{HEAD ~ These data} requiring storage are stored in {TAIL ~ a storage device} installed in the optical network unit 
are stored in
{ HEAD ~ These data } requiring storage are stored in { TAIL ~ a storage device } installed in the optical network unit
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH