If you are transiting at the terminal from a domestic to an overseas or another domestic flight, then both departure and arrival traffic are on the same level and intermingle. You won't have to go landside unless you don't have a boarding pass for your onward flight (though this could be obtained at the gate). However, if you are coming off an international flight connecting to a domestic or transborder flight, then you are channeled along an elevated corridor and then down escalators to the ground level arrivals area for processing through Immigration and Customs. Once landside, you must re-check your bag and head upstairs by escalator or elevator to clear security to get back airside. If you are connecting to a US flight from either a domestic or international, you must pre-clear US Immigration and Customs from the second floor departures area.