When should key refresh be initiated by the eNB?
When the PDCP COUNTs is about to be re-used with the same Radio Bearer identity and KeNB
When the PDCP COUNTs is about to be re-used with a different Radio Bearer identity and KeNB
After the eNB performs a handover to another cell
When the KeNB is updated by the MME
None of the above