CN106302176B

CN106302176B - It is a kind of for controlling the method and apparatus of multicast transmission

Info

Publication number: CN106302176B
Application number: CN201610674380.6A
Authority: CN
Inventors: 杨帆; 王东; 仇普祺
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2016-08-15
Filing date: 2016-08-15
Publication date: 2019-10-22
Anticipated expiration: 2036-08-15
Also published as: WO2018032869A1; CN106302176A

Abstract

The embodiment of the invention discloses a kind of for controlling the method and apparatus of multicast transmission, it is related to field of communication technology, 2nd PE equipment can be after the first PE equipment be restored normally to be upgraded to DR, the multicast forwarding list item saved in the 2nd PE equipment is deleted immediately, is simultaneously multicast receivers forwarding multicast flow so as to avoid the first PE equipment and the 2nd PE equipment.The specific scheme is that the 2nd PE equipment as BDR is upgraded to DR after the first PE equipment fault as DR, this method comprises: the 2nd PE equipment after the first PE equipment restores normal, determines that restoring normal first PE equipment is upgraded to DR；When determining that restoring normal first PE equipment is upgraded to DR, the first Assert message is sent to the first PE equipment, the first Assert message is used to obtain the information for carrying out Assert election from the normal first PE equipment of recovery.During the embodiment of the present invention is applied to multicast traffic transport.

Description

Method and equipment for controlling multicast transmission

Technical Field

The present invention relates to the field of communications technologies, and in particular, to a method and a device for controlling multicast transmission.

Background

In the multicast technology, different user private networks can be connected through the backbone network of an operator. Specifically, the backbone network may communicate with a multicast receiver in the private network through a Provider Edge (PE) device. The PE device communicating with the multicast receiver can receive the multicast flow from the multicast source and forward the multicast flow to the multicast receiver in the private network according to the multicast forwarding table.

In order to avoid abnormal multicast traffic transmission caused by failure of a PE device communicating with a multicast receiver, two PE devices communicating with the multicast receiver are generally configured, where the two PE devices include: a PE device 1 as a Designated Router (DR) and a PE device 2 as a Backup Designated Router (BDR). The PE device 1 as DR and the PE device 2 as BDR communicate with the multicast receiver through the two-layer switch. When the PE device 1 as the DR fails, the PE device 2 as the BDR is raised to the DR, and after obtaining the multicast forwarding entry, the multicast traffic is forwarded through the two-layer switch. And when the failed PE equipment 1 is recovered to be normal, the recovered normal PE equipment 1 is raised to DR, and the multicast flow is forwarded through the two-layer switch after the multicast forwarding table entry is obtained. When the normal PE device 1 is recovered to be upgraded to DR, the PE device 2 is upgraded from DR to BDR. The PE device 2 serving as the BDR sets a period suppression mechanism, so that the PE device 2 will determine whether the downstream interface of the PE device 2 receives the multicast traffic within the detection period at an interval of the detection period duration. If the PE device 1 as the DR recovers to normal in the detection period and sends the multicast traffic through its downstream interface, the PE device 2 will initiate assertion (english: Assert) election only after the detection period ends. The PE device 2 deletes the multicast forwarding entry on the PE device 2 after the Assert election fails. Therefore, in the detection period, even after the PE device 1 returns to normal, the PE device 2 still forwards the multicast traffic according to the multicast forwarding entry, and the multicast receiver receives the duplicate multicast traffic from the PE device 2 serving as the BDR and the PE device 1 serving as the DR through the two-layer switch.

Disclosure of Invention

The invention provides a method and equipment for controlling multicast transmission, which are beneficial to preventing a multicast receiver from receiving double multicast flows and saving network resources.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, a method for controlling multicast transmission is provided, in which a second PE device acting as a BDR rises to a DR after a failure of a first PE device acting as the DR, the method comprising: after the first PE equipment returns to be normal, the second PE equipment determines that the first PE equipment which returns to be normal rises to be the DR; and when the second PE equipment determines that the recovered first PE equipment is increased to DR, sending a first Assert message to the first PE equipment, wherein the first Assert message is used for obtaining information for performing Assert election from the recovered first PE equipment.

And under the condition that the first PE equipment is recovered to be normal in a detection period of a period suppression mechanism, the second PE equipment cannot sense the multicast traffic of the downstream interface of the second PE equipment in real time before the detection period is ended. However, the second PE device may send a first Assert message to the first PE device when determining that the first PE device that recovers to normal rises to DR, so as to obtain information for performing Assert election from the first PE device that recovers to normal. After the second PE device is elected to be reduced to BDR by Assert, the second PE device immediately deletes the multicast forwarding entry stored in the second PE device, thereby preventing the first PE device and the second PE device from forwarding multicast traffic for a multicast receiver at the same time.

In a possible implementation manner, the determining, by the second PE device, that the first PE device that recovers from normal is upgraded to DR after the first PE device recovers from normal includes: the second PE equipment receives a DR election message sent by the first PE equipment which is recovered to be normal, wherein the DR election message carries DR election information of the first PE equipment which is recovered to be normal; the second PE equipment performs DR election according to the recovered DR election information of the first PE equipment and the recovered DR election information of the second PE equipment; and the second PE equipment determines that the first PE equipment which is recovered to be normal is lifted to be DR according to the DR election result. The DR election information of the first PE device that recovers to normal may include a DR priority of the first PE device that recovers to normal and/or an Internet Protocol (IP) address of a downstream interface of the first PE device that recovers to normal. The DR election information of the second PE device may include a DR priority of the second PE device and/or an IP address of a downstream interface of the second PE device.

Wherein, the normal cycle suppression mechanism can only suppress the real-time perception of the downstream interface of the second PE device to the service packet (multicast traffic) in the detection cycle. The normal cycle suppression mechanism does not suppress the real-time perception of the downstream interface of the second PE device to the protocol packet in the detection cycle. And the DR election message sent by the first PE equipment to the second PE equipment which is recovered to be normal belongs to a protocol message. Therefore, the second PE device may determine in real time, through its downstream interface, that the DR election packet from the first PE device that recovers to normal is received. And the second PE equipment performs DR election according to the DR election message, and performs corresponding Assert election after determining that the first PE equipment is lifted to DR.

In a possible implementation manner, the determining, by the second PE device, that the first PE device that recovers from normal is upgraded to DR after the first PE device recovers from normal includes: and the second PE equipment detects that the downstream interface of the second PE equipment is converted from a first state to a second state, and the first PE equipment which is recovered to be normal is determined to be increased to DR. The first state is a state that the downstream interface of the second PE device does not receive the multicast traffic, and the second state is a state that the downstream interface of the second PE device receives the multicast traffic. The downstream interface of the second PE device is an interface capable of communicating with multicast recipients.

And the first PE device does not forward the multicast traffic after being used as the BDR. And the first PE equipment transmits multicast traffic after being used as DR. And if the downstream interface of the second PE device does not receive the multicast traffic, the first PE device is a BDR. And if the downstream interface of the second PE device receives the multicast traffic, the first PE device is upgraded from the BDR to the DR. Therefore, when the downstream interface of the second PE device is switched from a state of not receiving the multicast traffic to a state of receiving the multicast traffic, the second PE device may determine that the first PE device recovers to normal and increases to DR.

In a possible implementation manner, the multicast traffic may be multicast traffic that is sent by the first PE device that recovers from normal through a downstream interface of the first PE device that recovers from normal at a first time, where the first time is a time after a preset time length elapses from a time point at which the first PE device that has failed recovers from normal, where the preset time length is greater than or equal to an aging time of a cycle suppression mechanism, and the downstream interface of the first PE device that recovers from normal is an interface capable of communicating with a multicast receiver.

And when the recovered first PE device is upgraded to DR, the recovered first PE device does not immediately forward the multicast traffic. And after the aging time of the cycle suppression mechanism reaches, the first PE equipment which recovers to be normal sends multicast traffic through a downstream interface of the first PE equipment. And after the aging time of the cycle suppression mechanism is reached, the cycle suppression mechanism of the second PE device is disabled. Therefore, the second PE device may sense the multicast traffic of the downstream interface thereof in real time, so that the second PE device immediately sends the first Assert packet to the first PE device. In this way, the second PE device can immediately delete the multicast forwarding entry stored in the second PE device, thereby preventing the first PE device and the second PE device from forwarding the multicast traffic for the multicast receiver at the same time.

In a possible implementation manner, the method provided in the embodiment of the present invention may further include: the second PE equipment receives a second Assert message sent by the first PE equipment which recovers to normal, wherein the second Assert message comprises Assert election information of the first PE equipment; the second PE equipment performs Assert election according to Assert election information of the first PE equipment and Assert election information of the second PE equipment; and after the assertion election fails, the second PE device deletes the multicast forwarding table entry stored by the second PE device.

And the first Assert message is used for obtaining information for performing Assert election from the first PE equipment which recovers to normal. After receiving the first Assert message, the first PE device sends the Assert election information of the first PE device to the second PE device, for example, sends a second Assert message including the Assert election information of the first PE device, so that the second PE device performs Assert election.

Wherein the Assert election information of the first PE device may include: a unicast routing protocol priority of the first PE device and/or an IP address of a downstream interface of the first PE device. The Assert election information of the second PE device may include: a unicast routing protocol priority of the second PE device and/or an IP address of a downstream interface of the second PE device.

In a second aspect, there is provided a method for controlling multicast transmission, to which a second PE device acting as a BDR rises after a failure of a first PE device acting as a DR, the method comprising: after the failed first PE equipment is recovered to be normal, determining that the DR is increased; and after the recovered normal first PE equipment obtains a multicast forwarding table item, sending a first Assert message to the second PE equipment, wherein the first Assert message is used for indicating the second PE equipment to perform Assert election.

And under the condition that the first PE equipment is recovered to be normal in a detection period of the period suppression mechanism, the second PE equipment cannot sense the multicast flow of the downstream interface in real time in the detection period. However, the second PE device may receive the first Assert packet in real time through a downstream interface. Therefore, after obtaining the multicast forwarding table, the first PE device sends the first Assert message to the second PE device, so that the second PE device can immediately perform Assert election after receiving the first Assert message, and then delete the multicast forwarding table stored in the second PE device after the Assert election fails, thereby preventing the first PE device and the second PE device from forwarding multicast traffic for a multicast receiver at the same time.

In a possible implementation manner, after the failed first PE device recovers to normal and then changes to DR, and before the recovered first PE device sends the first Assert packet to the second PE device, the method provided in the embodiment of the present invention may further include: and the first PE equipment which is recovered to be normal sends a DR election message to the second PE equipment, wherein the DR election message comprises DR election information of the first PE equipment, and the DR election information of the first PE equipment comprises DR priority of the first PE equipment and/or an IP address of a downstream interface of the first PE equipment.

And in a detection period of a period suppression mechanism, the first PE equipment which is recovered to be normal sends the DR election message to the second PE equipment. Since the cycle suppression mechanism does not suppress the perception of the non-service message received in the detection cycle, the second PE device may perceive the DR election message of its downstream interface in real time. After the second PE device determines that the first PE device which recovers to normal is raised to DR according to the DR election result, it may send a second Assert message to the first PE device, so that the second PE device performs Assert election.

In a possible implementation manner, after the first PE device that recovers to normal obtains the multicast forwarding entry, the method provided in this embodiment of the present invention may further include: and the first PE equipment which is recovered to be normal sends multicast traffic through a downstream interface of the first PE equipment which is recovered to be normal, wherein the downstream interface of the first PE equipment which is recovered to be normal is an interface capable of communicating with a multicast receiver. Since the multicast traffic of the downstream interface of the second PE device changes from nothing to nothing, the second PE device can perform Assert election, so that the saved multicast forwarding table entry can be immediately deleted, and there is no problem that the first PE device and the second PE device simultaneously forward the multicast traffic for the multicast receiver.

In a possible implementation manner, after the first PE device that recovers to normal obtains the multicast forwarding entry, the method provided in the embodiment of the present invention further includes: and the first PE equipment which recovers to be normal sends the multicast flow through a downstream interface at the first moment. And the first moment is the moment when the first PE equipment with the fault recovers to be normal for a preset time length. The preset duration is greater than or equal to the aging time of the cycle suppression mechanism. And the downstream interface of the first PE device which is recovered to be normal is an interface capable of communicating with a multicast receiver.

Wherein at a first time, the cycle suppression mechanism of the second PE device has failed. If the downstream interface of the first PE device sends the multicast traffic at the first time, the second PE device may perceive the multicast traffic of the downstream interface in real time. Therefore, the second PE device may initiate Assert election after sensing the multicast traffic of its downstream interface, and immediately delete the multicast forwarding entry stored in the second PE device, so as to prevent the first PE device and the second PE device from forwarding the multicast traffic for the multicast receiver at the same time.

In the method provided by any one of the second aspect or any one of the possible implementation manners of the second aspect, the first PE device that recovers from normal may be used as a device that triggers Assert election, that is, the first PE device that recovers from normal may actively send the first Assert election packet to the second PE device after obtaining the multicast forwarding entry. Optionally, the first Assert election packet may be used as a response packet of the second Assert election packet from the second PE device, that is, before the first PE device that recovers to normal sends the first Assert packet to the second PE device, the method provided in the embodiment of the present invention further includes: and the first PE equipment receives a second Assert message from the second PE equipment, wherein the second Assert message is used for obtaining information for performing Assert election from the first PE equipment which is recovered to be normal.

In a third aspect, a method for controlling multicast transmission is provided, where the method for controlling multicast transmission includes: and obtaining and storing a first multicast forwarding table entry in the second PE device serving as the BDR, where the first multicast forwarding table entry includes a flag bit, and the flag bit is used to indicate that the first multicast forwarding table entry cannot be used to forward multicast traffic received by an upstream interface of the second PE device. Wherein the first multicast forwarding entry is not deleted after the second PE device is reduced from DR to BDR.

Optionally, after the second PE device is raised to DR, a second multicast forwarding entry may be obtained, where the second multicast forwarding entry is used to forward multicast traffic received by an upstream interface of the second PE device. The second multicast forwarding entry lacks the flag bit compared to the first multicast forwarding entry, and other contents of the second multicast forwarding entry and the first multicast forwarding entry are the same.

Wherein the flag bit in the first multicast forwarding entry indicates that the first multicast forwarding entry cannot be used for forwarding the multicast traffic received by the upstream interface of the second PE device. Therefore, even if the upstream interface of the second PE device, which is a BDR, receives the multicast traffic, the multicast traffic cannot be forwarded according to the first multicast forwarding entry. In this way, the second PE device pre-storing the first multicast forwarding entry does not cause the second PE device serving as the BDR and the first PE device serving as the DR to forward the multicast traffic to the multicast receiver at the same time. Further, the first multicast forwarding table entry enables the second PE device serving as the BDR not to start the cycle suppression mechanism after receiving the multicast traffic at its downstream interface. Under the condition that a periodic suppression mechanism is not started, the second PE device with DR reduced to BDR can sense the multicast traffic of a downstream interface in real time and initiate Assert election. In this way, the second PE device may immediately delete the second multicast forwarding entry, and may prevent the second PE device and the first PE device from forwarding the multicast traffic for the multicast receiver at the same time.

In a fourth aspect, there is provided a second PE device, a second PE device serving as a BDR increasing to DR after a failure of a first PE device serving as DR, the second PE device including: a determining unit and a transmitting unit. The determining unit is configured to determine, after the first PE device returns to normal, that the first PE device returning to normal rises to the DR. The sending unit is configured to send a first Assert message to the first PE device when the determining unit determines that the first PE device that recovers to normal rises to the DR, where the first Assert message is used to obtain information for performing Assert election from the first PE device that recovers to normal.

In a possible implementation manner, the determining unit may include: a receiving subunit, a DR election subunit, and a determining subunit. The receiving subunit is configured to receive a DR election message sent by the first PE device that recovers to normal, where the DR election message carries DR election information of the first PE device that recovers to normal, and the DR election information of the first PE device that recovers to normal includes a DR priority of the first PE device that recovers to normal and/or an IP address of a downstream interface of the first PE device that recovers to normal. The DR election subunit is configured to perform DR election according to the DR election information of the first PE device and the DR election information of the second PE device, which are received by the receiving subunit and are restored to normal, where the DR election information of the second PE device includes a DR priority of the second PE device and/or an IP address of a downstream interface of the second PE device. And the determining subunit is configured to determine, according to a DR election result obtained by performing DR election by the DR election subunit, that the first PE device that recovers to normal is elevated to DR.

In a possible implementation manner, the determining unit is specifically configured to: and detecting that the downstream interface of the second PE device is converted from the first state to the second state, and determining that the recovered first PE device is changed to DR. The first state is a state that the downstream interface of the second PE device does not receive multicast traffic, the second state is a state that the downstream interface of the second PE device receives multicast traffic, and the downstream interface of the second PE device is an interface capable of communicating with a multicast receiver.

In a possible implementation manner, the multicast traffic may be multicast traffic sent by the first PE device recovering to normal through a downstream interface of the first PE device recovering to normal at a first time, where the first time is a time after a preset time length elapses from a time point at which the first PE device recovering to normal with the fault, and the preset time length is greater than or equal to an aging time of a cycle suppression mechanism. And the downstream interface of the first PE device which returns to normal is an interface which can communicate with a multicast receiver.

In a possible implementation manner, the second PE device in the fourth aspect may further include: the system comprises a receiving unit, an assertion election unit and an entry deleting unit. The receiving unit is configured to receive a second Assert message sent by the first PE device that recovers to normal, where the second Assert message includes Assert election information of the first PE device. And the assertion election unit is used for performing Assert election according to the Assert election information of the first PE device and the Assert election information of the second PE device received by the receiving unit. And the entry deleting unit is configured to delete the multicast forwarding entry stored in the second PE device after the assertion election performed by the assertion election unit fails.

In addition, each functional unit of the fourth aspect and various possible implementations of the fourth aspect of the embodiment of the present invention is a logical partition performed on the second PE device in order to execute the method for controlling multicast transmission described in the first aspect and the various optional implementations of the first aspect. For a detailed description and a beneficial effect analysis of each functional unit of the fourth aspect and various possible implementations thereof, reference may be made to the corresponding description and technical effects in the first aspect and various possible implementations thereof, which are not described herein again.

In a fifth aspect, there is provided a first PE device, a second PE device as a BDR rising to a designated router DR after a failure of the first PE device, the first PE device comprising: a determining unit and a transmitting unit. The determining unit is configured to determine that the first PE device is increased to the DR after the failed first PE device is recovered to be normal. The sending unit is configured to send a first Assert message to the second PE device after the determining unit determines that the first PE device has risen to DR and obtains a multicast forwarding entry, where the first Assert message is used to instruct the second PE device to perform Assert election.

In a possible implementation manner, the sending unit in the fifth aspect is further configured to send a DR election packet to the second PE device after the determining unit determines that the first PE device is raised to DR and before the sending unit sends the first Assert packet to the second PE device. The DR election message includes DR election information of a first PE device, where the DR election information of the first PE device includes a DR priority of the first PE device and/or an IP address of a downstream interface of the first PE device.

In a possible implementation manner, the sending unit in the fifth aspect or the possible implementation manner of the fifth aspect is further configured to send the multicast traffic through the downstream interface of the recovered normal first PE device after the recovered normal first PE device obtains the multicast forwarding entry, where the recovered normal downstream interface of the first PE device is an interface capable of communicating with a multicast receiver.

In a possible implementation manner, the sending unit in the fifth aspect or the possible implementation manner of the fifth aspect is further configured to send, after the first PE device that recovers from the normal state obtains a multicast forwarding entry, a multicast traffic through a downstream interface of the first PE device that recovers from the normal state at a first time, where the downstream interface of the first PE device that recovers from the normal state is an interface capable of communicating with a multicast receiver, and the first time is a time after a preset time period elapses from a time point at which the first PE device that has failed recovers from the normal state, where the preset time period is greater than or equal to an aging time of a cycle suppression mechanism.

In the fifth aspect of the embodiment of the present invention and various possible implementations of the fifth aspect, functional units are logically divided into the first PE device in order to execute the method for controlling multicast transmission described in the second aspect and various optional implementations of the second aspect. For a detailed description and a beneficial effect analysis of each functional unit of the fifth aspect and various possible implementations thereof, reference may be made to the corresponding description and technical effects in the second aspect and various possible implementations thereof, which are not described herein again.

In a sixth aspect, there is provided a second PE device, a second PE device as a BDR rising to DR after a failure of a first PE device as the DR, the second PE device comprising: an acquisition unit and a storage unit. The obtaining unit is configured to obtain a first multicast forwarding entry. The storage unit is configured to store the first multicast forwarding entry obtained by the obtaining unit. The first multicast forwarding entry includes a flag bit, where the flag bit is used to indicate that the first multicast forwarding entry cannot be used to forward multicast traffic received by an upstream interface of the second PE device. Wherein the first multicast forwarding entry is not deleted after the second PE device is reduced from DR to BDR.

In a possible implementation manner, the obtaining unit is further configured to obtain a second multicast forwarding entry after the second PE device is upgraded to the DR, where the second multicast forwarding entry is used to forward the multicast traffic received by the upstream interface of the second PE device. The second multicast forwarding entry lacks the flag bit compared to the first multicast forwarding entry, and other contents of the second multicast forwarding entry and the first multicast forwarding entry are the same.

In a sixth aspect of the present invention, each functional unit is configured to logically divide the second PE device in order to execute the method for controlling multicast transmission according to the third aspect. For the detailed description and the beneficial effect analysis of each functional unit in the sixth aspect, reference may be made to the corresponding description and the technical effect in the third aspect, which are not described herein again.

In a seventh aspect, a second PE device is provided, wherein the second PE device acting as BDR goes up to DR after the failure of the first PE device acting as DR. The second PE device includes: a processor, a memory, a bus, and a communication interface. The memory is configured to store computer-executable instructions, the processor is connected to the memory through a bus, and when the second PE device runs, the processor executes the computer-executable instructions stored in the memory, so that the second PE device executes the method for controlling multicast transmission according to the first aspect and the various alternatives of the first aspect.

An eighth aspect provides a non-volatile storage medium, where one or more program codes are stored in the non-volatile storage medium, and when a processor of the second PE device in the seventh aspect executes the program codes, the second PE device executes the method for controlling multicast transmission according to the first aspect and the various options of the first aspect.

The processor in the seventh aspect may be an integration of the determining unit, the assertion election unit, and the entry deleting unit in the fourth aspect and various possible implementations thereof, and the communication interface in the seventh aspect may be an integration of the sending unit and the receiving unit in the fourth aspect and various possible implementations thereof, and is configured to implement information interaction between the second PE device and another communication device (e.g., the first PE device, the multicast receiver, or the upstream routing device). The second PE device and the specific technical effect of the second PE device executing the program stored in the computer-readable storage medium according to the eighth aspect and the related analysis process thereof may refer to description of the related technical effect in the first aspect of the embodiment of the present invention or any implementation manner of the first aspect, and are not described herein again.

In a ninth aspect, a first PE device is provided, wherein a second PE device acting as a BDR rises to a DR after a failure of the first PE device acting as the DR. The first PE device comprises: a processor, a memory, a bus, and a communication interface. The memory is configured to store computer-executable instructions, and the processor is connected to the memory through a bus, and when the first PE device runs, the processor executes the computer-executable instructions stored in the memory, so as to cause the first PE device to perform the method for controlling multicast transmission according to the second aspect and the various alternatives of the second aspect.

A tenth aspect provides a non-volatile storage medium having one or more program codes stored therein, wherein when the program codes are executed by a processor of the first PE device in the ninth aspect, the first PE device executes the method for controlling multicast transmission according to the second aspect and the various alternatives of the second aspect.

The processor in the ninth aspect may be an integration of functional units such as the determining unit in the fifth aspect and various possible implementations thereof, and the communication interface in the ninth aspect may be an integration of the sending unit and the receiving unit in the above fifth aspect and various possible implementations thereof, so as to implement information interaction between the first PE device and another communication device (e.g., the second PE device, the multicast receiver, or the upstream routing device). The first PE device of the ninth aspect and the specific technical effect of the first PE device executing the program stored in the computer-readable storage medium of the tenth aspect and the related analysis process thereof may refer to description of the related technical effect in any implementation manner of the second aspect or the second aspect of the embodiment of the present invention, and are not described herein again.

In an eleventh aspect, there is provided a second PE device, wherein the second PE device acting as a BDR rises to the DR upon failure of the first PE device acting as a DR. The second PE device comprises: a processor, a memory, a bus, and a communication interface. The memory is configured to store computer-executable instructions, and the processor is connected to the memory through a bus, and when the second PE device runs, the processor executes the computer-executable instructions stored in the memory, so as to cause the second PE device to perform the method for controlling multicast transmission according to the third aspect and the various alternatives of the third aspect.

A twelfth aspect provides a non-volatile storage medium having one or more program codes stored therein, wherein when the program codes are executed by a processor of the second PE device described in the eleventh aspect, the second PE device executes the method for controlling multicast transmission described in the third aspect and the various alternatives of the third aspect.

The processor in the eleventh aspect may be an integration of the functional units such as the acquiring unit in the sixth aspect, and the memory in the eleventh aspect may be the storage unit in the sixth aspect. The specific technical effect of the second PE device and the specific technical effect of the second PE device executing the program stored in the computer-readable storage medium according to the twelfth aspect and the related analysis process thereof according to the eleventh aspect may refer to the description of the related technical effect in any implementation manner of the third aspect or the third aspect of the embodiment of the present invention, and are not described herein again.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art according to the drawings.

Fig. 1 is a schematic network architecture diagram of a multicast network according to an embodiment of the present invention;

fig. 2 is a schematic network architecture diagram of another multicast network according to an embodiment of the present invention;

FIG. 3 is a schematic diagram illustrating state switching between a main PE device and a standby PE device;

fig. 4 is a flowchart of a method for controlling multicast transmission according to an embodiment of the present invention;

fig. 5 is a schematic diagram of a format of a header of a PIM packet according to an embodiment of the present invention;

fig. 6 is a flowchart of another method for controlling multicast transmission according to an embodiment of the present invention;

fig. 7 is a flowchart of another method for controlling multicast transmission according to an embodiment of the present invention;

fig. 8 is a flowchart of another method for controlling multicast transmission according to an embodiment of the present invention;

fig. 9 is a schematic structural diagram of a second PE device according to an embodiment of the present invention;

fig. 10 is a schematic structural diagram of another second PE device according to an embodiment of the present invention;

fig. 11 is a schematic structural diagram of another second PE device according to an embodiment of the present invention;

fig. 12 is a schematic structural diagram of another second PE device according to an embodiment of the present invention;

fig. 13 is a schematic structural diagram of a first PE device according to an embodiment of the present invention;

fig. 14 is a schematic structural diagram of another first PE device according to an embodiment of the present invention.

Detailed Description

The terms "first" and "second" and the like in the description of the present invention and the drawings are used for distinguishing different objects or for distinguishing different processes for the same object, and are not used for describing a specific order of the objects. For example, the first PE device and the second PE device may be different PE devices. The first Assert message and the second Assert message may be different Assert messages.

In the description of the present invention, the meaning of "a plurality" means two or more unless otherwise specified. For example, a multi-core processor refers to a processor that includes two or more physical cores.

Furthermore, the terms "comprising" and "having" and any variations thereof as referred to in the description of the invention are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements but may alternatively include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The method for controlling multicast transmission provided by the embodiment of the invention can be applied to the transmission process of multicast traffic, and particularly can be applied to a multicast transmission scene after a second PE device serving as a BDR goes up to DR after a first PE device serving as DR fails.

Referring to fig. 1, a schematic diagram of a network architecture of a multicast network to which the method for controlling multicast transmission according to the embodiment of the present invention is applied is shown.

As shown in fig. 1, the multicast network may include an operator's backbone network 10 and a plurality of subscriber private networks. The plurality of user private networks may include user private network 20, user private network 30, and user private network 40 of fig. 1. The backbone network 10 includes an operator (P) device 11 and a plurality of operator edge (PE) devices. The plurality of PE devices may include PE device 12, PE device 13, and PE device 14 in fig. 1. Each private network of a user includes a Customer Edge (CE) device. As shown in fig. 1, the consumer private network 20 includes a CE device 21, the CE device 21 communicating with the PE device 12. The consumer private network 30 comprises the CE device 31, the CE device 31 being in communication with the PE device 13. The consumer private network 40 includes the CE device 41, the CE device 41 communicating with the PE device 14.

Any one of the CE devices may be a router or a switch connected to the user host, or any one of the CE devices may be the user host or a server in the user private network. As shown in fig. 1, the network architecture of the multicast network applied in the embodiment of the present invention will be described by taking only the CE device 21 as a router or a switch connected to a subscriber host as an example. Devices in the private network 20 of the user to which the CE device 21 is connected request and receive multicast traffic. In the embodiment of the present invention, the CE device 21 may be regarded as a multicast receiver.

In order to avoid abnormal transmission of multicast traffic due to failure of a PE device 12 communicating with a multicast receiver, a backup PE device 22 may be generally configured for the PE device 12. As shown in fig. 2, the PE device 22 is a standby device of the PE device 12. The CE device 21 may have dual-homed access to the PE device 12 and the PE device 22 through the two-layer switch of fig. 2. The CE device 22 may have dual-homed access to the PE device 12 and the PE device 22 through the two-tier switch of fig. 2.

Under the condition that the PE device 12 is normal, the PE device 12 serves as a DR, and forwards the multicast traffic according to the multicast forwarding table entry stored therein. The PE device 22 serves as a BDR, and the multicast forwarding table entry is not stored in the PE device 22, and multicast traffic cannot be forwarded. Starting at time t1 and proceeding to time t4 as shown in FIG. 3, the PE device 12 acts as a DR and the PE device 22 acts as a BDR. When the PE device 12 as the DR fails at time t4 shown in fig. 3, the PE device 12 as the DR cannot forward the multicast traffic. The PE device 12 reduces to BDR at time t4, and deletes the multicast forwarding entry stored therein. Starting at time t4 shown in FIG. 3, the PE device 12 acts as a BDR and the PE device 22 acts as a DR until time t5 at which the PE device 12 returns to normal. After the DR is raised, the PE device 22 acquires and stores the multicast forwarding entry, and forwards the multicast traffic according to the multicast forwarding entry stored in the multicast forwarding entry. At time t5 shown in FIG. 3, the PE device 12 returns to normal. From time t5 shown in fig. 3, the PE device 12 returns to normal to raise DR and the PE device 22 lowers to BDR. The PE device 12 that returns to normal acquires and stores the multicast forwarding entry, and forwards the multicast traffic according to the multicast forwarding entry stored in the PE device. In the case that the PE device 22 does not enable the period suppression mechanism, the PE device 22 serving as the BDR may initiate an Assert election after determining that the downstream interface thereof receives the multicast traffic. The PE device 22 deletes the multicast forwarding entry stored in the PE device 22 after the Assert election fails. The switching between DR and BDR between the PE device 12 and the PE device 22 is realized by DR election, and the specific method for DR election by the PE device 12 and the PE device 22 refers to the following description of the embodiment of the present invention.

T shown in FIG. 3₁-t₄During this time, the downstream interface of the PE device 22 may receive the multicast traffic sent by the PE device 12 and forwarded by the layer two switch. Since the PE device 22 as BDR is not storedThe multicast forwarding table entry used for forwarding the multicast traffic, so that the PE device 22 serving as the BDR frequently reports the loss (miss) message to a Central Processing Unit (CPU) after receiving the multicast traffic. And the miss message is used for indicating that the forwarding table entry is lost. In order to avoid the impact of a large number of miss messages on the CPU of the BDR PE device 22, the BDR PE device 22 may enable a period suppression mechanism when receiving the multicast traffic on its downstream interface and the PE device 22 does not have a multicast forwarding entry for forwarding the multicast traffic.

Based on the above description, at t₁-t₄During this time, the downstream interface of the PE device 22 may receive multicast traffic, for example, the downstream interface of the PE device 22 is at t₂Multicast traffic is received at all times. Due to the fact that at t₁-t₄During this time, no multicast forwarding table entry that can be used for forwarding the multicast traffic is stored in the PE device 22, so at t₂At this point, if the downstream interface of the PE device 22 receives multicast traffic, the PE device 22 may enable a periodic suppression mechanism. As shown in fig. 3, if the detection period of the period suppression mechanism is X, the PE device 22 performs a process at t₃Detection period of end-of-time period suppression mechanism, i.e. t₂-t₃This time is one detection period. PE device 22 at t₂After the periodic throttling mechanism is enabled at this time, even if the downstream interface of the PE device 22 is at t₂-t₃When receiving the multicast traffic within this time, the PE device 22 does not report the miss message to its CPU in real time after receiving the multicast traffic, but instead reports the miss message to its CPU at t₃Time of day determination t₂-t₃And reporting the miss message after receiving the multicast flow in the period of time. The PE device 22 may periodically detect based on X before the aging time of the periodic throttling mechanism is reached. The aging time of the cycle inhibition mechanism is Y.

After the PE device 22 starts the period suppression mechanism, if the downstream interface does not receive the multicast traffic within the aging time Y of the period suppression mechanism, the period suppression mechanism fails. The PE device 22 may detect in real time after the cycle suppression mechanism failsAnd testing whether the downstream interface receives the multicast flow. The aging time Y of the cycle suppression mechanism is greater than the detection cycle X of the cycle suppression mechanism. At t₂-t₃When the downstream interface of the PE device 22 receives the multicast traffic in the corresponding detection period, the PE device 22 performs a process t₃Time-of-day refresh cycle suppression mechanism, i.e. the calculation time of the aging time Y of the cycle suppression mechanism becomes t₃The time of day. The PE device 22 begins at t₃-t₆During this period, multicast traffic is detected. Wherein, t₃-t₆This period corresponds to one detection period. t is t₃-t₆The corresponding detection period is t₂-t₃The next detection period of the corresponding detection period. The PE device 22 determines that its downstream interface is at t₃-t₇If no multicast traffic is received during this time Y, the PE device 22 may determine that the periodic suppression mechanism is disabled.

After the PE device 22 refreshes the cycle suppression mechanism at time t3, the PE device 12 resumes normal and is brought up to DR by BDR at time t 5. The downstream interface of PE device 22, beginning at time t5, may receive multicast traffic from PE device 12 forwarded by the layer two switch. Based on the above description, the cycle suppression mechanism of the PE device 22S is active during the time period t3-t 6. Thus, at t₅-t₆During this time, the PE device 22 cannot sense the multicast traffic of its downstream interface in real time. The PE device 22 will not be at t₅-t₆No Assert election will be initiated during this time. At t₅-t₆During this period, the PE device 22 still uses the multicast forwarding table entry stored therein to send the multicast traffic to the layer two switch. Thus, the CE device 12 will receive two identical multicast flows from the PE device 12 and the PE device 22 through a two-layer switch.

In order to solve the problem mentioned in the above scheme that a multicast receiver receives two identical multicast flows, embodiments of the present invention provide a method and an apparatus for controlling multicast transmission. In the solution provided in the embodiment of the present invention, through interaction of a protocol packet between the PE device 22 and the PE device 12, the PE device 22 is triggered to initiate Assert immediately after determining that the PE device 12 is raised to DR. In this way, the PE device 22 may immediately delete the multicast forwarding entry stored therein, and further, may prevent the PE device 12 and the PE device 22 from forwarding the multicast traffic for the multicast receiver at the same time.

For example, the failure of the PE device 12 and the inability to forward the multicast traffic may be that the PE device 12 itself fails and is unable to forward the multicast traffic to the two-layer switch through its downstream interface. Or the failure of the PE device 12 and the inability to forward the multicast traffic may be a failure of a link between the PE device 12 and the layer two switch, which results in that the layer two switch cannot receive the multicast traffic sent by the PE device 12.

For example, the multicast forwarding entry in the embodiment of the present invention may include a backbone multicast forwarding entry and a private multicast forwarding entry. The method for obtaining the multicast forwarding entry by the PE device 12 or the PE device 22 may refer to a general method for obtaining the multicast forwarding entry, and details of the embodiment of the present invention are not described here.

The switching between DR and BDR between the PE device 12 and the PE device 22 is realized by DR election. The PE device 12 and the PE device 22 in the embodiment of the present invention may use a Protocol Independent Multicast (PIM) Protocol. The PE device 12 and the PE device 22 may perform DR election through interaction of Hello packets. The PE device 12 sends a Hello packet carrying the DR priority of the PE device 12 to the PE device 22. The PE device 22 compares the DR priority of the PE device 12 carried in the Hello message with the DR priority of the PE device 22. If the DR priority of the PE device 12 is higher than the DR priority of the PE device 22, the PE device 22 fails in DR election. If the DR priority of the PE device 12 is lower than the DR priority of the PE device 22, the PE device 22 wins the DR election. The device that failed in the DR election served as the BDR. In the embodiment of the present invention, the DR priority of the PE device 12 is higher than the DR priority of the PE device 22, and if the PE device 22 performs DR election, the PE device 12 is DR and the PE device 22 is BDR.

Optionally, the Hello packet sent by the PE device 12 may further include an IP address of a downstream port of the PE device 12. If the PE device 12 and the PE device 22 do not support DR election based on DR priority or the DR priority of the PE device 12 and the DR priority of the PE device 22 are the same, the PE device 22 may further compare the IP address of the downstream interface of the PE device 12 with the IP address of the downstream interface of the PE device 22. If the IP address of the downstream interface of the PE device 12 is greater than the IP address of the downstream interface of the PE device 22, the PE device 22 fails in DR election; if the IP address of the downstream interface of the PE device 12 is smaller than the IP address of the downstream interface of the PE device 22, the PE device 22 wins the DR election. In this embodiment of the present invention, the IP address of the downstream interface of the PE device 12 is greater than the IP address of the downstream interface of the PE device 22, and if the PE device 22 performs DR election, the PE device 12 is DR and the PE device 22 is BDR.

In the embodiment of the present invention, the PE device 12 is taken as a first PE device, and the PE device 22 is taken as a second PE device, so as to describe the method and the device for controlling multicast transmission in detail. As shown in any one of fig. 4, 6 to 9, the method for controlling multicast transmission may include:

s101, DR election is carried out on the first PE device and the second PE device, the first PE device elects as DR, and the second PE device elects as BDR.

The specific method for performing DR election by the first PE device and the second PE device may refer to the above related description of the embodiments of the present invention.

And S102, starting a cycle suppression mechanism after the second PE device serving as the BDR receives the multicast traffic at the downstream interface of the BDR.

The principle and method for starting the cycle suppression mechanism after the second PE device serving as the BDR receives the multicast traffic on its downstream interface may refer to the foregoing description of the embodiment of the present invention.

And S103, deleting the multicast forwarding table entry stored in the first PE equipment after the first PE equipment serving as the DR fails.

And S104, the second PE device serving as the BDR is raised to DR after the first PE device serving as the DR fails, a multicast forwarding table item is obtained, and the multicast flow received by an upstream interface of the multicast receiver is sent to the multicast receiver through a downstream interface of the multicast forwarding table item.

Wherein the downstream interface of the second PE device is an interface capable of communicating with a multicast recipient. And the upstream interface of the second PE device is an interface capable of receiving multicast traffic sent by a multicast source. The second PE device as the BDR is increased to DR after the first PE device as the DR fails, and the first PE device is decreased to the BDR. For example, a method for determining that the first PE device serving as the DR has a fault by the second PE device serving as the BDR may adopt a common fault detection method, and details of the embodiment of the present invention are not described herein again.

After obtaining the multicast forwarding entry, the second PE device that is raised to DR may send the multicast traffic received by its upstream interface to the multicast receiver through its downstream interface according to the multicast forwarding entry. The downstream interface of the second PE device that rises to DR is an interface that is capable of communicating with multicast recipients.

In a first application scenario of the embodiment of the present invention, as shown in fig. 4, after S104, the method provided in the embodiment of the present invention may further include S201-S209:

s201, after the first PE device is recovered to be normal, sending a DR election message to the second PE device, wherein the DR election message carries DR election information of the first PE device recovered to be normal.

For example, the DR election information of the normalizing first PE device includes a DR priority of the normalizing first PE device and/or an IP address of a downstream interface of the normalizing first PE device. The DR election packet may be a Hello packet, that is, the DR election packet may be a PIM packet whose packet type is Hello. Please refer to fig. 5, which shows a schematic diagram of a header format of a PIM message. As shown in fig. 5, the header of the PIM packet may include: the device comprises a version field, a type field, a reserved field and a checksum field. The version field is used for indicating the version number of the PIM message, for example, the PIM message is a message based on a PIMv2 version format; the type field is used for indicating the message type of the PIM message, and if the PIM message is a Hello message; the reserved field is a reserved idle field; the checksum field is used for indicating information used for checking the PIM message.

For example, the Assert messages in the embodiment of the present invention, such as the first Assert message, the second Assert message, Assert message 1, and Assert message 2, are PIM messages whose message types are Assert.

S202, the second PE device receives the DR election message sent by the first PE device.

For example, the second PE device may receive, through its downstream interface, the DR election packet sent from the first PE device. Since the DR election packet does not belong to multicast traffic, even if the second PE device starts a periodic suppression mechanism, the downstream interface of the second PE device may receive the DR election packet in real time.

And S203, the second PE device performs DR election according to the recovered normal DR election information of the first PE device and the recovered DR election information of the second PE device.

Wherein the DR election information of the second PE device includes a DR priority of the second PE device and/or an IP address of a downstream interface of the second PE device.

And S204, the second PE equipment determines that the recovered first PE equipment is lifted to DR according to the DR election result.

The specific manner of determining that the recovered normal first PE device is raised to DR by the second PE device according to the result of DR election may refer to the detailed description of DR election performed by the first PE device and the second PE device in the embodiment of the present invention.

S205, when the second PE device determines that the first PE device that recovers to normal rises to DR, sending an Assert message 1 to the first PE device, where the Assert message 1 is used to obtain information for performing Assert election from the first PE device that recovers to normal.

In this embodiment of the present invention, the second PE device may obtain the Assert election information of the first PE device by sending Assert message 1 to the first PE device. The Assert election information of the first PE device may include: the unicast routing protocol priority of the first PE device which is recovered to be normal and/or the IP address of the downstream interface of the first PE device which is recovered to be normal.

And S206, the first PE device which is upgraded to DR receives the Assert message 1 sent by the second PE device.

S207, after receiving the Assert message 1, the first PE device raised to DR sends an Assert message 2 to the second PE device, where the Assert message 2 includes Assert election information of the first PE device.

In this embodiment, an Assert message 2 sent by a first PE device to a second PE device is used to indicate the second PE device to perform Assert election. The Assert message 1 sent by the second PE device to the first PE device is used to obtain information for performing Assert election from the recovered normal first PE device, that is, to indicate the recovered normal first PE device to feed back its Assert election information.

Wherein, the reserved field of the Assert message 1 is not an idle field. The reserved field of the Assert message 1 may indicate that the Assert message 1 is an extended Assert message. And the expanded Assert message is used for obtaining information for performing Assert election from the first PE equipment which is recovered to be normal. Generally, bytes 7 to 15 of a packet header of a PIM packet are reserved fields, and in the embodiment of the present invention, the Assert packet 1 may be extended by setting at least one bit in at least one byte in bytes 7 to 15 of the Assert packet 1. For example, bit 1 in byte 7 of Assert message 1 may be set to 1 to indicate that Assert message 1 is the extended Assert message.

S208, the second PE device receives the Assert message 2 sent by the first PE device.

S209, the second PE device performs Assert election according to the Assert election information of the first PE device and the Assert election information of the second PE device, and deletes the multicast forwarding entry stored in the second PE device after the Assert election fails.

For example, the Assert election information of the second PE device may include: a unicast routing protocol priority of the second PE device and/or an IP address of a downstream interface of the second PE device.

The method for performing Assert election by the second PE device according to the Assert election information of the first PE device and the Assert election information of the second PE device may include: and the second PE device compares the unicast routing protocol priority of the second PE device with the unicast routing protocol priority of the first PE device. And if the unicast routing protocol priority of the second PE device is higher than that of the first PE device, the second PE device wins the Assert election. And if the unicast routing protocol priority of the second PE device is lower than the unicast routing protocol priority of the first PE device, the second PE device fails in Assert election. If the unicast routing protocol priority of the second PE device is the same as the unicast routing protocol priority of the first PE device, the second PE device compares the IP address of the downstream interface of the second PE device with the IP address of the downstream interface of the first PE device. And if the unicast routing protocol priority of the second PE device is the same as the unicast routing protocol priority of the first PE device, and the IP address of the downstream interface of the second PE device is greater than the IP address of the downstream interface of the first PE device, winning the second PE device in the Assert election. If the unicast routing protocol priority of the second PE device is the same as the unicast routing protocol priority of the first PE device, and the IP address of the downstream interface of the second PE device is smaller than the IP address of the downstream interface of the first PE device, the second PE device fails in Assert election.

Based on the network scenario of the embodiment of the present invention, the unicast routing protocol priority of the first PE device is higher than the unicast routing protocol priority of the second PE device. The IP address of the downstream interface of the first PE device is larger than the IP address of the downstream interface of the second PE device. Therefore, if the second PE device performs Assert election with the first PE device, the second PE device may fail in Assert election.

In the method for controlling multicast transmission provided in the embodiment of the present invention, the first PE device recovers to normal and increases to DR before the aging time Y of the periodic suppression mechanism arrives. The periodic suppression mechanism started by the second PE device in S102 may also suppress the multicast traffic received by the downstream interface of the second PE device, but may not suppress the DR election packet received by the downstream interface of the second PE device. And when the second PE equipment determines that the first PE equipment which is recovered to be normal is lifted to be DR according to the DR election message, the second PE equipment immediately sends an Assert message 1 to the first PE equipment, and information for performing Assert election is obtained from the first PE equipment which is recovered to be normal. The second PE device performs Assert election without waiting for the end of the detection period and determining that the multicast traffic is received within the detection period, thereby preventing the second PE device and the first PE device from forwarding the multicast traffic for the multicast receiver at the same time.

Optionally, based on the first application scenario of the embodiment of the present invention, another implementation manner is further provided in the embodiment of the present invention, as shown in fig. 6. The scenario shown in fig. 6 differs from the scenario shown in fig. 4 in that S201-S204 included in fig. 4 may be replaced with S301 of fig. 6.

S301, the second PE device detects that a downstream interface of the second PE device is converted from a first state to a second state, and the first PE device which is recovered to be normal is determined to be changed to DR.

The first state is a state in which the downstream interface of the second PE device does not receive multicast traffic, and the second state is a state in which the downstream interface of the second PE device receives multicast traffic. The downstream interface of the second PE device is an interface capable of communicating with multicast recipients.

It is conceivable that, after the first PE device that recovers to normal obtains the multicast forwarding entry, the first PE device that recovers to normal may send the multicast traffic through the downstream interface of the first PE device that recovers to normal, where the downstream interface of the first PE device that recovers to normal is an interface capable of communicating with the multicast receiver. If the recovered normal first PE device sends the multicast traffic through its downstream interface, the downstream interface of the second PE device may receive the multicast traffic forwarded by the layer two switch, where the multicast traffic forwarded by the layer two switch is the multicast traffic sent by the recovered normal first PE device through its downstream interface that is received by the layer two switch.

And when the first PE device is a BDR, multicast traffic is not forwarded. Therefore, if the downstream interface of the second PE device does not receive the multicast traffic, it indicates that the downstream interface of the first PE device does not send the multicast traffic, that is, the first PE device is a BDR. If the downstream interface of the second PE device can receive the multicast traffic, the multicast traffic is sent by the downstream interface of the first PE device that is recovered to normal. If the downstream interface of the second PE device is converted from the first state to the second state, the second PE device may determine that the first PE device that returns to normal rises to DR. In this way, the second PE device may send the first Assert message to the first PE device when determining that the first PE device that recovers to normal rises to DR, so as to obtain information for performing Assert election from the first PE device that recovers to normal. After the second PE device is elected to be reduced to BDR by Assert, the second PE device immediately deletes the multicast forwarding entry stored in the second PE device, thereby preventing the first PE device and the second PE device from forwarding multicast traffic for a multicast receiver at the same time.

A second application scenario of an embodiment of the present invention is shown in fig. 7. The second application scenario shown in fig. 7 may be after S101-S104 included in fig. 4, and further include S401-S404:

s401, after the first PE device returns to normal, DR election is carried out with the second PE device, and it is determined that the first PE device is lifted to DR.

The specific method for determining that the first PE device is lifted to the DR may refer to the above related method for DR election, and details of the embodiment of the present invention are not repeated here.

S402, after obtaining the multicast forwarding entry, the first PE device recovering to normal and increasing to DR sends an Assert message 3 to the second PE device, where the Assert message 3 is used to indicate the second PE device to perform Assert election.

For example, the Assert message 3 may include Assert election information of the first PE device. Wherein the Assert election information of the first PE device may include: the unicast routing protocol priority of the first PE device which is recovered to be normal and/or the IP address of the downstream interface of the first PE device which is recovered to be normal.

S403, the second PE device receives the Assert packet 3 sent by the first PE device.

S404, the second PE device performs Assert election according to Assert election information of the second PE device and Assert election information of the first PE device included in the Assert message 3, and deletes the multicast forwarding entry stored in the second PE device after the Assert election fails.

The specific method for performing Assert election by the second PE device according to the Assert election information of the second PE device and the Assert election information of the first PE device included in the Assert packet 3 may refer to the description related to performing Assert election by the second PE device in the first application scenario of the embodiment of the present invention, which is not described herein again in the embodiment of the present invention.

In the method for controlling multicast transmission provided in the embodiment of the present invention, the first PE device may also actively trigger the second PE device to perform Assert after recovering to normal and increasing to the DR and obtaining the multicast forwarding entry. And the second PE device does not need to perform Assert election when it is determined that the multicast traffic is received within the detection period after the detection period is ended, thereby preventing the second PE device and the first PE device from forwarding the multicast traffic for the multicast receiver at the same time.

In the multiple implementation manners of the first scenario and the multiple implementation manners of the second scenario provided in the embodiments of the present invention, the first PE device recovers to normal and increases to DR before the aging time of the cycle suppression mechanism of the second PE device arrives. If the first PE device recovers to be normal and rises to be DR after the aging time of the periodic restraining mechanism of the second PE device is reached, the downstream interface of the second PE device can sense the received multicast flow in real time and perform Assert election. Therefore, the second PE device can immediately delete the forwarding table entry after the assertion election fails, thereby preventing the second PE device and the first PE device from forwarding the multicast traffic for the multicast receiver at the same time.

A third application scenario of an embodiment of the present invention may be as shown in fig. 8. The scenario shown in fig. 8 is after S101-S104 included in fig. 4, and further includes S501-S503.

S501, after the first PE device which recovers to normal and is upgraded to DR obtains the multicast forwarding item, the first PE device sends multicast traffic through a downstream interface at the first moment.

The first moment is the moment when the first PE equipment with the fault recovers to be normal and is after a preset duration, and the preset duration is greater than or equal to the aging time of the periodic inhibition mechanism. The downstream interface of the first PE device is an interface capable of communicating with a multicast recipient.

S502, the downstream interface of the second PE device receives a multicast traffic sent by the second layer switch, where the multicast traffic is sent to the second layer switch by the first PE device through the downstream interface thereof.

S503, when determining that the downstream interface of the second PE device receives the multicast traffic, performing Assert election, and deleting the multicast forwarding entry stored in the second PE device after the Assert election fails.

For example, the method for performing Assert election by the second PE device may be that the second PE device sends an Assert election message for obtaining Assert election information to the first PE device in the foregoing embodiment.

In the method for controlling multicast transmission provided in the embodiment of the present invention, the period suppression mechanism of the second PE device has failed at the first time. If the downstream interface of the first PE device sends the multicast traffic at the first time, that is, the second PE device sends the multicast traffic after the periodic suppression mechanism of the second PE device fails, the second PE device may sense the multicast traffic of the downstream interface in real time. The second PE device may initiate Assert election after sensing the multicast traffic of its downstream interface, and immediately delete the multicast forwarding entry stored in the second PE device, which may prevent the second PE device and the first PE device from forwarding the multicast traffic for the multicast receiver at the same time.

In the method for controlling multicast transmission, a first multicast forwarding entry may be pre-stored in a second PE device serving as the BDR, where the first multicast forwarding entry includes a flag bit, and the flag bit is used to indicate that the first multicast forwarding entry cannot be used to forward multicast traffic received by an upstream interface of the second PE device. Wherein the first multicast forwarding entry is not deleted after the second PE device is reduced from DR to BDR.

For example, after the second PE device is upgraded to DR, a second multicast forwarding entry may be obtained, where the second multicast forwarding entry is used to forward multicast traffic received by an upstream interface of the second PE device. The second multicast forwarding entry lacks the flag bit compared to the first multicast forwarding entry, and other contents of the second multicast forwarding entry and the first multicast forwarding entry are the same. And deleting the second multicast forwarding table entry after the second PE equipment performs Assert election and election fails.

In the method for controlling multicast transmission according to the embodiment of the present invention, since the predetermined flag bit in the first multicast forwarding entry indicates that the first multicast forwarding entry cannot be used to forward the multicast traffic received by the upstream interface of the first PE device, even if the multicast traffic received by the upstream interface of the second PE device serving as the BDR is the multicast traffic, the multicast traffic cannot be forwarded according to the first multicast forwarding entry. In this way, since the first multicast forwarding table entry is pre-stored in the second PE device, the second PE device serving as the BDR and the first PE device serving as the DR do not forward the multicast traffic to the multicast receiver at the same time. Further, since the first multicast forwarding table entry is pre-stored in the second PE device serving as the BDR, the second PE device does not enable a period suppression mechanism when receiving a multicast traffic on its downstream interface.

In the method provided by the embodiment of the present invention, after the aging time of the periodic suppression mechanism or the non-enabled periodic suppression mechanism is reached, the second PE device serving as the BDR may sense that the downstream interface receives the multicast traffic in real time, and initiate an Assert election. The second PE device serving as the BDR may delete the multicast forwarding entry stored in the second PE device immediately after the Assert election fails, thereby preventing the second PE device serving as the BDR and the first PE device serving as the DR from forwarding the multicast traffic for the multicast receiver at the same time.

The above description mainly introduces the solutions provided in the embodiments of the present invention from the perspective of interaction between a first PE device and a second PE device. It is understood that, in order to implement the above functions, the first PE device and the second PE device include hardware structures and/or software modules for performing the respective functions. Those of skill in the art will readily appreciate that the present invention can be implemented in hardware or a combination of hardware and computer software, in connection with the exemplary PE devices and algorithm steps described in connection with the embodiments disclosed herein. Whether a function is performed as hardware or computer software drives hardware depends upon the particular application and design constraints imposed on the solution. 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 invention.

In the embodiment of the present invention, according to the above method example, the first PE device and the second PE device may be divided into functional modules or functional units, for example, each functional module or functional unit may be divided corresponding to each function, or two or more functions may be integrated into one processing module. The integrated module may be implemented in a form of hardware, or may be implemented in a form of a software functional module or a functional unit. The division of the modules or units in the embodiments of the present invention is schematic, and is only a logic function division, and there may be another division manner in actual implementation.

Fig. 9 shows a schematic diagram of a possible structure of the second PE device involved in the above embodiment. The second PE device serving as a BDR rises to DR after the failure of the first PE device serving as DR, and the second PE device 900 includes: a determining unit 901 and a transmitting unit 902.

The determining unit 901 is configured to determine that the first PE device that recovers to be normal is increased to DR after the first PE device recovers to be normal. For example, the determining unit 901 is used to support S202, S203, S204 in fig. 4, S301 in fig. 6, and/or other processes for the techniques described herein.

The sending unit 902 is configured to send a first Assert message to the first PE device recovered to be normal when the determining unit 901 determines that the first PE device recovered to be normal is raised to DR, where the first Assert message is used to obtain information for performing Assert election from the first PE device recovered to be normal. The sending unit 902 interacts with the recovered first PE device, and obtains information for performing Assert election from the recovered first PE device. For example, the sending unit 902 is used to support S205 in fig. 4 and/or other processes for the techniques described herein.

Corresponding to the implementation shown in fig. 4, as shown in fig. 10, the determining unit 901 may include: a receive sub-unit 9011, a DR election sub-unit 9012, and a determine sub-unit 9013. The receiving subunit 9011 is configured to support S202 in fig. 4, the DR election subunit 9012 is configured to support S203 in fig. 4, and the determining subunit 9013 is configured to support S204 in fig. 4.

Further, as shown in fig. 11, the second PE device 900 may further include: a receiving unit 903, an assertion election unit 904, and an entry deletion unit 905. The receiving unit 903 is configured to receive a multicast flow, an Assert message, and/or a DR election message sent by the first PE device. For example, the receiving unit 903 is used to support S208 in fig. 4 or fig. 6, S403 in fig. 7, S502 in fig. 8, and/or other processes for the techniques described herein. The assertion election unit 904 is configured to perform Assert election according to the Assert packet sent by the first PE device. For example, the assertion election unit 904 may be configured to support the Assert election function in S209 of fig. 4 and 6, the Assert election function in S404 of fig. 7, the Assert election function in S503 of fig. 8, and/or other processes for the techniques described herein. The entry deleting unit 905 is configured to delete the multicast forwarding entry stored in the second PE device 900 after the Assert election fails, for example, the entry deleting unit 905 may be configured to support a multicast forwarding entry function in S209 in fig. 4 and fig. 6, a multicast forwarding entry function in S404 in fig. 7, a multicast forwarding entry function in S503 in fig. 8, and/or other processes used in the technology described herein. The second PE device 900 may further include a storage unit for storing program codes and data of the second PE device 900.

In the case of an Integrated unit, the determining unit 901, the assertion selecting unit 904, and the table entry deleting unit 905 may be Integrated into a processing unit, and the processing unit may be a Processor or a controller, such as a CPU, a general-purpose Processor, a Digital Signal Processor (DSP), an Application-Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), or any other Programmable logic device, transistor logic device, hardware component, or any combination thereof. Which may implement or execute the various illustrative logical blocks, modules, and circuits described in connection with the disclosure. The processing unit may also be a combination of computing functions, e.g., comprising one or more microprocessors, a combination of a DSP and a microprocessor, or the like. The sending unit 901 and the receiving unit 903 may be implemented in one integrated communication unit, which may be a communication interface, a transceiver circuit, a transceiver, or the like. The storage unit may be a memory.

When the processing unit is a processor, the communication unit is a communication interface, and the storage unit is a memory, the second PE device according to the embodiment of the present invention may be the second PE device 1200 shown in fig. 12.

Referring to fig. 12, the second PE device 1200 includes: a processor 1201, a communication interface 1202, a memory 1203, and a bus 1204. The processor 1201, the communication interface 1202, and the memory 1203 are connected to each other by a bus 1204. The bus 1204 may be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus. The bus 1204 may be divided into an address bus, a data bus, a control bus, and the like. For ease of illustration, only one thick line is shown in FIG. 12, but this is not intended to represent only one bus or type of bus.

An embodiment of the present invention further provides a non-volatile storage medium, where one or more program codes are stored in the non-volatile storage medium, and when the processor 1201 of the second PE device 1200 executes the program codes, the second PE device 1200 executes relevant method steps in any one of fig. 4, fig. 6, fig. 7, or fig. 8, and interacts with the first PE device to implement control over multicast transmission.

The detailed description of each functional unit or functional module in the second PE device and the technical effects of each functional unit or functional module after the function unit or functional module executes the related method steps in any one of fig. 4, fig. 6, fig. 7, or fig. 8 provided in the embodiment of the present invention may refer to the related description in the embodiment of the method of the present invention, and are not repeated herein.

Fig. 13 shows a schematic diagram of a possible structure of the first PE device involved in the above embodiment. The second PE device acting as BDR goes up to DR after the failure of the first PE device acting as DR, and the first PE device 1300 includes: a determining unit 1301 and a transmitting unit 1302. The determining unit 1301 is configured to determine that the failed first PE device is up to the DR after the failed first PE device is recovered to normal, for example, the determining unit 1301 is configured to support S401 in fig. 7 and/or other processes for the technology described herein. The sending unit 1302 is configured to interact with a second PE device when the determining unit 1301 determines that the first PE device recovering to normal rises to DR, and instruct the second PE device to perform Assert election. For example, the sending unit 1302 is configured to support S104, S201, and S207 in fig. 4, S104, S207 in fig. 6, S104, S402 in fig. 7, S104, S502 in fig. 8, and/or other processes for the techniques described herein.

Further, the first PE device 1303 may further include: a receiving unit and a DR election unit. The receiving unit is configured to receive multicast traffic, Assert messages, and DR election messages sent by the second PE device, for example, the receiving unit is configured to support S206 in fig. 4 or fig. 6 and/or other processes for the techniques described herein. The DR election unit is configured to perform DR election according to the DR election packet sent by the first PE device, for example, the DR election unit is configured to support S101 in fig. 4, 6, 7, or 8 and/or other processes for the techniques described herein. Of course, the first PE device 1300 may further include: an entry deleting unit, configured to delete the multicast forwarding entry saved in the first PE device 1300 after the first PE device 1300 fails, for example, the entry deleting unit may be configured to support S103 in fig. 4, 6, 7, or 8 and/or other processes for the techniques described herein. The first PE device 1300 may further include a storage unit for storing program codes and data of the first PE device 1300.

In the case of an integrated unit, the functional units such as the determining unit 1301, the DR election unit, and the table entry deleting unit may be integrated into one processing unit, and the processing unit may be a processor or a controller, for example, a CPU, a general processor, a DSP, an ASIC, an FPGA, or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. Which may implement or execute the various illustrative logical blocks, modules, and circuits described in connection with the disclosure. The processing unit may also be a combination of computing functions, e.g., comprising one or more microprocessors, a combination of a DSP and a microprocessor, or the like. The sending unit 1302 and the receiving unit may be implemented integrally in one communication unit, which may be a communication interface, a transceiver circuit or a transceiver, etc. The storage unit may be a memory.

When the processing unit is a processor, the communication unit is a communication interface, and the storage unit is a memory, the first PE device according to the embodiment of the present invention may be the first PE device 1400 shown in fig. 14.

Referring to fig. 14, the first PE device 1400 includes: a processor 1401, a communication interface 1402, a memory 1403, and a bus 1404. Wherein the processor 1401, the communication interface 1402, and the memory 1403 are connected to each other via a bus 1404. The bus 1404 may be a PCI bus, an EISA bus, or the like. The bus 1404 may be divided into an address bus, a data bus, a control bus, and the like. For ease of illustration, only one thick line is shown in FIG. 14, but this is not intended to represent only one bus or type of bus.

An embodiment of the present invention further provides a non-volatile storage medium, where one or more program codes are stored in the non-volatile storage medium, and when the processor 1401 of the first PE device 1400 executes the program codes, the first PE device 1400 executes related method steps in any one of fig. 4, fig. 6, fig. 7, or fig. 8, and interacts with a second PE device to implement control over multicast transmission.

For technical effects brought by the detailed description of each functional unit or functional module in the first PE device and the implementation of the relevant method steps in any one of fig. 4, fig. 6, fig. 7, or fig. 8 by each functional unit or functional module according to the embodiments of the present invention, reference may be made to the relevant description in the method embodiments of the present invention, which is not repeated herein.

An embodiment of the present invention further provides a second PE device, where the second PE device serving as a BDR is upgraded to DR after a failure of a first PE device serving as DR, and the second PE device includes: an acquisition unit and a storage unit. The obtaining unit is configured to obtain a first multicast forwarding entry. The storage unit is configured to store the first multicast forwarding entry obtained by the obtaining unit. The first multicast forwarding entry includes a flag bit, where the flag bit is used to indicate that the first multicast forwarding entry cannot be used to forward multicast traffic received by an upstream interface of the second PE device. Wherein the first multicast forwarding entry is not deleted after the second PE device is reduced from DR to BDR.

Of course, the second PE device may further include: the system comprises a receiving unit, a sending unit, a DR election unit, an item deleting unit and other functional units. For specific functions of the receiving unit, the sending unit, the DR election unit, the table entry deleting unit, and other functional units in the second PE device, reference may be made to the detailed description of the corresponding functional units in the foregoing embodiments, and details are not described here.

In the case of an integrated unit, the functional units such as the obtaining unit, the DR election unit, and the table entry deleting unit may be integrated into one processing unit, and the processing unit may be a processor or a controller, for example, a CPU, a general processor, a DSP, an ASIC, an FPGA, or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. Which may implement or execute the various illustrative logical blocks, modules, and circuits described in connection with the disclosure. The processing unit may also be a combination of computing functions, e.g., comprising one or more microprocessors, a combination of a DSP and a microprocessor, or the like. The receiving unit and the sending unit may be implemented in one integrated communication unit, which may be a communication interface, a transceiver circuit, a transceiver, or the like. The storage unit may be a memory.

