The repair server detects that packets are missing from the session it receives and in response, it sequentially requests the missing packets from respective ones of {TAIL ~ the plurality} of {HEAD ~ retransmit servers} 
The repair server detects that packets are missing from the session it receives and in response , it sequentially requests the missing packets from respective ones of { TAIL ~ the plurality } of { HEAD ~ retransmit servers }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD