3GPP TS 36.331 has defined the presence of "Need ON", "Need OP" and "Need OR" for an IE.
Need ON (Optionally Present, no action ) : If Need ON has been used for an IE then it means that take no action if information element if not received from eNodeB. And also continue with the old value of that IE.
Need OR (Optionally Present, release) : If Need OR has been used for an UE then it means that release the existing value of the IE if it is not received.
Need OP (Optionally Present ) : If IE is present then apply the configuration as per received values of that IE else take action as per procedural text.
All three have been used across all messages of RRC protocol.