The question is specifically asking about the LTE Control plane protocols from the Radio Interface perspective.
Therefore, lets focus specifically on the radio interface including the control plane protocols involved as shown below.
The protocols from the RAN perspective in control plane are shown above.
The brief functionality of each of the protocol layer is shown below.
Non-Access Stratum (NAS) : NAS consists of Session Management (SM) and EPS mobility management (EMM) layers. The functions performed by NAS are:
Physical Layer (PHY) : This protocol is responsible for following commands from MAC layer and perform functions such as modulation coding scheme etc. on bits which needs to be send over the interface.
Medium Access Control (MAC): The LTE scheduler resides at MAC layer of the eNodeB. MAC layer protocol at eNodeB performs multiplexing, scheduling, transport format selection, modulation scheme selection and QoS responsibilities etc. on the RAN side.
Radio Link Control (RLC) : Main functions for this protocol include concatenation and segmentation of data. In addition it has three modes of transportation based on the type of information passing through. Transparent mode, Acknowledged mode and Unacknowledged mode.
Packet Data Convergence Protocol (PDCP): It performs header compression and sequence numbering. For control plane traffic, PDCP perform both ciphering and integrity protection.
Radio Resource Control (RRC):The following control plane functions are agreed in 3GPP, to be performed by the RRC layer:
Mobility functions for RRC protocol includes:
On the network side, it has been agreed in 3GPP that RRC layer is to be terminated by the eNodeB