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