ATM cell creation => generating and adding a 5 byte cell header to the
48 byte payload received from the AAL (and giving the payload to the AAL at the receiving end)
Multiplexing (and demultiplexing) of the ATM cell flows from different
sources using appropriate identifiers (VCI and VPI) located in the cell headers
Cell routing (switching and/or relaying) within the
ATM network (also using VCI and VPI)
The ATM layer may also provide mechanisms for traffic management.