The Model S Smart Air Suspension was an option in 2014, and it became standard for all Model S trims from 2017 to mid-2019. The four-corner system is similar to those found on European cars and trucks. The system uses an air compressor, reservoir and valve block that are all mounted in the trunk.
The 2014 and 2015 Model S suspensions use a system made by Continental. The 2016 to 2019 models use an air suspension made by Firestone. Both systems use the same component locations. But, the only fundamental changes between the two systems are how your scan tool connects and how it calibrates, depressurizes and pressurizes the system.