Bit-indexed explicit copy exit protection

Abstract

A method implemented by a network node in a bit index explicit replication (BIER) domain for providing fast egress protection. The method comprises: receiving a type-length-value (TLV) structure, the TLV structure identifying a backup egress node of a target network node and including an entry indicating whether a primary egress node and the backup egress node transmit data packets to the same customer edge (CE) or to different customer edges (CEs); generating an egress protection bit index forwarding table (EP-BIFT), the EP-BIFT including the backup egress node and the entry indicating whether the primary egress node and the backup egress node transmit data packets to the same CE or to different CEs; and forwarding the data packets according to the EP-BIFT when the primary egress node fails.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the benefit of U.S. Provisional Patent Application No. 63 / 106,201, filed by Huaimo Chen on October 27, 2020, entitled “Bit Index Explicit Replication Egress Protection,” which is hereby incorporated by reference. Technical Field

[0003] The present invention generally relates to the field of egress protection, and more particularly to egress protection for node or link failures in a bit index explicit replication (BIER) domain. Background Art

[0004] The BIER mechanism provides optimized forwarding of multicast packets through a BIER domain. The BIER domain may not require the use of a protocol to explicitly construct a multicast distribution tree. In addition, the BIER domain may not require intermediate nodes to maintain any per-flow state. BIER is described in further detail in Internet engineering task force (IETF) document request for comment (RFC) 8279, entitled "Multicast Using Bit Index Explicit Replication (BIER)" by IJ. Wijnands et al., published in November 2017. Summary of the Invention

[0005] The disclosed aspects / embodiments provide fast egress protection (EP) for the BIER domain. To facilitate the fast egress protection process, the network node upstream of the egress node constructs an egress protection bit index forwarding table (EP-BIFT). EP-BIFT is used by the network node to forward data packets when an egress node fails. Therefore, packet routing within the BIER domain is improved.

[0006] The first aspect relates to a method implemented by a network node adjacent to a primary egress node in a bit index explicit replication (BIER) domain, the method comprising: receiving a type length value (TLV) structure, the TLV structure identifying a backup egress node of the primary egress node and including an entry indicating whether the primary egress node and the backup egress node transmit data packets to the same customer edge (CE) receiver or to different CE receivers; generating an egress protection bit index forwarding table (EP-BIFT), the EP-BIFT including the backup egress node and the entry indicating whether the primary egress node and the backup egress node transmit data packets to the same CE receiver or to different CE receivers; and forwarding the data packets according to the EP-BIFT when the primary egress node fails.

[0007] Optionally, in any one of the above aspects, another implementation of the aspect provides for receiving the TLV structure from a primary egress node.

[0008] Optionally, in any one of the above aspects, another implementation of the aspect provides for receiving the TLV structure from a neighboring network node.

[0009] Optionally, in any one of the above aspects, another implementation of the aspect provides that the EP-BIFT includes a backup entry active (BEA) field, wherein an entry in the BEA field is set to indicate whether the primary egress node is working or has failed.

[0010] Optionally, in any one of the above aspects, another implementation of the aspect stipulates that the entry indicating whether the primary egress node and the backup egress node transmit the data packet to the same CE receiver or to different CE receivers is set in the same CE receiver (SC) field in the EP-BIFT.

[0011] Optionally, in any one of the above aspects, another implementation of the aspect stipulates that the backup egress node is identified in a backup egress bit forwarding edge router (BE-BFER) field in the EP-BIFT.

[0012] Optionally, in any one of the above aspects, another implementation method of the aspect stipulates that generating the EP-BIFT includes: generating a backup forwarding bitmask (BF-BM) for the target network node by applying a logical OR operation to the bit string of the target network node in the EP-BIFT and the bit strings of other target nodes whose BFR-NBR is the same as the backup BFR-NBR (backup BFR-NBR, BBFR-NBR) of the target network node.

[0013] Optionally, in any one of the above aspects, another implementation of the aspect provides that the EP-BIFT includes a backup bit forwarding router neighbor (BBFR-NBR) field, wherein the entry in the BBFR-NBR field indicates the next hop on the shortest path to reach the backup egress node without using the primary egress node.

[0014] Optionally, in any one of the above aspects, another implementation of the aspect stipulates that the next hop identified in the backup bit forwarding router neighbor (BBFR-NBR) field of the primary egress node of the EP-BIFT is a basic loop-free alternate (LFA) bit forwarding router (BFR) of the backup egress node.

[0015] Optionally, in any one of the above aspects, another implementation of the aspect stipulates that the next hop identified in the backup bit forwarding router neighbor (BBFR-NBR) field of the primary egress node of the EP-BIFT is a remote loop-free alternate (LFA) bit forwarding router (BFR) of the backup egress node.

[0016] Optionally, in any one of the above aspects, another implementation of the aspect stipulates that the next hop identified in the backup bit forwarding router neighbor (BBFR-NBR) field of the primary egress node of the EP-BIFT is a topology-independent loop-free alternate (LFA) bit forwarding router (BFR) of the backup egress node.

[0017] Optionally, in any one of the above aspects, another implementation of the aspect stipulates that the next hop identified in the backup bit forwarding router neighbor (BBFR-NBR) field of the primary exit node of the EP-BIFT is the backup exit node through a tunnel to the backup exit node without passing through the primary exit node.

[0018] The second aspect relates to a network node adjacent to a primary egress node in a bit index explicit replication (BIER) domain, the network node comprising: a memory storing instructions; one or more processors coupled to the memory, wherein the one or more processors are used to execute the instructions so that the network node: receives a type length value (TLV) structure, the TLV structure identifies a backup egress node of the primary egress node and includes entries indicating whether the primary egress node and the backup egress node transmit data packets to the same customer edge (CE) receiver or to different CE receivers; generates an egress protection bit index forwarding table (EP-BIFT), the EP-BIFT including the backup egress node and the entries indicating whether the primary egress node and the backup egress node transmit the data packets to the same CE receiver or to different CE receivers; and forwards the data packets according to the EP-BIFT when the primary egress node fails.

[0019] Optionally, in any one of the above aspects, another implementation of the aspect provides for receiving the TLV structure from a primary egress node.

[0020] Optionally, in any one of the above aspects, another implementation of the aspect provides for receiving the TLV structure from a neighboring network node.

[0021] Optionally, in any one of the above aspects, another implementation of the aspect provides that the EP-BIFT includes a backup entry active (BEA) field of the primary egress node, wherein the entry in the BEA field is set to indicate whether the primary egress node is working or failing.

[0022] Optionally, in any one of the above aspects, another implementation of the aspect stipulates that the entry indicating whether the primary egress node and the backup egress node transmit the data packet to the same CE or to different CEs is set in the same CE receiver (SC) field of the EP-BIFT.

[0023] Optionally, in any one of the above aspects, another implementation of the aspect stipulates that the backup egress node is identified in a backup egress bit forwarding edge router (BE-BFER) field in the EP-BIFT.

[0024] Optionally, in any one of the above aspects, another implementation method of the aspect stipulates that generating the EP-BIFT includes: generating a backup forwarding bitmask (BF-BM) for the target network node by applying a logical OR operation to the bit string of the target network node in the EP-BIFT and the bit strings of other target nodes whose BFR-NBR is the same as the backup BFR-NBR (backup BFR-NBR, BBFR-NBR) of the target network node.

[0025] Optionally, in any one of the above aspects, another implementation of the aspect provides that the EP-BIFT includes a backup bit forwarding router neighbor (BBFR-NBR) field of the primary egress node, wherein the entry in the BBFR-NBR field indicates the next hop on the shortest path to the backup egress node without using the primary egress node.

[0026] Optionally, in any one of the above aspects, another implementation of the aspect stipulates that the next hop identified in the backup bit forwarding router neighbor (BBFR-NBR) field of the primary egress node of the EP-BIFT is a basic loop-free alternate (LFA) bit forwarding router (BFR) of the backup egress node.

[0027] Optionally, in any one of the above aspects, another implementation of the aspect stipulates that the next hop identified in the backup bit forwarding router neighbor (BBFR-NBR) field of the primary egress node of the EP-BIFT is a remote loop-free alternate (LFA) bit forwarding router (BFR) of the backup egress node.

[0028] Optionally, in any one of the above aspects, another implementation of the aspect stipulates that the next hop identified in the backup bit forwarding router neighbor (BBFR-NBR) field of the primary egress node of the EP-BIFT is a topology-independent loop-free alternate (LFA) bit forwarding router (BFR) of the backup egress node.

[0029] Optionally, in any one of the above aspects, another implementation of the aspect stipulates that the next hop identified in the backup bit forwarding router neighbor (BBFR-NBR) field of the primary exit node of the EP-BIFT is the backup exit node through a tunnel to the backup exit node without passing through the primary exit node.

[0030] The third aspect relates to a method implemented by a network node in a bit index explicit replication (BIER) domain, the method comprising: generating a type length value (TLV) structure, wherein the TLV structure identifies a backup exit node of a primary exit node and includes entries indicating whether the primary exit node and the backup exit node transmit data packets to the same customer edge (CE) or to different customer edges (CE); and transmitting the TLV structure to a neighboring network node of the primary exit node.

[0031] Optionally, in any one of the above aspects, another implementation of the aspect stipulates that the TLV structure is an open shortest path first (OSPF) backup egress TLV.

[0032] Optionally, in any one of the above aspects, another implementation of the aspect stipulates that the TLV structure is an intermediate system-intermediate system (IS-IS) backup egress TLV.

[0033] The fourth aspect relates to a network node adjacent to a primary egress node in a bit index explicit replication (BIER) domain, the network node comprising: a receiving device for receiving a type length value (TLV) structure, the TLV structure identifying a backup egress node of the primary egress node and including entries indicating whether the primary egress node and the backup egress node transmit data packets to the same customer edge (CE) or different customer edges (CE); a generating device for generating an egress protection bit index forwarding table (EP-BIFT), the EP-BIFT including the backup egress node and the entry indicating whether the primary egress node and the backup egress node transmit the data packets to the same CE or different CEs; and a forwarding device for forwarding the data packets according to the EP-BIFT when the primary egress node has failed.

[0034] The fifth aspect relates to a network node in a bit index explicit replication (BIER) domain, the network node comprising: a generating device for generating a type length value (TLV) structure, wherein the TLV structure identifies a backup exit node of a primary exit node and includes entries indicating whether the primary exit node and the backup exit node transmit data packets to the same customer edge (CE) or to different customer edges (CE); and a transmitting device for transmitting the TLV structure to a neighboring network node of the primary exit node.

[0035] For clarity, any of the above-described embodiments may be combined with any one or more of the other embodiments described above to create new embodiments within the scope of the invention.

[0036] These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] For a more complete understanding of the present invention, reference is now made to the following brief description taken in conjunction with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.

[0038] Figure 1 Schematic diagram of the BIER topology including the BIER domain.

[0039] Figure 2 FIG. 1 is a schematic diagram of an egress protection bit index forwarding table (EP-BIFT) of a network node according to an embodiment of the present invention.

[0040] Figure 3 Schematic diagram of EP-BIFT of a backup egress node according to an embodiment of the present invention.

[0041] Figure 4 Schematic diagram of EP-BIFT of a network node according to an embodiment of the present invention.

[0042] Figure 5 Schematic diagram of EP-BIFT of a backup egress node according to an embodiment of the present invention.

[0043] Figure 6 It is an Open Shortest Path First (OSPF) type length value (TLV) structure according to an embodiment of the present invention.

[0044] Figure 7 This is an intermediate system-intermediate system (IS-IS) type length value (TLV) structure according to an embodiment of the present invention.

[0045] Figure 8 This is an algorithm for implementing a part of the forwarding process using EP-BIFT according to an embodiment of the present invention.

[0046] Figure 9 A method implemented by a network node in a BIER domain according to an embodiment of the present invention.

[0047] Figure 10 FIG. 1 is a schematic diagram of a network device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0048] First, it should be understood that although illustrative implementations of one or more embodiments are provided below, the disclosed systems and / or methods can be implemented using any number of techniques, whether currently known or in existence. The present invention is in no way limited to the illustrative implementations, drawings, and techniques illustrated below, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents.

[0049] Currently, there is no technology for fast protection against failure of egress nodes in the BIER domain. Therefore, when an egress node in the BIER domain fails, the customer edge (CE) receiver will not receive the requested data packet.

[0050] This article discloses a fast egress protection (EP) for the BIER domain. To facilitate the fast egress protection process, network nodes upstream of the egress node construct an egress protection bit index forwarding table (EP-BIFT). EP-BIFT is used by network nodes to forward data packets when an egress node fails. As a result, packet routing within the BIER domain is improved.

[0051] Figure 11 is a schematic diagram of a BIER topology 100 including a BIER domain 102. The BIER domain 102 may be part of a larger BIER domain (not shown). Therefore, the BIER domain 102 may be referred to herein as a BIER subdomain. The BIER domain 102 includes a plurality of network nodes 104, 106, 108, 110, 112, 114, 116, and 118. Although eight network nodes 104 to 118 are shown in the BIER domain 102, more or fewer nodes may be included in actual applications.

[0052] For ease of discussion, all network nodes 104 through 118 are given alphabetical names. For example, network node 104 has name A, network node 106 has name B, network node 108 has name C, network node 110 has name D, network node 112 has name E, network node 114 has name F, network node 116 has name G, and network node 118 has name H.

[0053] Each of the network nodes 104 to 118 is a bit forwarding router (BFR). Some of the network nodes, namely network nodes 104, 110, 112, 114 and 118, are set at the edge of the BIER domain 102. The network nodes 104, 110, 112, 114 and 118 that receive multicast packets from outside the BIER domain 102 can be referred to as bit forwarding ingress routers (BFIRs). The network nodes 104, 110, 112, 114 and 118 that transmit multicast packets from the BIER domain 102 can be referred to as bit forwarding egress routers (BFERs). Depending on the direction of the multicast packet traffic, each of the network nodes 104 to 118 can act as a BFIR or a BFER.

[0054] Each of the network nodes 104, 110, 112, 114, and 118 may be referred to herein as a target network node. Each of the network nodes 104, 110, 112, 114, and 118 is assigned a BFR identifier (BFR-id), a set index (SI), and a bit string. For example, the BFR-id of the network node 110 is 1, the SI is 0, and the bit string is 00001 (in Figure 100001). Network node 114 has a BFR-id of 2, an SI of 0, and a bit string of 00010 (collectively referred to as 2 (0:00010)). Network node 112 has a BFR-id of 3, an SI of 0, and a bit string of 00100 (collectively referred to as 3 (0:00100)). Network node 118 has a BFR-id of 4, an SI of 0, and a bit string of 01000 (collectively referred to as 4 (0:01000)). Network node 104 has a BFR-id of 5, an SI of 0, and a bit string of 10000 (collectively referred to as 5 (0:10000)).

[0055] Each of the network nodes 104 to 118 has one or more neighbor nodes. As used herein, a neighbor node refers to a network node that is only one hop away from the network node. For example, the network node 106 is Figure 1 There are four neighbor nodes in , namely, network node 104, network node 108, network node 112, and network node 116. In fact, each of network node 104, network node 108, network node 112, and network node 116 is only one hop away from network node 106.

[0056] Figure 1 The network nodes 104 to 118 in FIG. 1 are coupled to each other via links 120 and communicate with each other. Links 120 may be wired, wireless, or some combination thereof. Each of links 120 has a cost. For example, the cost of the link between network node 106 and network node 112 is 4, as shown in FIG. Figure 1 Likewise, the cost of the link between network node 106 and network node 116 is 2, and the cost of the link between network node 116 and network node 110 is also 2. Figure 1 For any link 120 that does not have a numerical value displayed next to it, the default cost is 1. For example, the link between network node 106 and network node 104 has a cost of 1.

[0057] Network node 110 may be referred to herein as a primary exit node (or simply an exit node), and network node 118 may be referred to herein as a backup exit node for primary exit node 110. In one embodiment, the primary exit node is a network node that serves as the primary exit point for traffic received from neighboring nodes when the network node is operating normally. In one embodiment, the backup exit node is a network node that serves as a backup exit point for traffic received from neighboring nodes when the primary exit node is operating abnormally or fails. As shown in the figure, network node 110 and network node 118 are each coupled to a first customer edge (CE) receiver 122 outside the BIER domain 102. Therefore, the first CE 122 is used to receive data packets from network node 110 and network node 118, and to send data packets to network node 110 and network node 118. Network node 118 is coupled to a second CE receiver 124 outside the BIER domain 102. Therefore, the second CE 124 is used to receive data packets from network node 118 and to send data packets to network node 118.

[0058] Figure 2 FIG. 1 is a schematic diagram of an egress protection bit index forwarding table (EP-BIFT) 200 of a network node. Figure 1 Each of the network nodes 104 to 118 in the BIER topology 100 generates an EP-BIFT 200. In one embodiment, the EP-BIFT is generated based on a bit routing table (BIRT) (not shown) constructed by the network nodes 104 to 118.

[0059] Figure 2 The EP-BIFT 200 depicted in the Figure 1EP-BIFT 200 on the network node 108 in the BIER topology 100. As shown in the figure, the EP-BIFT 200 includes eight columns of information. The first column 202 includes the BFR-id of each target network node in the BIER topology 100. The second column 204 includes a forwarding bit mask (F-BM). The third column 206 identifies the neighbor nodes (BFR-NBR) of the network node 108 used to reach the target network node identified in the first column 202, which is why the neighbor nodes in the third column 206 can also be referred to as the next hop of the network node 108. The first column 202, the second column 204 and the third column 206 in the EP-BIFT 200 can be used by the network node 108 during normal operation (i.e., when the primary egress node 110 for the network node 108 is operating normally). That is, these columns are used when the entry in the backup entry active (BEA) field is set to zero.

[0060] Because the target network nodes with BFR-IDs 2 and 3 in the second row 210 and third row 212 of EP-BIFT 200 each have an SI of 0 and each have the same BFR-NBR of network node F in third column 206, the F-BMs in these rows are a combination of the bit strings of the target nodes with BFR-IDs 2 and 3. Specifically, a logical OR operation is applied to the bit strings of the target nodes with BFR-IDs 2 and 3. The logical OR of the bit strings 00010 and 00100 results in the F-BMs in the second row 210 and third row 212 of EP-BIFT 200 being 00110.

[0061] Because no target network node other than target network node D (also known as network node 110) has the BFR-NBR of network node D in third column 206, the F-BM in first row 208 of EP-BIFT 200 is the same as the bit string of target network node D, i.e., 00001. Similarly, because no target network node other than target network node H (also known as network node 118) has the BFR-NBR of network node H in third column 206, the F-BM in fourth row 214 of EP-BIFT 200 is the same as the bit string of target network node H, i.e., 01000. Finally, because no target network node other than target network node A (also known as network node 104) has the BFR-NBR of network node B in third column 206, the F-BM in fifth row 216 of EP-BIFT 200 is the same as the bit string of target network node A, i.e., 10000.

[0062] Fourth column 218 includes a backup entry active (BEA) field. The entry in the BEA field is set to indicate whether the primary egress node is functioning or has failed. For example, when the entry in the BEA field is set to zero, the primary egress node (e.g., network node 110) is functioning normally. However, when the entry in the BEA field is set to one, the primary egress node is not functioning normally (i.e., has failed).

[0063] Fifth column 220 includes a same receiver (SC) field. Entries in the SC field indicate whether the primary egress node (e.g., network node 110) and the backup egress node (e.g., network node 118) transmit the payload of the data packet to the same CE receiver (e.g., CE receiver 122) or to different CE receivers (e.g., CE receiver 122 and CE receiver 124). For example, when the entry in the SC field is set to one, the primary egress node and the backup egress node transmit the payload of the data packet to the same CE receiver. When the entry in the SC field is set to zero, the primary egress node and the backup egress node transmit the data packet to different CE receivers.

[0064] Sixth column 222 includes a backup egress BFER (BE-BFER) field. Entries in the BE-BFER field identify backup egress nodes for a primary egress node. For example, the BE-BFER field in first row 208 of EP-BIFT 200 indicates that network node H (e.g., network node 118) with the bit string (01000) is the backup egress node for primary egress node D (e.g., network node 110). The BE-BFER field in second row 210 of EP-BIFT 200 indicates that network node E (e.g., network node 112) with the bit string (00100) is the backup egress node for primary egress node F (e.g., network node 114). The BE-BFER field in third row 212 of EP-BIFT 200 indicates that network node F (e.g., network node 114) with the bit string (00010) is the backup egress node for primary egress node E (e.g., network node 112). The BE-BFER field in the fourth row 214 of the EP-BIFT 200 indicates that the network node D (e.g., network node 110) having the bit string (00001) is a backup egress node for the primary egress node H (e.g., network node 118). It is worth noting that the BE-BFER field in the fifth row 216 is set to zero because the network node C (e.g., network node 108) cannot protect the network node A (e.g., network node 104) because the network node C does not have any information about the backup egress node of the network node A, which is the primary egress node, or is not a neighbor of the network node A. In other words, the network node C is not immediately adjacent to or directly connected to the network node A.

[0065] Seventh column 224 includes a backup F-BM (BF-BM) field. The value in a row's BF-BM is a combination of the bit string of the target network node in that row and the bit string of the target node whose BFR-NBR is the same as the backup BFR-NBR (BBFR-NBR) in that row. First row 208 in EP-BIFT 200 has a target network node with a BFR-ID of 1 and a BBFR-NBR of H. Because the target network node with a BFR-ID of 4 in fourth row 214 of EP-BIFT 200 has an SI of 0 and a BFR-NBR H that is the same as the BBFR-NBR H in first row 208, the BF-BM in first row 208 is a combination of the bit strings of target nodes with BFR-IDs 1 and 4. Specifically, a logical OR operation is applied to the bit strings of target nodes with BFR-IDs 1 and 4. The logical OR of the bit strings 00001 and 01000 results in the BF-BM in the first row 208 and the fourth row 214 in the EP-BIFT 200 being 01001.

[0066] The second row 210 in the EP-BIFT 200 has a target network node with a BFR-id of 2 and a BBFR-NBR of network node E. Because no other target network node has the same BFR-NBR as the BBFR-NBR of network node E, the BF-BM in the second row 210 of the EP-BIFT 200 is the bit string of the target node with a BFR-id of 2, i.e., 00010.

[0067] The third row 212 in the EP-BIFT 200 has a target network node with a BFR-ID of 3 and a BBFR-NBR of network node F. Because the target network node with a BFR-ID of 2 in the second row 210 in the EP-BIFT 200 has an SI of 0 and a BFR-NBR identical to that of network node F, the BF-BM in the third row is a combination of the bit strings of the target nodes with BFR-IDs 2 and 3. Specifically, a logical OR operation is applied to the bit strings of the target nodes with BFR-IDs 2 and 3. The logical OR of the bit strings 00010 and 00100 results in a BF-BM of 00110 in the third row 212 in the EP-BIFT 200.

[0068] The fourth row 214 in the EP-BIFT 200 has a target network node with a BFR-ID of 4 and a BBFR-NBR of network node D. Because the target network node with a BFR-ID of 1 in the first row 208 of the EP-BIFT 200 has an SI of 0 and a BFR-NBR identical to that of network node D, the BF-BM in the fourth row is a combination of the bit strings of the target nodes with BFR-IDs 1 and 4. Specifically, a logical OR operation is applied to the bit strings of the target nodes with BFR-IDs 1 and 4. The logical OR of the bit strings 00001 and 01000 results in the BF-BM in the fourth row 214 of the EP-BIFT 200 being 01001. For the target network node A with a BFR-ID of 5 in the fifth row 216 of the EP-BIFT 200, network node C cannot provide egress protection for network node A (e.g., network node 104), and the BF-BM in the fifth row 216 is empty.

[0069] The eighth column 226 in the EP-BIFT 200 includes a backup BFR-NBR (BBFR-NBR) field. In one embodiment, when the SC field in a row is one, the BBFR-NBR in the row is set to the next hop on the shortest path to the BE-BFER (i.e., the backup egress node) without passing through the target network node in the row (i.e., the primary egress node). In one embodiment, when the SC field in a row is one, the BBFR-NBR in the row is set to a basic loop-free alternate (LFA) BFR for the backup egress node in the row. Basic LFA is described in detail in IETF request for comment (RFC) 5286, "Basic Specification for IP Fast Reroute: Loop-Free Alternates," by A. Atlas et al., published in September 2008. In one embodiment, when the SC field in a row is one, the BBFR-NBR in the row is set to the remote LFA-BFR for the backup egress node in the row. Remote LFA is described in detail in IETF document RFC 7490, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)" by S. Bryant et al., published in April 2015. In one embodiment, when the SC field in a row is one, the BBFR-NBR in the row is set to the topology independent loop-free alternate (TI-LFA) for the backup egress node in the row. TI-LFA is described in detail in an Internet engineering task force (IETF) document titled "Topology Independent Fast Reroute using Segment Routing" by S. Litkowski et al., published in June 2021.If the SC field is zero, and the BBFR-NBR field is set to one in the row, and the BE-BFER field is different from the BE-BFER field in the row, and the BE-BFER is not on the shortest path from the BBFR-NBR to the primary egress node (i.e., the target network node in the row) without passing through an intermediate primary egress node, then the BBFR-NBR is set to the BE-BFER through a tunnel such as a segment routing (SR) tunnel (also known as a TI-LFA tunnel) to the BE-BFER without passing through the primary egress node. For example, if the SC field in the first row is one, and the entry for H in the first row 208 of the BBFR-NBR field indicates that node H (e.g., network node 118) is the next hop on the shortest path to the backup egress node H without using the primary egress node D (e.g., network node 110).

[0070] The SC field in the second row 210 is zero. The entry E (TI-LFA) in the second row 210 of the BBFR-NBR field indicates that the TI-LFA tunnel from network node C to network node E is a TI-LFA for the backup egress node E, without going through the primary egress node F (i.e., the target network node F in the row). Network node B is not the next hop on the shortest path to network node E without using the primary egress node F (e.g., network node 114). Therefore, when network node F fails, packets intended for egress node F are transmitted to network node E (i.e., the backup egress node) using the topology independent loop-free alternate (TI-LFA) tunnel.

[0071] The SC field in third row 212 is zero. The entry F in third row 212 of the BBFR-NBR field indicates that node F (e.g., network node 114) is the next hop on the shortest path to backup egress node F, and that backup egress node F is on the shortest path from F's BBFR-NBR to primary egress node E (i.e., target network node E in the row) without using an intermediate primary egress node E (e.g., network node 114). The SC field in fourth row 214 is one. The entry D in fourth row 214 of the BBFR-NBR field indicates that node D (e.g., network node 110) is the next hop on the shortest path to backup egress node D without using primary egress node H (e.g., network node 118).

[0072] Because node C cannot provide egress protection for the target network node (ie, network node A) whose BFR-id is 5 in the fifth row 216 in the EP-BIFT 200, the BBFR-NBR field in the fifth row 216 is empty.

[0073] The fourth column 218, the fifth column 220, the sixth column 222, the seventh column 224, and the eighth column 226 in the EP-BIFT 200 may be used by the network node 108 during abnormal operation (i.e., when the primary egress node 110 is not operating normally or has failed). That is, these columns are used when the entry in the BEA field is set to one.

[0074] Figure 3 FIG. 3 is a schematic diagram of an EP-BIFT 300 of a backup egress node according to an embodiment of the present invention. Figure 3 The EP-BIFT 300 depicted in the Figure 1 EP-BIFT 300 on network node 118 in the BIER topology 100, network node 118 is a backup egress node for network node 110. As shown in the figure, EP-BIFT 300 includes eight columns of information. The first column 302 includes the BFR-id of each target network node in the BIER topology 100. The second column 304 includes the F-BM. The third column 306 identifies the BFR-NBR of network node 118 used to reach the target network node identified in the first column 302, which is why the neighbor node in the third column 306 can also be called the next hop of network node 118. The first column 302, the second column 304 and the third column 306 in EP-BIFT 300 can be used by network node 118 during normal operation. That is, these columns are used when the entry in the BEA field is set to zero.

[0075] Because the target network nodes with BFR-IDs 1, 2, 3, and 5 in the first row 308, second row 310, third row 312, and fifth row 316 of the EP-BIFT 300 each have an SI of 0 and each have the same BFR-NBR of network node C in the third column 306, the F-BMs in these rows are combinations of the bit strings of the target nodes with BFR-IDs 1, 2, 3, and 5. A logical OR operation is applied to the bit strings of the target nodes with BFR-IDs 1, 2, 3, and 5. The logical OR of the bit strings 00001, 00010, 00100, and 10000 results in the F-BMs in the first row 308, second row 310, third row 312, and fifth row 316 of the EP-BIFT 300 being 10111.

[0076] Because no other target network node except target network node H has the BFR-NBR of network node H in the third column 306 , the F-BM in the fourth row 314 of the EP-BIFT 300 is the same as the bit string of target network node H, ie, 01000.

[0077] The BEA field, SC field, BE-BFER field, and BF-BM field in EP-BIFT 300 are similar to the BEA field, SC field, BE-BFER field, and BF-BM field in EP-BIFT 200. Therefore, a full discussion of these fields will not be repeated. The first row 308 in EP-BIFT 300 has a target network node with a BFR-id of 1 and a BBFR-NBR of CE1. Because no target network node has a BFR-NBR for the CE1 receiver, the BF-BM in the first row 308 of EP-BIFT 300 is the bit string of the target node with a BFR-id of 1, i.e., 00001. It is worth noting that several fields in EP-BIFT 300 are blank because network node H is the target egress node in BIER domain 100 and a backup egress node only for the primary egress node D (i.e., the target network node in the first row 308). Entries in the fields are not required.

[0078] When the entry in the BEA field of EP-BIFT 300 is set to zero or the entry in the SC field of EP-BIFT 300 is set to one, network node H forwards the packet using first column 302, second column 304, and third column 306. In fact, first column 302, second column 304, and third column 306 are the same as the normal BIFT without egress protection that network node H would use.

[0079] When the entry in the BEA field in the first row 308 of the EP-BIFT 300 is set to one (meaning that the primary egress node D has failed) and the entry in the SC field 320 in row 308 of the EP-BIFT 300 is zero, the network node H uses the fourth column 318, the fifth column 320, the sixth column 322, the seventh column 324, and the eighth column 326 in row 308 of the EP-BIFT 300 to forward packets destined for the network node D. When the entry in the SC field in row 308 of the EP-BIFT 300 is set to zero (meaning that the primary egress node D and the backup egress node H send packets to different CE receivers), when the network node H receives a packet destined for the network node D, the network node H will transmit the packet to the CE1 receiver (CE receiver 122).

[0080] Figure 4 FIG. 4 is a schematic diagram of an EP-BIFT 400 of a network node according to an embodiment of the present invention. Figure 4 The EP-BIFT 400 depicted in the Figure 1 EP-BIFT 400 on the network node 108 in . EP-BIFT 400 is similar to Figure 2EP-BIFT 200. As shown, EP-BIFT 400 includes five columns of information. The first column 402 includes the BFR-id of each target network node in the BIER topology 100. The second column 404 includes the F-BM. The third column 406 identifies the BFR-NBR of the network node 108 used to reach the target network node identified in the first column 402.

[0081] Fourth column 420 includes an SC field. Entries in the SC field indicate whether the primary egress node (e.g., network node 110) and the backup egress node (e.g., network node 118) transmit packets to the same CE receiver (e.g., CE receiver 122) or to different CE receivers (e.g., CE receiver 122 and CE receiver 124). For example, when the entry in the SC field is set to one, the primary egress node and the backup egress node transmit packets to the same CE receiver. When the entry in the SC field is set to zero, the primary egress node and the backup egress node transmit packets to different CE receivers.

[0082] The fifth column 422 includes a BE-BFER field. An entry in the BE-BFER field identifies a backup egress node for a primary egress node. For example, the BE-BFER field in the first row 408 of the EP-BIFT 400 indicates that network node H (e.g., network node 118) is a backup egress node for primary egress node D (e.g., network node 110). Figure 4 The EP-BIFT 400 only considers failures of the primary egress node D (i.e., the target network node D in the first row 408). Therefore, some entries in the second row 410, the third row 412, the fourth row 414, and the fifth row 416 have been left blank. The entries in the BFR-NBR field in the first row 408 (i.e., the third column 406) are set to Figure 2 The corresponding BBFR-NBR H in EP-BIFT 200 in the network node is shown. For each primary egress node (i.e., a network destination node) that is a neighbor of the network node (e.g., network node 108), the network node constructs an EP-BIFT that accounts for failures of the primary egress node. When the network node detects a failure of the primary egress node, the network node forwards the data packet using the EP-BIFT that accounts for the failure of the primary egress node.

[0083] When network node 108 detects a failure of primary egress node D (e.g., a destination node having a bit string of 00001), network node 108 forwards a data packet using EP-BIFT 400. In this regard, network node 108 transmits the data packet to network node H after clearing the bits in the bit string of primary egress node D and adding the bits of backup egress node H because the entry in the SC field is 1. If the entry in the SC field is set to zero, network node 108 transmits the data packet to network node H without clearing the bits of primary egress node D or adding the bits of backup egress node H. After receiving the data packet intended for primary egress node D, backup egress node H transmits the payload of the data packet to CE1 receiver.

[0084] Figure 5 FIG. 5 is a schematic diagram of an EP-BIFT 500 of a backup egress node according to an embodiment of the present invention.

[0085] Figure 5 The EP-BIFT 500 depicted in the Figure 1 EP-BIFT 500 on the network node 118 in . EP-BIFT 500 is similar to Figure 3 EP-BIFT 300. As shown, EP-BIFT 500 includes five columns of information. The first column 502 includes the BFR-id of each target network node in the BIER topology 100. The second column 504 includes the F-BM. The third column 506 identifies the BFR-NBR of the network node 108 used to reach the target network node identified in the first column 502.

[0086] Fourth column 520 includes an SC field. Entries in the SC field indicate whether the primary egress node (e.g., network node 110) and the backup egress node (e.g., network node 118) transmit packets to the same CE receiver (e.g., CE receiver 122) or to different CE receivers (e.g., CE receiver 122 and CE receiver 124). For example, when the entry in the SC field is set to one, the primary egress node and the backup egress node transmit packets to the same CE receiver. When the entry in the SC field is set to zero, the primary egress node and the backup egress node transmit packets to different CE receivers.

[0087] The fifth column 522 includes a BE-BFER field. An entry in the BE-BFER field identifies a backup egress node for a primary egress node. For example, the BE-BFER field in the first row 508 of the EP-BIFT 500 indicates that network node H (e.g., network node 118) is a backup egress node for primary egress node D (e.g., network node 110). Figure 5The EP-BIFT 500 only considers failures of the primary egress node D. Therefore, some entries in the second row 510, the third row 512, the fourth row 514, and the fifth row 516 have been left blank. The entries in the BFR-NBR field in the first row 508 (i.e., the third column 506) are set to Figure 3 The corresponding BBFR-NBR CE1 in the EP-BIFT 300 is shown. For each primary egress node (i.e., a network destination node) of the backup egress node (e.g., network node 118), the network node (i.e., the backup egress node) constructs an EP-BIFT that accounts for the failure of the primary egress node. When the network node detects a failure of the primary egress node, it forwards the packet using the EP-BIFT that accounts for the failure of the primary egress node.

[0088] When network node 118 detects a failure of primary egress node D (e.g., a destination node with bit string 00001), network node 118 forwards data packets using EP-BIFT 500. In this regard, network node 118 transmits the payload of the data packet destined for network node D to CE1 receiver.

[0089] It is noteworthy that one or more network nodes described herein may use, for example, bidirectional forwarding detection (BFD) to detect failures in neighboring network nodes. A network node that is not directly coupled to or not immediately adjacent to another node may use, for example, multi-hop BFD to detect a failure in another network node.

[0090] Figure 6 6 is an OSPF TLV structure 600 according to an embodiment of the present invention. In one embodiment, OSPF TLV structure 600 is initiated by a primary egress node (e.g., network node 110) and transmitted to another network node (e.g., network node 108). OSPF TLV structure 600 can be used to construct EP-BIFT as discussed herein.

[0091] As shown, OSPF TLV structure 600 includes a type field 602, a length field 604, a reserved field 606, an S field 608, a BFR-ID of a backup egress node field 610, and an optional sub-TLV field 612. The type field 602 is two octets and is used to include a value (also known as an entry) that has not yet been assigned by the Internet Assigned Numbers Authority (IANA). The length field 604 is two octets and is used to include a value indicating the length of the TLV structure excluding the type field and the length field. In one embodiment, when the sub-TLV is not included in the sub-TLV field 612, the value is 4, and when the sub-TLV is included in the sub-TLV field 612, the value is 4 plus the length of the sub-TLV.

[0092] The reserved field 606 is 15 bits. In one embodiment, when the OSPF TLV structure 600 is transmitted, the reserved field 606 is filled with all zeros, and when the OSPF TLV structure 600 is received, the reserved field 606 is ignored.

[0093] The S field 608 is a bit (also known as a one-bit flag). The flag is set to one to indicate that the primary egress node and the backup egress node transmit the payload of the data packet to the same CE receiver (e.g., CE receiver 122). The flag is set to zero to indicate that the primary egress node and the backup egress node transmit the payload of the data packet to different CE receivers (e.g., CE receiver 122 and CE receiver 124).

[0094] The BFR-id of the backup egress node field 610 is two octets. The value in the BFR-id of the backup egress node field 610 is the BFR-id of the backup egress node used to prevent the primary egress node (i.e., the node that originates the OSPF TLV structure 600) from failing.

[0095] Figure 7 700 according to an embodiment of the present invention. In one embodiment, IS-IS TLV structure 700 is initiated by a primary egress node (e.g., network node 110) and transmitted to another network node (e.g., network node 108). IS-IS TLV structure 700 may be used to construct EP-BIFT as discussed herein.

[0096] As shown, IS-IS TLV structure 700 includes a type field 702, a length field 704, a reserved field 706, an S field 708, a BFR-ID of a backup egress node field 710, and an optional sub-TLV field 712. The type field 702 is an octet and is used to include a value that has not yet been assigned by IANA. The length field 704 is an octet and is used to include a value indicating the length of the TLV structure excluding the type and length fields. In one embodiment, when the sub-TLV is not included in the sub-TLV field 712, the value is 4, and when the sub-TLV is included in the sub-TLV field 712, the value is 4 plus the length of the sub-TLV.

[0097] The reserved field 706 is 15 bits. In one embodiment, when the IS-IS TLV structure 700 is transmitted, the reserved field 706 is filled with all zeros, and when the IS-IS TLV structure 700 is received, the reserved field 706 is ignored.

[0098] The S field 708 is a bit (also known as a one-bit flag). The flag is set to one to indicate that the primary egress node and the backup egress node transmit the payload of the data packet to the same CE receiver (e.g., CE receiver 122). The flag is set to zero to indicate that the primary egress node and the backup egress node transmit the payload of the data packet to different CE receivers (e.g., CE receiver 122 and CE receiver 124).

[0099] The BFR-id of the backup egress node field 710 is two octets and contains the BFR-id of the backup egress node used to prevent the primary egress node (i.e., the node that originates the IS-IS TLV structure 700) from failing.

[0100] Figure 8 The algorithm 800 is an algorithm for implementing a portion of a forwarding process using EP-BIFT according to an embodiment of the present invention. The algorithm 800 can be used to remove bits or add bits in the bit string of the data packet as described above.

[0101] Upon receiving a packet, for each BFER k (starting from the right side of the packet's bit string), the network node (aka BFR) replicates the packet and sends the copy to the multicast stream overlay, and clears bit k in the packet's bit string if BFER k is BFR. When BFER k is not BFR, the network node uses the set index and the bit string as the key / index to look up the entry for the BIER domain (aka subdomain) in EP-BIFT.

[0102] When the primary egress node fails (e.g., the value of BEA in the entry for the primary egress node as the network destination node is one), the network node (e.g., acting as a backup egress node) sends the packet's payload to the CE receiver when the BBFR-NBR in the entry is a CE receiver. When the value of SC is one, the network node (e.g., acting as a point of local repair (PLR)) clears bit k from the packet's bit string, where bit k corresponds to the primary egress BFER (PE-BEFR) node, and adds bit j to the packet's bit string, where bit j corresponds to the backup egress BFER (BE-BEFR) node. When the value of SC is zero, the network node does not update the packet's bit string. Thereafter, the network node makes a copy of the packet (or an updated packet), updates the copy's bit string by applying a logical AND operation to the copy's bit string and the BF-BM, and sends the updated copy to the BBFR-NBR. The network node updates the bit string of the data packet by applying a logical AND operation to the bit string of the data packet and the inverse of BF-BM (also known as ~BF-BM).

[0103] When the primary egress node has not failed (e.g., the value of BEA is zero), the network node copies the packet and updates the bit string of the copied packet by applying a logical AND operation to the bit string of the copied packet and the F-BM. Thereafter, the network node sends the updated copy of the packet to the BFR-NBR and updates the bit string of the packet by applying a logical AND operation to the bit string of the packet and the inverse of the F-BM (also known as ~F-BM).

[0104] Figure 9 9 is a method 900 implemented by a network node (eg, network node 108) in a BIER domain according to an embodiment of the present invention. The method may be executed by the network node.

[0105] In block 902, a network node receives a TLV structure that identifies a backup egress node for a primary egress node and includes an entry indicating whether the primary egress node and the backup egress node transmit packets to the same CE receiver or to different CE receivers. In one embodiment, the TLV structure is received from the primary egress node. In another embodiment, the TLV structure is received from a neighboring network node.

[0106] In block 904, the network node generates an EP-BIFT that includes a backup egress node and an entry indicating whether the primary egress node and the backup egress node transmit packets to the same CE receiver or to different CE receivers. In one embodiment, the EP-BIFT includes a BEA field, and the entry in the BEA field is set to indicate whether the primary egress node is functioning or has failed. In one embodiment, the entry indicating whether the primary egress node and the backup egress node transmit packets to the same CE receiver or to different CE receivers is set in the SC field of the EP-BIFT. In one embodiment, the backup egress node is identified in the BE-BFER field of the EP-BIFT.

[0107] In one embodiment, generating the EP-BIFT includes generating a BF-BM for the target network node by applying a logical OR operation to a bit string of the target network node having a BBFR-NBR in the EP-BIFT and a bit string of other target nodes having the same BFR-NBR as the BBFR-NBR. In one embodiment, the EP-BIFT includes a BBFR-NBR field, and an entry in the BBFR-NBR field indicates a next hop on a shortest path to the backup egress node without using the primary egress node.

[0108] In one embodiment, the next hop identified in the BBFR-NBR field of the EP-BIFT is a basic LFA BFR for the backup egress node. In one embodiment, the next hop identified in the BBFR-NBR field of the EP-BIFT is a remote LFA BFR for the backup egress node. In one embodiment, the next hop identified in the BBFR-NBR field of the EP-BIFT is a topology-independent LFA BFR for the backup egress node.

[0109] In block 906, when the primary egress node fails, the network node forwards the data packet according to EP-BIFT.

[0110] Figure 1010 is a schematic diagram of a network device 1000 (e.g., a network node, a destination node, a neighboring node, etc.). Network device 1000 is suitable for implementing the disclosed embodiments as described herein. Network device 1000 includes: an ingress port / ingress device 1010 and a receiver unit (Rx) / receiving device 1020 for receiving data; a processor, logic unit, or central processing unit (CPU) / processing device 1030 for processing data; a transmitter unit (Tx) / transmitting device 1040 and an egress port / egress device 1050 for transmitting data; and a memory / memory device 1060 for storing data. Network device 1000 may also include optical-to-electrical (OE) and electrical-to-optical (EO) components coupled to ingress port / ingress device 1010, receiver unit / receiving device 1020, transmitter unit / transmitting device 1040, and egress port / egress device 1050 for exiting or entering optical or electrical signals.

[0111] The processor / processing device 1030 is implemented by hardware and software. The processor / processing device 1030 can be implemented as one or more CPU chips, cores (for example, as a multi-core processor), a field-programmable gate array (FPGA), an application specific integrated circuit (ASIC) and a digital signal processor (DSP). The processor / processing device 1030 communicates with the inlet port / inlet device 1010, the receiver unit / receiving device 1020, the transmitter unit / transmitting device 1040, the outlet port / exit device 1050 and the memory / memory device 1060. The processor / processing device 1030 includes a BIER fast exit protection module 1070. The BIER fast exit protection module 1070 can implement the method disclosed herein. Therefore, including the BIER fast exit protection module 1070 provides a substantial improvement to the functionality of the network device 1000 and enables the transformation of the network device 1000 to different states. Alternatively, the BIER rapid exit protection module 1070 is implemented as instructions stored in the memory / memory device 1060 and executed by the processor / processing device 1030.

[0112] Network device 1000 may also include input and / or output (I / O) devices or I / O devices 1080 for communicating data to and from a user. I / O devices or I / O devices 1080 may include output devices, such as a display for displaying video data, speakers for outputting audio data, etc. I / O devices or I / O devices 1080 may also include input devices, such as a keyboard, a mouse, a trackball, etc., and / or corresponding interfaces for interacting with these output devices.

[0113] Memory / storage device 1060 includes one or more magnetic disks, one or more tape drives, and one or more solid-state drives, and can be used as an overflow data storage device to store programs when such programs are selected for execution, as well as to store instructions and data read during the execution of the programs. Memory / storage device 1060 can be volatile and / or non-volatile and can be read-only memory (ROM), random access memory (RAM), ternary content-addressable memory (TCAM), and / or static random-access memory (SRAM).

[0114] Although the present invention provides several embodiments, it should be understood that the disclosed systems and methods may also be embodied in a variety of other specific forms without departing from the spirit or scope of the present invention. The present examples are to be considered illustrative rather than restrictive, and the present invention is not intended to be limited to the details given herein. For example, various elements or components may be combined or integrated into another system, or some features may be omitted or not implemented.

[0115] In addition, the techniques, systems, subsystems, and methods described and illustrated as discrete or separate in various embodiments may be combined or integrated with other systems, components, techniques, or methods without departing from the scope of the present invention. Those skilled in the art may determine other examples of changes, substitutions, and modifications, and may make changes, substitutions, and modifications without departing from the spirit and scope disclosed herein.

Claims

1. A method implemented by a network node adjacent to a primary egress node in a bit index explicit replication (BIER) domain, characterized in that: The method comprises: receiving a type-length-value (TLV) structure identifying a backup egress node of the primary egress node and including an entry indicating whether the primary egress node and the backup egress node transmit data packets to the same customer edge (CE) receiver or to different CE receivers; generating an egress protection bit index forwarding table (EP-BIFT), the EP-BIFT including the backup egress node and the entry indicating whether the primary egress node and the backup egress node transmit the data packet to the same CE receiver or to different CE receivers; When the primary egress node fails, the data packet is forwarded according to the EP-BIFT.

2. The method according to claim 1, characterized in that The TLV structure is received from the primary egress node.

3. The method according to claim 1, characterized in that The TLV structure is received from a neighboring network node.

4. The method according to claim 1, wherein The EP-BIFT includes a backup entry active (BEA) field, wherein an entry in the BEA field is set to indicate whether the primary egress node is working or has failed.

5. The method according to claim 1, wherein The entry indicating whether the primary egress node and the backup egress node transmit the data packet to the same CE receiver or to different CE receivers is set in a same CE receiver (SC) field in the EP-BIFT.

6. The method according to claim 1, characterized in that The backup egress node is identified in the backup egress bit forwarding edge router (BE-BFER) field in the EP-BIFT.

7. The method according to claim 1, characterized in that Generating the EP-BIFT includes: generating a backup forwarding bitmask (BF-BM) for the target network node by applying a logical OR operation to the bit string of the target network node in the EP-BIFT and the bit strings of other target nodes whose BFR-NBR is the same as the backup BFR-NBR (backupBFR-NBR, BBFR-NBR) of the target network node.

8. The method according to claim 1, characterized in that The EP-BIFT includes a backup bit forwarding router neighbor (BBFR-NBR) field, wherein an entry in the BBFR-NBR field indicates a next hop on the shortest path to the backup egress node without using the primary egress node.

9. The method according to claim 1, characterized in that The next hop identified in the backup bit forwarding router neighbor (BBFR-NBR) field of the primary egress node of the EP-BIFT is a basic loop-free alternate (LFA) bit forwarding router (BFR) of the backup egress node.

10. The method according to claim 1, characterized in that The next hop identified in the backup bit forwarding router neighbor (BBFR-NBR) field of the primary egress node of the EP-BIFT is a remote loop-free alternate (LFA) bit forwarding router (BFR) of the backup egress node.

11. The method according to claim 1, wherein The next hop identified in the backup bit forwarding router neighbor (BBFR-NBR) field of the primary egress node of the EP-BIFT is a topology-independent loop-free alternate (LFA) bit forwarding router (BFR) of the backup egress node.

12. The method according to claim 1, characterized in that The next hop identified in the backup bit forwarding router neighbor (BBFR-NBR) field of the primary egress node of the EP-BIFT is the backup egress node through a tunnel to the backup egress node without passing through the primary egress node.

13. A network node adjacent to a primary egress node in a bit index explicit replication (BIER) domain, characterized in that: The network node includes: a memory for storing instructions; one or more processors coupled to the memory, wherein the one or more processors are configured to execute the instructions to cause the network node to: receiving a type-length-value (TLV) structure identifying a backup egress node of the primary egress node and including an entry indicating whether the primary egress node and the backup egress node transmit data packets to the same customer edge (CE) receiver or to different CE receivers; generating an egress protection bit index forwarding table (EP-BIFT), the EP-BIFT including the backup egress node and the entry indicating whether the primary egress node and the backup egress node transmit the data packet to the same CE receiver or to different CE receivers; When the primary egress node fails, the data packet is forwarded according to the EP-BIFT.

14. The network node according to claim 13, characterized in that The TLV structure is received from a primary egress node.

15. The network node according to claim 13, characterized in that The TLV structure is received from a neighboring network node. The network node according to claim 13 , wherein: The EP-BIFT includes a backup entry active (BEA) field of a primary egress node, wherein an entry in the BEA field is set to indicate whether the primary egress node is working or has failed.

17. The network node according to claim 13, characterized in that The entry indicating whether the primary egress node and the backup egress node transmit the data packet to the same CE or to different CEs is set in a same CE receiver (SC) field in the EP-BIFT.

18. The network node according to claim 13, characterized in that The backup egress node is identified in the backup egress bit forwarding edge router (BE-BFER) field in the EP-BIFT.

19. The network node according to claim 13, characterized in that Generating the EP-BIFT includes: generating a backup forwarding bitmask (BF-BM) for the target network node by applying a logical OR operation to the bit string of the target network node in the EP-BIFT and the bit strings of other target nodes whose BFR-NBR is the same as the backup BFR-NBR (backupBFR-NBR, BBFR-NBR) of the target network node.

20. The network node according to claim 13, wherein: The EP-BIFT includes a backup bit forwarding router neighbor (BBFR-NBR) field of a primary egress node, wherein an entry in the BBFR-NBR field indicates a next hop on the shortest path to the backup egress node without using the primary egress node.

21. The network node according to claim 13, characterized in that The next hop identified in the backup bit forwarding router neighbor (BBFR-NBR) field of the primary egress node of the EP-BIFT is a basic loop-free alternate (LFA) bit forwarding router (BFR) of the backup egress node.

22. The network node according to claim 13, characterized in that The next hop identified in the backup bit forwarding router neighbor (BBFR-NBR) field of the primary egress node of the EP-BIFT is a remote loop-free alternate (LFA) bit forwarding router (BFR) of the backup egress node.

23. The network node according to claim 13, characterized in that The next hop identified in the backup bit forwarding router neighbor (BBFR-NBR) field of the primary egress node of the EP-BIFT is a topology-independent loop-free alternate (LFA) bit forwarding router (BFR) of the backup egress node.

24. The network node according to claim 13, characterized in that The next hop identified in the backup bit forwarding router neighbor (BBFR-NBR) field of the primary egress node of the EP-BIFT is the backup egress node through a tunnel to the backup egress node without passing through the primary egress node.

25. A method implemented by a network node in a bit index explicit replication (BIER) domain, characterized in that: The method comprises: generating a type-length-value (TLV) structure, wherein the TLV structure identifies a backup egress node of a primary egress node and includes an entry indicating whether the primary egress node and the backup egress node transmit data packets to the same customer edge (CE) or to different customer edges (CE); The TLV structure is transmitted to a neighboring network node of the primary egress node.

26. The method according to claim 25, characterized in that The TLV structure is an Open Shortest Path First (OSPF) backup egress TLV.

27. The method according to claim 25, characterized in that The TLV structure is an intermediate system-intermediate system (IS-IS) backup egress TLV.

28. A network node adjacent to a primary egress node in a bit index explicit replication (BIER) domain, characterized in that: The network node includes: a receiving device, configured to receive a type-length-value (TLV) structure, the TLV structure identifying a backup egress node of the primary egress node and including an entry indicating whether the primary egress node and the backup egress node transmit data packets to the same customer edge (CE) or to different customer edges (CE); a generating device, configured to generate an egress protection bit index forwarding table (EP-BIFT), the EP-BIFT including the backup egress node and the entry indicating whether the primary egress node and the backup egress node transmit the data packet to the same CE or to different CEs; A forwarding device is used to forward the data packet according to the EP-BIFT when the main egress node fails.

29. A network node in a bit index explicit replication (BIER) domain, characterized in that: The network node includes: a generating device, configured to generate a type-length-value (TLV) structure, wherein the TLV structure identifies a backup egress node of a primary egress node and includes an entry indicating whether the primary egress node and the backup egress node transmit data packets to the same customer edge (CE) or to different customer edges (CE); The transmission device is used to transmit the TLV structure to the neighboring network node of the main egress node.

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