Sub-TLA
+--+--------+---------+---+--------+
+--+--------+---------+---+--------+
|FP| TLA ID | Sub-TLA |Res| NLA ID |
+--+--------+---------+---+--------+
1st TLA ID is used for sub-TLAs (and reserved field is used)
- A TLA Registry first gets sub-TLA, when fully used up they will get full TLA