WO2007082432A1

WO2007082432A1 - A rerouting method

Info

Publication number: WO2007082432A1
Application number: PCT/CN2006/002756
Authority: WO
Inventors: Hejun Li
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2006-01-20
Filing date: 2006-10-18
Publication date: 2007-07-26
Also published as: CN101005442B; CN101005442A

Abstract

A rerouting method is disclosed. When fault link or fault router is appeared in the network switch paths, the downstream router rebuilds the switch path to the source router, and the downstream router is bordered upon the fault link or the fault router. Meanwhile, it is disclosed that the source router determines whether the path between the source router and the destination router is the shortest path by sending the path detection information; if the determined result is no, the destination router rebuilds the shortest path by sending the path modify information. Accordingly, the comeback time for rerouting to build the switch path is short, and the constringency speed is fast.

Description

The present invention claims priority to Chinese Patent Application No. 200610033235.6, entitled "Re-routing Method", filed on January 20, 2006, the entire contents of which are incorporated by reference. In this application.

The present invention relates to the field of network communication technologies, and in particular, to a rerouting method. Background technique

Multi-Protocol Label Switching (MPLS) is a method of introducing IP into a communication network such as Asynchronous Transfer Mode (AM) or Frame Relay (FR). , efficient transmission technology. The application field of MPLS is expanding. With the continuous development of the Internet, the use of MPLS-capable IP routers and MPLS-capable ATM switches to form a future broadband integrated service communication network has become a hot spot in the industry. The value of MPLS is the ability to introduce a connection-oriented mechanism in a connectionless network. The advantage is that it reduces the complexity of the network and is compatible with existing network technologies. At the same time, MPLS comprehensively utilizes the core switching technology of the network and the IP routing technology at the edge of the network to move the route to the edge of the network, and the network core performs label forwarding. Therefore, the label distribution technology is a very important part of MPLS.

With the application of MPLS in the field of multicast, the label distribution technology of Point to Muliti-Point (P2MP) in MPLS has become a major research focus in the development of MPLS. The current P2MP label distribution technology is mainly The unicast routing table information generated by the routing protocol is used to generate a P2MP Label Switched Path (LSP) from each destination label switching router (LSR) to the root LSR. The leaf LSR is responsible for initiating the establishment and revocation of the P2MP LSP. The method for determining the upstream LSR of a node on the P2MP LSP is: The shortest path from the node to the root node according to the unicast routing information generated by the routing protocol (the shortest path is the routing protocol, and the sum of the metric values from the leaf node to the root node is the smallest. The next hop router on that path is the upstream LSR of the node.

In network technology, the source router is the sender of the data, and the destination router is the destination of the data transmission. For ease of description, the rules are as follows:

1. P2MP FEC element (point-to-multipoint forwarding equivalence class element) is represented by <R, G>, R is the address of the source label switching router (label switching router that sends data), and G is the unique value Opaque.

2. The label mapping message of P2MP is represented by <R, QL>, where <1, 0> is? 2:^? FEC element , L is the label assigned to the P2MP FEC element.

3. The P2MP tag revocation message is represented by (R, G, L), where (R, G) is the P2MP FEC element and L is the tag assigned to the P2MP FEC element.

4. P2MPLSP is represented by (R, G), R is the source label switching router address, and G is the Opaque value.

5. On the intermediate LSR, use L' -> {<11, Ll> <I2, L2> <In, Ln>} to indicate the state of one-to-one P2MPLSP multicast forwarding state: When receiving a carry L ' Packets are copied when a packet is replaced with L on the II interface, the label is issued after the L1 tag, and so on until <In, Ln>.

The establishment process of the P2MP LSP in the current technology is:

(1) The leaf LSR actively allocates the P2MP LSP label L and distributes the label mapping message < , ! to the upstream LSR along the path to the source label switching router.

(2) After receiving the label mapping message <1, 0, 1 sent by the downstream interface, the intermediate LSR first checks whether the multicast forwarding state associated with it is established. If not, the intermediate LSR allocates the P2MP LSP. The label L' is simultaneously installed with the forwarding state L' -> {<1, L>}, and then the label mapping message <R, QL' is sent to its upstream LSR; if the upstream LSR has a forwarding state, only the forwarding state needs to be updated. For example, the original multicast forwarding status is L'-> {<11, Ll> <12, L2> <In, Ln>}, and 4 bar is changed to: L'-> {<11, Ll> <I2 , L2> <In, Ln>, <I, L>}.

(3) The source label switching router receives the label mapping message sent by the downstream interface 1

After <R, G, L>, first check whether there is a multicast forwarding state associated with it. If not, the source label switching router establishes a forwarding state for adding the label L to the header of the packet of the group G it receives; if there is a forwarding state, adding the label L when the group G packet is received in the state. And the status issued from interface I. The revocation process of the P2MP LSP is:

(1), Leaf The LSR sends the label revocation message (R, G, L) to the upstream LSR.

(2) After receiving the label revocation message (R, G, L), the intermediate LSR deletes the content of the label L from the multicast forwarding state, and sends a label revocation message to the upstream if its multicast forwarding status is empty (R). , QL, ), stop if it is not empty.

(3) After the source label switching router receives the label revocation message (R, G, L) sent downstream, the operation is similar to the intermediate LSR, except that the label revocation message (R, G, L) is no longer sent upstream.

As can be seen from the above description, P2MPLSP is the shortest path tree established based on the unicast routing table information generated by the routing protocol. However, in practical applications, P2MPLSP also needs to solve the rerouting problem in the following three cases: network failure (network node or link failure); due to the addition of a new link, there is a shorter path due to the management plane Routing changes.

The above three types of re-routings will change the upstream LSR of an LSR in the P2MP LSP. If the upstream LSR occurs, the current PSRMPLSP update method is: When an LSR node finds its own upstream LSR from the U When it changes to U, the node updates its own multicast forwarding state, deletes the forwarding state of the label L associated with the U, allocates the L' tag and establishes a new multicast forwarding state, and sends a label mapping message <R to the U. G, L, > sends a label revocation message (R, G, L) to U to undo the original multicast forwarding status. In an MPLS network, when the local route changes, the routing information may be transmitted to the upstream LSR of the LSR at the same time. The process of processing the P2MP LSP in the change of the upstream LSR is applicable to all LSRs that are changed by the upstream LSR node. This change is a network-wide change and is not only concentrated on one LSR. Since each LSR is unique to the P2MPLSP operation (routing information), after a period of time, the entire P2MPLSP will converge to a new shortest path tree. The specific process is shown in Figure 1) to (c). In the figure, each R1, R2, etc. node is an LSR, where R1 is the source label switching router, and R5 and R6 are destination label switching routers (the destination label switching router for data transmission) ), the number between adjacent LSRs is a measure between the two. As shown in Figure 1 (a), two P2MP LSPs, R1-R2-R4-R6 and R1-R2-R4-R5, have been established according to the establishment principle of the P2MP LSP. When R2 fails, the entire link is shown in Figure 1 ( b) The label is removed and redistributed as shown, and eventually reaches the steady state of Figure 1 (c). According to the prior art, when there are a large number of multicast services in the MPLS network (the shortest path tree of a P2MP LSP exists in each multicast service), if the local route is for some reason (network failure, new link) After the change or propagation of the management plane, etc., changes to the entire MPLS network, the following situations may occur: In each P2MP LSP shortest path tree, there will be many LSRs whose upstream LSRs have changed, and they are revoked almost simultaneously. The label and the assignment label operate to correct the P2MP LSP that it is in, so that it can be returned to the P2MP LSP shortest path tree, as shown in Figures 1 (a) to (c), including R2, R3, R4, R5, and R6. All label switching routers participate in the label undo and allocate process, and in the actual network structure, it is often more complicated than the network structure shown in Figure 1 (a) to (c) and the P2MP LSP in the network. many. This will result in a sudden and dramatic increase in the load of a large number of LSR nodes, and even CPU utilization will reach 100% for a long time. As a result, the time for the P2MP LSP to be switched to the shortest path P2MP LSP is greatly increased. The data stream is interrupted before the establishment of the new P2MP LSP, and the multicast data stream is interrupted on each P2MP LSP. It will increase greatly, data loss is serious, and it also affects the large-scale deployment of multicast services in MPLS networks. Summary of the invention

The object of the present invention is to provide a rerouting method, which can quickly repair the switching path between the source node and the destination node when the network link or the router fails, and avoid the router caused by the adjustment operation of a large number of routers in the network when the switching path is re-established. The load on the node suddenly increases sharply, and the data stream is interrupted for a long time. A rerouting method according to the present invention includes:

The network switching path has a failed link or a failed router, and the path to the source node is re-established by the downstream router adjacent to the failed link or the failed router.

The method is applied to a label switched path system, the switching is label switching, and the router is a label switching router. The source node is a label switching router.

The label switching is a multi-protocol label switching.

Preferably, the label switching path is established by the following steps:

In the label switched path, the label adjacent to the failed link or the failed label switching router Change the router to determine whether the failed link or the failed label switching router is upstream;

If so, the label switching router re-establishes the label switching path from its direction to the source node.

Preferably, the method further comprises the steps of:

It is determined whether the type of the forwarding state of the label switching path is multicast. If the type of the forwarding state is multicast, the forwarding state does not change with the unicast routing.

Preferably, the following steps are used to determine whether the failed link is upstream

After detecting the link failure, the label switching router determines whether the interface where the failed link is located is an inbound interface corresponding to the forwarding state of the label switching path;

If so, the failed link is upstream of the label switching router.

Preferably, the following steps are used to determine whether the failed label switching router is upstream of its label switched path:

After detecting that the label switching router is invalid, the label switching router determines whether the next hopping out interface of the failed label switching router is an inbound interface of the label switching path corresponding to the forwarding state;

If so, the expired label switching router is upstream.

Preferably, the label switching path re-established to the source node is implemented by the label switching router sending a label mapping message upstream of the unicast shortest path to the source node for label mapping;

The label switching router that receives the label mapping message continues to send the label mapping message upstream for label mapping until the label switching path to the source node is re-formed.

Another rerouting method provided by the present invention includes:

The source node sends the path detection information to determine whether the path from the source node to the destination node is the shortest path;

If it is not the shortest path, the destination node sends the path modification information to re-establish the shortest path. Preferably, the method is applied to a label switched path system, said switching is label switching, said router is a label switching router, and said source node is a label switching router.

The label switching is a multi-protocol label switching.

More suitably, the label switching shortest path is established by the following steps: In the label switching path in which the unicast routing status changes, the source node sends a path detection message along the label switching path to the downstream to detect whether the existing label switching path is the shortest path, and if it is the shortest path, the end step;

Otherwise, a path modification message is issued upstream along the unicast shortest path from the destination node to the source node, and the label switched path from the destination node to the source node is adjusted to the shortest path.

Preferably, the method further comprises the steps of:

Preferably, the following step is used to detect whether the existing label switching path is the shortest path: after the source node sets the timer to a predetermined time, the path detection message with the flag bit is sent downstream along the label switching path;

The label switching router that receives the path detection message determines whether the next hopping interface of the shortest path of the source node is the inbound interface in the multicast forwarding state, and if so, directly forwards the path detection message to the downstream; otherwise, the path detection is changed. The flag of the message is forwarded to the downstream to forward the path detection message.

Preferably, the label switching path from the destination node to the source node is adjusted to be the shortest path by the following steps:

The path modification message is sent upstream along the unicast shortest path from the destination node to the source node, and the destination node that sends the path modification message and the label switching router that receives the path modification message determine the next bounce of each of the shortest paths to the source node. Whether the interface is the inbound interface of its multicast forwarding state;

If yes, the device sends a path modification message to the upstream label switching router. Otherwise, the next hop interface of the unicast shortest path is added to the inbound interface of the multicast forwarding state, and the label mapping message and the path modification message are sent to the upstream.

Preferably, after the label switching path from the destination node to the source node is the shortest path, the label switching router that receives the unknown multicast data determines whether the multicast forwarding has only one inbound interface, and if so, performs hardware delivery, otherwise The inbound interface forwarding state of the shortest label switching path is delivered by the hardware. The other inbound interfaces are removed from the upstream label switching path and the corresponding hardware entries are deleted. In summary, according to the rerouting method provided by the present invention,

In the case of network failure, the time for data stream recovery is relatively short. Due to the partial repair method, the exchange repair time is very short and the convergence speed is fast.

When adjusting from the non-shortest switching path to the shortest switching path, since only a small number of routers are adjusted, the adjustment time is short and the switching operation is fast; and the original switching path is retained before the adjustment operation is completed, so that the adjustment process can be guaranteed. The data is not interrupted.

In the present invention, when the network link or the router fails, the switching path between the source router and the destination router is quickly repaired, and the load of the router node caused by the adjustment operation of a large number of routers in the network when the re-establishment of the switching path is avoided is suddenly increased sharply and long. Time occupies CPU resources and long interruptions in data flow. Detecting a switched path that is re-established due to network failure or other reasons, causing the switched path after the unicast route to change and adjusting it to the shortest path, so as to avoid the long-term occupation of CPU resources and the data flow is almost uninterrupted, Establish the shortest exchange path.

The invention makes it easier to deploy large-scale multicast services. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1(a), 1(b) and 1(c) are schematic diagrams showing the principle of P2MPLSP rerouting after a label switching router on a P2MP LSP fails in a prior art MPLS network;

2(a), 2(b) and 2(c) are schematic illustrations of a rerouting principle in accordance with an embodiment of the present invention;

3(a), 3(b), 3(c) and 3(d) are diagrams showing a label switching path that meets the shortest path requirement in accordance with another embodiment of the present invention;

4(a) and 4(b) are diagrams showing the label switching path for deleting a non-compliant shortest path requirement according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The core idea of the rerouting method of the present invention is: when a route change occurs when a network link or a router fails in a network switching path, by establishing a link between the adjacent downstream router of the failed router or the failed link and the source router Mode, fast ^ the switching path from the source router to the destination router, and the downstream router of the router that re-establishes the link remains unchanged Line adjustment. At the same time, the present invention further detects whether the repaired exchange path or the exchange path formed by the route change due to other reasons is the shortest path, and if not, adjusts it to the shortest path. In the prior art, when the local route changes, all the adjacent or non-adjacent routers located downstream of the changed routing part need to be adjusted accordingly to re-establish the path as the routing information is transmitted throughout the network. These adjust the routers to communicate with each other at the same time to establish and revoke the link relationship information and perform new configuration on itself, resulting in a drastic increase in CPU load. As a result, each router takes a long time (often it will last for several times). Minutes) can be adjusted, and the transmission of network data is forced to be lost or even interrupted during the adjustment process, so the transmission of network data also has a great impact.

The node updates its forwarding state, deletes the forwarding state of the U-related label L, allocates L, labels and establishes the forwarding state, and sends a label mapping message <R, G, L, > to the U, and sends the label undo to the U. Message (R, G, L). In an MPLS network, when a local route changes, the routing information may be transmitted across the entire network, which may cause changes in the upstream LSR of many LSRs. The process of processing the P2MP LSP for the upstream LSR changes is applicable to all LSRs that change upstream LSR nodes. This change is a change in the whole network, not just a change in one LSR. Since the basis (routing information) of each LSR to P2MP LSP operation is unique, after a period of time, the entire P2MP LSP will converge to a new shortest path tree. The specific process is shown in Figures 2 (a), 2 (b) and 2 (c).

The invention will be described in detail below with reference to the accompanying drawings in conjunction with specific embodiments. For ease of description, the following embodiments are described by taking an MPLS network point-to-multipoint label switching as an example.

Example 1

2(a), 2(b) and 2(c) are schematic diagrams showing the principle of rerouting according to a specific embodiment of the present invention.

As shown in FIG. 2( a ), the network structure of this embodiment is consistent with that shown in FIGS. 1( a ), 1 ( b ) and 1 ( c ), and the MPLS network includes R1, R2, R3, R4, R5, and R6 has a total of 6 label switching routers, in which R1 is used to send data as a source label switching router, and R5 and R6 are both destined for destination label switching routers, and digital labeling between different label switching routers represents a measure between the two. Values, according to the principle of the shortest path with the smallest sum of metrics, two multicast label switching paths of Rl -> R2 -> R4 -> R5 and Rl -> R2 -> R4 -> R6 have been established. If the unicast route changes, the label switching router with the label switching router or the failed link in the network is detected to determine whether the failed label switching router or the failed link is upstream. In this embodiment, after the link between R2 or R2 and R4 fails, the label switching router directly connected to it detects the failure of the label switching router in the network or detects that there is a link failure in the network. In the case of R2 failure, the failed label switching router is detected to include R1 and R4 directly connected thereto. The two determine whether the next hop-out interface of R2 is the inbound interface of the point-to-multipoint label switching path corresponding to the forwarding state. In this embodiment, the result of R4 is yes. Therefore, R4 is a point-to-multipoint label. The downstream adjacent label switching router of R2 on the switching path. The next hopping interface of R1 to R2 is not the inbound interface of the point-to-multipoint label switching path corresponding to the forwarding state. Therefore, R1 is not the downstream neighbor of R2. Label switching router. For the link failure between R2 and R4, it is detected that the label switching routers with link failure in the network are R2 and R4. Therefore, both R2 and R4 determine whether the interface where the failed link is located is the point-to-multipoint label switching of its maintenance. The path corresponds to the inbound interface of the forwarding state. In this embodiment, the determination result of R4 is YES, and the judgment result of R2 is YES, so the failed link is upstream of R4.

At the same time, after the label switching router or the link fails to cause the routing information to change, each label switching router in the multi-protocol label switching network determines whether the type of the forwarding state of the label switching path is multicast, and the result is a label switching router. The forwarding state does not change with unicast routing changes.

Referring to FIG. 2(b), the downstream label switching router R4 of the failed link or the failed label switching router repairs the P2MP LSP partially disconnected due to network failure, and R4 sends along the unicast shortest path to the source label switching router R1. Label mapping. In this embodiment, the R4 sending label is mapped to R3. After receiving the label mapping message sent by the downstream label switching router, R3 checks whether it has established the multicast forwarding state related to R4. Since R3 does not establish R4 related. The multicast forwarding state, so R3 first establishes its multicast forwarding state related to R4, and then continues to send the label mapping message to its upstream label switching recorder R1. R1 also establishes the relevant multicast forwarding state but because it is the source label. The switching router does not send the label mapping message again, and re-establishes the label switching path R1->R3->R4 from R1 to R4.

Referring to Figure 2 (c), after the completion of 2 (b) operation, the source label switching route is re-established. Two label switching paths from R1 to destination label switching routers R5 and R6: R1->R3->R4->R5 and R1->R3->R4->R6.

It can be seen from the above process that in this implementation, only R4 sends a label mapping to R3, R3 sends a label mapping to R1, and performs corresponding operations, and does not need to perform global changes, and the process is obviously much more than the prior art. Therefore, the repair time is short and the convergence speed is fast.

Example 2

3(a), 3(b), 3(c) and 3(d) are diagrams showing the principle of rerouting according to another embodiment of the present invention.

As shown in FIG. 3), the MPLS network structure in this embodiment is basically the same as that in the first embodiment, including R1, R2, R3, R4, R5, R6, and R7, and a total of seven label switching routers, where R1 is a source label switching. Routers, R6 and R7 are destination label switching routers, and have established R1 ->R2->R4->R5->R6 and Rl->R2->R4->R5->R7 two multicast label switching path.

After the link between R1 and R2 in FIG. 3) fails, according to the method in the foregoing first embodiment of the present invention, the downstream label switching router R2 of the failed link partially disconnects the P2MP LSP due to network failure. A repair operation is performed to re-establish the label switching link from the source label switching routers R1 to R2.

Referring to FIG. 3 (b), when the label switching router R2 completes the repair operation, the two label switching paths from the source label switching router R1 to the destination label switching routers R6 and R7 are re-established: R1->R3->R4-> R5->R6 and R1->R3->R4->R5->R7. However, according to the principle of the shortest path with the smallest sum of metrics, the newly established Rl->R3->R4->R5->R6 and R1->R3->R4->R5->R7 label switching paths It is not the shortest path, that is, the P2MP label switching path shown in Figure 3(b) is not the optimal label switching path. In addition to the failure condition of the above-mentioned network node or link, if a new link is added and a shorter path exists, or the route caused by the management plane changes, the current label switching path may no longer be caused. The shortest path occurs.

For this reason, after a routing condition change occurs, if there is a reason other than the failure condition of the above network node or link, the routing changes (for example, due to the addition of a new link, a shorter path exists or a management plane) When the route changes), the first multi-protocol label is handed over. Each label switching router in the network determines whether the forwarding state of the label switching path is multicast, and the forwarding state of the label switching router that is determined to be yes does not change with the unicast routing. Since the network failure has been judged, the judgment is not repeated here.

Then, a timer is set for the label switching path on the source label switching router R1, and the timer is set to cycle when the timer is switched over for a fixed period of time. Whenever the timer corresponding to the label switching path is exhausted, R1 sends a path detection message downstream along the point-to-multipoint label switching path. The path detection message includes a path status, where the path status indicates whether the existing label switching path in the path detection is the shortest with different values of 1, 0. Path, and add a path modification flag in the multicast forwarding state of all label switching routers. The flag is used to identify whether the label switching router where the multicast forwarding status is located has received the label switching in the point-to-multipoint label switching path. The path modification message sent by the router indicates whether it has received the path modification message with its different values of 1, 0, and R3, R4, R5, R6, and R7 respectively perform reverse path check and other related operations when receiving the path detection message. The specific process is as follows:

(1) After the time of the R1 timer of the source label switching router is exhausted, the path detection message with the path status 0 is sent along the label switching path;

(2) R3 receives the path detection message and performs the reverse path check. The detection result is that the label switching path of R3 to R1 conforms to the shortest path principle and is the shortest path. Therefore, the path state of the path detection information is kept unchanged, and since Receiving the path modification message, so the value of the path modification flag bit of R3 is set to 0, and the path detection message is continued to be forwarded along the label switching path;

(3) After receiving the path detection message forwarded by R3, R4 also performs the reverse path check. It is found that the label switching path of R4 to R1 is the shortest path, so the path state of the path detection information is kept unchanged, and To the path modification message, the value of the path modification flag bit of R4 is set to 0, and the path detection message is further forwarded along the label switching path. (4) After receiving the path detection message forwarded by R4, R5 performs reverse path check, and checks to find the current The label switching path of R5 to R1 is not the shortest path, so the value of the path state of the path detection information is set to 1, and since the path change message has not been received, the value of the path modification flag of R5 is set to 0, and continues. Forwarding the path detection message along the label switching path;

(5) R6 detects the path status of the path after receiving the path detection message forwarded by R5. The value is already 1, indicating that the corresponding label switching path is definitely not the shortest path. Therefore, R6 no longer performs the reverse path check. Since the path modification message has not been received, the value of the path modification flag of R6 is set to 0. After receiving the path detection message forwarded by R5, R7 detects that the path status of the path is 1, indicating that the corresponding label switching path is definitely not the shortest path, so the reverse path check is no longer performed, because the path has not been received yet. The message is modified, so the value of the path 4 tamper flag of R7 is set to zero.

Referring to FIG. 3 (c), since the path status in the path detection message received by R6 and R7 is 1, it indicates that the existing label switching path of the R6 and R7 to the source label switching router is not the unicast shortest path, so R6 And R7 both correct the current label switching path shown in FIG. 3(b) along the unicast shortest-radius radial upstream label switching router to R1, the path modification message including the path modification status and the path modification status. The 0, 1 value indicates whether the path modification is successful, performs the reverse path check and corrects the label switching path related operations, so that the shortest path becomes the label switching path. The following assumes that each label switching router path modification is successful, the process is as follows :

(1) R7 performs reverse path check on the inbound interface of the multicast forwarding state (link R5->R7 on R7), and detects that the inbound interface of the R7 multicast forwarding state is the shortest path from R7 to R1 unicast. On the outbound interface, the destination label switching router R7 sends a path modification message to the R5, where the value of the path modification state is 0, and the path modification flag of the R7 multicast forwarding state is set to 1, indicating that the R7 has received the path modification message; The label switching router R6 also performs a reverse path check on the inbound interface of the multicast forwarding state. The inbound interface that detects the R6 multicast forwarding state is the next hop outbound interface of the R6 to R1 unicast shortest path, and sends a path modification message to the R5. The value of the path modification status in the modified message is 0. At the same time, the path modification flag of the multicast forwarding state on R6 is 1.

