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