Old IPv6 Address Boundaries
+--+-----+-----+---+-----+------+------------------+
| 3| 13 | 13 | 6 | 13 | 16 | 64 bits |
+--+-----+-----+---+-----+------+------------------+
|FP| TLA | sub |Res| NLA | SLA | Interface |
| | ID | TLA | | ID | ID | ID |
+--+-----+--+--+---+-----+------+------------------+
(RFC 2374 - Mixes technology and policy)