CN102510356B - Forwarding entry deletion method and root node - Google Patents

Abstract

The invention discloses a method and a root node for deleting a forwarding entry. The method includes: after the root node of the multicast tree detects that the multicast traffic of the multicast tree is cut off, sending the first A multicast tree disconnection message, so that the first-level downstream multicast neighbor nodes that receive the first multicast tree disconnection message delete the forwarding table entries of the multicast tree maintained by themselves; After the multicast traffic to the multicast tree is cut off, delete the forwarding entry of the multicast tree maintained by the root node. An advantage of the present invention is that, since the root node deletes the forwarding entry of the multicast tree maintained by itself, some or all of the first-level downstream multicast neighbor nodes of the root node delete The forwarding entry of the multicast tree maintained by itself realizes the rapid deletion of multiple multicast entries on the multicast tree based on the notification mechanism.

Description

A method and root node for deleting forwarding entry

technical field

The present invention relates to the field of communications, in particular to a method for deleting a forwarding entry and a root node

Background technique

Internet Protocol (IP) multicasting is the use of a protocol to transmit IP packets from one source to multiple destinations, sending a copy of the message to a set of addresses to all recipients who want to receive it. IP multicast is the "best effort" transmission of IP data packets to a set of hosts forming a multicast group, and each member of the group can be distributed on each independent physical network. The relationship between members in an IP multicast group is dynamic. The host can join and exit the group at any time. The membership of the group determines whether the host receives the multicast data packets sent to the group. Hosts that are not members of a certain group It is also possible to send multicast packets to the group. Multimedia conferencing is a relatively new field of communication applications. With the popularization of video conferencing applications, IP multicast network technology has also developed rapidly.

Multicast routing protocols in IP multicast network technology can be divided into three categories: dense mode protocols, sparse mode protocols and link state protocols. Currently commonly used are protocol independent multicast (PIM) dense mode protocol and protocol independent multicast (PIM) sparse mode protocol. PIM does not depend on a specific unicast routing protocol. It can use the unicast routing table established by various unicast routing protocols to complete the RPF check function instead of maintaining a separate multicast routing table to implement multicast forwarding. Because PIM does not need to send and receive multicast routing updates, compared with other multicast protocols, the overhead of PIM is much lower.

Since the multicast source of the video conference is constantly changing, a multicast tree 1 may be established in which the multicast source is source 1 and the multicast group is group 1, namely (S1, G1). At the second moment, the previously established multicast tree 1 may have failed but has not been deleted, and the multicast tree for forwarding data may have become the multicast source as source 2 and the multicast group as group 1, that is (S2 , G1) multicast tree 2. At this time, although the previously established multicast tree 1 has failed, there are still forwarding entries of the multicast tree 1 remaining in the network. When there are many participants in the video conference on the network, or there are many video conferences held, there will be more forwarding entries in the invalid multicast tree of the entire network, and these invalid forwarding entries will occupy more network resources. .

Contents of the invention

An object of the present invention is to provide a method and a root node for deleting a forwarding entry.

One embodiment of the present invention discloses a method for deleting a forwarding entry, which includes:

After the root node of the multicast tree detects that the multicast traffic of the multicast tree is disconnected, it sends a first multicast tree disconnection message to some or all of the first-level downstream multicast neighbor nodes of the root node. message, so that the first-level downstream multicast neighbor node that receives the first multicast tree disconnection message deletes the forwarding entry of the multicast tree maintained by itself;

The root node deletes the forwarding entry of the multicast tree maintained by the root node after detecting that the multicast traffic of the multicast tree is cut off.

An embodiment of this aspect discloses a root node, including:

The first sending unit is configured to, after the root node detects that the multicast traffic of the multicast tree where the root node is located is cut off, to multicast part or all of the first-level downstream neighbor nodes of the root node Sending the first multicast tree disconnection message respectively, so that the first-level downstream multicast neighbor nodes that receive the first multicast tree disconnection message respectively delete the forwarding entries of the multicast tree maintained by themselves;

The forwarding entry deletion unit is configured to delete the forwarding entry of the multicast tree maintained by the root node after the root node detects that the multicast traffic of the multicast tree is interrupted.

An embodiment of the present invention has the advantage that, since the root node deletes the forwarding entry of the multicast tree maintained by itself, some or all of the first-level downstream multicast neighbor nodes of the root node The forwarding table items of the multicast tree maintained by itself are respectively deleted, thereby realizing the rapid deletion of multiple multicast table items on the multicast tree based on the notification mechanism.

Description of drawings

Fig. 1 shows the method flow chart of embodiment one of the present invention;

FIG. 2 is a schematic diagram of a multicast tree in Embodiment 2 of the present invention;

FIG. 3 is a schematic diagram of a multicast tree according to Embodiment 4 of the present invention;

Figure 4 is a schematic diagram of a device according to Embodiment 5 of the present invention;

Fig. 5 is a schematic diagram of a device according to Embodiment 5 of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. However, it should be noted that the following embodiments are only examples for helping to understand the technical solutions, and are not intended to limit the present invention.

The content of the first embodiment of the present invention is as follows.

FIG. 1 is a flow chart of the method in Embodiment 1 of the present invention.

101. After the root node of the multicast tree detects that the multicast traffic of the multicast tree is cut off, it sends the first multicast tree to some or all of the first-level downstream multicast neighbor nodes of the root node respectively. The disconnection message, so that the first-level downstream multicast neighbor nodes that receive the first multicast tree disconnection message respectively delete the forwarding entries of the multicast tree maintained by themselves.

The first-level downstream multicast neighbor node may be one node or multiple nodes. When the first-level downstream multicast neighbor node is only one node, some or all of the nodes are one node.

102. After the root node detects that the multicast traffic of the multicast tree is cut off, delete the forwarding entry of the multicast tree maintained by the root node.

Optionally, step 102 may be performed after step 101, or may be performed before step 101.

If step 102 is to be performed after step 101, then the root node may firstly broadcast part of the first-level downstream multicast neighbor nodes of the root node according to the forwarding entry of the multicast tree maintained by the root node Or all nodes respectively send the first multicast tree disconnection message, and then delete the forwarding entry of the multicast tree maintained by the root node. That is to say, sending the first multicast tree disconnection message to some or all of the first-level downstream multicast neighbor nodes of the root node includes: according to the multicast tree maintained by the root node The forwarding table item sends the first multicast tree disconnection message to the part or all nodes in the first-level downstream multicast neighbor nodes of the root node; After the flow is cut off, deleting the forwarding table entry of the multicast tree maintained by the root node includes: the root node detects that the multicast flow of the multicast tree is cut off and the first multicast tree is cut off After the flow message is sent, delete the forwarding entry of the multicast tree maintained by the root node.

If step 102 is to be performed before step 101, the root node pre-records the outgoing ports of the neighbor nodes connected to the part or all of the first-level downstream multicast neighbor nodes on the root node, so that In the case that the forwarding entry of the multicast tree on the root node has been deleted, the root node can multicast neighbor nodes to the first-level downstream multicast neighbor nodes of the root node according to the pre-recorded egress port Part or all of the nodes respectively send the first multicast tree disconnection message. That is to say, after the root node of the multicast tree detects that the multicast traffic of the multicast tree is cut off, it sends the first The multicast tree disconnection message includes: after the root node detects that the multicast traffic of the multicast tree is disconnected and the forwarding entry of the multicast tree on the root node is deleted, according to the The pre-recorded egress port respectively sends the first multicast tree disconnection message to the part or all of the first-level downstream multicast neighbor nodes of the root node.

Since the root node deletes the forwarding table entry of the multicast tree maintained by itself, some or all of the first-level downstream multicast neighbor nodes of the root node delete the multicast tree maintained by itself. The forwarding entry of the tree realizes the rapid deletion of multiple multicast entries on the multicast tree based on the notification mechanism.

Preferably, this embodiment further includes step 103 .

