After {HEAD ~ the routing data} is added to the data frame, the buffer transmits {TAIL ~ the data frame} to the switching system 
After { HEAD ~ the routing data } is added to the data frame , the buffer transmits { TAIL ~ the data frame } to the switching system
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH