What are all actions taken at time of MAC reconfiguration ?

Question

When target eNodeB is not able to allocate resource for all the bearers which comes as part of Handover Request message, it sends handover request ack with partial success since "E-RABs Failed to Setup List" is present in HOReqAck message.
What MME or source eNodeB does in that case ? Does any action taken by MME for the E-RABs which failed to setup at target eNodeB or some other actions taken ?

Answer 1

Whenever Upper layers trigger reconfiguration for MAC layer, following actions are taken:
- Upon addition of SCell (Secondary Cell) in case of Carrier aggregation, initialize the corresponding HARQ entity.
- Upon removal of SCell (Secondary Cell), remove the corresponding HARQ entity.
- For timers apply the new value when the timer is (re)started.
- When counters are initialized apply the new maximum parameter value.
- For other parameters, apply immediately the configurations received from upper layers.