WO2009146622A1

WO2009146622A1 - Method, router and system for implementing multicast

Info

Publication number: WO2009146622A1
Application number: PCT/CN2009/071597
Authority: WO
Inventors: 彭敏
Original assignee: 华为技术有限公司
Priority date: 2008-06-03
Filing date: 2009-04-30
Publication date: 2009-12-10
Also published as: CN101599841A

Abstract

A method, router and system for implementing multicast are provided, said method comprising: receiving a Join message through a physical interface, said Join message including the loop-back address of a downstream router; joining the physical interface into the out-interface list of the multicast group G, and searching for the matching TE tunnel based on said loop-back address and physical interface; replacing the physical interface in the out-interface list with the matching TE tunnel port to obtain a new out-interface list; according to the new out-interface list, sending the multicast message to the downstream router through the matching TE tunnel.

Description

Method, router and system for implementing multicast

This application claims priority to Chinese Patent Application No. 200810085933. X, entitled "Methods for Implementing Multicast, Routers and Systems", filed on June 3, 2008, the entire contents of which are incorporated by reference. In this application.

Technical field

The present invention relates to the field of communications technologies, and in particular, to a method, a router, and a system for implementing multicast. Background technique

With the development of communication technology, the demand for data transmission is increasing. Multicast is a point-to-multipoint efficient data transmission technology in an Internet Protocol (IP) network. In the multicast mode, a single information flow is simultaneously sent to a group of users along a tree path. The same multicast data stream is in the same way. There is only one copy per link. The most important part of the multicast technology is the construction of the multicast distribution tree. The Protocol Independent Multicast-Sparse Mode (PIM-SM) protocol is usually used. PIM uses the existing unicast routing information to perform reverse path forwarding (RPF) check on multicast packets to create multicast routing entries and construct a multicast distribution tree. The multicast routing table records all the PIM routing entries and sends them to the forwarding table. The forwarding entries directly direct multicast packet forwarding.

The multicast routing table records all PIM routing entries and sends them to the forwarding table. The forwarding entry directly directs multicast packet forwarding. There are two forwarding entries in PIM: (S, G) or (*, G). S indicates a multicast source, G indicates a multicast group, and * indicates an arbitrary number.

( S, G ) is only applicable to multicast messages whose source address is S and whose group address is G. Generally, a multicast packet whose source address is S and whose group address is G is represented as (S, G) packets.

( * , G ) applies to multicast packets with a group address of G. That is, no matter which multicast source is sent, any multicast packet sent to multicast group G should be forwarded from the downstream interface in the (*, G) entry.

There may be multiple forwarding entries on the PIM router. When receiving a multicast packet whose source address is S and the group address is G, and the RPF check is performed, the following rules are forwarded:

If there is an (S, G) entry, the (S, G) entry guides the packet forwarding.

If no (S, G) entry exists, the (S, G) entry is created according to the (*, G) entry, and the (S, G) entry is used to guide the packet forwarding.

In the traditional multicast technology, the outbound interface of a PIM routing entry can only be a physical interface. The common IP routing and forwarding mode lacks a fast protection mechanism. When the network topology changes, the convergence of multicast traffic will be slow. At the same time, due to the lack of bandwidth guarantee, it is difficult to provide stable multicast services when the backbone network services are busy. service quality.

Summary of the invention

The purpose of the embodiments of the present invention is to provide a method, a router, and a system for implementing multicast, which improve the service quality of a multicast service.

The embodiment of the present invention provides a method for implementing multicast. A traffic engineering TE tunnel exists between a downstream router and an upstream router, and the method includes:

Receiving, by the physical interface, a Join message sent by the downstream router to the upstream router by the multicast group G, where the Join message includes a loopback address of the loopback interface of the downstream router;

Adding the physical interface to the outbound interface list of the multicast group G, and searching for a matching TE tunnel according to the loop-back address and the physical interface;

Replacing the physical interface in the outbound interface list with the matched TE tunnel interface, and obtaining a new outbound interface list, and sending the multicast packet to the downstream through the matched TE tunnel according to the new outgoing interface list. router.

The embodiment of the present invention further provides an upstream router that implements a multicast, where the upstream router and the downstream router have a traffic engineering TE tunnel, and the upstream router includes:

a receiving unit, configured to receive a Join message sent by the downstream router to the multicast group G, where the Join message includes a loopback address of the loopback interface of the downstream router;

a routing unit, configured to add a physical interface that receives the Join message in the receiving unit to an outbound interface list of the multicast group G;

a searching unit, configured to search for a matching TE tunnel according to the loop-back address in the Join message received by the receiving unit, and the physical interface; and replace the physics in the outbound interface list in the routing unit with the matched TE tunnel interface Interface, get a list of new outgoing interfaces;

And a sending unit, configured to send, according to the new outbound interface list in the routing unit, the multicast packet received by the receiving unit to the downstream router by using a matching TE tunnel.

The embodiment of the present invention further provides a downstream router that implements a multicast, where the downstream router and the upstream router have a traffic engineering TE tunnel, and the downstream router includes:

a message unit, configured to generate a Join message for the multicast group G, where the Join message includes the downstream message Loopback address of the loopback of the router;

a sending unit, configured to send a Join message generated by the message unit to the upstream router, and a receiving unit, configured to receive a multicast message sent by the upstream router by using a matching TE tunnel, where the matched TE tunnel is used by the The upstream router adds the physical interface that receives the Join message to the outbound interface list of the multicast group G, and searches for the loop-back address and the physical interface. The multicast packet is used by the upstream router. The matching TE tunnel interface replaces the physical interface in the outbound interface list, and obtains a new outbound interface list, and sends the new outbound interface list according to the new outgoing interface list.

The embodiment of the present invention further provides a system for implementing multicast, including: an upstream router and a downstream router, where the downstream router and the upstream router have a traffic engineering TE tunnel, where

The downstream router is configured to send a Join message to the upstream router for the multicast group G, where the Join message includes a loopback address of the loopback interface of the downstream router;

The upstream router is configured to receive the Join message through a physical interface, add the physical interface to an outbound interface list of the multicast group G, and search for a matching TE according to the loop-back address and the physical interface. The tunnel is replaced with a matching TE tunnel interface to obtain a new outbound interface list, and according to the new outgoing interface list, the multicast packet is sent to the Downstream router.

In the embodiment of the present invention, the TE tunnel is used to find the matching TE tunnel, and the TE tunnel interface is used to replace the physical outbound interface in the outbound interface list of the upstream router, so that the multicast forwarding can utilize the TE tunnel for fault protection, resource reservation, and tunnel encapsulation. , can improve the quality of service of the multicast service.

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 embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description are only It is a certain embodiment of the present invention, and other drawings can be obtained from those skilled in the art without any inventive labor.

1 is a schematic flowchart of implementing a multicast method according to Embodiment 1 of the present invention;

2 is a schematic structural diagram of implementing a multicast system according to Embodiment 2 of the present invention;

3 is a schematic structural diagram of an upstream router implementing multicast in Embodiment 3 of the present invention; FIG. 4 is a schematic structural diagram of a downstream router implementing multicast in Embodiment 4 of the present invention.

detailed description

BRIEF DESCRIPTION OF THE DRAWINGS The technical solutions in the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without the creative work are all within the scope of the present invention.

The specific embodiments of the embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

The first embodiment is a method for implementing multicast. A traffic engineering TE (Traffic Engineering) tunnel is used between the downstream router and the upstream router. The TE tunnel is a Constraint-Based Label Switch Path. The unidirectional tunnel encapsulation technology of the CR-LSP, the Multi-Protocol Label Switching (MPLS) TE, in the process of establishing an LSP tunnel, can reserve resources to ensure the quality of service; MPLS TE also implements a mechanism for path backup and fast reroute, which can be switched in time when there is a problem with the link.

Referring to Figure 1, the method can include:

101. The downstream router sends a join message to the upstream router for the multicast group G. The join message includes the loopback address of the loopback port of the downstream router.

Currently, the Join message can also include:

1 encoded upstream neighbor address Upstream Neighbor Address ;

m encoded multicast group addresses Multicast group address (where m is a natural number). In the Join message, each of the multicast group addresses can be followed by:

n coded requirements. The source address of the incoming Join Source Address; and the source address of the n coded pruning required Pruned Source Address (where n is a natural number).

In this embodiment, for the current Join message format, the loop-back address of the downstream router may be included in the Join message in the following manner:

A multicast group Multicast Grou field is appended to the Join message; the Multicast Group field is followed by an encoded source address Joined Source Address and a source address that is encoded to require pruning. The Runed Source Address is included in the Joined Source Address. The loop-back address of the downstream router; the Pruned Source Address contains the identifier of the multicast group field. The identifier of the multicast group field is used to indicate that the Join message contains the loop-back of the downstream router. The address, you can use the value that has not been defined in the current multicast protocol, for example, set all the bytes of the Pruned Source Address to zero.

Further, the Multicast Grou field and the subsequent Joined Source Address have an address family Address family different from the Upstream Neighbor Address in the Join message of this embodiment. For the upstream router supporting the multicast method in this embodiment, the loop-back address can be obtained directly from the Joined Source Address of the Multicast Grou field; for the upstream router that does not support the multicast method in this embodiment, according to Currently, the multicast protocol RFC2362 stipulates that when the corresponding fields of the Address family and the Upstream neighbor address of a Multicast Group or a Joined Source Address are different, the upstream router ignores the Multicast Group field, so the method for implementing multicast in this embodiment is used. It can be compatible with current routers and achieve good interoperability with current technologies.

102. The upstream router receives the Join message through the physical interface.

103. The upstream router adds the physical interface that receives the Join message to the outbound interface list of the multicast group G entry.

104. Find a matching TE tunnel according to the loop-back address and the physical interface that receives the Join message.

The matching principle is that if the destination address and the outbound interface of a TE tunnel are the same as the loop-back address of the Join message and the physical interface of the Join message, the match is considered successful. :

Conditions 1. Find whether there is a TE tunnel with the same destination address as the loop-back address.

Condition 2: Find out whether there is a TE tunnel with the same outbound interface as the physical interface.

The TE tunnels that meet the conditions 1 and 2 are matched TE tunnels.

105. Replace the physical interface that receives the Join message in the interface list with the matching TE tunnel interface, and obtain a new outbound interface list.

Further, in this embodiment, the method may further include:

106. The upstream router receives the multicast packet.

107. The upstream router sends the multicast packet to the downstream router through the matched TE tunnel according to the new outbound interface list.

Further, the method may further include establishing a mapping relationship between the label and the port (the first interface), The specific implementation process can be:

The downstream router searches for the first interface, where the first interface is the outbound interface of the matching TE tunnel source address in the unicast routing table; the unicast routing table is on the downstream router.

109. The downstream router establishes a mapping relationship between the label of the multicast packet and the first interface.

Further, the method may further include:

110. The downstream router determines the type of the received multicast packet.

111. When the multicast packet is an Internet Protocol IP packet, the downstream router performs the reverse path forwarding check of the IP packet. The downstream router checks whether the second interface is the same as the third interface. If the packets are inconsistent, the multicast packets are discarded. The second interface is the interface that receives the multicast packets from the downstream router. The third interface is the unicast routing table of the downstream router and multicast. The outbound interface corresponding to the source address of the source;

When the multicast packet is an MPLS packet, the downstream router performs the reverse path forwarding check of the MPLS packet. Since the matched TE tunnel includes the primary tunnel and the protection tunnel, the multicast packet may reach through the primary tunnel or the protection tunnel. On the downstream router, the downstream router may receive multiple multicast packets. The path of the tunnel forwarding path and the reverse unicast route are inconsistent. The reverse path forwarding check fails. The mapping between the label of the multicast packet and the first interface is established. The reverse path forwarding check can also be performed when the multicast packet is an MPLS packet. The specific check method is as follows:

As a result of the MPLS packet, the MPLS packet is sent from the primary tunnel or the protection tunnel. The MPLS packet contains the same label when it reaches the destination address. Therefore, the multicast packet is a multi-protocol label distribution protocol. The downstream router searches for the mapping according to the label of the multicast packet to obtain the corresponding first interface. The downstream router checks whether the first interface is the same as the fourth interface. If the packets are consistent, the multicast packet is forwarded through the reverse path. If the packets are inconsistent, the multicast packets are discarded. The fourth interface is the outbound interface corresponding to the source address of the multicast packet in the unicast routing table of the downstream router.

。 Multicast in the above manner. When a multicast packet is an MPLS packet, there is a premise that the router in the TE tunnel cannot use the penultimate hop popup when performing MPLS label distribution. The so-called penultimate hop pop-up method is, according to the current MPLS transport protocol, when the MPLS packet is transmitted to the penultimate router, in order to reduce the work of the last router, the second to last The router removes the MPLS label of the MPLS packet. If the second-to-last hop is used, the TE tunnel also includes other protection paths. If the multicast packets received by the downstream router from the interface other than the fourth interface have been removed from the MPLS label, the mapping relationship cannot be searched. Therefore, the reverse path forwarding check cannot be performed. Therefore, in this embodiment, when the multicast packet is an MPLS packet, the penultimate hop popup mode is not used.

The technical solution of the embodiment is used to enable the multicast packet to be forwarded through the TE tunnel. Since the encapsulation technology is applied to the TE tunnel, the intermediate node of the tunnel does not need to reserve the multicast forwarding table, and the intermediate router may not even support the multicast protocol. Packet forwarding can be implemented across multicast domains.

In addition, when the multicast packet is an MPLS packet, the multicast packet is encapsulated in the MPLS packet, and the intermediate router cannot identify the content, thus ensuring the security of the multicast content.

At the same time, the TE tunnel has a large number of fault protection mechanisms, such as fast reroute, LSP (label switch path), and tunnel protection group. When the primary path fails, it can quickly detect and switch to the alternate path. This process is transparent to the outside world, so it can ensure that the multicast route does not need to re-converge when the path fails, and the multicast traffic is not interrupted.

Similarly, the bandwidth guarantee and differential services of the TE tunnel provide a good guarantee for the quality of the multicast service.

Further, the mapping between the label and the port is established, so that the MPLS packet can be forwarded through the multicast reverse path to ensure the continuity of the multicast service. Embodiment 2, this embodiment is a main body of a method for implementing an embodiment, and a system for implementing multicast. Referring to FIG. 2, the system may include: an upstream router 201 and a downstream router 202, and between a downstream router and an upstream router. Traffic engineering TE tunnel, where

The downstream router 202 is configured to send a Join message to the upstream router for the multicast group G, where the Join message includes a loopback address of the loopback port of the downstream router;

The upstream router 201 is configured to receive a Join message through the physical interface; add the physical interface to the outbound interface list of the multicast group G; and find a matching TE tunnel according to the loop-back address and the physical interface that receives the Join message; The TE tunnel interface replaces the physical interface in the outbound interface list to obtain a new outbound interface list. The multicast tunnel is sent to the downstream router through the matching TE tunnel. Further, the downstream router 202 can include:

The message unit 202-1 is configured to generate a Join message for the multicast group G.

The sending unit 202-2 is configured to send a Join message generated by the message unit to the upstream router 201. Further, the upstream router 201 can include:

The receiving unit 201-1 is configured to receive a Join message and/or a multicast message.

The routing unit 201-2 is configured to add the physical interface that receives the Join message in the receiving unit 201-1 to the outbound interface list of the multicast group G.

The searching unit 201-3 is configured to search for a matching TE tunnel according to the loop-back address and the physical interface in the Join message received by the receiving unit 201-1; and replace the outbound interface list in the routing unit 201-2 with the matched TE tunnel port. The physical interface in the middle, get a list of new outgoing interfaces;

The sending unit 201-4 is configured to send the multicast message received by the receiving unit 201-1 to the downstream router 202 through the matched TE tunnel according to the new outbound interface list in the routing unit 201-2.

Further, the downstream router 202 may further include:

The mapping unit 202-3 is configured to find the outbound interface of the matched TE tunnel source address in the unicast routing table, and obtain the first interface; the unicast routing table is on the downstream router; and establish the label of the multicast packet and the first The mapping relationship of the interface.

Further, the downstream router 202 may further include:

The receiving unit 202-4 is configured to receive a multicast packet from the upstream router 201.

The determining unit 202-5 is configured to determine the type of the multicast packet received by the receiving unit 202-4. The checking unit 202-6 is configured to: when the determining unit 202-5 determines that the multicast packet is an Internet Protocol IP packet, Check whether the second interface is the same as the third interface. If the packets are the same, the multicast packets are forwarded through the reverse path. If the packets are inconsistent, the multicast packets are discarded. The second interface is the downstream router. The third interface is the outbound interface corresponding to the multicast packet in the unicast routing table of the downstream router; this case is not shown in FIG. 2;

When the determining unit 202-5 determines that the multicast packet is a multi-protocol label distribution protocol MPLS packet, the mapping relationship between the mapping unit 202-3 of the multicast packet is obtained, and the corresponding first interface is obtained; Whether the interface is the same as the fourth interface. If the interface is consistent, the multicast packets are forwarded through the reverse path. If the packets are inconsistent, the multicast packets are discarded. The fourth interface is the unicast routing table and group of the downstream router. The outgoing interface corresponding to the source address of the broadcast source. The third embodiment is an upstream router that implements multicast in the second embodiment. A traffic engineering TE tunnel exists between the upstream router and the downstream router. Referring to FIG. 3, the upstream router may include:

The receiving unit 301 is configured to receive a Join message sent by the downstream router for the multicast group G, where the Join message includes a loopback address of the loopback port of the downstream router.

The routing unit 302 is configured to add the physical interface that receives the Join message in the receiving unit 301 to the outbound interface list of the multicast group G.

The searching unit 303 is configured to search for a matching TE tunnel according to the loop-back address and the physical interface in the Join message received by the receiving unit 301, and replace the physical interface in the outbound interface list in the routing unit 302 with the matched TE tunnel interface, New outgoing interface list;

The sending unit 304 is configured to send the multicast packet received by the receiving unit 301 to the downstream router through the matched TE tunnel according to the new outbound interface list in the routing unit 302. The fourth embodiment is a downstream router that implements multicast in the second embodiment. A traffic engineering TE tunnel exists between the downstream router and the upstream router. Referring to FIG. 4, the downstream router may include:

The message unit 401 is configured to generate a Join message for the multicast group G, where the Join message includes a loopback address of the loopback port of the downstream router.

The sending unit 402 is configured to send a Join message generated by the message unit 401 to the upstream router. The receiving unit 403 is configured to receive the multicast message sent by the upstream router through the matched TE tunnel, and the matched TE tunnel receives the Join message by the upstream router. The physical interface is added to the outbound interface list of the multicast group G, and is obtained based on the loop-back address and the physical interface. The multicast router replaces the physical interface in the interface list with the matching TE tunnel interface. The interface list is sent through the matching TE tunnel according to the new outgoing interface list.

Further, the downstream router may further include:

The mapping unit 404 is configured to search for an outbound interface of the matched TE tunnel source address in the unicast routing table, to obtain a first interface, where the unicast routing table is on the downstream router, and establish the multicast packet A mapping relationship between the label of the text and the first interface.