(2) At this time, R5 may first receive the path change message sent by R6, and R5 performs the reverse path check. The inbound interface of the R5 multicast forwarding state is not the next hop outbound interface of the R5 to R1 unicast shortest path. Assign a new label to R5, and continue to send a label mapping message to R3, and then modify the multicast forwarding status inbound interface information, and set the value of the path modification flag in the multicast forwarding state of R5 to 1, and finally, R3 sends a path modification message, where the value of the path modification status is 0. (3) Next, when R5 receives the path modification message sent by R7, the value of the path modification flag in the multicast forwarding state corresponding to R5 is already 1, indicating that it has received the path modification message, so R5 does not Do any more.

(4) After R3 receives the path modification message sent by R5, according to the result of the reverse path check, the inbound interface of the R3 multicast forwarding state is the next hop outbound interface of the R3 to R1 unicast shortest path, and R3 sends the path to R1. The message is modified, where the value of the path modification state is 0, and the value of the path modification flag bit of the R3 multicast forwarding state is set to 1.

(5) Finally, when R1 receives the path message sent by R3, it checks the value of the path modification state. In this embodiment, the value is 0, indicating that the path adjustment is successful. If the path of the label switching router fails to be modified in the above steps, the label switching router that fails the modification sets the value of the path modification state to 1, and then sends a path modification message to the source label switching router R1, and then waits for the timer time corresponding to R1 to be consumed again. After that, re-do a new round of label path modification.

Referring to FIG. 3 (d), after the path modification operation is completed, the source label switching router R1 to the destination label switching routers R6 and R7 are divided by the original R1->R3->R4->R5->R6 and R1->R3- >R4->R5->R7 two label switching paths, newly established R1->R3->R5->R6 and R 1 ->R3 ->R5 ->R7 two label switching paths, the first two labels The switched path is not the shortest path, and the newly established two label switched paths are the shortest paths. At the same time, in the MPLS technology, the interface and label information of the multicast forwarding state of each label switching router in the label switching path must be sent to the Incoming Label Map (ILM) entry of the hardware to establish the corresponding ILM hardware. The table item can be used for the actual data transmission. Another difference between this embodiment and the current technology is that the newly established label switching path is not issued due to the data transmission until the data transmission is performed. The operation of the hair.

Referring to Figures 4(a) and 4(b), the two non-shortest label switching paths of R1->R3->R4->R5->R6 and R1->R3->R4->R5->R7 are revoked, and The hardware is issued for R1->R3->R5->R6 and R1->R3->R5->R7 to enable the two newly established label switching paths to actually transmit data.

As shown in Fig. 4 (a), R1 -> R3 -> R4 -> R5 -> R7 are two non-shortest paths, and Figure 4 (a) performs the following operations: (1) Since R3 has been sent by hardware before, the data arrives at R3 and then transmits downward through R4 and R5. When the multicast data packet reaches R5 through R3->R5 link, R5 needs The hardware ILM entry is used to check the forwarding of the multicast data packet. The R5 cannot be found in the hardware. Therefore, the multicast datagram cannot be found. The text is used as unknown multicast data.

(2) After receiving the unknown multicast data packet, R5 detects the corresponding multicast forwarding state. Since R5 detects that the multicast forwarding state has two inbound interfaces corresponding to R3 and R4, the two pairs are The inbound interface performs a reverse path check to determine whether each label switching path is the shortest path. In this embodiment, the interface reverse path of the R4->R5 label switching path on R5 is checked to be not the shortest path, so R5 sends a label revocation message to R4 and deletes the inbound interface information in the multicast forwarding state, and deletes the corresponding information. The hardware ELM entry, and then R4 continues to send the label revocation message to R3. After receiving the label revocation message, R3 performs the same operation as R4 to finally delete the path. Meanwhile, the R3->R5 label switching path passes through the interface on R5. The reverse path check proves to be the shortest path. R5 sends the interface and label information in the multicast forwarding state to the hardware ILM entry for subsequent data transmission.

Referring to FIG. 4(b), after completing the operation in FIG. 4), there are only two label switching paths in the P2MP label switching path from R1 to R6 and R7: R1->R3->R5->R6 and R1->R3 ->R5->R7, these two paths are the shortest path.

As can be seen from the above process, in the foregoing modification process of the embodiment, the entire path modification process is along the unicast shortest path R6 (or R7) to R1 -> R5-> R3 -> Rl Adjusting hop by hop, this will not cause the load of R6, R5, R3 and R1 to increase at the same time. Secondly, the adjustment process is only performed on the label switching router R5 where the reverse path check fails on the unicast shortest path instead of the P2MP label switched path. All the reverse path check fails on the label switching router, which reduces the network load caused by the path adjustment. Finally, since the non-shorter label switching path remains used until the shortest label switching path is established, the entire tuning process group The broadcast stream is almost never interrupted.

In the process of establishing the label switching path established in the foregoing Embodiment 1 and Embodiment 2, the following may exist: After a label switching router receives the label mapping message and modifies the corresponding multicast forwarding state, the multicast forwarding state is There may be an interface that is both an inbound interface and Is the error condition of the outgoing interface. For this case, the solution of the present invention is the same as the method of deleting the non-shortest label switching path in Embodiment 2: After receiving the label mapping message, if the label switching router detects the entry in one of its own multicast forwarding states An interface is an interface that receives a label mapping message, and adds the interface and label information to the outbound interface list of the multicast forwarding state, but does not send the interface to the outbound interface list of the corresponding hardware entry. When receiving the unknown multicast data, the label switching router deletes the inbound interface that fails the reverse path check in the multicast forwarding state according to the result of the reverse path check, and checks whether the deleted inbound interface is in the outbound interface list of the multicast forwarding state. The interface is immediately sent to the outbound interface list of the corresponding hardware entry.

However, the invention is not limited to this,

The above embodiments are intended to illustrate and explain the principles of the invention. It is to be understood that the specific embodiments of the present invention are not limited thereto. Various changes and modifications may be made without departing from the spirit and scope of the invention.

Claims

Rights request

A rerouting method, comprising:

2. The rerouting method according to claim 1, wherein the method is applied to a label switched path system, the switching is label switching, and the router is a label switching router. The source node is a label switching router.

The rerouting method according to claim 1, wherein the label switching is a multi-protocol label switching.

4. The rerouting method according to claim 2, wherein the label switching path is established by the following steps:

In the label switching path, the label switching router adjacent to the failed link or the failed label switching router determines whether the failed link or the failed label switching router is upstream;

5. The rerouting method according to claim 4, further comprising the steps of:

The rerouting method according to claim 4, wherein the failure of the failed link is determined by the following steps

If so, the failed link is upstream of the label switching router.

7. The rerouting method according to claim 4, wherein the failure of the failed label switching router on the label switching path is determined by the following steps:

After detecting that the label switching router is invalid, the label switching router determines whether the next hopping out interface of the failed label switching router is an inbound interface of the label switching path corresponding to the forwarding state; If so, the expired label switching router is upstream.

8. The rerouting method according to claim 4, wherein the re-establishing a label switching path to the source node is implemented by the following steps

The label switching router sends a label mapping message upstream of the unicast shortest path to the source node for label mapping;

9. A rerouting method, comprising:

If it is not the shortest path, the destination node sends the path modification information to re-establish the shortest path.

10. The rerouting method according to claim 9, wherein the method is applied to a label switching path system, the switching is label switching, the router is a label switching router, and the source node is a label switching router. .

The rerouting method according to claim 10, wherein the label switching is a multi-protocol label switching.

12. The rerouting method according to claim 10, wherein the label switching shortest path is established by the following steps:

In the label switching path in which the unicast routing status changes, the source node sends a path detection message along the label downstream of the label switching path to detect whether the existing label switching path is the shortest path, and if it is the shortest path, the end step;

The rerouting method according to claim 12, further comprising the following steps:

14. The rerouting method according to claim 12, wherein the existing label switching path is detected as the shortest path by the following steps: Setting a timer at the source node, and after the timer reaches a predetermined time, sending a path detection message with a flag bit downstream along the label switching path;

.

The rerouting method according to claim 12, wherein the adjusting the label switching path from the destination node to the source node to the shortest path is implemented by the following steps:

The rerouting method according to claim 12, wherein after the label switching path from the destination node to the source node is adjusted to be the shortest path,

The label switching router that receives the unknown multicast data determines whether the multicast forwarding has only one inbound interface. If yes, the hardware is delivered. Otherwise, only the inbound interface forwarding state on the shortest label switching path is sent by the hardware. The interface goes to the upstream label switching path and deletes the corresponding hardware entry.