{HEAD ~ Two exemplary types} of {TAIL ~ service level layers} are peak signal to noise ratio layers and bitrate layers 
of
{ HEAD ~ Two exemplary types } of { TAIL ~ service level layers } are peak signal to noise ratio layers and bitrate layers
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH