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