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