Further, the downstream router may further include:

The determining unit 405 is configured to determine a type of the multicast packet received by the receiving unit 403. The checking unit 406 is configured to: when the determining unit 403 determines that the multicast packet is an Internet Protocol IP packet, check whether the second interface is consistent with the third interface, and if the consistency is the same, the multicast packet is forwarded through the reverse path. If the packets are inconsistent, the multicast packet is discarded; wherein the second interface is an interface that receives the multicast packet in the downstream router, and the third interface is a unicast of the downstream router. An outbound interface corresponding to the multicast packet in the routing table;

When the determining unit determines that the multicast packet is a multi-protocol label distribution protocol MPLS packet, the mapping relationship in the mapping unit is searched according to the label of the multicast packet to obtain a corresponding first interface; Whether the first interface is consistent with the fourth interface. If the first interface is the same, the multicast packet is forwarded through the reverse path. If the packet is inconsistent, the multicast packet is discarded. An outbound interface corresponding to the source address of the multicast packet in the unicast routing table of the downstream router.

Through the description of the above embodiments, those skilled in the art can clearly understand that the present invention can be implemented by means of software plus a necessary hardware platform, and of course, all can be implemented by hardware. Based on such understanding, all or part of the technical solution of the present invention contributing to the background art may be embodied in the form of a software product, which may be stored in a storage medium such as a ROM/RAM, a magnetic disk, an optical disk, or the like. A number of instructions are included to cause a computer device (which may be a personal computer, server, or network device, etc.) to perform the methods described in various embodiments of the present invention or portions of the embodiments.

The above is only a specific embodiment of the present invention, and it should be noted that those skilled in the art can also make some improvements and retouching without departing from the principles of the present invention. It is considered as the scope of protection of the present invention.

Claims

Rights request

A method for implementing multicast, the traffic engineering TE tunnel is used between the downstream router and the upstream router in the multicast network, and the TE tunnel is used for multicast traffic forwarding, and the method includes:

Receiving, by the physical interface, the joining of the downstream router to the upstream router for the multicast group G

a Join message, where the Join message includes a loopback address of the loopback port of the downstream router;

Replacing the physical interface in the outbound interface list with the matched TE tunnel interface, and obtaining a new outbound interface list, and sending, according to the new outgoing interface list, the multicast message to the Downstream router.

The method according to claim 1, wherein the Join message further comprises: a multicast group field; the multicast group field includes an encoded source address Joined Source Address and an encoded request header. The source address of the branch is Pruned Source Address;

The Joined Source Address includes a loop-back address of the downstream router;

The Pruned Source Address contains the identity of the multicast group field.

The method according to claim 2, wherein the multicast group field further includes an address family Address family and a multicast encoded upstream neighbor address Upstream neighbor address, the Address family and the Upstream neighbor address. The value is different.

The method according to claim 1, wherein the searching for the matching TE tunnel according to the loop-back address and the physical interface includes:

Find whether there is a TE tunnel with the same destination address as the loop-back address.

Find out whether there is an TE tunnel with the same outbound interface as the physical interface.

The TE tunnel that meets the same destination address as the loop-back address and the outbound interface and the physical interface is the matching TE tunnel.

5. The method according to claim 1, wherein the method further comprises:

The downstream router searches for an outbound interface of the matched TE tunnel source address in the unicast routing table to obtain a first interface; the unicast routing table is on the downstream router;

The downstream router establishes a mapping relationship between the label of the multicast packet and the first interface.

The method according to claim 5, wherein the method further comprises: determining, by the downstream router, the type of the received multicast packet;

When the multicast packet is an Internet Protocol (IP) packet, the downstream router checks whether the second interface is the same as the third interface. If the packets are the same, the multicast packet is forwarded through the reverse path. The second interface is an interface that receives the multicast packet in the downstream router, and the third interface is an outbound interface corresponding to the multicast packet in the unicast routing table of the downstream router;

When the multicast packet is a multi-protocol label distribution protocol MPLS packet, the downstream router searches for the mapping relationship according to the label of the multicast packet; and the downstream router checks whether the first interface and the fourth interface check whether the first interface and the fourth interface are If the packets are consistent, the multicast packet is forwarded through the reverse path. The fourth interface is the outbound interface corresponding to the multicast packet in the unicast routing table of the downstream router. The matching TE tunnel includes a primary tunnel and a protection tunnel.