When the processing unit is a processor, the communication unit is a communication interface, and the storage unit is a memory, the second PE device according to the embodiment of the present invention may include: a processor, a communication interface, a memory, and a bus. Wherein the processor, the communication interface, and the memory are connected to each other by a bus. The bus may be a PCI bus or an EISA bus, etc. The bus may be divided into an address bus, a data bus, a control bus, etc.

An embodiment of the present invention further provides a non-volatile storage medium, where a first multicast forwarding entry and one or more program codes are stored in the non-volatile storage medium, and when a processor of a second PE device executes the program codes, the second PE device does not enable a cycle suppression mechanism when a communication interface of the second PE device receives multicast traffic through a downstream interface of the second PE device.

The detailed description and the technical effects of each functional unit or functional module in the second PE device provided in the embodiment of the present invention may refer to the related description in the embodiment of the method of the present invention, and are not described herein again.

The steps of a method or algorithm described in connection with the disclosure herein may be embodied in hardware or in software instructions executed by a processor. The software instructions may be composed of corresponding software modules, and the software modules may be stored in a Random Access Memory (RAM), a flash Memory, a Read Only Memory (ROM), an Erasable Programmable Read Only Memory (EPROM), an Electrically Erasable Programmable Read Only Memory (EEPROM), a register, a hard disk, a removable hard disk, a compact disc Read Only Memory (CD-ROM), or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. Of course, the storage medium may also be integral to the processor. The processor and the storage medium may reside in an ASIC. Additionally, the ASIC may reside in a core network interface device. Of course, the processor and the storage medium may reside as discrete components in a core network interface device.

Those skilled in the art will recognize that, in one or more of the examples described above, the functions described in this invention may be implemented in hardware, software, firmware, or any combination thereof. When implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a general purpose or special purpose computer.

The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made on the basis of the technical solutions of the present invention should be included in the scope of the present invention.

Claims

1. A method for controlling multicast transmissions, a second operator edge PE device acting as a back-up designated router BDR rising to a designated router DR upon failure of a first PE device acting as the DR, the method comprising:

after the first PE equipment is recovered to be normal, the second PE equipment determines that the recovered first PE equipment is increased to be DR;

when the second PE equipment determines that the first PE equipment which is recovered to be normal rises to the DR, a first assertion Assert message is sent to the first PE equipment, and the first Assert message is used for obtaining information for performing Assert election from the first PE equipment which is recovered to be normal;

wherein:

after the second PE device returns to normal from the first PE device, determining that the first PE device that returns to normal rises to the DR includes: the second PE device receives a DR election message sent by the first PE device which is recovered to be normal, wherein the DR election message carries DR election information of the first PE device which is recovered to be normal, and the DR election information of the first PE device which is recovered to be normal comprises DR priority of the first PE device which is recovered to be normal and/or an Internet Protocol (IP) address of a downstream interface of the first PE device which is recovered to be normal; the second PE device performs DR election according to the recovered normal DR election information of the first PE device and the recovered DR election information of the second PE device, wherein the DR election information of the second PE device comprises DR priority of the second PE device and/or an IP address of a downstream interface of the second PE device; the second PE equipment determines that the first PE equipment which returns to normal rises to be the DR according to the DR election result;

or,

after the second PE device returns to normal from the first PE device, determining that the first PE device that returns to normal rises to the DR includes: the second PE device detects that a downstream interface of the second PE device is converted from a first state to a second state, and determines that the first PE device that recovers to normal rises to the DR, where the first state is a state where the downstream interface of the second PE device does not receive multicast traffic, the second state is a state where the downstream interface of the second PE device receives the multicast traffic, and the downstream interface of the second PE device is an interface capable of communicating with a multicast receiver.

2. The method according to claim 1, wherein the multicast traffic is multicast traffic sent by the first PE device that recovers from normal through a downstream interface of the first PE device that recovers from normal at a first time, the first time is a time after a preset time period elapses from a time when the first PE device that has failed recovers from normal, the preset time period is greater than or equal to an aging time of a cycle suppression mechanism, and the downstream interface of the first PE device that recovers from normal is an interface capable of communicating with a multicast receiver.

3. The method according to any one of claims 1 to 2, further comprising:

the second PE equipment receives a second Assert message sent by the first PE equipment which recovers to normal, wherein the second Assert message comprises Assert election information of the first PE equipment;

the second PE equipment performs Assert election according to Assert election information of the first PE equipment and Assert election information of the second PE equipment;

and after the assertion election fails, the second PE device deletes the multicast forwarding table entry stored by the second PE device.

4. A method for controlling multicast transmissions, a second operator edge PE device acting as a back-up designated router BDR rising to a designated router DR upon failure of a first PE device acting as the DR, the method comprising:

after the failed first PE equipment is recovered to be normal, determining that the DR is increased;

and after the recovered normal first PE equipment obtains the multicast forwarding table item, sending a first assertion Assert message to second PE equipment, wherein the first assertion message is used for indicating the second PE equipment to perform assertion election.

5. The method according to claim 4, wherein after the failed first PE device recovers to normal and then becomes DR, before the recovered first PE device sends a first Assert packet to the second PE device, the method further comprises:

and the first PE equipment which is recovered to be normal sends a DR election message to the second PE equipment, wherein the DR election message comprises DR election information of the first PE equipment, and the DR election information of the first PE equipment comprises DR priority of the first PE equipment and/or an Internet Protocol (IP) address of a downstream interface of the first PE equipment.

6. The method according to claim 4 or 5, wherein after the recovered-to-normal first PE device obtains a multicast forwarding entry, the method further comprises:

and the first PE equipment which is recovered to be normal sends multicast traffic through a downstream interface of the first PE equipment which is recovered to be normal, wherein the downstream interface of the first PE equipment which is recovered to be normal is an interface capable of communicating with a multicast receiver.

7. A second provider edge PE device, a second PE device acting as a back-up designated router BDR rising to a designated router DR upon failure of a first PE device acting as the DR, the second PE device comprising:

a determining unit, configured to determine, after the first PE device recovers to be normal, that the recovered first PE device is raised to the DR;

a sending unit, configured to send a first assertion Assert message to the first PE device when the determining unit determines that the first PE device that recovers to normal rises to the DR, where the first assertion message is used to obtain information for performing Assert election from the first PE device that recovers to normal;

wherein,

the determination unit includes:

a receiving subunit, configured to receive a DR election message sent by the first PE device that recovers to normal, where the DR election message carries DR election information of the first PE device that recovers to normal, and the DR election information of the first PE device that recovers to normal includes a DR priority of the first PE device that recovers to normal and/or an internet protocol IP address of a downstream interface of the first PE device that recovers to normal;

a DR election subunit, configured to perform DR election according to the DR election information of the first PE device and the DR election information of the second PE device that are received by the receiving subunit and are restored to normal, where the DR election information of the second PE device includes a DR priority of the second PE device and/or an IP address of a downstream interface of the second PE device;

a determining subunit, configured to determine, according to a result of the DR election obtained by the DR election performed by the DR election subunit, that the first PE device that returns to normal rises to the DR;

or,

the determining unit is specifically configured to:

detecting that a downstream interface of the second PE device is converted from a first state to a second state, and determining that the recovered first PE device is raised to the DR, where the first state is a state where the downstream interface of the second PE device does not receive multicast traffic, the second state is a state where the downstream interface of the second PE device receives the multicast traffic, and the downstream interface of the second PE device is an interface capable of communicating with a multicast receiver.

8. The second PE device of claim 7, wherein the multicast traffic is multicast traffic sent by the first PE device that recovers from normal through the downstream interface of the first PE device that recovers from normal at a first time, the first time is a time after a preset time period elapses from a time when the first PE device that has failed recovers from normal, the preset time period is greater than or equal to an aging time of a cycle suppression mechanism, and the downstream interface of the first PE device that recovers from normal is an interface capable of communicating with a multicast receiver.

9. The second PE device of any of claims 7 through 8, wherein the second PE device further comprises:

a receiving unit, configured to receive a second Assert message sent by the first PE device that recovers to normal, where the second Assert message includes Assert election information of the first PE device;

an assertion election unit, configured to perform Assert election according to the Assert election information of the first PE device and the Assert election information of the second PE device received by the receiving unit;

and the table item deleting unit is used for deleting the multicast forwarding table item stored by the second PE device after the assertion election unit fails to perform the Assert election.

10. A first operator edge PE device, a second PE device acting as a back-up designated router BDR rising to a designated router DR upon failure of the first PE device acting as the DR, the first PE device comprising:

a determining unit, configured to determine that the first PE device is increased to the DR after the failed first PE device is recovered to normal;

a sending unit, configured to send a first assertion Assert message to the second PE device after the determining unit determines that the first PE device has risen to the DR and obtains the multicast forwarding entry, where the first assertion message is used to instruct the second PE device to perform Assert election.

11. The first PE device of claim 10, wherein the sending unit is further configured to, after the determining unit determines that the first PE device is up to the DR, before the sending unit sends the first Assert packet to the second PE device,

and sending a DR election message to the second PE device, wherein the DR election message comprises DR election information of the first PE device, and the DR election information of the first PE device comprises DR priority of the first PE device and/or an Internet Protocol (IP) address of a downstream interface of the first PE device.

12. The first PE device of claim 10 or 11, wherein the sending unit is further configured to send the multicast traffic through a downstream interface of the recovered normal first PE device after the recovered normal first PE device obtains the multicast forwarding entry, where the downstream interface of the recovered normal first PE device is an interface capable of communicating with a multicast receiver.