Another way this can be accomplished is by transmitting the missing packets in {HEAD ~ a unicast session} from {TAIL ~ the retransmit servers} to the repair server 
Another way this can be accomplished is by transmitting the missing packets in { HEAD ~ a unicast session } from { TAIL ~ the retransmit servers } to the repair server
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH