In this chapter we shall see how an RLC entity is established, re-established and released.
RLC entity establishment procedure
When any upper layer request an RLC entity establishment, the UE will:
1. Establish a RLC entity.
2. Set the state variables of the RLC entity to initial values.
3. Then perform Data transfer procedures
RLC entity re-establishment
When upper layers request an RLC entity re-establishment, the UE shall:
1. Discard all RLC SDUs, RLC SDU segments, and RLC PDUs, if any;
2. Stop and reset all timers;
3. Reset all state variables to their initial values.
RLC entity release
When upper layers request an RLC entity release, the UE shall:
1. Discard all RLC SDUs, RLC SDU segments, and RLC PDUs, if any;
2. Release the RLC entity
SDU Discard procedure
If the upper layer like PDCP informs RLC to drop the SDU, then the AM RLC entity and UM RLC entity need to drop the packet provided:
1. If the RLC SDU or the RLC SDU segment has not been submitted to lower layer like MAC.
2. If the packet has been submitted, then RLC entity cannot discard the packet as to avoid the SN gaps at the sender RLC entity.
TS 138 322 V16.1.0