36.322 R9定义am模式的LI域为11bit，为什么R12版本增加了15bit？

francyhe

Length Indicator (LI) field
Length: 11 bits for RLC UM, 11 bits or 15 bits for RLC AM. The length of the LI field for RLC AM is configured by upper layers.
The LI field indicates the length in bytes of the corresponding Data field element present in the RLC data PDU delivered/received by an UM or an AM RLC entity. The first LI present in the RLC data PDU header corresponds to the first Data field element present in the Data field of the RLC data PDU, the second LI present in the RLC data PDU header corresponds to the second Data field element present in the Data field of the RLC data PDU, and so on. The value 0 is reserved.

难道是为了迎合IPV6吗？