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