Portion of data stream or {HEAD ~ data block} 200 is sent from {TAIL ~ one or more clients}  
Portion of data stream or { HEAD ~ data block } 200 is sent from { TAIL ~ one or more clients }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH