Multicast data transmission method, related apparatus, and system

1. A method implemented by a first bit-forwarding ingress router (BFIR) in a first bit index explicit replication (BIER) domain, the method comprising:

determining a bitstring and a bit index forwarding table identifier (BIFT-id) that correspond to multicast data in a second BIER domain, wherein the BIFT-id is based on a subset identifier (SI) to which a bit-forwarding router identifier (BFR-id) of a first bit-forwarding egress router (BFER) belongs and a bitstring length supported by the first BFER, wherein the bitstring is based on the BFR-id, and wherein the first BFER is in the second BIER domain and is for receiving the multicast data;

encapsulating the multicast data into a BIER data packet, wherein the BIER data packet comprises a BIER header, and wherein the BIER header comprises the BIFT-id and the bitstring;

labeling the BIER data packet with a label to create a labeled BIER data packet, wherein the label corresponds to a prefix of a second BFIR in the second BIER domain;

sending the labeled BIER data packet to the second BFIR;

sending, to a BFIR and a BFIR in the second BIER domain and through a Border Gateway Protocol (BGP) connection a first BGP message comprising an intra P-multicast service interface auto-discovery (PMSI A-D) route, wherein the intra PMSI A-D route comprises a BIER identifier and a first identifier of a multicast group corresponding to the multicast data; and

receiving, liom the second BFIR and through the BGP connection, a second BGP message comprising a first leaf auto-discovery (A-D) route, wherein the first leaf A-D route comprises the prefix and a second identifier of the second BIER domain.

2. The method of claim 1 , further comprising further determining the bitstring and the BIFT-id from a first mapping table comprising the BIFT-id and the bitstring that correspond to the multicast data in at least one BIER domain.

3. The method of claim 1 , wherein before labeling the BIER data packet, the method further comprises determining a prefix of a logical next hop of the first BFIR in the second BIER domain, wherein the logical next hop is the second BFIR.

4. The method of claim 3 , further comprising further determining the prefix from a second mapping table comprising the BIFT-id and the prefix, wherein the prefix corresponds to the BIFT-id.

5. The method of claim 1 , furhter comprising receiving, from the first BFER and through the BGP connection, a third BGP message comprising a second leaf A-D route, wherein the second leaf A-D route comprises the BFR-id, the SI, and the second identifier.

6. The method of claim 5 , wherein the second leaf A-D route further comprises a sub-domain to which the first BFER belongs.

7. The method of claim 5 , wherein the second leaf A-D route further comprises the bitstring length.

8. The method of claim 1 , wherein the BIFT-id is further based on a sub-domain to which the first BFER belongs.

9. A method implemented by a first bit-forwarding ingress router (BFIR) in a first bit index explicit replication (BIER) domain, the method comprising:

receiving, from a second BFIR in a second BIER domain, a labeled BIER data packet comprising a label corresponding to a prefix of the first BFIR;

removing the label to obtain a BIER data packet comprising multicast data and a BIER header, wherein the BIER header comprises a bitstring and a bit index forwarding table identifier (BIFT-id) that correspond to the multicast data in the first BIER domain, wherein the BIFT-id is based on a subset identifier (SI) to which a bit-forwarding router identifier (BFR-id) of a first bit-forwarding egress router (BFER) belongs and a bitstring length supported by the first BFER, wherein the bitstring is based on the BFR-id, and wherein the first BFER is in the second BIER domain and is for receiving the multicast data;

obtaining the BIFT-id and the bitstring from the BIER header;

forwarding the BIER data packet to the first BFER based on the bitstring and a BIFT indicated by the BIFT-id;

receiving, from the second BFIR and through a Border Gateway Protocol (BGP) connection, a first BGP message comprising an intra P-multicast service interface auto-discovery (PMSI A-D) route, wherein the intra PMSI A-D route comprises a BIER identifier and a first identifier of a multicast group corresponding to the multicast data; and

sending, to the second BFIR, through the BGP connection, and in response to the first BGP message, a second BGP message comprising a leaf auto-discovery (A-D) route, wherein the leaf A-D route comprises the prefix and a second identifier of the first BIER domain.

10. The method of claim 9 , wherein the BIFT-id is further based on a sub-domain to which the first BFER belongs.

11. A method implemented by a first bit-forwarding egress router (BFER) in a first bit index explicit replication (BIER) domain, the method comprising:

receiving, from a second BFIR in a second BIER domain and through a border gateway protocol (BGP) connection, a first BGP message comprising an intra P-multicast service interface auto-discovery (PMSI A-D) route, wherein the intra PMSI A-D route comprises a BIER identifier and a first identifier of a multicast group corresponding to multicast data;

sending, to the second BFIR through the BGP connection, a second BGP message comprising a leaf auto-discovery (A-D) route, wherein the leaf A-D route comprises a bit-forwarding router identifier (BFR-id) of the first BFER, an SI to which the BFR-id belongs, and a second identifier of the first BIER domain;

receiving, from a first BFIR in the first BIER domain, a BIER data packet;

decapsulating the BIER data packet to obtain the multicast data and a BIER header, wherein the BIER header comprises a bitstring and a bit index forwarding table identifier (BIFT-id) that correspond to the multicast data in the first BIER domain, wherein the BIFT-id is based on a subset identifier (SI) to which the BFR-id belongs and a bitstring length supported by the first BFER, and wherein the bitstring is based on the BFR-id; and

sending the multicast data to a user-side device.

12. The method of claim 11 , wherein the leaf A-D route further comprises a sub-domain to which the first BFER belongs.

13. The method of claim 11 , wherein the leaf A-D route further comprises the bitstring length.

14. The method of claim 11 , wherein the BIFT-id is further based on a sub-domain to which the first BFER belongs.

15. A first bit-forwarding ingress router (BFIR) in a first bit index explicit replication (BIER) domain and comprising:

a memory configured to store instructions; and

a processor coupled to the memory and configured to execute the instructions to cause the first BFIR to:

determine a bitstring and a bit index forwarding table identifier (BIFT-id) that correspond to multicast data in a second BIER domain, wherein the BIFT-id is based on a subset identifier (SI) to which a bit-forwarding router identifier (BFR-id) of a first bit-forwarding egress router (BFER) belongs and a bitstring length supported by the first BFER, wherein the bitstring is based on the BFR-id, and wherein the first BFER is in the second BIER domain and is for receiving the multicast data;

encapsulate the multicast data into a BIER data packet, wherein the BIER data packet comprises a BIER header, and wherein the BIER header comprises the BIFT-id and the bitstring;

label the BIER data packet with a label to create a labeled BIER data packet, wherein the label corresponds to a prefix of a second bit-forwarding ingress router (BFIR) in the second BIER domain;

send the labeled BIER data packet to the second BFIR;

send, to a BFIR and a BFER in the second BIER domain and through a Border Gateway Protocol (BGP) connection, a first BGP message comprising an intra P-multicast service interface auto-discovery (PMSI A-D) route, wherein the intra PMSI A-D route comprises a BIER identifier and first identifier of a multicast group corresponding to the multicast data; and

receive, from the second BFIR and through the BGP connection, a second BGP message comprising a first leaf auto-discovery (A-D) route, wherein the first leaf A-D route comprises the prefix and a second iden.tifier of the second BIER domain.

16. The first BFIR of claim 15 , wherein the processor is further configured to execute the instructions to cause the first BFIR to further determine the bitstring and the BIFT-id from a first mapping table comprising the BIFT-id and the bitstring that correspond to the multicast data in at least one BIER domain.

17. The first BFIR of claim 15 , wherein before labeling the BIER data packet, the processor is further configured to execute the instructions to cause the first BFIR to determine a prefix of a logical next hop of the first BFIR in the second BIER domain, wherein the logical next hop is the second BFIR.

18. A first bit-forwarding ingress router (BFIR) in a first bit index explicit replication (BIER) domain and comprising:

a memory configured to store instructions; and

a processor coupled to the memory and configured to execute the instructions to cause the first BFIR to:

receive, from a second BFIR in a second BIER domain, a labeled BIER data packet comprising a label corresponding to a prefix of the first BFIR;

remove the label to obtain a BIER data packet comprising multicast data and a BIER header, wherein the BIER header comprises a bitstring and a bit index forwarding table identifier (BIFT-id) that correspond to the multicast data in the first BIER domain, wherein the BIFT-id is based on a subset identifier (SI) to which a bit-forwarding router identifier (BFR-id) of a first bit-forwarding egress router (BFER) belongs and a bitstring length supported by the first BFER, wherein the bitstring is based on the BFR-id, and wherein the first BFER is in the second BIER domain and is for receiving the multicast data;

obtain the BIFT-id and the bitstring from the BIER header;

forward the BIER data packet to the first BFER based on the bitstring and a BIFT indicated by the BIFT-id;

receive, from the second BFIR and through a Border Gateway Protocol (BGP) connection, a first BGP message comprising an intra P-multicast service interface auto-discovery (PMSI A-D) route, wherein the intra PMSI A-D route comprises a BIER identifier and a first identifier of a multicast group corresponding to the multicast data; and

send, to the second BFIR, through the BGP connection, and in response to the first BGP message, a second BGP message comprising a leaf auto-discovery (A-D) route, wherein the leaf A-D route comprises the prefix and a second identifier of the first BIFR domain.

19. The first BFIR of claim 18 , wherein the BIFT-id is further based on a sub-domain to which the first BFER belongs.

20. A first bit-forwarding egress router (BFER) in a first bit index explicit replication (BIER) domain and comprising:

a memory configured to store instructions; and

a processor coupled to the memory and configured to execute the instructions to cause the first BFER to:

receive, from a second BFIR in a second BIER domain and through a border gateway protocol (BGP) connection, a first BGP message comprising an intra P-multicast service interface auto-discovery (PMSI A-D) route, wherein the intra PMSI A-D route comprises a BIER identifier and a first identifier of a multicast group corresponding to multicast data;

send, to the second BFIR through the BGP connection, a second BGP message comprising a leaf auto-discovery (A-D) route, wherein the leaf A-D route comprises a bit-forwarding router identifier (BFR-id) of the first BFER, an SI to which the BFR-id belongs, and a second identifier of the first BIER domain;

receive, from a first BFIR in the first BIER domain, a BIER data packet;

decapsulate the BIER data packet to obtain the multicast data and a BIER header, wherein the BIER header comprises a bitstring and a bit index forwarding table identifier (BIFT-id) that correspond to the multicast data in the first BIER domain, wherein the BIFT-id is based on a subset identifier (SI) to which the BIFT-id belongs and a bitstring length supported by the first BFER, and wherein the bitstring is based on the BFR-id; and

send the multicast data to a user-side device.