Complex sentence: AAL2 is further separated into two sub-layers that helps with the mapping from upper layer services to ATM cells: the Service Specific Convergence Sub-layer (SSCS) and the Common Part Sub-layer (CPS).
Split into simpler sentences: AAL2 is further separated into two sub-layers that help with the mapping from upper layer services to ATM cells. These are named Service Specific Convergence Sub-layer (SSCS) and Common Part Sub-layer (CPS).