One reason for this is the limited capability of these systems to actually ensure {HEAD ~ proper performance} of {TAIL ~ the client clocks} 
of
One reason for this is the limited capability of these systems to actually ensure { HEAD ~ proper performance } of { TAIL ~ the client clocks }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL