UMTS Layer 2

Layer 2 is comprised of Medium Access Control (MAC), Radio Link Control (RLC),
Packet Data Convergence Protocol (PDCP) and Broadcast Multicast Control (BMC).
Transport Channels form the service access points between MAC and the physical
layer. Logical channels form the service access points between MAC and RLC. Radio
Bearers or Radio Signalling Bearers form service access points between L2 and
higher layers (e.g. Radio Resource Control or RRC).
Peer RRC, RLC and MAC entities exist in the UE and either the Node B (idle mode) or
SRNC (connected mode).
RRC controls the L2 protocols to set up, maintain and clear down connections with
appropriate QoS.

UMTS Layer 2 pdf

source : m2vtelecom.blogspot.com