Subnetwork Dependent Convergence Protocol:-
.Multiplexer/demultiplexer for different network layer entities onto LLC layer
.Compression of protocol control information (e.g. TCP/IP header)
.Compression of data content (if used)
.Segmentation/de-segmentation of data to/from LLC layer
Logical Link Control (LLC) Layer:-
.Reliable logical connection between SGSN and MS
.Independent of underlying radio interface protocols