103. After detecting that the multicast traffic of the multicast tree is cut off, the root node sends a multicast flow cut-off message of the sink node to the sink node of the multicast tree, so that the sink node deletes the traffic flow maintained by itself. The forwarding entry of the multicast tree. Preferably, if the convergence node maintains a forwarding entry of the multicast tree when receiving the convergence node multicast disconnection message, the convergence node multicast disconnection message triggers the convergence node to forward The downstream multicast neighbor node of the convergence node sends a new multicast disconnection message, and then deletes the forwarding entry of the multicast tree maintained by itself.

Preferably, step 103 may be performed before step 102, or may be performed after step 102.

If step 103 is to be performed after step 102, it is necessary to pre-record the egress port of the aggregation node connected to the aggregation node on the root node, so that the root node is on the root node of the multicast tree When the forwarding entry has been deleted, the aggregation node multicast tree disconnection message may be sent to the aggregation node according to the pre-recorded egress port of the aggregation node.

Preferably, the first-level downstream multicast neighbor nodes that have received the first multicast tree disconnection message respectively delete the forwarding entries of the multicast tree maintained by themselves.

Preferably, the first node among the first-level downstream multicast neighbor nodes that receives the first multicast tree disconnection message determines that it is not the terminal leaf node of the multicast tree, and maintains the group The forwarding entry of the broadcast tree. That is to say, the first node has a downstream multicast neighbor node, and the downstream multicast neighbor node of the first node is also a secondary downstream multicast neighbor node of the root node. In this embodiment, a downstream multicast neighbor node of the first node is called a second node. At this time, the first node sends a second multicast tree disconnection message to the second node.

The sending of the second multicast tree disconnection message may be performed before the first node deletes the forwarding entry of the multicast tree maintained by itself, or may be performed after the first node deletes the forwarding entry of the multicast tree maintained by itself. Executed after the forwarding entries of the multicast tree.

If sending the second multicast tree disconnection message is executed after the first node deletes the forwarding entry of the multicast tree maintained by itself, it needs to pre-record that the first node is connected to the second node outbound port of the first node, so that when the forwarding entry of the multicast tree on the first node has been deleted, it can use the pre-recorded outbound port connected to the second node The port sends the second multicast tree disconnection message to the second node.

Optionally, in this embodiment, each downstream multicast neighbor node, such as a first-level downstream multicast neighbor node, a second-level downstream multicast neighbor node, or an N-level downstream multicast neighbor node, receives the After the message that the multicast tree is disconnected, the operation similar to the operation of the first-level downstream multicast neighbor node is performed. In this way, a terminal leaf node on the multicast tree can receive a message for notifying the multicast tree of a disconnection, so as to delete the forwarding entry of the multicast tree on the terminal leaf node. And because each node that sends the message for notifying the multicast tree that the flow break occurs will delete the forwarding table of the multicast tree maintained by itself if it maintains the forwarding table item of the multicast tree Therefore, on the multicast forwarding path between the root node of the multicast tree and the terminal leaf node, the forwarding table entries of the multicast tree on the root node, the leaf node and all the multicast neighbor nodes will be deleted, so as to realize the rapid deletion of multiple multicast entries on the multicast tree based on the notification mechanism.

Optionally, each downstream multicast neighbor node on the multicast tree, such as a first-level downstream multicast neighbor node, a second-level downstream multicast neighbor node, or an N-level downstream multicast neighbor node, determines that it is not the After the end leaf node of the multicast tree maintains the forwarding table entry of the multicast tree, it sends a multicast tree disconnection message to each of its downstream multicast neighbor nodes, and deletes the multicast tree maintained by itself. The forwarding entry of the multicast tree. In this way, the forwarding table entries of the multicast tree on the root node on the multicast tree, the terminal leaf nodes on each forwarding path, and all multicast neighbor nodes on each forwarding path will be deleted, thereby Realized the rapid deletion of all multicast entries on the multicast tree based on the notification mechanism.

Second Embodiment of the Invention

FIG. 2 is a schematic diagram of a multicast tree in the second embodiment.

In Fig. 2, the root node of the multicast tree is router 1 (R1), and R1 is a source designated router (DR); router 2 (R2) is the first-level downstream multicast neighbor node of R1; router 3 (R3) It is the second-level downstream multicast neighbor node of R1; router 4 (R4) is the third-level downstream multicast neighbor node of R1, and R4 is also a rendezvous node (RP); router R5 is the fourth-level downstream multicast neighbor node of R1, R5 is a client designated router (DR), and is the terminal leaf node of the multicast tree. The multicast tree includes R1, R2, R3, R4 and R5.

When R1 detects that the multicast traffic of the multicast tree is disconnected, it sends a first multicast tree disconnection message to R2 according to the forwarding entry of the multicast tree on R1.

After sending the first multicast tree disconnection message, R1 deletes the forwarding entry of the multicast tree maintained by itself.

After receiving the first multicast tree disconnection message, R2 sends the second multicast tree disconnection message to R3 according to the forwarding entry of the multicast tree on R2.

After sending the second multicast tree disconnection message, R2 deletes the forwarding entry of the multicast tree maintained by itself.

After receiving the second multicast tree disconnection message, R3 sends the third multicast tree disconnection message to R4 according to the forwarding entry of the multicast tree on R3.

After sending the third multicast tree disconnection message, R3 deletes the forwarding entry of the multicast tree maintained by itself.

After receiving the third multicast tree disconnection message, R4 sends the fourth multicast tree disconnection message to R5 according to the forwarding entry of the multicast tree on 4.

After sending the fourth multicast tree disconnection message, R4 deletes the forwarding entry of the multicast tree maintained by itself.

After receiving the fourth multicast tree disconnection message, R5 deletes the forwarding entry of the multicast tree maintained by itself.

In this way, the root node on the forwarding path of the multicast tree, all multicast neighbor nodes, and the RP have deleted the forwarding entry of the multicast tree, thereby realizing the notification mechanism based on the multicast tree. Fast deletion of multicast entries.

The third embodiment of the present invention

In this embodiment, the structure of the multicast tree is the same as the structure of the multicast tree shown in Figure 2 in the second embodiment, that is, the root node of the multicast tree is router 1 (R1), and R1 is a source designated router (DR); Router 2 (R2) is the first-level downstream multicast neighbor node of R1; Router 3 (R3) is the second-level downstream multicast neighbor node of R1; Router 4 (R4) is the third-level downstream multicast neighbor node of R1 node, while R4 is also a rendezvous node (RP); router 5 (R5) is the four-level downstream multicast neighbor node of R1, and R5 is a client designated router (DR), which is the terminal leaf node of the multicast tree. The multicast tree includes R1, R2, R3, R4 and R5.

The processing method in this embodiment is as follows.

When R1 detects that the multicast traffic of the multicast tree is disconnected, it sends a first multicast tree disconnection message to R2 according to the forwarding entry of the multicast tree on R1. R1 also sends an RP multicast tree disconnection message to the RP, that is, R4. Afterwards, R1 deletes the forwarding entry of the multicast tree maintained by itself. After the RP receives the RP multicast tree disconnection message, the RP determines whether the forwarding entry of the multicast tree maintained by the RP exists. If it exists, then the RP deletes the forwarding entry of the multicast tree maintained by itself, and sends a fourth multicast tree disconnection message to the downstream multicast neighbor node R5 of the RP, so that R5 deletes the group maintained on R5 The forwarding entry of the broadcast tree.

After receiving the first multicast tree disconnection message, R2 sends the second multicast tree disconnection message to R3 according to the forwarding entry of the multicast tree on R2.

After sending the second multicast tree disconnection message, R2 deletes the forwarding entry of the multicast tree maintained by itself.

After receiving the second multicast tree disconnection message, R3 sends the third multicast tree disconnection message to R4 according to the forwarding entry of the multicast tree on R3.

After sending the third multicast tree disconnection message, R3 deletes the forwarding entry of the multicast tree maintained by itself.

R4, that is, the RP, after receiving the third multicast tree disconnection message, determines whether the forwarding entry of the multicast tree maintained by itself exists.

If it exists, send a fourth multicast tree disconnection message to R5 according to the forwarding entry of the multicast tree on R4. Afterwards, R4 deletes the forwarding entry of the multicast tree maintained by itself.

If it does not exist, it means that R4 has received the RP multicast tree disconnection message. Preferably, since the RP will send the fourth multicast tree disconnection message to R5 after receiving the RP multicast tree disconnection message, there is no need for R4 to repeatedly send the fourth multicast tree disconnection message to R5.

After receiving the fourth multicast tree disconnection message, R5 deletes the forwarding entry of the multicast tree maintained by itself.

In Embodiment 3, the root node of the multicast tree separately sends an RP multicast tree disconnection message to the RP to notify the RP that the traffic of the multicast tree is disconnected. Therefore, even when the RP is not in the forwarding path of the multicast tree When the RP is up, the forwarding entries of the multicast tree maintained on the RP will also be deleted in time. Fourth Embodiment of the Invention

FIG. 3 is a schematic diagram of a multicast tree according to Embodiment 4 of the present invention.

In Fig. 3, the root node of the multicast tree is router 1 (R1), and R1 is a source designated router (DR); Router 2 (R2) is the rendezvous node (RP) of the multicast tree, and the RP Not on the forwarding path of the multicast tree; router 3 (R3) is the first-level downstream multicast neighbor node of R1; router 4 (R4) and router 5 (R5) are the second-level downstream multicast neighbor node of R1, R4 and R5 are two client designated routers (DRs), which are end leaf nodes of the multicast tree. The multicast tree includes R1, R3, R4, R5 and RP.

The processing method in this embodiment is as follows.

When R1 detects that the multicast traffic of the multicast tree is disconnected, it sends an RP multicast tree disconnection message to the RP, that is, R2. In addition, R1 also sends the first multicast tree disconnection message to R3 according to the forwarding entry of the multicast tree on R1.

The RP, that is, R2, deletes the forwarding entry of the multicast tree on the RP after receiving the RP multicast tree disconnection message. Since the RP is not on the forwarding path of the multicast tree, there is no outbound interface information on the RP to R3, R4 or R5. Therefore, the RP will not send a multicast tree disconnection message to R3, R4 or R5.

After receiving the first multicast tree disconnection message, R3 sends the second multicast tree to all downstream multicast neighbor nodes of R3, that is, R4 and R5, according to the forwarding entry of the multicast tree on R3. Cut off message. In addition, R3 also deletes the forwarding entry of the multicast tree on R3.

Both R4 and R5 are end leaf nodes of the multicast tree, and R4 and R5 delete the forwarding entries of the multicast tree respectively maintained after receiving the second multicast tree disconnection message.

In this way, the root node on the forwarding path of the multicast tree, all multicast neighbor nodes, and the RP have deleted the forwarding entry of the multicast tree, thereby realizing the notification mechanism based on the multicast tree. Fast deletion of multicast entries.

Fifth Embodiment of the Invention

As shown in Fig. 4, this embodiment discloses a root node (400), and the root node includes a first sending unit (401) and a forwarding entry deletion unit (402).

The first sending unit (401) is configured to, after the root node detects that the multicast traffic of the multicast tree where the root node is located is cut off, to multicast the first-level downstream neighbor nodes of the root node Part or all of the nodes respectively send the first multicast tree disconnection message, so that the first-level downstream multicast neighbor nodes that receive the first multicast tree disconnection message respectively delete the Forward entry.

The first-level downstream multicast neighbor node may be one node or multiple nodes. When the first-level downstream multicast neighbor node is only one node, some or all of the nodes are one node.

The forwarding entry deletion unit (402) is configured to delete the forwarding entry of the multicast tree maintained by the root node after the root node detects that the multicast traffic of the multicast tree is interrupted.

Since the root node deletes the forwarding table entry of the multicast tree maintained by itself, some or all of the first-level downstream multicast neighbor nodes of the root node delete the multicast tree maintained by itself. The forwarding entry of the tree realizes the rapid deletion of multiple multicast entries on the multicast tree based on the notification mechanism.

Optionally, in this embodiment, the first sending unit (401) multicasts to the first-level downstream neighbor nodes of the root node according to the forwarding entry of the multicast tree maintained by the root node The part or all of the nodes respectively send the first multicast tree disconnection message. The forwarding entry deletion unit (402) deletes the forwarding entry of the multicast tree maintained by the root node after the first multicast tree disconnection message is sent. That is to say, the root node first sends the first multicast tree disconnection message, and then deletes the forwarding entry of the multicast tree on the root node.

Optionally, in this embodiment, the root node further includes an egress port recording unit, and the egress port recording unit is used to pre-record the The egress port of a neighbor node to which some or all nodes are connected.

After the egress port recording unit pre-records the egress ports of the neighbor nodes connected to the part or all of the first-level downstream multicast neighbor nodes on the root node, the first sending unit (401) After the forwarding entry of the multicast tree on the root node is deleted, according to the egress port recorded in advance by the egress port recording unit, the first-level downstream multicast neighbor node of the root node The part or all of the nodes respectively send the first multicast tree disconnection message. In this way, the root node may first delete the forwarding entry of the multicast tree maintained by itself, and then send the first multicast tree disconnection information to its first-level downstream multicast neighbor node.

Preferably, as shown in FIG. 5, the root node further includes a second sending unit (403) in addition to the first sending unit (401) and the forwarding entry deletion unit (402), the The second sending unit (403) is configured to send a convergence node multicast flow disconnection message to the convergence node of the multicast tree after the root node detects that the multicast traffic of the multicast tree is disconnected, so that all The aggregation node deletes the forwarding entry of the multicast tree maintained by itself.

Preferably, if the convergence node maintains a forwarding entry of the multicast tree when receiving the convergence node multicast disconnection message, the convergence node multicast disconnection message triggers the convergence node to forward The downstream multicast neighbor node of the convergence node sends a new multicast disconnection message, and then deletes the forwarding entry of the multicast tree maintained by itself.

The root node can not only delete the forwarding table entries of the multicast tree maintained in itself and some or all of its downstream multicast neighbor nodes, but also delete the multicast tree maintained in the sink node Forwarding table entries, so as to better realize the rapid deletion of multiple multicast table entries on the multicast tree based on the notification mechanism.

Those of ordinary skill in the art can understand that all or part of the steps for realizing the above-mentioned method embodiments can be completed by hardware related to program instructions, and the aforementioned program can be stored in a computer-readable storage medium. When the program is executed, the It includes the steps of the above method embodiments; and the aforementioned storage medium includes: ROM, RAM, magnetic disk or optical disk and other various media that can store program codes.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person familiar with the technology can easily think of changes or replacements within the technical scope disclosed in the present invention. , should be covered within the protection scope of the present invention.

Claims (12)

1. delete a method for forwarding-table item, it is characterized in that, comprising:

The root node of multicast tree is after the flux of multicast cutout described multicast tree being detected, the first multicast tree cutout message is sent respectively, with the forwarding-table item making the one-level downstream multicast neighbor node receiving described first multicast tree cutout message delete the described multicast tree of self maintained respectively to the part or all of node in the one-level downstream multicast neighbor node of described root node;

Described root node, after the flux of multicast cutout described multicast tree being detected, deletes the forwarding-table item of the described multicast tree that described root node is safeguarded.

