(Link) IPv6 using 128-bits
Category addressing:
1. Unicast - Identify a single interface
3 bits | 13 bits | 8 bits | 24 bits | 16 bits | 64 bits |
FP | TLA ID | RES | NLA ID | SLA ID | Int ID |
FP - Format Prefix (001); TLA ID – Top Level Aggregation Identifier; RES – Reserved for Future Use; NLA ID – Next Level Aggregation Identifier; SLA ID – Site Leve Aggregation Identifier; Int ID – Interface ID.
The first 48 bits represent the public topology from (FP-NLA ID). The next 16 bits represent the site topology (SLA ID).
The SLA ID field is used by an individual organization to create its own local addressing hierarchy and to identify subnets. This is analogous to subnets in IPv4 except that each organization has a much greater number of subnets. The 16 bit SLA ID field supports 65,535 individual subnets.