MAC routing information for the EBGP neighbor, and reduce the priority of the first MAC routing information by modifying the attribute value of the MED attribute of the first MAC routing information, thereby guiding the remote PE to select a proper packet forwarding path according to the priority of the routing.

For example, assuming that the default attribute value of the MED attribute is 0, when the first PE is switched from the DF of the CE to the non DF, the first PE may advertise the first MAC routing information of the CE, and set the attribute value of the MED attribute of the first MAC routing information to be greater than the default attribute value of the MED attribute, for example, to be 50, which indicates that the priority of the first MAC routing information is a low priority, and the packet forwarding path indicated by the first MAC routing information and reaching the CE via the first PE is an alternative path. When the second PE is switched from the non DF of the CE to the DF and receives an uplink packet from the CE, the second PE may also notify the second MAC routing information of the CE, and set an attribute value of an MED attribute of the second MAC routing information to be equal to a default attribute value of the MED attribute, for example, to be 0, which indicates that the priority of the first MAC routing information is a normal priority, a default priority, or a high priority, and the packet forwarding path indicated by the second MAC routing information and reaching the CE via the second PE is a main path (or may also be referred to as a default path, a preferred path, or the like). Thus, after the far-end PE receives the first MAC routing information from the first PE and the second MAC routing information from the second PE, the far-end PE may perform path selection on the packet sent to the CE according to the first MAC routing information and the second MAC routing information, and preferentially adopt the packet forwarding path indicated by the second MAC routing information with a higher priority, and send the packet to the second PE, that is, the current DF.

As an example, the route advertisement packet (e.g., the first route advertisement packet and the second route advertisement packet) in the embodiment of the present application may adopt a packet structure as shown in fig. 6a, where the packet structure includes the following fields: length of route to withdraw (routes length), route to withdraw (routes), total length of path attribute (total path attribute length), path attribute value (path attributes), network layer reachability information (network layer reachability information). Illustratively, the lengths of the fields may be: the withdrawn route is 2 bytes in length, the route to be withdrawn is variable in length (variable), the total length of the path attribute is 2 bytes, the path attribute value is variable in length (variable), and the network layer reachability information is variable in length (variable).

The field of the path attribute value of the packet structure may include a plurality of routing attributes (or simply attributes), and the structure of each attribute may include an attribute flag (attr. flags) and an attribute type Code (attr. type Code) as shown in fig. 6 b. Both the LOCAL _ PREF attribute and the MED attribute referred to in this application can be located in the field of a path attribute value, the attribute type code of the LOCAL _ PREF attribute is 5, and the attribute type code of the MED attribute is 4.

Please refer to fig. 7, which is a flowchart illustrating another method for switching back a failure in an EVPN network according to an embodiment of the present disclosure. The method comprises the following steps:

step S701, the far-end PE receives a route advertisement message from the second PE, where the route advertisement message is used to advertise the second MAC routing information of the CE.

In this embodiment of the present application, the CE accesses the first PE and the second PE. In one possible embodiment, the CE may have dual-homed access to a first PE and a second PE, and the first PE and the second PE operate in a single-alive mode. In another possible embodiment, the CE may also access the first PE, the second PE, and more other PEs in a multi-homed manner, without limitation, at this time, the multiple PEs where the CE accesses in a multi-homed manner still operate in a single active mode. For the explanation of the access method of the CE, please refer to the related description above, and will not be repeated.

The embodiment is also applied to a fault switchback scenario, where a first PE refers to a PE that switches a DF corresponding to a CE to a non DF during the fault switchback, a second PE refers to a PE that switches a non DF corresponding to a CE to a DF during the fault switchback, and a remote PE refers to a PE accessed by a remote CE communicating with the CE or a DF in multiple accessed PEs. For the introduction of the first PE, the second PE and the remote PE, please refer to the related description above, which is not repeated.

It should be noted that, when the first PE is switched from the DF corresponding to the CE to the non DF, the first PE may not withdraw the first MAC routing information of the CE via the first PE, that is, the first PE may not send a routing withdrawal packet to the far-end PE to withdraw the first MAC routing information. And after the second PE is switched from the non DF corresponding to the CE to the DF, when the second PE receives the uplink packet from the CE, the second PE is triggered to notify the remote PE of the second MAC routing information of the CE via the second PE, that is, the second PE sends a routing notification packet to the remote PE to notify the remote PE of the second MAC routing information.

Step S702, if the second MAC routing information is the MAC routing information of the CE that the remote PE received last time, the remote PE determines to forward the packet of the CE through the second PE according to the second MAC routing information.

For example, as shown in fig. 8, after the far-end PE receives the second MAC routing information from the second PE, because the second MAC routing information is the last MAC routing information of the CE received by the far-end PE, according to the principle of taking the last updated MAC routing information as the standard, when the far-end PE needs to forward a packet from the far-end CE and sent to the CE, the far-end PE may forward the packet to the second PE according to the second MAC routing information. The packet refers to a unicast packet sent by a remote CE to the CE, and optionally, the packet may be a unicast data packet. By adopting the technical scheme, the routing principle of the far-end PE is set to take the MAC routing information updated for the last time as priority, so that the unicast routing from the far-end CE to the CE can be quickly converged to the DF corresponding to the CE at the moment, thereby effectively shortening the forwarding time of the message and avoiding the overlong bypass time of the message in the network.

It can also be understood that, in a case that the first MAC routing information of the CE is not revoked by the first PE, the remote PE receives the second MAC routing information from the second PE again, and because the first MAC routing information and the second MAC routing information both point to the CE and Ethernet Segment Identifiers (ESIs) of the first MAC routing information and the second MAC routing information are the same, at this time, the remote PE may determine that the last MAC routing information received is the standard, determine that a forwarding path corresponding to the second MAC routing information is a primary forwarding path (or a preferred forwarding path), and determine that a forwarding path corresponding to the first MAC routing information is a secondary forwarding path (or an alternative forwarding path).

It can be seen that the method shown in fig. 7 is different from the method shown in fig. 4 in that, in the manner shown in fig. 7, the far-end PE uses the newly received MAC routing information as the basis of the packet forwarding path, rather than deciding the packet forwarding path according to the priority of the route.

Referring to fig. 9, a schematic structural diagram of a fault switchback device provided in an embodiment of the present application is further provided, where the fault switchback device 900 includes: a transceiver module 910 and a processing module 920.

The fault switchback device can be used for realizing that the first PE or the remote PE is involved in any one of the above method embodiments. For example, the apparatus may be a chip or a circuit included in the PE or the router.

For example, when the fault switchback apparatus executes the operation or step corresponding to the first PE in the embodiment of the method shown in fig. 4, the processing module 920 is configured to determine that a DF corresponding to a CE is switched to a non DF, where the CE is connected to the first PE and the second PE, and the first PE and the second PE operate in a single live mode; the transceiving module 910 is configured to send a first route advertisement message to a far-end PE, where the first route advertisement message is used to advertise first MAC routing information of the CE, and a priority of the first MAC routing information is lower than a preset priority.

In one possible design, if the remote PE is an EBGP neighbor of the first PE, the priority of the first MAC routing information may be indicated by the MED attribute of the first MAC routing information; as such, the priority of the first MAC routing information being lower than the preset priority may refer to: the attribute value of the MED attribute of the first MAC routing information is greater than the attribute value of the MED attribute corresponding to the preset priority.

When the fault cutback apparatus executes the operation or step corresponding to the remote PE in the method embodiment shown in fig. 7, the transceiver module 910 is configured to receive a route advertisement message from the second PE, where the route advertisement message is used to advertise the second MAC routing information of the CE, the CE is accessed to the first PE and the second PE, and the first PE and the second PE operate in a single active mode; the processing module 920 is configured to, if the second MAC routing information is the MAC routing information of the CE that is received by the apparatus for the last time, determine, by the remote PE, to forward the packet of the CE through the second PE according to the second MAC routing information.

The processing module 920 involved in the fault switchback apparatus may be implemented by at least one processor or processor-related circuit component, and the transceiver module 910 may be implemented by at least one transceiver or transceiver-related circuit component or communication interface. The operations and/or functions of the modules in the communication apparatus are respectively for implementing the corresponding flows of the methods shown in fig. 4, fig. 5, fig. 7, and fig. 8, and are not described herein again for brevity. Optionally, the fault switchback device may further include a storage module, where the storage module may be configured to store data and/or instructions, and the transceiver module 910 and/or the processing module 920 may read the data and/or instructions in the access module, so as to enable the fault switchback device to implement the corresponding method. The memory module may be implemented, for example, by at least one memory.

The storage module, the processing module and the transceiver module may be separated, or all or part of the modules may be integrated, for example, the storage module and the processing module are integrated, or the processing module and the transceiver module are integrated.

Please refer to fig. 10, which is another structural schematic diagram of a fail-back switch device provided in the embodiment of the present application. The failure switchback device may be configured to implement a function corresponding to the first PE or the remote PE in the foregoing method embodiment, for example, the failure switchback device may be a PE, or a device capable of supporting the PE to implement a corresponding function in the foregoing method embodiment.

The communication device may include a processor 1001, a communication interface 1002, and a memory 1003. The communication interface 1002 is used for communicating with other devices through a transmission medium, and the communication interface 1002 may be a transceiver or an interface circuit such as a transceiver circuit or a transceiver chip. The memory 1003 is used for storing program instructions and/or data, and the processor 1001 is used for executing the program instructions stored in the memory 1003, so as to implement the method in the above method embodiments. Optionally, the memory 1003 is coupled to the processor 10901, and the coupling is an indirect coupling or communication connection between devices, units or modules, which may be electrical, mechanical or in other forms, and is used for information exchange between the devices, units or modules.

In an embodiment, the communication interface 1002 may be specifically configured to perform the actions of the transceiver module 1010, and the processor 1001 may be specifically configured to perform the actions of the processing module 1020, which are not described herein again.

In the embodiment of the present application, a specific connection medium among the communication interface 1002, the processor 1001, and the memory 1003 is not limited. In the embodiment of the present application, the memory 1003, the processor 1001, and the communication interface 1002 are connected by the bus 1004 in fig. 10, the bus is represented by a thick line in fig. 10, and the connection manner between other components is merely illustrative and not limited. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one thick line is shown in FIG. 10, but this is not intended to represent only one bus or type of bus.

An embodiment of the present application further provides a chip system, including: a processor coupled with a memory for storing a program or instructions which, when executed by the processor, cause the system-on-chip to implement the method of the corresponding terminal or the method of the corresponding network device in any of the above method embodiments.

Optionally, the system on a chip may have one or more processors. The processor may be implemented by hardware or by software. When implemented in hardware, the processor may be a logic circuit, an integrated circuit, or the like. When implemented in software, the processor may be a general-purpose processor implemented by reading software code stored in a memory.

Optionally, the memory in the system-on-chip may also be one or more. The memory may be integrated with the processor or may be separate from the processor, which is not limited in this application. For example, the memory may be a non-transitory processor, such as a read only memory ROM, which may be integrated with the processor on the same chip or separately disposed on different chips, and the type of the memory and the arrangement of the memory and the processor are not particularly limited in this application.

The chip system may be a Field Programmable Gate Array (FPGA), an Application Specific Integrated Circuit (ASIC), a system on chip (SoC), a Central Processor Unit (CPU), a Network Processor (NP), a Digital Signal Processor (DSP), a Microcontroller (MCU), a Programmable Logic Device (PLD) or other integrated chips.

It will be appreciated that the steps of the above described method embodiments may be performed by integrated logic circuits of hardware in a processor or instructions in the form of software. The steps of the method disclosed in connection with the embodiments of the present application may be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules in a processor.

The embodiment of the present application further provides a computer-readable storage medium, where computer-readable instructions are stored in the computer-readable storage medium, and when the computer-readable instructions are read and executed by a computer, the computer is enabled to execute the method in any of the above method embodiments.

The embodiments of the present application further provide a computer program product, which when read and executed by a computer, causes the computer to execute the method in any of the above method embodiments.

An embodiment of the present application further provides a communication system, where the communication system includes a CE, a first PE, and a second PE. Optionally, the communication system may further include a far-end PE. Optionally, the communication system may further include a far-end CE.

It should be understood that the processor referred to in the embodiments of the present application may be a CPU, but may also be other general purpose processors, DSPs, ASICs, FPGAs, or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.

It will also be appreciated that the memory referred to in the embodiments of the application may be either volatile memory or nonvolatile memory, or may include both volatile and nonvolatile memory. The non-volatile memory may be a read-only memory (ROM), a programmable ROM, an erasable programmable ROM, an electrically erasable programmable ROM, or a flash memory. Volatile memory can be Random Access Memory (RAM), which acts as external cache memory. By way of example, and not limitation, many forms of RAM are available, such as static random access memory, dynamic random access memory, synchronous dynamic random access memory, double data rate synchronous dynamic random access memory, enhanced synchronous dynamic random access memory, synchronous link dynamic random access memory, and direct memory bus random access memory.

It should be noted that when the processor is a general-purpose processor, a DSP, an ASIC, an FPGA or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component, the memory (memory module) is integrated in the processor.

It should be noted that the memory described herein is intended to comprise, without being limited to, these and any other suitable types of memory.

It should be understood that the various numerical references mentioned in the various embodiments of the present application are merely for convenience of description and differentiation, and the serial numbers of the above-mentioned processes or steps do not imply any order of execution, and the execution order of the processes or steps should be determined by their functions and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and 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 units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit.

The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application or portions thereof that substantially contribute to the prior art may be embodied in the form of a software product stored in a storage medium and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: various media capable of storing program codes, such as a U disk, a removable hard disk, a ROM, a RAM, a magnetic disk, or an optical disk.

In the embodiments of the present application, unless otherwise specified or conflicting with respect to logic, the terms and/or descriptions in different embodiments have consistency and may be mutually cited, and technical features in different embodiments may be combined to form a new embodiment according to their inherent logic relationship.

Claims

1. A method of fault cutback in an ethernet virtual private network, the method comprising:

a first Provider Edge (PE) determines that a Designated Forwarder (DF) corresponding to a Customer Edge (CE) is switched to a non-designated forwarder (non-DF), the CE is accessed to the first PE and a second PE, and the first PE and the second PE work in a single-alive mode;

the first PE sends a first routing notification message to a far-end PE, the first routing notification message is used for notifying first MAC routing information of the CE, and the priority of the first MAC routing information is lower than a preset priority.

2. The method according to claim 1, wherein if the remote PE is an IBGP neighbor of the first PE, the priority of the first MAC routing information is indicated by a LOCAL priority LOCAL _ PREF attribute of the first MAC routing information;

the priority of the first MAC routing information is lower than a preset priority, including:

and the attribute value of the LOCAL _ PREF attribute of the first MAC routing information is smaller than the attribute value of the LOCAL _ PREF attribute corresponding to the preset priority.

3. The method according to claim 1, wherein if the remote PE is an EBGP neighbor of the first PE, the priority of the first MAC routing information is indicated by a multi-egress identification, MED, attribute of the first MAC routing information;

and the attribute value of the MED attribute of the first MAC routing information is greater than the attribute value of the MED attribute corresponding to the preset priority.

4. A method of fault cutback in an ethernet virtual private network, EVPN, the method comprising:

a far-end Provider Edge (PE) receives a route notification message from a second PE, wherein the route notification message is used for notifying second MAC (media access control) route information of a Customer Edge (CE), the CE is accessed to a first PE and the second PE, and the first PE and the second PE work in a single-active mode;

and if the second MAC routing information is the MAC routing information of the CE received by the far-end PE last time, the far-end PE determines to forward the message of the CE through the second PE according to the second MAC routing information.

5. A fail-back device, comprising:

a processing module, configured to determine that a designated forwarder DF corresponding to a customer edge device CE is switched to a non-designated forwarder non DF, where the CE is accessed to the apparatus and a second provider edge device PE, and the apparatus and the second PE operate in a single-alive mode;

and the transceiver module is used for sending a first route notification message to the far-end PE, wherein the first route notification message is used for notifying first MAC (media access control) route information of the CE, and the priority of the first MAC route information is lower than the preset priority.

6. The apparatus of claim 5, wherein if the remote PE is an IBGP neighbor of the apparatus, the priority of the first MAC routing information is indicated by a LOCAL priority LOCAL _ PREF attribute of the MAC routing information, and an attribute value of the LOCAL _ PREF attribute of the first MAC routing information is smaller than an attribute value of a LOCAL _ PREF attribute corresponding to the preset priority.

7. The apparatus according to claim 5, wherein if the far-end PE is an EBGP neighbor of the apparatus, the priority of the first MAC routing information is indicated by a multi-egress identification, MED, attribute of the first MAC routing information, and an attribute value of the MED attribute of the first MAC routing information is greater than an attribute value of the MED attribute corresponding to the preset priority.

8. A fail-back device, comprising:

a transceiver module, configured to receive a route advertisement message from a second provider edge PE, where the route advertisement message is used to advertise second MAC routing information of a customer edge CE, the CE is accessed to a first PE and a second PE, and the first PE and the second PE operate in a single active mode;

and the processing module is configured to determine to forward the packet of the CE through the second PE according to the second MAC routing information if it is determined that the second MAC routing information is the MAC routing information of the CE received by the apparatus for the last time.

9. A fail-back apparatus, the apparatus comprising at least one processor coupled with at least one memory:

the at least one processor configured to execute computer programs or instructions stored in the at least one memory to cause the apparatus to perform the method of any one of claims 1 to 3 or to cause the apparatus to perform the method of claim 4.

10. A computer-readable storage medium storing instructions that, when executed, cause the method of any one of claims 1 to 3 to be implemented, or cause the method of claim 4 to be implemented.

11. A fail-back apparatus comprising a processor and an interface circuit;

the interface circuit is used for interacting code instructions or data with the processor;

the processor is configured to perform the method of any one of claims 1 to 3 or configured to perform the method of claim 4.