An upstream router that implements multicast, wherein the upstream router and the downstream router have a traffic engineering TE tunnel, and the upstream router includes:

A downstream router for implementing multicast, characterized in that: the downstream router and the upstream router have a traffic engineering TE tunnel, and the downstream router includes:

a message unit, configured to generate a Join message for the multicast group G, where the Join message includes a loopback address of the loopback interface of the downstream router;

a sending unit, configured to send a Join message generated by the message unit to the upstream router, and a receiving unit, configured to receive a multicast message sent by the upstream router by using a matching TE tunnel, where the matched TE tunnel is used by the The upstream router adds the physical interface that receives the Join message to the group. The outbound interface list of the broadcast group G is obtained by the loop-back address and the physical interface; the multicast packet is replaced by the upstream router by the matching TE tunnel interface. The physical interface obtains a new outbound interface list and sends the same through the matched TE tunnel according to the new outgoing interface list.

The downstream router according to claim 8, wherein the downstream router further comprises:

a mapping unit, configured to find an outbound interface of the matched TE tunnel source address in the unicast routing table, to obtain a first interface, where the unicast routing table is on the downstream router, and establish the multicast packet The mapping relationship between the label and the first interface.

The downstream router according to claim 9, wherein the downstream router further comprises:

a determining unit, configured to determine a type of the multicast packet received by the receiving unit;

The checking unit is configured to: when the determining unit determines that the multicast message is the Internet Protocol IP 4, check whether the second interface is consistent with the third interface, and if the information is consistent, the multicast packet passes the reverse path. Forwarding check; if not, discarding the multicast packet; wherein the second interface is an interface that receives the multicast packet in the downstream router, and the third interface is the downstream router An outbound interface corresponding to the multicast packet in the unicast routing table;

A system for implementing multicast, comprising: an upstream router and a downstream router, wherein the downstream router and the upstream router have a traffic engineering TE tunnel, where

The upstream router is configured to receive the Join message through a physical interface, add the physical interface to an outbound interface list of the multicast group G, and search for a matching TE tunnel according to the loop-back address and the physical interface. Replace the physical interface in the outbound interface list with a matching TE tunnel interface. A new outgoing interface list is obtained, and the multicast packet is sent to the downstream router by using the matched TE tunnel according to the new outgoing interface list.

The system according to claim 11, wherein the downstream router includes: a message unit, configured to generate a Join message for the multicast group G;

And a sending unit, configured to send, to the upstream router, a Join message generated by the message unit.

13. The system of claim 11 or 12, wherein the upstream router comprises:

a receiving unit, configured to receive the Join message and/or the multicast message;

The system according to claim 13, wherein the downstream router further comprises: a mapping unit, configured to search for an outbound interface of the matched TE tunnel source address in the unicast routing table, to obtain a first interface The unicast routing table is on the downstream router; and the mapping relationship between the label of the multicast packet and the first interface is established.

The system according to claim 14, wherein the downstream router further comprises: a receiving unit, configured to receive a multicast packet from the upstream router;

The checking unit is configured to: when the determining unit determines that the multicast message is the Internet Protocol IP 4, check whether the second interface is consistent with the third interface, and if the information is consistent, the multicast packet passes the reverse path. Forwarding check; wherein the second interface is an interface that receives the multicast packet in the downstream router, and the third interface is a unicast routing table of the downstream router that corresponds to the multicast packet Outlet interface

When the determining unit determines that the multicast packet is a multi-protocol label distribution protocol MPLS packet, the mapping relationship in the mapping unit is searched according to the label of the multicast packet to obtain a corresponding first interface; Checking whether the first interface is the same as the fourth interface. If the first interface is the same, the multicast packet is forwarded through the reverse path. The fourth interface is the unicast routing table of the downstream router. The outbound interface corresponding to the source address of the multicast source.