{HEAD ~ Arbiter} 16 receives requests for access from any of a number of {TAIL ~ requesters} 
{ HEAD ~ Arbiter } 16 receives requests for access from any of a number of { TAIL ~ requesters }
HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL