Management framework for BIER in-band traffic accounting and path monitoring

1. A method comprising:

at a router configured to perform Bit Index Explicit Replication (BIER) forwarding of multicast packets in a network:

upon receiving a multicast packet of a multicast flow, accessing flow mappings in which multicast flows are mapped to fixed accounting values corresponding to the multicast flows;

generating a BIER header for the multicast packet by encoding a multi-segment entropy field of the BIER header with (i) a first segment that includes a variable entropy value for equal-cost multi-path (ECMP) load balancing, and (ii) a second segment that includes a fixed accounting value among the fixed accounting values that is mapped to the multicast flow in the flow mappings;

encoding a reserved field of the BIER header with an accounting flag configured to indicate that the multi-segment entropy field includes the fixed accounting value, and to trigger next hop BIER routers to perform flow accounting for the multicast flow and reporting accounting results along with the fixed accounting value;

encapsulating the multicast packet with the BIER header to produce a BIER packet; and

forwarding the BIER packet.

2. The method of claim 1 , further comprising, at the router:

determining whether the multicast packet belongs to any of the multicast flows in the flow mappings; and

when the multicast packet belongs to the multicast flow in the flow mappings, performing the generating.

3. The method of claim 2 , wherein:

the flow mappings include (source address (S), multicast group address (G)) (S, G) identifiers of the multicast flows that are mapped to the fixed accounting values, and the multicast packet includes an (S, G) identifier of the multicast flow; and

the determining includes matching the (S, G) identifier of the multicast packet to the (S, G) identifiers of the flow mappings.

4. The method of claim 2 , further comprising, at the router:

when the multicast packet does not belong to any of the multicast flows in the flow mappings, not performing the generating and the encapsulating; and

encapsulating the multicast packet with a conventional BIER header having an entropy field that only includes a second variable entropy value for the ECMP load balancing.

5. The method of claim 1 , wherein the accounting flag is further configured to trigger the next hop BIER routers to perform reporting their identifiers.

6. The method of claim 1 , wherein each of the multicast flows is mapped to a distinct fixed accounting value among the fixed accounting values in the flow mappings.

7. The method of claim 1 , wherein the multicast flows are divided into distinct sets associated with distinct virtual private networks (VPNs) and each of the distinct sets is mapped to a distinct fixed accounting value among the fixed accounting values of the flow mappings.

8. The method of claim 1 , wherein:

the generating further includes encoding the reserved field of the BIER header with an egress timestamp corresponding to when the forwarding occurs.

9. The method of claim 8 , wherein:

the generating further includes encoding the reserved field with a timing flag to indicate that the reserved field includes the egress timestamp.

10. The method of claim 1 , wherein the fixed accounting values include one or more virtual private network (VPN) identifiers.

11. The method of claim 1 , wherein the router is an ingress router of the network.

12. The method of claim 1 , further comprising, at a second router in the network:

receiving the BIER packet forwarded by the router;

parsing the BIER header to retrieve the fixed accounting value; and

sending, to a controller of the network, a message including an identifier of the second router and the fixed accounting value.

13. An apparatus comprising:

multiple network input/output interfaces; and

a processor of a router configured to perform Bit Index Explicit Replication (BIER) forwarding of multicast packets in a network, the processor coupled to the multiple network input/output interfaces and configured to perform:

upon receiving a multicast packet of a multicast flow, accessing flow mappings in which multicast flows are mapped to fixed accounting values corresponding to the multicast flows;

generating a BIER header for the multicast packet by encoding a multi-segment entropy field of the BIER header with (i) a first segment that includes a variable entropy value for equal-cost multi-path (ECMP) load balancing, and (ii) a second segment that includes a fixed accounting value among the fixed accounting values that is mapped to the multicast flow in the flow mappings;

encoding a reserved field of the BIER header with an accounting flag configured to indicate that the multi-segment entropy field includes the fixed accounting value, and to trigger next hop BIER routers to perform flow accounting for the multicast flow and reporting accounting results along with the fixed accounting value;

encapsulating the multicast packet with the BIER header to produce a BIER packet; and

forwarding the BIER packet.

14. The apparatus of claim 13 , wherein the processor is further configured to perform:

determining whether the multicast packet belongs to any of the multicast flows in the flow mappings; and

when the multicast packet belongs to the multicast flow in the flow mappings, performing the generating.

15. The apparatus of claim 13 , wherein the accounting flag is further configured to trigger the next hop BIER routers to perform reporting their identifiers.

16. The apparatus of claim 13 , wherein:

the generating further includes encoding the reserved field of the BIER header with an egress timestamp corresponding to when the forwarding occurs.

17. The apparatus of claim 16 , wherein:

the generating further includes encoding the reserved field with a timing flag to indicate that the reserved field includes the egress timestamp.

18. A non-transitory computer readable medium encoded with instructions that, when executed by a processor of a router configured to perform Bit Index Explicit Replication (BIER) forwarding of multicast packets in a network, cause the processor to perform:

upon receiving a multicast packet of a multicast flow, accessing flow mappings in which multicast flows are mapped to fixed accounting values corresponding to the multicast flows;

generating a BIER header for the multicast packet by encoding a multi-segment entropy field of the BIER header with (i) a first segment that includes a variable entropy value for equal-cost multi-path (ECMP) load balancing, and (ii) a second segment that includes a fixed accounting value among the fixed accounting values that is mapped to the multicast flow in the flow mappings;

encoding a reserved field of the BIER header with an accounting flag configured to indicate that the multi-segment entropy field includes the fixed accounting value, and to trigger next hop BIER routers to perform flow accounting for the multicast flow and reporting accounting results along with the fixed accounting value;

encapsulating the multicast packet with the BIER header to produce a BIER packet; and

forwarding the BIER packet.

19. The non-transitory computer readable medium of claim 18 , wherein the accounting flag is further configured to trigger the next hop BIER routers to perform reporting their identifiers.

20. The non-transitory computer readable medium of claim 18 , wherein the instructions to cause the processor to perform the generating include instructions to cause the processor to perform encoding the reserved field of the BIER header with an egress timestamp corresponding to when the forwarding occurs.