2. method according to claim 1, is characterized in that, wherein

Described to the part or all of node in the one-level downstream multicast neighbor node of described root node send respectively first multicast tree cutout message comprise:

The forwarding-table item of the described multicast tree safeguarded according to described root node sends the first multicast tree cutout message respectively to the described part or all of node in the one-level downstream multicast neighbor node of described root node;

Described root node is after the flux of multicast cutout described multicast tree being detected, and the forwarding-table item deleting the described multicast tree that described root node is safeguarded comprises:

Described root node, the flux of multicast cutout of described multicast tree being detected and described first multicast tree cutout after message is sent out, deletes the forwarding-table item of the described multicast tree that described root node is safeguarded.

3. method according to claim 1, is characterized in that, the neighbor node outbound port that the pre-recorded described root node of wherein said root node is connected with the described part or all of node in the multicast neighbor node of described one-level downstream.

4. method according to claim 3, it is characterized in that, the root node of wherein said multicast tree, after the flux of multicast cutout described multicast tree being detected, sends the first multicast tree cutout message respectively to the part or all of node in the one-level downstream multicast neighbor node of described root node and comprises:

Described root node the flux of multicast cutout of described multicast tree detected and the forwarding-table item of described multicast tree on described root node deleted after, send described first multicast tree cutout message according to described pre-recorded outbound port respectively to the described part or all of node in the described one-level downstream multicast neighbor node of described root node.

5. method according to any one of claim 1 to 4, is characterized in that, described method also comprises:

Described root node is after the flux of multicast cutout described multicast tree being detected, and the aggregation node to described multicast tree sends aggregation node multicast cutoff message, with the forwarding-table item making described aggregation node delete the described multicast tree of self maintained.

6. method according to claim 5, it is characterized in that, if wherein described aggregation node safeguards the forwarding-table item having described multicast tree when receiving described aggregation node multicast cutoff message, then aggregation node described in described aggregation node multicast cutoff message trigger first sends new multicast cutoff message to the downstream multicast neighbor node of described aggregation node, then deletes the forwarding-table item of described multicast tree of self maintained.

7. a root node, is characterized in that, comprising:

First transmitting element, after detecting that at described root node the flux of multicast of the multicast tree at described root node place stops, the first multicast tree cutout message is sent respectively, with the forwarding-table item making the one-level downstream multicast neighbor node receiving described first multicast tree cutout message delete the described multicast tree of self maintained respectively to the part or all of node in the one-level downstream multicast neighbor node of described root node;

Forwarding-table item delete cells, after detecting that at described root node the flux of multicast of described multicast tree stops, deletes the forwarding-table item of the described multicast tree that described root node is safeguarded.

8. root node according to claim 7, is characterized in that, wherein,

The forwarding-table item of the described multicast tree that described first transmitting element is safeguarded according to described root node sends described first multicast tree cutout message respectively to the described part or all of node in the one-level downstream multicast neighbor node of described root node;

Described forwarding-table item delete cells, after described first multicast tree cutout message is sent out, deletes the forwarding-table item of the described multicast tree that described root node is safeguarded.

9. root node according to claim 7, is characterized in that, described root node also comprises:

Outbound port record cell, the neighbor node outbound port be connected with the described part or all of node in the multicast neighbor node of described one-level downstream on pre-recorded described root node.

10. root node according to claim 9, it is characterized in that, after the forwarding-table item of the described multicast tree of wherein said first transmitting element on described root node is deleted, the outbound port pre-recorded according to described outbound port record cell, sends described first multicast tree cutout message respectively to the described part or all of node in the described one-level downstream multicast neighbor node of described root node.

11. root nodes according to any one of claim 7 to 10, it is characterized in that, described root node also comprises:

Second transmitting element, after detecting that at described root node the flux of multicast of described multicast tree stops, aggregation node to described multicast tree sends aggregation node multicast cutoff message, with the forwarding-table item making described aggregation node delete the described multicast tree of self maintained.

12. root nodes according to claim 11, it is characterized in that, if wherein described aggregation node safeguards the forwarding-table item having described multicast tree when receiving described aggregation node multicast cutoff message, then aggregation node described in described aggregation node multicast cutoff message trigger first sends new multicast cutoff message to the downstream multicast neighbor node of described aggregation node, then deletes the forwarding-table item of described multicast tree of self maintained.