BIER Forwarding Plane Fundamentals
Bit Index Forwarding Table Establishment
In a BIER domain, each edge node in a BIER sub-domain must be configured with a BFR-ID that is unique in the sub-domain.
BFR-IDs in the BIER sub-domain, together with other information (for example, nodes' IP addresses), are flooded through the IGP. Each node on the network generates its BIER forwarding information. After receiving a BIER packet carrying a BitString, each node performs packet replication and forwarding according to the BitString in the packet.
- The ID refers to a BFR-ID. When the next hop of a BFR-ID is reached, the record needs to be queried.
- F-BM is short for Forwarding BitMask. It indicates the set of BIER domain edge nodes that are reachable through the next hop after packets are replicated and sent to the next hop.
- NBR is short for neighbor. It indicates the next hop neighbor of a BFR-ID.
BIER Multicast Traffic Forwarding
As shown in Table 9-3, when PE4 needs to send the multicast traffic (S1, G1) to PE1, PE2, and PE3, PE4 encapsulates the BitString (0111). The multicast traffic is sent as follows.
Link |
BitString in the Packet |
Description |
|---|---|---|
PE4 → P1 |
BitString(0111) |
In the packet sent from PE4 to P1, the BitString contains the set of BFR-IDs of PE1, PE2, and PE3. |
P1 → PE3 |
BitString(0100) |
In the packet sent from P1 to PE3, the BitString contains the BFR-ID of PE3. |
P1 → P2 |
BitString(0011) |
In the packet sent from P1 to P2, the BitString contains the set of BFR-IDs of PE1 and PE2, with the BFR-ID of PE3 removed. |
P2 → PE1 |
BitString(0001) |
In the packet sent from P2 to PE1, the BitString contains the BFR-ID of PE1. |
P2 → PE2 |
BitString(0010) |
In the packet sent from P2 to PE2, the BitString contains the BFR-ID of PE2. |
