A BIER forwarding table is built based on the combination of:
Set ID (SI)
BIER String Length (BSL)
Sub Domain (SD)
and saved in the format <SD, BSL, SI>. Figure: BIER forwarding tables shows an example of how forwarding tables are built.
Figure: BIER forwarding tables
For example, if there are 2 SDs and there are 256 PEs in each SD, there are two forwarding tables, one for each SD. One for <SD=0, BSL=256, SI=0> and the other for <SD=1, BSL=256, SI=0>.
Similarly, if there are 512 PEs in an SD and the BSL is 256, there are two forwarding tables, one for <SD=0, BSL=256, SI=0> and the other for <SD=0, BSL=256, SI=1>.
An MPLS label is assigned locally for each BIER routing table, and advertised.