develop a response message to be sent to the first computer over {TAIL ~ the communications link} advising the first computer of {HEAD ~ a successful or unsuccessful receipt} of the communications packet, and 
develop a response message to be sent to the first computer over { TAIL ~ the communications link } advising the first computer of { HEAD ~ a successful or unsuccessful receipt } of the communications packet , and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH