Is PDCP a layer 2?

The 5G layer-2 include MAC, RLC and PDCP . The 5G layer-3 is RRC layer as shown in 5G protocol stack. The Figure-1 depicts 5G Protocol Stack consisting of both User Plane and Control Plane protocol layers.

PDCP is located in the Radio Protocol Stack in the UMTS/LTE/5G air interface on top of the RLC layer . PDCP provides its services to the RRC and user plane upper layers, e.g. IP at the UE or to the relay at the base station.

From UMTS, the main function of the PDCP layer has been the header compression of IP packets – this is the reason why it is called the Packet Data Convergence Protocol. In LTE, the PDCP layer has evolved to support a security function; that is, integrity protection and ciphering.

The main services and functions of the PDCP for the control plane include: Ciphering and Integrity Protection; Transfer of control plane data .