The RA provides a subsystem with a mechanism for sending {HEAD ~ read and write requests} to {TAIL ~ the DA} of another subsystem 
to
The RA provides a subsystem with a mechanism for sending { HEAD ~ read and write requests } to { TAIL ~ the DA } of another subsystem
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH